Development and Characterization of a Ribbon-Type Ion Beam Source Test Bench for Ion Implantation Applications

Development and Characterization of a Ribbon-Type Ion Beam Source Test Bench for Ion Implantation Applications | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Development and Characterization of a Ribbon-Type Ion Beam Source Test Bench for Ion Implantation Applications Junbeom Park, Minkeun Lee, Wooyoung Choi, Daehyun Kim, Kyoung-Jae Chung This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8477349/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract As semiconductor manufacturing processes become increasingly advanced and diversified, ion implantation processes capable of precisely controlling ion energy and implantation current are increasingly required, leading to growing demand for reliable ion source evaluation testbench. In this study, a ribbon-type ion beam source test bench is designed and constructed to investigate ion beam extraction characteristics for ion implantation applications. The developed test bench enables independent control of plasma generation conditions and ion beam extraction parameters, and employs a multi-channel Faraday cup as the primary diagnostic tool to directly measure spatially resolved ion beam current distributions. Unlike conventional evaluation approaches based solely on integrated beam current, the present system allows the analysis of beam focusing behavior using two-dimensional beam current profiles resolved along both the major and minor axes of the ribbon beam. Experiments are conducted by varying the extraction voltage, arc current, and electrode spacing, demonstrating that a limited extraction condition exists under which beam spreading is minimized in both axes. The results show that adjustments of extraction and discharge parameters are inherently accompanied by changes in beam focusing behavior in a three-electrode extraction system, highlighting the importance of spatially resolved diagnostics for evaluating ion source performance. The developed test bench thus provides a practical and flexible platform for assessing extraction characteristics and electrode configurations, while offering a foundation for future extensions incorporating additional diagnostics for comprehensive beam quality evaluation. Ion implantation Ribbon-type ion beam Ion source test bench Multi-channel Faraday cup Beam extraction diagnostics Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 I. INTRODUCTION Ion implantation is a technique that enables precise control of impurity concentration, depth, and spatial distribution by directly introducing high-energy ions into solid materials. Unlike diffusion-based processes, ion implantation allows independent control of ion fluence and energy, enabling nanometer-scale depth control and abrupt concentration profiles while operating at relatively low substrate temperatures. [1, 2] These advantages make ion implantation highly compatible with advanced semiconductor fabrication processes, particularly through selective implantation using photoresist or hard masks. Consequently, ion implantation has been widely used as a core doping technique in semiconductor devices and has also been applied to surface modification of ceramic and metallic materials. [3–8] The importance of ion implantation has further increased with the rapid adoption of wide-bandgap semiconductors such as SiC and GaN in power electronics.[9– 14] In particular, SiC offers superior properties, including high thermal conductivity, high critical electric field strength, low power loss, and excellent thermal stability, making it well suited for high-voltage, high-temperature, and high-frequency applications. However, due to its strong covalent bonding and extremely low impurity diffusion coefficients, conventional thermal diffusion is ineffective for SiC, rendering ion implantation essentially the only viable doping method for SiC power semiconductor devices. Modern SiC power devices consist of multiple functional regions—such as source/drain regions, P⁺ contacts, guard rings, edge termination structures, and p-wells—each requiring distinct ion species, fluence, and implantation depths. [11–14] Satisfying these diverse requirements necessitates ion sources capable of operating over wide energy ranges, providing flexible fluence control, and stably supplying various ion species. However, simply adjusting ion source operating conditions presents inherent limitations, as parameters such as discharge power, gas pressure, and magnetic field strength strongly influence plasma density, ion fraction, and discharge stability. [15–18] Changes in these parameters can induce plasma instabilities, including rotating spokes, which degrade plasma uniformity at the extraction region and adversely affect beam stability. While such instabilities have been reported in various plasma sources, their direct impact on ion beam characteristics relevant to practical ion implantation processes remains insufficiently understood. To address this issue, the present study focuses on developing a dedicated ion beam source test bench to evaluate how plasma instabilities arising from ion source operating conditions influence the characteristics of extracted ion beams. The test bench enables quantitative measurements of beam current density, spatial distribution, and energy characteristics under controlled conditions, providing a platform for correlating internal plasma behavior with actual beam quality in ion implantation applications. The remainder of this paper is organized as follows. First, the design and configuration of the ribbon-type ion beam source test bench and the associated diagnostic system are described, with emphasis on the independent control of plasma generation and extraction parameters. Next, experimental procedures and operating conditions for ion beam extraction are presented, followed by measurements of extracted beam current and two-dimensional beam profiles obtained using the multi-channel Faraday cup. The experimental results are then discussed in terms of extraction characteristics and beam focusing behavior as functions of extraction voltage, arc current, and electrode spacing. Finally, the main findings of the study are summarized, and the limitations of the present diagnostic approach and directions for future extensions of the test bench are briefly discussed. II. Ion Beam Source Test Bench and Experimental Setup 1. Configuration of the Ion Beam Source Test Bench Figure 1. (a) Schematic diagram of the ion beam source test bench. (b) Photograph of the experimental setup. The labeled components are: (1) gas box with arc, bias, and filament power supplies, (2) turbomolecular pump (TMP), (3) high-voltage bushing, (4) electromagnets for Penning discharge, (5) multi-channel Faraday cup (MCFC) stage, and (6) isolation transformer. Figure 2 Photograph of the ribbon-type ion beam extraction and diagnostic system installed inside the vacuum chamber. The labeled components are: (1) high-voltage insulating bushing, (2) indirectly heated cathode Penning ion source, (3) slit-type plasma electrode, (4) source magnet, (5) acceleration electrode, (6) deceleration electrode forming a three-electrode extraction system, (7) multi-channel Faraday cup (MCFC), and (8) beam dump. To evaluate the performance of ion sources for ion implantation, an ion beam source test bench is constructed, and the overall system configuration, together with the gas, power, and signal interconnections between subsystems, is shown in Fig. 1. The test bench allows independent control of plasma generation parameters and beam extraction conditions, enabling flexible adjustment of discharge power, magnetic field, gas flow, and electrode configuration during ion beam extraction experiments. Figure 1(a) presents a schematic diagram of the entire system, including the power supply, gas delivery, cooling, vacuum, and diagnostic subsystems, while Fig. 1(b) shows a photograph of the experimental test bench, illustrating the implementation of each functional component depicted in the schematic. Figure 2 presents the internal configuration of the vacuum chamber shown in Fig. 1(b), together with the spatial arrangement of the beamline components presented in Fig. 1. The region indicated by thick black lines in Fig. 1(a) represents the lead shielding encloser, while the gray area corresponds to the shielding door. When high-energy ion beams strike the beam dump, radiation including X-rays can be generated; therefore, this region is shielded with lead to ensure operator safety. As a result, direct manual operation is not permitted during experiments, and system control and diagnostics are performed remotely via optical or electrical signal communication. This shielding and remote operation scheme satisfies essential safety requirements for high-energy ion beam experiments. Gas and electrical power required for ion source operation are supplied through the gas box (Fig. 1(b)-(1)). The gas box houses the arc, bias, and filament power supplies, and the discharge gas flow rate is precisely controlled using a mass flow controller (MFC). In this study, argon gas is used for baseline characterization to investigate the physical operation of the ion source, plasma density variations with arc power, plasma oscillations associated with operating recipes, and ion beam extraction characteristics. The gas lines are constructed from stainless steel tubing to ensure corrosion and chemical resistance, allowing compatibility with implantation gases such as BF₃. During ion beam extraction, the ion source is electrically floated at high voltage with respect to the chamber. The gas box, which is electrically connected to the ion source, is maintained at the same floating potential. Electrical isolation is achieved using a 1:1 isolation transformer (Fig. 1(b)-(6)), which provides electrically isolated power delivery. Under non-extraction conditions, the gas box is grounded by direct contact with a grounding rod to ensure operational safety. The ion source used in this study is an indirectly heated cathode Penning ion source (Fig. 1(b)-(4) and Fig. 2-(2)). Thermionic electrons emitted from the filament first heat the cathode, after which electrons emitted from the heated cathode discharge and sustain the plasma. Because the filament does not directly contact the plasma, this configuration reduces ion bombardment damage and extends filament lifetime, while the large cathode emission area enables stable plasma generation at relatively low filament power. The filament power is kept constant during experiments, and plasma discharge characteristics are primarily controlled by the bias and arc power supplies. The magnetic field required for Penning discharge is generated by electromagnets located at both ends of the ion source (Fig. 1(b)-(4) and Fig. 2-(4)), with the magnet power supplies positioned outside the gas box. Both the ion source and electromagnets are water-cooled, with coolant supplied from a chiller and passed through a heat exchanger to control water resistivity. This design prevents leakage currents through the cooling water under high-voltage conditions while ensuring thermal stability. The ion source is connected to the grounded chamber via a high-voltage insulating bushing for electrical isolation, as shown in Fig. 1(b)-(3) and Fig. 2-(1). The bushing is designed to withstand extraction voltages exceeding 40 kV and incorporates internal cooling lines to remove heat generated near the ion source. The internal dimensions of the vacuum chamber are 490 mm in width (along the long axis of the ribbon beam), 580 mm in depth (beam extraction direction), and 720 mm in height. A turbomolecular pump (TMP) maintains a base pressure of approximately 3 × 10⁻⁷ Torr (Fig. 1(b)-(2)), which is critical for stable plasma formation and collisionless beam extraction. Linear plates are installed along the chamber walls to facilitate maintenance in the event of localized damage or deposition caused by ion beam exposure. The extracted ion beam has a ribbon-shaped profile; accordingly, the plasma electrode features a slit geometry elongated in one direction (Fig. 2-(3)). In this study, the term “plasma electrode” refers to the electrode or assembly containing the slit at the ion source exit for ion extraction. The long dimension of the slit is defined as the major axis, and the short dimension as the minor axis; subsequent beam profile and uniformity analyses are conducted based on this coordinate system. After passing through the plasma electrode, the ion beam traverses a three-electrode extraction system consisting of acceleration and deceleration electrodes (Fig. 2-(5) and (6)). This electrode assembly is mounted on a manipulator that allows adjustment of the distance from the plasma electrode. The manipulator provides a travel range from 13.6 mm to 48.9 mm relative to the plasma electrode, enabling investigation of changes in plasma meniscus shape and ion beam characteristics as a function of manipulator position. The extracted ion beam is delivered to a multi-channel Faraday cup (MCFC), as shown in Fig. 1(b)-(5) and Fig. 2-(7), where spatially resolved beam current distributions are measured. The MCFC is positioned 275 mm downstream from the plasma electrode. The MCFC stage translates the MCFC along the long axis of the beam, allowing position control within ±120 mm relative to the beam center with a resolution of 0.1 mm. This stage also serves as a vacuum boundary, transmitting collected ion current signals to the exterior of the vacuum chamber. Because the MCFC directly intercepts the ion beam and experiences significant thermal loading, a water-cooling structure is employed. Cooling water is supplied via flexible stainless-steel tubing connected to the MCFC stage, enabling stable cooling while maintaining vacuum condition. Position control of the MCFC stage and data acquisition are performed using an external PC. Ion beams not captured by the MCFC are absorbed by the beam dump shown in Fig. 1(a) and Fig. 2-(8). Ion beam dump is also water-cooled. 2. Multi-Channel Faraday Cup Diagnostics To diagnose the spatial distribution of the extracted ion beam, the MCFC is employed in this study. An alternative approach combining a single Faraday cup with two-dimensional positional scanning is possible; however, this method requires external implementation of two-dimensional motion, which imposes limitations on the scanning range due to structural constraints associated with passing through the vacuum boundary. In practice, such configuration is insufficient to fully cover the expected beam spread, particularly for ribbon-type ion beams that are extended along the major axis, thereby limiting diagnostics of the beam profile. Installing a two-dimensional motion stage inside the vacuum chamber could alleviate this limitation, but would significantly increase system complexity due to motor heating, ion beam induced damage, and the need for additional cooling and shielding structures. Considering these constraints, the MCFC provides a suitable diagnostic solution for the ribbon-type ion beam source test bench developed in this study, as it enables simultaneous spatially resolved ion current measurements while maintaining a relatively simple system configuration. The MCFC used in this work consists of 15 individual Faraday cup channels arranged linearly along the short axis of the ion beam. Each channel has an aperture diameter of 4.5 mm, and the center-to-center spacing between adjacent channels is 8.5 mm. As a result, ion currents can be measured simultaneously at 15 spatial positions along the minor axis, covering a total width of 127.5 mm (15 × 8.5 mm). This channel arrangement allows the MCFC to acquire the ion current distribution along the minor axis in a single measurement, while spatial variation along the major axis is obtained by translating the MCFC stage. The MCFC stage provides position control along the major axis with a resolution of 0.1 mm. Each MCFC channel operates by directly collecting and measuring the extracted ion beam current. By spatially arranging the ion beam current obtained from individual Faraday cups, the two-dimensional ion current distribution is reconstructed, enabling comparison of beam focusing characteristics and distribution changes under different extraction conditions. Because secondary electron emission (SEE) can lead to overestimation of the true ion current, a permanent-magnet-based SEE suppression scheme is adopted instead of the suppression electrode. Compared to electrode-based suppression methods that require additional power supplies, the permanent magnet approach offers a simpler structure with minimal electrical connections. Figure 3 Cross-sectional views of the multi-channel Faraday cup (MCFC) assembly. The labeled components are: (1) graphite shield, (2) SmCo permanent magnets, (3) water cooling connectors, (4) micro-Faraday cup array, (5) internal water-cooling lines, and (6) O-rings. The internal structure and main components of the MCFC are shown in Fig. 3. The front surface exposed to the ion beam, as well as the signal lines and cooling lines, are shielded with graphite to minimize sputtering caused by high-energy ion impacts (Fig. 3-(1)). Samarium–cobalt (SmCo) permanent magnets are installed behind each Faraday cup channel to effectively suppress secondary electrons (Fig. 3-(2)). These magnets provide sufficiently strong magnetic fields and exhibit high Curie temperatures, ensuring stable magnetic performance even under elevated temperature. Since the MCFC directly intercepts high-energy ion beams and is subjected to significant thermal flux, an integrated water-cooling structure is implemented. Cooling water is supplied through water-cooling connectors (Fig. 3-(3)) and circulates through internal cooling lines (Fig. 3-(5)). O-rings (Fig. 3-(6)) used to prevent leakage under vacuum conditions. This design allows stable long-duration operation of the MCFC even under high-current and high-energy beam conditions. The array of Faraday cups used for direct ion current collection is illustrated in Fig. 3-(4). The ion current signals collected by each Faraday cup channel are electrically connected via bolted contacts at the rear of each cup. Hole-type contacts are formed on a printed circuit board (PCB), and the signals are mechanically and electrically secured using bolts to ensure stable connections. Signals from all 15 channels are transmitted outside the vacuum chamber through a 15-pin D-sub connector and cable, and subsequently routed through the MCFC stage to the data acquisition system. Data acquisition (DAQ) is performed using a multi-channel current module (National Instruments, NI-9208 current input), which provides a total sampling rate of up to 500 samples/s. With 15 channels operated simultaneously, the maximum sampling rate per channel is approximately 30 samples/s. The DAQ system operates with a 24-bit analog-to-digital converter over a ±20 mA input range, corresponding to a theoretical current resolution of approximately 2.4 nA. In the present experiments, ion current signals are acquired at 10 samples/s per channel, and data collected over 1 s are averaged to obtain the current value at each spatial position. The standard deviation of the measured current signals is approximately 150 nA, which is comparable to the system noise level and indicates that a sufficient signal-to-noise ratio is achieved for ion beam current distribution analysis using the MCFC. The NI-9208-based data acquisition system has limited capability in resolving plasma oscillations at frequencies of several kilohertz or higher, such as rotating spokes. To address this limitation at the instrumentation level, the signal line between the MCFC and the DAQ is designed to allow the insertion of a 10 kΩ resistor, enabling differential voltage measurements using an external oscilloscope. Although oscilloscope-based measurements are not utilized in the present study, the diagnostic system is designed to be flexible. The DAQ is used for measuring DC beam current under stable plasma conditions, whereas an oscilloscope can be employed to analyze time-resolved beam current fluctuations when necessary. 3. Experimental Conditions for Ion Beam Extraction In this study, experiments are conducted by stepwise control of plasma discharge conditions and ion beam extraction conditions to evaluate the extraction characteristics of a ribbon-type ion beam source. Plasma generation conditions are determined by the arc, bias, and filament power supplies, as well as the discharge gas and magnetic field conditions, and all experiments are performed within regimes where the discharge remains temporally stable. The objective of this study is not to optimize the discharge conditions, but rather to quantitatively compare the effects of extraction electrode configuration and extraction voltage on ion beam characteristics under well-established and stable plasma conditions. Accordingly, discharge-related parameters are restricted to conditions whose stability is verified through preliminary experiments. Both the filament and bias power supplies operate in current-control mode. The filament current is fixed at 42.0 A throughout the experiments, corresponding to a filament voltage of 4.9 V. The filament current directly determines the cathode temperature and thermionic electron emission, which in turn influence plasma density and bias conditions. Since the bias power supply also operates in current-control mode, variations in filament current simultaneously alter the bias voltage and bias power. For this reason, the filament current is fixed to constrain the bias conditions. The selected filament condition ensures stable discharge operation while minimizing fluctuations in bias voltage, and no additional filament-related variables are introduced during the experiments. The stability of the plasma discharge is governed by the combined effects of arc conditions, magnetic field configuration, and discharge gas parameters. According to previous experimental results and prior studies, plasma oscillations readily occur under conditions of low arc voltage and high arc current[18], and such oscillations induce temporal fluctuations in ion density near the plasma electrode. As a consequence, the plasma meniscus shape varies with time, leading to degraded ion beam angular distribution and reduced reproducibility of extraction characteristics. To avoid these effects, the arc voltage is fixed at 100 V, while the arc current is varied within the range of 1.1–2.3 A. The arc current is adjusted manually by controlling the bias current, and experimental conditions are selected within stable regimes where plasma oscillations are not observed. Under these conditions, the bias voltage remains in the range of approximately 394–402 V. Increasing the bias current enhances cathode heating and raises the cathode temperature. As a result, thermionic emission increases, leading to a higher arc current. Because the arc current is directly correlated with plasma density, variations in arc current are used as an indicator of plasma density changes in this study. To maintain a stable Penning discharge, current is supplied to the electromagnets installed at both ends of the ion source to generate an axial magnetic field of approximately 100 G at the ion source center. This magnetic field suppresses radial electron transport and increases electron residence time in the discharge region, enabling stable plasma formation even at relatively low discharge power. Argon is used as the discharge gas, and the gas flow rate is fixed at 3 sccm. If the neutral density is too low, temporal density fluctuations such as breathing-mode oscillation occurs. Therefore, a sufficiently high gas flow rate ensuring stable discharge is employed. Throughout this study, the magnetic field strength and gas flow rate are held constant so that their effects do not introduce additional variations in extraction characteristics. Consequently, all ion beam extraction results presented here are obtained under identical magnetic field and gas conditions. The extraction voltage applied for ion beam extraction is varied in the range of 10–25 kV, while the acceleration electrode voltage is fixed at -3 kV. The upper limit of the extraction voltage is restricted to 25 kV in consideration of system safety and electrode thermal loading. It is experimentally observed that the combination of high plasma density and high extraction voltage leads to melting of the plasma electrode surface and erosion of the acceleration electrode. Such electrode damage degrades system reliability and complicates repeated experiments. Therefore, extraction voltages are varied only within stable operating regimes that allow long-duration operation. The observed extracted ion current ranges 4–20 mA. Under these stable discharge conditions, the extraction electrode position is varied stepwise using a manipulator, starting from a distance of 15.7 mm from the plasma electrode and incremented in steps of 2.3 mm. The manipulator allows movement up to a maximum distance of 45.3 mm. At each position, the extracted ion beam is measured using the MCFC to obtain two-dimensional current distributions, which are then used to compare changes in plasma meniscus shape and beam focusing characteristics as a function of extraction electrode position. In this study, the condition of “optimal focusing” is defined as the extraction condition at which the beam widths along both the major and minor axes are minimized in the two-dimensional ion beam current distribution measured by the MCFC. III. Results and Discussion 1. Dependence of Extracted Ion Beam Current on Extraction Voltage, Arc Current, and Electrode Spacing Figure 4 (a) Extracted ion current as a function of the distance between the plasma electrode and the extraction electrode for different extraction voltages at a fixed arc current. (b) Extracted ion current as a function of the electrode distance for different arc current values at a fixed extraction voltage. Figure 4(a) presents the extracted ion beam current as a function of the distance between the plasma electrode and the acceleration electrode at different extraction voltages, with the arc current fixed at 1.3 A. Normal extraction is defined by the absence of acceleration electrode current, while abnormal extraction is associated with finite current collection at the acceleration electrode. The extracted current trends with electrode spacing provide a basis for identifying the spacing range corresponding to normal ion beam extraction. Under normal extraction conditions, where the ion beam is extracted without impinging on the acceleration electrode, different electrode spacing ranges are formed depending on the extraction voltage. Specifically, for an extraction voltage of 10 kV, stable extracted current is observed in the range of approximately 17.9–24.8 mm, while at 15 kV the stable range expands to approximately 17.9–36.2 mm. When the extraction voltage increases to 20 kV, the normal extraction region extends from 17.9 mm up to the manipulator travel limit of 45.3 mm. In contrast, at 25 kV the normal extraction region becomes restricted again to approximately 33.9–45.3 mm. Such changes in the width and position of the electrode spacing window with extraction voltage are attributed to variations in the extraction electric field strength, which modify the plasma meniscus shape. Within the normal extraction region, the extracted ion current decreases gradually with increasing electrode spacing for all extraction voltage conditions. This trend can be attributed to the weakening of the extraction electric field as the electrode spacing increases at a fixed extraction voltage. The reduced electric field lowers the curvature of the plasma meniscus, thereby decreasing the effective area from which ions are efficiently extracted. These observations confirm that the extracted ion current is strongly governed by the extraction electric field. Abnormal extraction behavior is observed when the electrode spacing decreases below approximately 17.9 mm for extraction voltages of 10, 15, and 20 kV, while for the 25 kV condition, the onset of abnormal extraction shifts to electrode spacings below approximately 31.6 mm. In this regime, the electrode spacing becomes excessively small, resulting in an overly enhanced extraction electric field that pushes the plasma meniscus inward. Consequently, the ion beam is formed in an overfocused state, where ion trajectories cross near the acceleration electrode and subsequently diverge, producing a current on the acceleration electrode that should otherwise remain current-free under normal transport conditions. This observation indicates that the ion beam directly impinges on the acceleration electrode. Conversely, abnormal extraction behavior is also observed when the electrode spacing becomes sufficiently large. For an extraction voltage of 10 kV, increasing the spacing beyond approximately 27.1 mm, and for 15 kV beyond approximately 36.2 mm, leads to insufficient formation of the extraction electric field. Under these conditions, the plasma meniscus becomes flattened or protrudes outward, and the ion beam propagates in an underfocused, divergent state. As a result, a portion of the ions again collides with the acceleration electrode. This underfocus regime appears at smaller electrode spacings for lower extraction voltages. These results indicate that the extracted ion beam current does not vary monotonically with electrode spacing. Instead, different focusing regimes are formed depending on the interplay between the extraction electric field strength and the plasma meniscus shape. For each extraction voltage, the normal ion beam extraction occurs only within a distinct electrode spacing window. Figure 4(b) compares the extracted ion beam current as a function of the electrode spacing while varying the arc current at a fixed extraction voltage of 20 kV. Whereas Fig. 4(a) analyzes extraction characteristics primarily from the perspective of electric field effects associated with extraction voltage, Fig. 4(b) illustrates how changes in plasma density influence the plasma meniscus shape and ion beam focusing by distinguishing normal and abnormal extraction regions as the electrode spacing varies. As in Fig. 4(a), a window of electrode spacing that allows normal ion beam extraction is formed depending on the electrode configuration, and the position of this window is observed to shift with arc current. The normal extraction regime spans different electrode spacing ranges depending on the arc current. For an arc current of 1.1 A, the normal extraction region forms at electrode spacings larger than 27.1 mm. When the arc current increases to 1.3 A, the normal extraction region expands to spacings larger than 15.7 mm, and at 1.5 A the normal extraction regime extends over the range of 15.7–45.3 mm. With a further increase in arc current to 1.9 A, the normal extraction regime becomes restricted again to 17.9–36.2 mm, and at 2.1 A arc currents the region shifts further to 17.9–31.6 mm. This shift of the normal extraction regime toward the plasma electrode with increasing arc current is interpreted as resulting from the higher plasma density, which requires a stronger extraction electric field to maintain a similar plasma meniscus shape. Within the normal extraction region, a gradual decrease in extracted current with increasing electrode spacing is observed for all arc current conditions. This trend arises because, at a fixed extraction voltage, increasing the electrode spacing weakens the extraction electric field and reduces the curvature of the plasma meniscus, thereby decreasing the number of ions effectively extracted. However, as the arc current increases, the plasma density becomes higher, allowing relatively higher extracted currents to be maintained even at the same electrode spacing. This observation indicates that the extracted ion current depends not only on the extraction electric field but also on the plasma density. When the electrode spacing decreases below the lower boundary of the normal extraction region, an overfocus regime forms for all arc current conditions. In this regime, the extraction electric field becomes excessively strong due to the small electrode spacing, and the plasma meniscus is pushed deeply into the plasma. As a result, the ion beam becomes overfocused, with trajectories crossing in front of the acceleration electrode and subsequently diverging, causing a fraction of the ions to collide with the acceleration electrode. As the arc current increases and the plasma density rises, a stronger electric field is required to form a comparable meniscus, and the boundary at which overfocusing occurs shifts toward the plasma electrode. In contrast, when the electrode spacing exceeds the upper boundary of the normal extraction region, an underfocus regime is formed. In this regime, the extraction electric field is insufficient due to the large electrode spacing, and the plasma meniscus becomes flattened or protrudes relative to the plasma electrode, causing the ion beam to diverge without adequate focusing. Consequently, some ions collide with the acceleration electrode, and a current is detected. The underfocus regime appears at smaller electrode spacings under lower arc current conditions and shifts toward the plasma electrode as the arc current increases. This behavior can be understood as reflecting the increasingly stringent electric field conditions required to form a required meniscus at higher plasma densities. Overall, the results in Fig. 4(b) clearly show that the normal extraction region shifts with arc current, that is, with plasma density, and that a window of electrode spacing exists between the overfocus and underfocus regimes in which normal ion beam extraction is achieved. In particular, when a target ion energy and extracted current are specified, the manipulator position satisfying normal ion beam extraction converges to a limited range. Thus, for a given combination of plasma generation conditions and extraction voltage, the electrode spacing does not act as an independently selectable parameter, but rather as a dependent parameter constrained within the normal extraction regime. 2. Two-Dimensional Ion Beam Profile Analysis Using a Multi-Channel Faraday Cup In this section, two-dimensional ion beam current distributions measured using a MCFC are presented, and the spatial focusing characteristics of the ribbon-type ion beam are analyzed as functions of extraction conditions and electrode configuration more deeply. Even under identical extracted current conditions, the spatial spreading characteristics of the beam can vary significantly depending on the plasma meniscus shape, and such differences are directly related to the practical applicability of the beam. Therefore, the beam shape is evaluated in greater detail based on spatially resolved current distributions. In this study, the condition at which focusing along both the long and short axes is simultaneously satisfied is defined as the optimum focusing condition. Two-dimensional current distribution measurements using the MCFC are performed by stepwise translation of the MCFC along the major axis of the beam. In the present experiments, the MCFC position is varied at intervals of 10 mm along the major axis, and ion currents are simultaneously measured at each position using the 15 Faraday cup channels arranged along the minor axis. The discrete current data acquired along the major and minor axes are then reconstructed into continuous two-dimensional current distributions by applying linear interpolation between adjacent measurement points. Through this procedure, the overall spatial distribution and focusing characteristics of the ion beam are visualized and analyzed, despite the finite spatial resolution of the MCFC. Figure 5 Two-dimensional ion beam current profile measured by the multi-channel Faraday cup at an extraction voltage of 20 kV and an arc current of 1.3 A (manipulator position: 33.9 mm). The dashed contour denotes 10% of the maximum beam current. Figure 5 shows a representative two-dimensional ion beam current distribution measured at an extraction voltage of 20 kV and an arc current of 1.3 A with the manipulator positioned at 33.9 mm. A high beam current density is observed at the center of the distribution, confirming the formation of a typical ribbon-type ion beam structure elongated along the major axis. Along the minor axis, the current decreases relatively rapidly, whereas a more gradual decrease is observed along the major axis. The white dashed contour shown in the figure corresponds to 10% of the maximum current value and is used as a reference to compare the effective beam spread and focusing state. This contour provides an intuitive representation of the actual spatial extent of the beam and is useful for quantitative comparison of focusing characteristics under different extraction conditions. Figure 6 Two-dimensional ion beam current profiles measured using the multi-channel Faraday cup at a fixed arc current of 1.3 A for different extraction voltages and manipulator positions. The dashed lines denote the 10% maximum current contour, and shaded regions indicate conditions where current flows to the acceleration electrode. Figure 6 compares the two-dimensional ion beam current distributions measured while varying the extraction voltage and the distance between the plasma electrode and the acceleration electrode at a fixed arc current of 1.3 A. This figure directly illustrates how the spatial focusing characteristics of the ribbon-type ion beam change with extraction voltage under identical discharge conditions. When the extraction voltage is 10 kV, a focused beam state in which beam spreading is minimized along both the major and minor axes is formed at a manipulator position of 20.2 mm; for 15 kV, this condition occurs at 24.8 mm; and for 20 kV, at 38.4 mm. Under these conditions, not only is the beam thickness along the minor axis minimized based on the 10% maximum current contour, but beam spreading along the major axis is also suppressed, resulting in the most tightly focused ion beam distribution. As the extraction voltage increases, the electrode spacing at which optimum focusing is achieved gradually shifts farther away from the plasma electrode. This trend arises because an increase in extraction voltage strengthens the electric field in the extraction region, thereby modifying the electrode configuration required to maintain a similar plasma meniscus shape. In contrast, for an extraction voltage of 25 kV, a distinct condition at which beam spreading is simultaneously minimized along both axes cannot be clearly identified within the electrode spacing range accessible in the present experiments. Nevertheless, the maximum current measured in the two-dimensional current distributions continues to increase with extraction voltage, suggesting that the optimum focusing position under the 25 kV condition is likely formed at electrode spacings of at least 45.3 mm or larger. This implies that the optimum focusing point lies beyond the experimental range explored in this study, and additional measurements with an extended manipulator travel range are required to clearly identify this condition. When the electrode spacing deviates from the optimum focusing position, the spatial distribution of the ion beam degrades in distinct ways. At electrode spacings smaller than the optimum position, an overfocus condition is formed, in which the plasma meniscus is pushed inward and the ion beam spreads again along both axes. Conversely, when the electrode spacing exceeds the optimum focusing position, the extraction electric field becomes relatively weak. As a result, the plasma meniscus curvature decreases or protrudes beyond the plasma electrode, and the ion beam propagates in an underfocused, divergent state. These overfocus and underfocus behaviors are clearly distinguished in the two-dimensional current distributions through the direction and extent of beam spreading. Figure 7 Two-dimensional ion beam current profiles measured by the MCFC at an extraction voltage of 20 kV for different arc currents. The dashed lines denote the 10% maximum current contour, and shaded regions indicate conditions where current flows to the acceleration electrode. Figure 7 compares the two-dimensional ion beam current distributions measured as a function of the distance between the plasma electrode and the acceleration electrode while varying the arc current at a fixed extraction voltage of 20 kV. This figure extends the behavior observed in Fig. 6 and illustrates how increases in plasma density associated with changes in arc current affect the plasma meniscus shape and ion beam focusing characteristics. In particular, the two-dimensional current distributions clearly demonstrate that, even under the same extraction voltage, both the optimum focusing position and the spatial beam distribution vary significantly with arc current. Based on the two-dimensional current distributions, the optimum focusing condition shifts with arc current. The most tightly focused beam is observed at a manipulator position of approximately 22.5 mm for an arc current of 2.3 A, 27.1 mm for 1.9 A, 33.9 mm for 1.5 A, and 38.4 mm for 1.3 A. In contrast, for an arc current of 1.1 A, it is difficult to clearly identify a position within the electrode spacing range accessible in the present. These results indicate that, as the arc current decreases, the electrode spacing at which optimum focusing is achieved shifts progressively farther away from the plasma electrode. This shift is attributed to changes in plasma meniscus curvature resulting from variations in plasma density with arc current. As plasma density increases, a stronger extraction electric field is required to satisfy the same focusing condition, causing the electrode spacing corresponding to optimum focusing to move toward the plasma electrode. In the two-dimensional current distributions of Fig. 7, this behavior is clearly manifested by an increase in the central beam current and by simultaneous minimization of beam spreading along both axes at the optimum focusing position. As in Fig. 6, distinct overfocus and underfocus behaviors are observed when the electrode spacing deviates from the optimum focusing position. When the electrode spacing is smaller than the optimum position, the plasma meniscus retracts toward the electrode, forming an overfocus condition in which the ion beam becomes overly focused and subsequently diverges. In the two-dimensional current distributions, this behavior appears as an increase in beam thickness and non-uniform expansion of the current contours. Conversely, when the electrode spacing exceeds the optimum focusing position, the extraction electric field is no longer sufficiently maintained, the meniscus curvature decreases or protrudes relative to the electrode, and an underfocus condition is formed in which the ion beam diverges without adequate focusing. This underfocus state is also clearly identified in the two-dimensional current distributions through beam broadening and expansion of the current contours. In addition, a clear increase in the maximum current measured over the entire two-dimensional current distribution is observed as the arc current increases. This trend directly reflects the increase in plasma density and the corresponding increase in ion flux supplied by the plasma to the meniscus. Thus, the arc current not only determines the absolute level of the extracted ion beam current but also governs both the electrode spacing at which optimum focusing is achieved and the resulting spatial beam distribution. These results clearly demonstrate the importance of MCFC-based two-dimensional diagnostics in the optimization of ion source extraction conditions. The extraction current based analysis presented in Fig. 4 is effective in defining the normal extraction regime with the presence or absence of current on the acceleration electrode. However, this approach can only indirectly infer overfocus and underfocus states and has limitations in quantitatively distinguishing variations in the actual beam focusing state within the normal extraction regime. In contrast, the MCFC based two-dimensional current distributions presented in Figs. 6 and 7 provide direct spatial information that enables clear discrimination between overfocus and underfocus conditions relative to the optimum focusing position by simultaneously evaluating beam spreading along both the major and minor axes. Even within the same normal extraction regime, the beam focusing characteristics can vary significantly depending on the plasma meniscus shape, and such differences are difficult to identify solely from the magnitude of the extracted current. Therefore, the MCFC diagnostics employed in this study are confirmed to be a key tool for precisely evaluating ion source extraction conditions and electrode configurations from the perspective of actual beam focusing behavior. IV. Conclusions In this study, a ribbon-type ion beam source test bench equipped with a multi-channel Faraday cup is developed to investigate ion beam extraction characteristics for ion implantation applications. Using this system, the extracted ion current is measured as a function of electrode spacing, extraction voltage, and arc current, and the beam focusing characteristics are examined based on two-dimensional beam current profiles. The results show that, once the extraction voltage and arc current are specified, the electrode position at which the beam profile becomes optimal is uniquely determined. This behavior indicates that the emittance of the extracted ion beam is effectively fixed when the beam energy and extracted current are set. Therefore, variations in electrode configuration that increase the extracted current inevitably modify the beam profile and degrade beam transport characteristics. This coupling between extraction characteristics and beam transport leads to an intrinsic trade off in three-electrode extraction systems, representing a fundamental limitation of conventional electrode-based control. Despite the effectiveness of the developed test bench in characterizing two-dimensional beam current distributions, several limitations remain in its present configuration. The current diagnostic system does not allow direct measurement of the beam divergence angle or transverse emittance, which are critical parameters for evaluating beam transport and implantation performance; therefore, an Allison scanner is required in future work. In addition, this study is limited to argon plasmas for baseline characterization, whereas practical ion implantation commonly employs molecular source gases such as BF₃, for which multiple ion species are simultaneously extracted. Under such conditions, beam current measurements alone are insufficient to determine the ion fraction, and the incorporation of mass spectrometric diagnostics will be necessary to fully assess source performance under realistic implantation conditions. Declarations Author Contribution Junbeom Park contributed to the methodology, formal analysis, and experimental investigation, and led the preparation of the original draft as well as the review and editing of the manuscript. Minkeun Lee contributed to the conceptualization and methodology of the study. Wooyoung Choi participated in the experimental investigation and contributed to manuscript review and editing. Daehyun Kim contributed to manuscript review and editing. Kyoung-Jae Chung provided research resources, supervised the overall research, and contributed to manuscript review and editing. ACKNOWLEDGEMENT This work was supported by the Technology Innovation Program (No. RS-2022-00154978, Pilot Equipment Development of Semiconductor Low Energy High Current Ion Implanter) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea), the Samsung Electronics' University R&D program (Project No.: IO241210-11444-01), the Technology Innovation Program Development Program-Public-Private Joint Investment Program for Advanced Semiconductor Talent Development(RS-2024-00405103, Development of energy and incident angle control technique of ribbon-type ion beam for ion beam etching process) funded by the Ministry of Trade, Industry & Energy(MOTIE, Korea) and the Commercialization Promotion Agency for R&D Outcomes(COMPA) funded by the Ministry of Science and ICT(MSIT)(2710084640). References Krause, H. Ryssel and P. Pichler, Journal of Applied Physics 91 (9), 5645-5649 (2002). doi: 10.1063/1.1465501 L. J. Kroko and A. G. Milnes, Solid-State Electronics 9 (11), 1125-1134 (1966). doi: https://doi.org/10.1016/0038-1101(66)90137-7 L. Huang, H. Wu, G. Cai, S. Wu, D. Li, T. Jiang, B. Qiao, C. Jiang and F. Ren, ACS Nano 18 (4), 2578-2610 (2024). doi: 10.1021/acsnano.3c07896 [Brittle-Plastic]Q. Kang, X. Fang, C. Wu, H. Sun, Z. Fang, B. Tian, L. Zhao, S. Wang, N. Zhu, P. Verma, M. Ryutaro and Z. Jiang, Ceramics International 48 (18), 27076-27087 (2022). doi: https://doi.org/10.1016/j.ceramint.2022.06.019 Laput, I. V. Vasenina, V. V. Botvin and I. A. Kurzina, Journal of Materials Science 57 (4), 2335-2361 (2022). doi: 10.1007/s10853-021-06687-3 T. R. Rautray, R. Narayanan, T.-Y. Kwon and K.-H. Kim, Journal of Biomedical Materials Research Part B: Applied Biomaterials 93B (2), 581-591 (2010). doi: https://doi.org/10.1002/jbm.b.31596 X. Wu, X. Luo, H. Cheng, R. Yang and X. Chen, Nanoscale 15 (20), 8925-8947 (2023). doi: 10.1039/D3NR01366A F. I. Allen, Beilstein Journal of Nanotechnology 12, 633-664 (2021). doi: 10.3762/bjnano.12.52 T. Kachi, T. Narita, H. Sakurai, M. Matys, K. Kataoka, K. Hirukawa, K. Sumida, M. Horita, N. Ikarashi, K. Sierakowski, M. Bockowski and J. Suda, Journal of Applied Physics 132 (13) (2022). doi: 10.1063/5.0107921 J. Ye, Y. Peng, C. Luo, H. Wang, X. Zhou, T. Guo, J. Sun, Q. Yan, Y. Zhang and C. Wu, Journal of Luminescence 261, 119903 (2023). doi: https://doi.org/10.1016/j.jlumin.2023.119903 Hallén and M. Linnarsson, Surface and Coatings Technology 306, 190-193 (2016). doi: https://doi.org/10.1016/j.surfcoat.2016.05.075 T. Kimoto, K. Kawahara, H. Niwa, N. Kaji and J. Suda, presented at the 2014 International Workshop on Junction Technology (IWJT), 2014 (unpublished). F. Roccaforte, F. Giannazzo and G. Greco, Micro 2 (1), 23-53 (2022). doi: 10.3390/micro2010002 Z. Yang, Y. Zuo, X. Wang, H. Zhou, H. Tang, C. Zheng, R. Zhang, Z. Tang, K. Dai, X. Fan, G. Zhang and J. Fan, Applied Surface Science 712, 164204 (2025). doi: https://doi.org/10.1016/j.apsusc.2025.164204 C. Cheon, J. Choi, J. B.-W. Koo and J. Y. Kim, Plasma Sources Science and Technology 32 (7) (2023). doi: 10.1088/1361-6595/ace650 J. Choi, C. Cheon, Y. S. Hwang, K.-J. Chung and J. Y. Kim, Plasma Sources Science and Technology 32 (1) (2023). doi: 10.1088/1361-6595/acb28a J. Y. Kim, J. Choi, J. Choi, Y. S. Hwang and K.-J. Chung, Plasma Sources Science and Technology 31 (5) (2022). doi: 10.1088/1361-6595/ac6a76 M. Lee, C. Cheon, J. Choi, H. J. Lee, Y. S. Hwang, K.-J. Chung and J. Y. Kim, Physics of Plasmas 30 (10) (2023). doi: 10.1063/5.0154617 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 07 Mar, 2026 Reviews received at journal 07 Mar, 2026 Reviewers agreed at journal 31 Jan, 2026 Reviewers invited by journal 28 Jan, 2026 Editor assigned by journal 28 Jan, 2026 Submission checks completed at journal 07 Jan, 2026 First submitted to journal 29 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8477349","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":581528295,"identity":"547b12db-8012-4e0f-9a52-98a6691a758f","order_by":0,"name":"Junbeom Park","email":"","orcid":"","institution":"Seoul National University, South Korea","correspondingAuthor":false,"prefix":"","firstName":"Junbeom","middleName":"","lastName":"Park","suffix":""},{"id":581528296,"identity":"422f86cf-e783-41b2-a58e-fa206ff3b848","order_by":1,"name":"Minkeun Lee","email":"","orcid":"","institution":"Seoul National University, South Korea","correspondingAuthor":false,"prefix":"","firstName":"Minkeun","middleName":"","lastName":"Lee","suffix":""},{"id":581528297,"identity":"09a7d335-6812-433f-833d-bc727ee638d9","order_by":2,"name":"Wooyoung Choi","email":"","orcid":"","institution":"Seoul National University, South Korea","correspondingAuthor":false,"prefix":"","firstName":"Wooyoung","middleName":"","lastName":"Choi","suffix":""},{"id":581528298,"identity":"dbd1b58d-5234-4f5c-be44-7000a34daa2b","order_by":3,"name":"Daehyun Kim","email":"","orcid":"","institution":"Seoul National University, South Korea","correspondingAuthor":false,"prefix":"","firstName":"Daehyun","middleName":"","lastName":"Kim","suffix":""},{"id":581528299,"identity":"7fea21cf-ce91-43fb-b676-0a0279c35a25","order_by":4,"name":"Kyoung-Jae Chung","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1UlEQVRIie3PMQrCMBTG8S84uNj9DcVeIaVQHXqYFEGXCo4ORTJlirgWHLyCbo6RgpMHcHDQ3QPYQTAOuqajYP5bQn68F8Dn+8GYRm6YpP7ngrchwpJh0p6gB1gyz2Vr0tHmemj2NNmsNcejRDKQDsKWUtTBiabby4kzfUQaGhdZQdRMWUIFRyCRkWuxNzk0iiZRVXD2bEXsYiZQJHAueMdOSd1EG/sXRfH2PJ7V4ZESJ4l1kd8atYiiarS73cssrpxE9sT3YADnDCBC17hf+Xw+33/3AtJSP7XQHpLdAAAAAElFTkSuQmCC","orcid":"","institution":"Seoul National University, South Korea","correspondingAuthor":true,"prefix":"","firstName":"Kyoung-Jae","middleName":"","lastName":"Chung","suffix":""}],"badges":[],"createdAt":"2025-12-30 04:53:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8477349/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8477349/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":101511953,"identity":"266fcf81-44f8-4259-9cb2-c0a86ff4bae6","added_by":"auto","created_at":"2026-01-30 15:18:24","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":374689,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic diagram of the ion beam source test bench. (b) Photograph of the experimental setup. The labeled components are: (1) gas box with arc, bias, and filament power supplies, (2) turbomolecular pump (TMP), (3) high-voltage bushing, (4) electromagnets for Penning discharge, (5) multi-channel Faraday cup (MCFC) stage, and (6) isolation transformer.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8477349/v1/2290b8851be302675b2ed0f7.png"},{"id":101511957,"identity":"2dc83cde-79ec-4cd8-a36c-4cfe2ed76996","added_by":"auto","created_at":"2026-01-30 15:18:24","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":637040,"visible":true,"origin":"","legend":"\u003cp\u003ePhotograph of the ribbon-type ion beam extraction and diagnostic system installed inside the vacuum chamber. The labeled components are: (1) high-voltage insulating bushing, (2) indirectly heated cathode Penning ion source, (3) slit-type plasma electrode, (4) source magnet, (5) acceleration electrode, (6) deceleration electrode forming a three-electrode extraction system, (7) multi-channel Faraday cup (MCFC), and (8) beam dump.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8477349/v1/88e62ca9f42c4095e74862b9.png"},{"id":101511959,"identity":"19715be8-babf-4569-a8e4-6a9748461189","added_by":"auto","created_at":"2026-01-30 15:18:24","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":169640,"visible":true,"origin":"","legend":"\u003cp\u003eCross-sectional views of the multi-channel Faraday cup (MCFC) assembly. The labeled components are: (1) graphite shield, (2) SmCo permanent magnets, (3) water cooling connectors, (4) micro-Faraday cup array, (5) internal water-cooling lines, and (6) O-rings.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8477349/v1/ba42be73e17f63be321ce570.png"},{"id":101511954,"identity":"cb168594-08a1-40a6-851c-daa9702a682c","added_by":"auto","created_at":"2026-01-30 15:18:24","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":97315,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Extracted ion current as a function of the distance between the plasma electrode and the extraction electrode for different extraction voltages at a fixed arc current. (b) Extracted ion current as a function of the electrode distance for different arc current values at a fixed extraction voltage.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8477349/v1/42666ff7b0127e4f87730b4a.png"},{"id":101511955,"identity":"f426cb7a-b8bd-4df6-affc-49c46731bde3","added_by":"auto","created_at":"2026-01-30 15:18:24","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":73358,"visible":true,"origin":"","legend":"\u003cp\u003eTwo-dimensional ion beam current profile measured by the multi-channel Faraday cup at an extraction voltage of 20 kV and an arc current of 1.3 A (manipulator position: 33.9 mm). The dashed contour denotes 10% of the maximum beam current.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8477349/v1/6a9e62255863948f08c16df6.png"},{"id":101752103,"identity":"6328f72c-c640-42af-8966-9a3857402ae6","added_by":"auto","created_at":"2026-02-03 10:25:26","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":219477,"visible":true,"origin":"","legend":"\u003cp\u003eTwo-dimensional ion beam current profiles measured using the multi-channel Faraday cup at a fixed arc current of 1.3 A for different extraction voltages and manipulator positions. The dashed lines denote the 10% maximum current contour, and shaded regions indicate conditions where current flows to the acceleration electrode.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8477349/v1/1d0240c7b3ed8eddc15b7eb3.png"},{"id":101511956,"identity":"b4d2ea7d-dfc8-4581-8ffc-b83ebf1d6e1d","added_by":"auto","created_at":"2026-01-30 15:18:24","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":279742,"visible":true,"origin":"","legend":"\u003cp\u003eTwo-dimensional ion beam current profiles measured by the MCFC at an extraction voltage of 20 kV for different arc currents. The dashed lines denote the 10% maximum current contour, and shaded regions indicate conditions where current flows to the acceleration electrode.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8477349/v1/4e1481be251e94e5c52a5a37.png"},{"id":101755259,"identity":"10b23df7-35d6-4dbb-a9ef-fb42b5de23aa","added_by":"auto","created_at":"2026-02-03 10:50:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2357921,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8477349/v1/d33f6a6f-a81e-4c36-aec7-f6ed932b14bc.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Development and Characterization of a Ribbon-Type Ion Beam Source Test Bench for Ion Implantation Applications","fulltext":[{"header":"I. INTRODUCTION","content":"\u003cp\u003eIon implantation is a technique that enables precise control of impurity concentration, depth, and spatial distribution by directly introducing high-energy ions into solid materials. Unlike diffusion-based processes, ion implantation allows independent control of ion fluence and energy, enabling nanometer-scale depth control and abrupt concentration profiles while operating at relatively low substrate temperatures. [1, 2] These advantages make ion implantation highly compatible with advanced semiconductor fabrication processes, particularly through selective implantation using photoresist or hard masks. Consequently, ion implantation has been widely used as a core doping technique in semiconductor devices and has also been applied to surface modification of ceramic and metallic materials. [3\u0026ndash;8]\u003c/p\u003e\n\u003cp\u003eThe importance of ion implantation has further increased with the rapid adoption of wide-bandgap semiconductors such as SiC and GaN in power electronics.[9\u0026ndash; 14] In particular, SiC offers superior properties, including high thermal conductivity, high critical electric field strength, low power loss, and excellent thermal stability, making it well suited for high-voltage, high-temperature, and high-frequency applications. However, due to its strong covalent bonding and extremely low impurity diffusion coefficients, conventional thermal diffusion is ineffective for SiC, rendering ion implantation essentially the only viable doping method for SiC power semiconductor devices.\u003c/p\u003e\n\u003cp\u003eModern SiC power devices consist of multiple functional regions\u0026mdash;such as source/drain regions, P⁺ contacts, guard rings, edge termination structures, and p-wells\u0026mdash;each requiring distinct ion species, fluence, and implantation depths. [11\u0026ndash;14] Satisfying these diverse requirements necessitates ion sources capable of operating over wide energy ranges, providing flexible fluence control, and stably supplying various ion species. However, simply adjusting ion source operating conditions presents inherent limitations, as parameters such as discharge power, gas pressure, and magnetic field strength strongly influence plasma density, ion fraction, and discharge stability. [15\u0026ndash;18] Changes in these parameters can induce plasma instabilities, including rotating spokes, which degrade plasma uniformity at the extraction region and adversely affect beam stability. While such instabilities have been reported in various plasma sources, their direct impact on ion beam characteristics relevant to practical ion implantation processes remains insufficiently understood.\u003c/p\u003e\n\u003cp\u003eTo address this issue, the present study focuses on developing a dedicated ion beam source test bench to evaluate how plasma instabilities arising from ion source operating conditions influence the characteristics of extracted ion beams. The test bench enables quantitative measurements of beam current density, spatial distribution, and energy characteristics under controlled conditions, providing a platform for correlating internal plasma behavior with actual beam quality in ion implantation applications.\u003c/p\u003e\n\u003cp\u003eThe remainder of this paper is organized as follows. First, the design and configuration of the ribbon-type ion beam source test bench and the associated diagnostic system are described, with emphasis on the independent control of plasma generation and extraction parameters. Next, experimental procedures and operating conditions for ion beam extraction are presented, followed by measurements of extracted beam current and two-dimensional beam profiles obtained using the multi-channel Faraday cup. The experimental results are then discussed in terms of extraction characteristics and beam focusing behavior as functions of extraction voltage, arc current, and electrode spacing. Finally, the main findings of the study are summarized, and the limitations of the present diagnostic approach and directions for future extensions of the test bench are briefly discussed.\u003c/p\u003e"},{"header":"II. Ion Beam Source Test Bench and Experimental Setup","content":"\u003cp\u003e1. \u0026nbsp; \u0026nbsp; Configuration of the Ion Beam Source Test Bench\u003c/p\u003e\n\u003cp\u003eFigure 1. (a) Schematic diagram of the ion beam source test bench. (b) Photograph of the experimental setup. The labeled components are: (1) gas box with arc, bias, and filament power supplies, (2) turbomolecular pump (TMP), (3) high-voltage bushing, (4) electromagnets for Penning discharge, (5) multi-channel Faraday cup (MCFC) stage, and (6) isolation transformer.\u003c/p\u003e\n\u003cp\u003eFigure 2 Photograph of the ribbon-type ion beam extraction and diagnostic system installed inside the vacuum chamber. The labeled components are: (1) high-voltage insulating bushing, (2) indirectly heated cathode Penning ion source, (3) slit-type plasma electrode, (4) source magnet, (5) acceleration electrode, (6) deceleration electrode forming a three-electrode extraction system, (7) multi-channel Faraday cup (MCFC), and (8) beam dump.\u003c/p\u003e\n\u003cp\u003eTo evaluate the performance of ion sources for ion implantation, an ion beam source test bench is constructed, and the overall system configuration, together with the gas, power, and signal interconnections between subsystems, is shown in Fig. 1. The test bench allows independent control of plasma generation parameters and beam extraction conditions, enabling flexible adjustment of discharge power, magnetic field, gas flow, and electrode configuration during ion beam extraction experiments. Figure 1(a) presents a schematic diagram of the entire system, including the power supply, gas delivery, cooling, vacuum, and diagnostic subsystems, while Fig. 1(b) shows a photograph of the experimental test bench, illustrating the implementation of each functional component depicted in the schematic. Figure 2 presents the internal configuration of the vacuum chamber shown in Fig. 1(b), together with the spatial arrangement of the beamline components presented in Fig. 1.\u003c/p\u003e\n\u003cp\u003eThe region indicated by thick black lines in Fig. 1(a) represents the lead shielding encloser, while the gray area corresponds to the shielding door. When high-energy ion beams strike the beam dump, radiation including X-rays can be generated; therefore, this region is shielded with lead to ensure operator safety. As a result, direct manual operation is not permitted during experiments, and system control and diagnostics are performed remotely via optical or electrical signal communication. This shielding and remote operation scheme satisfies essential safety requirements for high-energy ion beam experiments.\u003c/p\u003e\n\u003cp\u003eGas and electrical power required for ion source operation are supplied through the gas box (Fig. 1(b)-(1)). The gas box houses the arc, bias, and filament power supplies, and the discharge gas flow rate is precisely controlled using a mass flow controller (MFC). In this study, argon gas is used for baseline characterization to investigate the physical operation of the ion source, plasma density variations with arc power, plasma oscillations associated with operating recipes, and ion beam extraction characteristics. The gas lines are constructed from stainless steel tubing to ensure corrosion and chemical resistance, allowing compatibility with implantation gases such as BF₃. During ion beam extraction, the ion source is electrically floated at high voltage with respect to the chamber. The gas box, which is electrically connected to the ion source, is maintained at the same floating potential. Electrical isolation is achieved using a 1:1 isolation transformer (Fig. 1(b)-(6)), which provides electrically isolated power delivery. Under non-extraction conditions, the gas box is grounded by direct contact with a grounding rod to ensure operational safety.\u003c/p\u003e\n\u003cp\u003eThe ion source used in this study is an indirectly heated cathode Penning ion source (Fig. 1(b)-(4) and Fig. 2-(2)). Thermionic electrons emitted from the filament first heat the cathode, after which electrons emitted from the heated cathode discharge and sustain the plasma. Because the filament does not directly contact the plasma, this configuration reduces ion bombardment damage and extends filament lifetime, while the large cathode emission area enables stable plasma generation at relatively low filament power. The filament power is kept constant during experiments, and plasma discharge characteristics are primarily controlled by the bias and arc power supplies. The magnetic field required for Penning discharge is generated by electromagnets located at both ends of the ion source (Fig. 1(b)-(4) and Fig. 2-(4)), with the magnet power supplies positioned outside the gas box. Both the ion source and electromagnets are water-cooled, with coolant supplied from a chiller and passed through a heat exchanger to control water resistivity. This design prevents leakage currents through the cooling water under high-voltage conditions while ensuring thermal stability.\u003c/p\u003e\n\u003cp\u003eThe ion source is connected to the grounded chamber via a high-voltage insulating bushing for electrical isolation, as shown in Fig. 1(b)-(3) and Fig. 2-(1). The bushing is designed to withstand extraction voltages exceeding 40 kV and incorporates internal cooling lines to remove heat generated near the ion source. The internal dimensions of the vacuum chamber are 490 mm in width (along the long axis of the ribbon beam), 580 mm in depth (beam extraction direction), and 720 mm in height. A turbomolecular pump (TMP) maintains a base pressure of approximately 3 \u0026times; 10⁻⁷ Torr (Fig. 1(b)-(2)), which is critical for stable plasma formation and collisionless beam extraction. Linear plates are installed along the chamber walls to facilitate maintenance in the event of localized damage or deposition caused by ion beam exposure.\u003c/p\u003e\n\u003cp\u003eThe extracted ion beam has a ribbon-shaped profile; accordingly, the plasma electrode features a slit geometry elongated in one direction (Fig. 2-(3)). In this study, the term \u0026ldquo;plasma electrode\u0026rdquo; refers to the electrode or assembly containing the slit at the ion source exit for ion extraction. The long dimension of the slit is defined as the major axis, and the short dimension as the minor axis; subsequent beam profile and uniformity analyses are conducted based on this coordinate system. After passing through the plasma electrode, the ion beam traverses a three-electrode extraction system consisting of acceleration and deceleration electrodes (Fig. 2-(5) and (6)). This electrode assembly is mounted on a manipulator that allows adjustment of the distance from the plasma electrode. The manipulator provides a travel range from 13.6 mm to 48.9 mm relative to the plasma electrode, enabling investigation of changes in plasma meniscus shape and ion beam characteristics as a function of manipulator position.\u003c/p\u003e\n\u003cp\u003eThe extracted ion beam is delivered to a multi-channel Faraday cup (MCFC), as shown in Fig. 1(b)-(5) and Fig. 2-(7), where spatially resolved beam current distributions are measured. The MCFC is positioned 275 mm downstream from the plasma electrode. The MCFC stage translates the MCFC along the long axis of the beam, allowing position control within \u0026plusmn;120 mm relative to the beam center with a resolution of 0.1 mm. This stage also serves as a vacuum boundary, transmitting collected ion current signals to the exterior of the vacuum chamber. Because the MCFC directly intercepts the ion beam and experiences significant thermal loading, a water-cooling structure is employed. Cooling water is supplied via flexible stainless-steel tubing connected to the MCFC stage, enabling stable cooling while maintaining vacuum condition. Position control of the MCFC stage and data acquisition are performed using an external PC. Ion beams not captured by the MCFC are absorbed by the beam dump shown in Fig. 1(a) and Fig. 2-(8). Ion beam dump is also water-cooled.\u003c/p\u003e\n\u003cp\u003e2.\u0026nbsp; \u0026nbsp; \u0026nbsp;Multi-Channel Faraday Cup Diagnostics\u003c/p\u003e\n\u003cp\u003eTo diagnose the spatial distribution of the extracted ion beam, the MCFC is employed in this study. An alternative approach combining a single Faraday cup with two-dimensional positional scanning is possible; however, this method requires external implementation of two-dimensional motion, which imposes limitations on the scanning range due to structural constraints associated with passing through the vacuum boundary. In practice, such configuration is insufficient to fully cover the expected beam spread, particularly for ribbon-type ion beams that are extended along the major axis, thereby limiting diagnostics of the beam profile. Installing a two-dimensional motion stage inside the vacuum chamber could alleviate this limitation, but would significantly increase system complexity due to motor heating, ion beam induced damage, and the need for additional cooling and shielding structures. Considering these constraints, the MCFC provides a suitable diagnostic solution for the ribbon-type ion beam source test bench developed in this study, as it enables simultaneous spatially resolved ion current measurements while maintaining a relatively simple system configuration.\u003c/p\u003e\n\u003cp\u003eThe MCFC used in this work consists of 15 individual Faraday cup channels arranged linearly along the short axis of the ion beam. Each channel has an aperture diameter of 4.5 mm, and the center-to-center spacing between adjacent channels is 8.5 mm. As a result, ion currents can be measured simultaneously at 15 spatial positions along the minor axis, covering a total width of 127.5 mm (15 \u0026times; 8.5 mm). This channel arrangement allows the MCFC to acquire the ion current distribution along the minor axis in a single measurement, while spatial variation along the major axis is obtained by translating the MCFC stage. The MCFC stage provides position control along the major axis with a resolution of 0.1 mm.\u003c/p\u003e\n\u003cp\u003eEach MCFC channel operates by directly collecting and measuring the extracted ion beam current. By spatially arranging the ion beam current obtained from individual Faraday cups, the two-dimensional ion current distribution is reconstructed, enabling comparison of beam focusing characteristics and distribution changes under different extraction conditions. Because secondary electron emission (SEE) can lead to overestimation of the true ion current, a permanent-magnet-based SEE suppression scheme is adopted instead of the suppression electrode. Compared to electrode-based suppression methods that require additional power supplies, the permanent magnet approach offers a simpler structure with minimal electrical connections.\u003c/p\u003e\n\u003cp\u003eFigure 3 Cross-sectional views of the multi-channel Faraday cup (MCFC) assembly. The labeled components are: (1) graphite shield, (2) SmCo permanent magnets, (3) water cooling connectors, (4) micro-Faraday cup array, (5) internal water-cooling lines, and (6) O-rings.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe internal structure and main components of the MCFC are shown in Fig. 3. The front surface exposed to the ion beam, as well as the signal lines and cooling lines, are shielded with graphite to minimize sputtering caused by high-energy ion impacts (Fig. 3-(1)). Samarium\u0026ndash;cobalt (SmCo) permanent magnets are installed behind each Faraday cup channel to effectively suppress secondary electrons (Fig. 3-(2)). These magnets provide sufficiently strong magnetic fields and exhibit high Curie temperatures, ensuring stable magnetic performance even under elevated temperature. Since the MCFC directly intercepts high-energy ion beams and is subjected to significant thermal flux, an integrated water-cooling structure is implemented. Cooling water is supplied through water-cooling connectors (Fig. 3-(3)) and circulates through internal cooling lines (Fig. 3-(5)). O-rings (Fig. 3-(6)) used to prevent leakage under vacuum conditions. This design allows stable long-duration operation of the MCFC even under high-current and high-energy beam conditions. The array of Faraday cups used for direct ion current collection is illustrated in Fig. 3-(4).\u003c/p\u003e\n\u003cp\u003eThe ion current signals collected by each Faraday cup channel are electrically connected via bolted contacts at the rear of each cup. Hole-type contacts are formed on a printed circuit board (PCB), and the signals are mechanically and electrically secured using bolts to ensure stable connections. Signals from all 15 channels are transmitted outside the vacuum chamber through a 15-pin D-sub connector and cable, and subsequently routed through the MCFC stage to the data acquisition system.\u003c/p\u003e\n\u003cp\u003eData acquisition (DAQ) is performed using a multi-channel current module (National Instruments, NI-9208 current input), which provides a total sampling rate of up to 500 samples/s. With 15 channels operated simultaneously, the maximum sampling rate per channel is approximately 30 samples/s. The DAQ system operates with a 24-bit analog-to-digital converter over a \u0026plusmn;20 mA input range, corresponding to a theoretical current resolution of approximately 2.4 nA. In the present experiments, ion current signals are acquired at 10 samples/s per channel, and data collected over 1 s are averaged to obtain the current value at each spatial position. The standard deviation of the measured current signals is approximately 150 nA, which is comparable to the system noise level and indicates that a sufficient signal-to-noise ratio is achieved for ion beam current distribution analysis using the MCFC.\u003c/p\u003e\n\u003cp\u003eThe NI-9208-based data acquisition system has limited capability in resolving plasma oscillations at frequencies of several kilohertz or higher, such as rotating spokes. To address this limitation at the instrumentation level, the signal line between the MCFC and the DAQ is designed to allow the insertion of a 10 k\u0026Omega; resistor, enabling differential voltage measurements using an external oscilloscope. Although oscilloscope-based measurements are not utilized in the present study, the diagnostic system is designed to be flexible. The DAQ is used for measuring DC beam current under stable plasma conditions, whereas an oscilloscope can be employed to analyze time-resolved beam current fluctuations when necessary.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e3.\u0026nbsp; \u0026nbsp; \u0026nbsp;Experimental Conditions for Ion Beam Extraction\u003c/p\u003e\n\u003cp\u003eIn this study, experiments are conducted by stepwise control of plasma discharge conditions and ion beam extraction conditions to evaluate the extraction characteristics of a ribbon-type ion beam source. Plasma generation conditions are determined by the arc, bias, and filament power supplies, as well as the discharge gas and magnetic field conditions, and all experiments are performed within regimes where the discharge remains temporally stable. The objective of this study is not to optimize the discharge conditions, but rather to quantitatively compare the effects of extraction electrode configuration and extraction voltage on ion beam characteristics under well-established and stable plasma conditions. Accordingly, discharge-related parameters are restricted to conditions whose stability is verified through preliminary experiments.\u003c/p\u003e\n\u003cp\u003eBoth the filament and bias power supplies operate in current-control mode. The filament current is fixed at 42.0 A throughout the experiments, corresponding to a filament voltage of 4.9 V. The filament current directly determines the cathode temperature and thermionic electron emission, which in turn influence plasma density and bias conditions. Since the bias power supply also operates in current-control mode, variations in filament current simultaneously alter the bias voltage and bias power. For this reason, the filament current is fixed to constrain the bias conditions. The selected filament condition ensures stable discharge operation while minimizing fluctuations in bias voltage, and no additional filament-related variables are introduced during the experiments.\u003c/p\u003e\n\u003cp\u003eThe stability of the plasma discharge is governed by the combined effects of arc conditions, magnetic field configuration, and discharge gas parameters. According to previous experimental results and prior studies, plasma oscillations readily occur under conditions of low arc voltage and high arc current[18], and such oscillations induce temporal fluctuations in ion density near the plasma electrode. As a consequence, the plasma meniscus shape varies with time, leading to degraded ion beam angular distribution and reduced reproducibility of extraction characteristics. To avoid these effects, the arc voltage is fixed at 100 V, while the arc current is varied within the range of 1.1\u0026ndash;2.3 A. The arc current is adjusted manually by controlling the bias current, and experimental conditions are selected within stable regimes where plasma oscillations are not observed. Under these conditions, the bias voltage remains in the range of approximately 394\u0026ndash;402 V. Increasing the bias current enhances cathode heating and raises the cathode temperature. As a result, thermionic emission increases, leading to a higher arc current. Because the arc current is directly correlated with plasma density, variations in arc current are used as an indicator of plasma density changes in this study.\u003c/p\u003e\n\u003cp\u003eTo maintain a stable Penning discharge, current is supplied to the electromagnets installed at both ends of the ion source to generate an axial magnetic field of approximately 100 G at the ion source center. This magnetic field suppresses radial electron transport and increases electron residence time in the discharge region, enabling stable plasma formation even at relatively low discharge power. Argon is used as the discharge gas, and the gas flow rate is fixed at 3 sccm. If the neutral density is too low, temporal density fluctuations such as breathing-mode oscillation occurs. Therefore, a sufficiently high gas flow rate ensuring stable discharge is employed. Throughout this study, the magnetic field strength and gas flow rate are held constant so that their effects do not introduce additional variations in extraction characteristics. Consequently, all ion beam extraction results presented here are obtained under identical magnetic field and gas conditions.\u003c/p\u003e\n\u003cp\u003eThe extraction voltage applied for ion beam extraction is varied in the range of 10\u0026ndash;25 kV, while the acceleration electrode voltage is fixed at -3 kV. The upper limit of the extraction voltage is restricted to 25 kV in consideration of system safety and electrode thermal loading. It is experimentally observed that the combination of high plasma density and high extraction voltage leads to melting of the plasma electrode surface and erosion of the acceleration electrode. Such electrode damage degrades system reliability and complicates repeated experiments. Therefore, extraction voltages are varied only within stable operating regimes that allow long-duration operation. The observed extracted ion current ranges 4\u0026ndash;20 mA.\u003c/p\u003e\n\u003cp\u003eUnder these stable discharge conditions, the extraction electrode position is varied stepwise using a manipulator, starting from a distance of 15.7 mm from the plasma electrode and incremented in steps of 2.3 mm. The manipulator allows movement up to a maximum distance of 45.3 mm. At each position, the extracted ion beam is measured using the MCFC to obtain two-dimensional current distributions, which are then used to compare changes in plasma meniscus shape and beam focusing characteristics as a function of extraction electrode position. In this study, the condition of \u0026ldquo;optimal focusing\u0026rdquo; is defined as the extraction condition at which the beam widths along both the major and minor axes are minimized in the two-dimensional ion beam current distribution measured by the MCFC.\u003c/p\u003e"},{"header":"III. Results and Discussion","content":"\u003cp\u003e1. \u0026nbsp; \u0026nbsp; Dependence of Extracted Ion Beam Current on Extraction Voltage, Arc Current, and Electrode Spacing\u003c/p\u003e\n\u003cp\u003eFigure 4 (a) Extracted ion current as a function of the distance between the plasma electrode and the extraction electrode for different extraction voltages at a fixed arc current. (b) Extracted ion current as a function of the electrode distance for different arc current values at a fixed extraction voltage.\u003c/p\u003e\n\u003cp\u003eFigure 4(a) presents the extracted ion beam current as a function of the distance between the plasma electrode and the acceleration electrode at different extraction voltages, with the arc current fixed at 1.3 A. Normal extraction is defined by the absence of acceleration electrode current, while abnormal extraction is associated with finite current collection at the acceleration electrode. The extracted current trends with electrode spacing provide a basis for identifying the spacing range corresponding to normal ion beam extraction.\u003c/p\u003e\n\u003cp\u003eUnder normal extraction conditions, where the ion beam is extracted without impinging on the acceleration electrode, different electrode spacing ranges are formed depending on the extraction voltage. Specifically, for an extraction voltage of 10 kV, stable extracted current is observed in the range of approximately 17.9\u0026ndash;24.8 mm, while at 15 kV the stable range expands to approximately 17.9\u0026ndash;36.2 mm. When the extraction voltage increases to 20 kV, the normal extraction region extends from 17.9 mm up to the manipulator travel limit of 45.3 mm. In contrast, at 25 kV the normal extraction region becomes restricted again to approximately 33.9\u0026ndash;45.3 mm. Such changes in the width and position of the electrode spacing window with extraction voltage are attributed to variations in the extraction electric field strength, which modify the plasma meniscus shape.\u003c/p\u003e\n\u003cp\u003eWithin the normal extraction region, the extracted ion current decreases gradually with increasing electrode spacing for all extraction voltage conditions. This trend can be attributed to the weakening of the extraction electric field as the electrode spacing increases at a fixed extraction voltage. The reduced electric field lowers the curvature of the plasma meniscus, thereby decreasing the effective area from which ions are efficiently extracted. These observations confirm that the extracted ion current is strongly governed by the extraction electric field.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAbnormal extraction behavior is observed when the electrode spacing decreases below approximately 17.9 mm for extraction voltages of 10, 15, and 20 kV, while for the 25 kV condition, the onset of abnormal extraction shifts to electrode spacings below approximately 31.6 mm. In this regime, the electrode spacing becomes excessively small, resulting in an overly enhanced extraction electric field that pushes the plasma meniscus inward. Consequently, the ion beam is formed in an overfocused state, where ion trajectories cross near the acceleration electrode and subsequently diverge, producing a current on the acceleration electrode that should otherwise remain current-free under normal transport conditions. This observation indicates that the ion beam directly impinges on the acceleration electrode.\u003c/p\u003e\n\u003cp\u003eConversely, abnormal extraction behavior is also observed when the electrode spacing becomes sufficiently large. For an extraction voltage of 10 kV, increasing the spacing beyond approximately 27.1 mm, and for 15 kV beyond approximately 36.2 mm, leads to insufficient formation of the extraction electric field. Under these conditions, the plasma meniscus becomes flattened or protrudes outward, and the ion beam propagates in an underfocused, divergent state. As a result, a portion of the ions again collides with the acceleration electrode. This underfocus regime appears at smaller electrode spacings for lower extraction voltages.\u003c/p\u003e\n\u003cp\u003eThese results indicate that the extracted ion beam current does not vary monotonically with electrode spacing. Instead, different focusing regimes are formed depending on the interplay between the extraction electric field strength and the plasma meniscus shape. For each extraction voltage, the normal ion beam extraction occurs only within a distinct electrode spacing window.\u003c/p\u003e\n\u003cp\u003eFigure 4(b) compares the extracted ion beam current as a function of the electrode spacing while varying the arc current at a fixed extraction voltage of 20 kV. Whereas Fig. 4(a) analyzes extraction characteristics primarily from the perspective of electric field effects associated with extraction voltage, Fig. 4(b) illustrates how changes in plasma density influence the plasma meniscus shape and ion beam focusing by distinguishing normal and abnormal extraction regions as the electrode spacing varies. As in Fig. 4(a), a window of electrode spacing that allows normal ion beam extraction is formed depending on the electrode configuration, and the position of this window is observed to shift with arc current.\u003c/p\u003e\n\u003cp\u003eThe normal extraction regime spans different electrode spacing ranges depending on the arc current. For an arc current of 1.1 A, the normal extraction region forms at electrode spacings larger than 27.1 mm. When the arc current increases to 1.3 A, the normal extraction region expands to spacings larger than 15.7 mm, and at 1.5 A the normal extraction regime extends over the range of 15.7\u0026ndash;45.3 mm. With a further increase in arc current to 1.9 A, the normal extraction regime becomes restricted again to 17.9\u0026ndash;36.2 mm, and at 2.1 A arc currents the region shifts further to 17.9\u0026ndash;31.6 mm. This shift of the normal extraction regime toward the plasma electrode with increasing arc current is interpreted as resulting from the higher plasma density, which requires a stronger extraction electric field to maintain a similar plasma meniscus shape.\u003c/p\u003e\n\u003cp\u003eWithin the normal extraction region, a gradual decrease in extracted current with increasing electrode spacing is observed for all arc current conditions. This trend arises because, at a fixed extraction voltage, increasing the electrode spacing weakens the extraction electric field and reduces the curvature of the plasma meniscus, thereby decreasing the number of ions effectively extracted. However, as the arc current increases, the plasma density becomes higher, allowing relatively higher extracted currents to be maintained even at the same electrode spacing. This observation indicates that the extracted ion current depends not only on the extraction electric field but also on the plasma density.\u003c/p\u003e\n\u003cp\u003eWhen the electrode spacing decreases below the lower boundary of the normal extraction region, an overfocus regime forms for all arc current conditions. In this regime, the extraction electric field becomes excessively strong due to the small electrode spacing, and the plasma meniscus is pushed deeply into the plasma. As a result, the ion beam becomes overfocused, with trajectories crossing in front of the acceleration electrode and subsequently diverging, causing a fraction of the ions to collide with the acceleration electrode. As the arc current increases and the plasma density rises, a stronger electric field is required to form a comparable meniscus, and the boundary at which overfocusing occurs shifts toward the plasma electrode.\u003c/p\u003e\n\u003cp\u003eIn contrast, when the electrode spacing exceeds the upper boundary of the normal extraction region, an underfocus regime is formed. In this regime, the extraction electric field is insufficient due to the large electrode spacing, and the plasma meniscus becomes flattened or protrudes relative to the plasma electrode, causing the ion beam to diverge without adequate focusing. Consequently, some ions collide with the acceleration electrode, and a current is detected. The underfocus regime appears at smaller electrode spacings under lower arc current conditions and shifts toward the plasma electrode as the arc current increases. This behavior can be understood as reflecting the increasingly stringent electric field conditions required to form a required meniscus at higher plasma densities.\u003c/p\u003e\n\u003cp\u003eOverall, the results in Fig. 4(b) clearly show that the normal extraction region shifts with arc current, that is, with plasma density, and that a window of electrode spacing exists between the overfocus and underfocus regimes in which normal ion beam extraction is achieved. In particular, when a target ion energy and extracted current are specified, the manipulator position satisfying normal ion beam extraction converges to a limited range. Thus, for a given combination of plasma generation conditions and extraction voltage, the electrode spacing does not act as an independently selectable parameter, but rather as a dependent parameter constrained within the normal extraction regime.\u003c/p\u003e\n\u003cp\u003e2.\u0026nbsp; \u0026nbsp; \u0026nbsp;Two-Dimensional Ion Beam Profile Analysis Using a Multi-Channel Faraday Cup\u003c/p\u003e\n\u003cp\u003eIn this section, two-dimensional ion beam current distributions measured using a MCFC are presented, and the spatial focusing characteristics of the ribbon-type ion beam are analyzed as functions of extraction conditions and electrode configuration more deeply. Even under identical extracted current conditions, the spatial spreading characteristics of the beam can vary significantly depending on the plasma meniscus shape, and such differences are directly related to the practical applicability of the beam. Therefore, the beam shape is evaluated in greater detail based on spatially resolved current distributions. In this study, the condition at which focusing along both the long and short axes is simultaneously satisfied is defined as the optimum focusing condition.\u003c/p\u003e\n\u003cp\u003eTwo-dimensional current distribution measurements using the MCFC are performed by stepwise translation of the MCFC along the major axis of the beam. In the present experiments, the MCFC position is varied at intervals of 10 mm along the major axis, and ion currents are simultaneously measured at each position using the 15 Faraday cup channels arranged along the minor axis. The discrete current data acquired along the major and minor axes are then reconstructed into continuous two-dimensional current distributions by applying linear interpolation between adjacent measurement points. Through this procedure, the overall spatial distribution and focusing characteristics of the ion beam are visualized and analyzed, despite the finite spatial resolution of the MCFC.\u003c/p\u003e\n\u003cp\u003eFigure 5 Two-dimensional ion beam current profile measured by the multi-channel Faraday cup at an extraction voltage of 20 kV and an arc current of 1.3 A (manipulator position: 33.9 mm). The dashed contour denotes 10% of the maximum beam current.\u003c/p\u003e\n\u003cp\u003eFigure 5 shows a representative two-dimensional ion beam current distribution measured at an extraction voltage of 20 kV and an arc current of 1.3 A with the manipulator positioned at 33.9 mm. A high beam current density is observed at the center of the distribution, confirming the formation of a typical ribbon-type ion beam structure elongated along the major axis. Along the minor axis, the current decreases relatively rapidly, whereas a more gradual decrease is observed along the major axis. The white dashed contour shown in the figure corresponds to 10% of the maximum current value and is used as a reference to compare the effective beam spread and focusing state. This contour provides an intuitive representation of the actual spatial extent of the beam and is useful for quantitative comparison of focusing characteristics under different extraction conditions.\u003c/p\u003e\n\u003cp\u003eFigure 6 Two-dimensional ion beam current profiles measured using the multi-channel Faraday cup at a fixed arc current of 1.3 A for different extraction voltages and manipulator positions. The dashed lines denote the 10% maximum current contour, and shaded regions indicate conditions where current flows to the acceleration electrode.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFigure 6 compares the two-dimensional ion beam current distributions measured while varying the extraction voltage and the distance between the plasma electrode and the acceleration electrode at a fixed arc current of 1.3 A. This figure directly illustrates how the spatial focusing characteristics of the ribbon-type ion beam change with extraction voltage under identical discharge conditions. When the extraction voltage is 10 kV, a focused beam state in which beam spreading is minimized along both the major and minor axes is formed at a manipulator position of 20.2 mm; for 15 kV, this condition occurs at 24.8 mm; and for 20 kV, at 38.4 mm. Under these conditions, not only is the beam thickness along the minor axis minimized based on the 10% maximum current contour, but beam spreading along the major axis is also suppressed, resulting in the most tightly focused ion beam distribution.\u003c/p\u003e\n\u003cp\u003eAs the extraction voltage increases, the electrode spacing at which optimum focusing is achieved gradually shifts farther away from the plasma electrode. This trend arises because an increase in extraction voltage strengthens the electric field in the extraction region, thereby modifying the electrode configuration required to maintain a similar plasma meniscus shape. In contrast, for an extraction voltage of 25 kV, a distinct condition at which beam spreading is simultaneously minimized along both axes cannot be clearly identified within the electrode spacing range accessible in the present experiments. Nevertheless, the maximum current measured in the two-dimensional current distributions continues to increase with extraction voltage, suggesting that the optimum focusing position under the 25 kV condition is likely formed at electrode spacings of at least 45.3 mm or larger. This implies that the optimum focusing point lies beyond the experimental range explored in this study, and additional measurements with an extended manipulator travel range are required to clearly identify this condition.\u003c/p\u003e\n\u003cp\u003eWhen the electrode spacing deviates from the optimum focusing position, the spatial distribution of the ion beam degrades in distinct ways. At electrode spacings smaller than the optimum position, an overfocus condition is formed, in which the plasma meniscus is pushed inward and the ion beam spreads again along both axes. Conversely, when the electrode spacing exceeds the optimum focusing position, the extraction electric field becomes relatively weak. As a result, the plasma meniscus curvature decreases or protrudes beyond the plasma electrode, and the ion beam propagates in an underfocused, divergent state. These overfocus and underfocus behaviors are clearly distinguished in the two-dimensional current distributions through the direction and extent of beam spreading.\u003c/p\u003e\n\u003cp\u003eFigure 7 Two-dimensional ion beam current profiles measured by the MCFC at an extraction voltage of 20 kV for different arc currents. The dashed lines denote the 10% maximum current contour, and shaded regions indicate conditions where current flows to the acceleration electrode.\u003c/p\u003e\n\u003cp\u003eFigure 7 compares the two-dimensional ion beam current distributions measured as a function of the distance between the plasma electrode and the acceleration electrode while varying the arc current at a fixed extraction voltage of 20 kV. This figure extends the behavior observed in Fig. 6 and illustrates how increases in plasma density associated with changes in arc current affect the plasma meniscus shape and ion beam focusing characteristics. In particular, the two-dimensional current distributions clearly demonstrate that, even under the same extraction voltage, both the optimum focusing position and the spatial beam distribution vary significantly with arc current.\u003c/p\u003e\n\u003cp\u003eBased on the two-dimensional current distributions, the optimum focusing condition shifts with arc current. The most tightly focused beam is observed at a manipulator position of approximately 22.5 mm for an arc current of 2.3 A, 27.1 mm for 1.9 A, 33.9 mm for 1.5 A, and 38.4 mm for 1.3 A. In contrast, for an arc current of 1.1 A, it is difficult to clearly identify a position within the electrode spacing range accessible in the present. These results indicate that, as the arc current decreases, the electrode spacing at which optimum focusing is achieved shifts progressively farther away from the plasma electrode. This shift is attributed to changes in plasma meniscus curvature resulting from variations in plasma density with arc current. As plasma density increases, a stronger extraction electric field is required to satisfy the same focusing condition, causing the electrode spacing corresponding to optimum focusing to move toward the plasma electrode. In the two-dimensional current distributions of Fig. 7, this behavior is clearly manifested by an increase in the central beam current and by simultaneous minimization of beam spreading along both axes at the optimum focusing position.\u003c/p\u003e\n\u003cp\u003eAs in Fig. 6, distinct overfocus and underfocus behaviors are observed when the electrode spacing deviates from the optimum focusing position. When the electrode spacing is smaller than the optimum position, the plasma meniscus retracts toward the electrode, forming an overfocus condition in which the ion beam becomes overly focused and subsequently diverges. In the two-dimensional current distributions, this behavior appears as an increase in beam thickness and non-uniform expansion of the current contours. Conversely, when the electrode spacing exceeds the optimum focusing position, the extraction electric field is no longer sufficiently maintained, the meniscus curvature decreases or protrudes relative to the electrode, and an underfocus condition is formed in which the ion beam diverges without adequate focusing. This underfocus state is also clearly identified in the two-dimensional current distributions through beam broadening and expansion of the current contours.\u003c/p\u003e\n\u003cp\u003eIn addition, a clear increase in the maximum current measured over the entire two-dimensional current distribution is observed as the arc current increases. This trend directly reflects the increase in plasma density and the corresponding increase in ion flux supplied by the plasma to the meniscus. Thus, the arc current not only determines the absolute level of the extracted ion beam current but also governs both the electrode spacing at which optimum focusing is achieved and the resulting spatial beam distribution.\u003c/p\u003e\n\u003cp\u003eThese results clearly demonstrate the importance of MCFC-based two-dimensional diagnostics in the optimization of ion source extraction conditions. The extraction current based analysis presented in Fig. 4 is effective in defining the normal extraction regime with the presence or absence of current on the acceleration electrode. However, this approach can only indirectly infer overfocus and underfocus states and has limitations in quantitatively distinguishing variations in the actual beam focusing state within the normal extraction regime. In contrast, the MCFC based two-dimensional current distributions presented in Figs. 6 and 7 provide direct spatial information that enables clear discrimination between overfocus and underfocus conditions relative to the optimum focusing position by simultaneously evaluating beam spreading along both the major and minor axes. Even within the same normal extraction regime, the beam focusing characteristics can vary significantly depending on the plasma meniscus shape, and such differences are difficult to identify solely from the magnitude of the extracted current. Therefore, the MCFC diagnostics employed in this study are confirmed to be a key tool for precisely evaluating ion source extraction conditions and electrode configurations from the perspective of actual beam focusing behavior.\u003c/p\u003e"},{"header":"IV. Conclusions","content":"\u003cp\u003eIn this study, a ribbon-type ion beam source test bench equipped with a multi-channel Faraday cup is developed to investigate ion beam extraction characteristics for ion implantation applications. Using this system, the extracted ion current is measured as a function of electrode spacing, extraction voltage, and arc current, and the beam focusing characteristics are examined based on two-dimensional beam current profiles. The results show that, once the extraction voltage and arc current are specified, the electrode position at which the beam profile becomes optimal is uniquely determined. This behavior indicates that the emittance of the extracted ion beam is effectively fixed when the beam energy and extracted current are set. Therefore, variations in electrode configuration that increase the extracted current inevitably modify the beam profile and degrade beam transport characteristics. This coupling between extraction characteristics and beam transport leads to an intrinsic trade off in three-electrode extraction systems, representing a fundamental limitation of conventional electrode-based control.\u003c/p\u003e\n\u003cp\u003eDespite the effectiveness of the developed test bench in characterizing two-dimensional beam current distributions, several limitations remain in its present configuration. The current diagnostic system does not allow direct measurement of the beam divergence angle or transverse emittance, which are critical parameters for evaluating beam transport and implantation performance; therefore, an Allison scanner is required in future work. In addition, this study is limited to argon plasmas for baseline characterization, whereas practical ion implantation commonly employs molecular source gases such as BF₃, for which multiple ion species are simultaneously extracted. Under such conditions, beam current measurements alone are insufficient to determine the ion fraction, and the incorporation of mass spectrometric diagnostics will be necessary to fully assess source performance under realistic implantation conditions.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJunbeom Park contributed to the methodology, formal analysis, and experimental investigation, and led the preparation of the original draft as well as the review and editing of the manuscript. Minkeun Lee contributed to the conceptualization and methodology of the study. Wooyoung Choi participated in the experimental investigation and contributed to manuscript review and editing. Daehyun Kim contributed to manuscript review and editing. Kyoung-Jae Chung provided research resources, supervised the overall research, and contributed to manuscript review and editing.\u003c/p\u003e\u003ch2\u003eACKNOWLEDGEMENT\u003c/h2\u003e \u003cp\u003eThis work was supported by the Technology Innovation Program (No. RS-2022-00154978, Pilot Equipment Development of Semiconductor Low Energy High Current Ion Implanter) funded by the Ministry of Trade, Industry \u0026amp; Energy (MOTIE, Korea), the Samsung Electronics' University R\u0026amp;D program (Project No.: IO241210-11444-01), the Technology Innovation Program Development Program-Public-Private Joint Investment Program for Advanced Semiconductor Talent Development(RS-2024-00405103, Development of energy and incident angle control technique of ribbon-type ion beam for ion beam etching process) funded by the Ministry of Trade, Industry \u0026amp; Energy(MOTIE, Korea) and the Commercialization Promotion Agency for R\u0026amp;D Outcomes(COMPA) funded by the Ministry of Science and ICT(MSIT)(2710084640).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eKrause, H. 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Kim, Plasma Sources Science and Technology 32 (1) (2023). doi: 10.1088/1361-6595/acb28a\u003c/li\u003e\n \u003cli\u003eJ. Y. Kim, J. Choi, J. Choi, Y. S. Hwang and K.-J. Chung, Plasma Sources Science and Technology 31 (5) (2022). doi: 10.1088/1361-6595/ac6a76\u003c/li\u003e\n \u003cli\u003eM. Lee, C. Cheon, J. Choi, H. J. Lee, Y. S. Hwang, K.-J. Chung and J. Y. Kim, Physics of Plasmas 30 (10) (2023). doi: 10.1063/5.0154617\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-the-korean-physical-society","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Journal of the Korean Physical Society](https://link.springer.com/journal/40042)","snPcode":"40042","submissionUrl":"https://submission.springernature.com/new-submission/40042/3","title":"Journal of the Korean Physical Society","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Ion implantation, Ribbon-type ion beam, Ion source test bench, Multi-channel Faraday cup, Beam extraction diagnostics","lastPublishedDoi":"10.21203/rs.3.rs-8477349/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8477349/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"As semiconductor manufacturing processes become increasingly advanced and diversified, ion implantation processes capable of precisely controlling ion energy and implantation current are increasingly required, leading to growing demand for reliable ion source evaluation testbench. In this study, a ribbon-type ion beam source test bench is designed and constructed to investigate ion beam extraction characteristics for ion implantation applications. The developed test bench enables independent control of plasma generation conditions and ion beam extraction parameters, and employs a multi-channel Faraday cup as the primary diagnostic tool to directly measure spatially resolved ion beam current distributions. Unlike conventional evaluation approaches based solely on integrated beam current, the present system allows the analysis of beam focusing behavior using two-dimensional beam current profiles resolved along both the major and minor axes of the ribbon beam. Experiments are conducted by varying the extraction voltage, arc current, and electrode spacing, demonstrating that a limited extraction condition exists under which beam spreading is minimized in both axes. The results show that adjustments of extraction and discharge parameters are inherently accompanied by changes in beam focusing behavior in a three-electrode extraction system, highlighting the importance of spatially resolved diagnostics for evaluating ion source performance. The developed test bench thus provides a practical and flexible platform for assessing extraction characteristics and electrode configurations, while offering a foundation for future extensions incorporating additional diagnostics for comprehensive beam quality evaluation.","manuscriptTitle":"Development and Characterization of a Ribbon-Type Ion Beam Source Test Bench for Ion Implantation Applications","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-30 15:18:19","doi":"10.21203/rs.3.rs-8477349/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-08T02:28:43+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-07T08:34:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"264358869795079044592447413708546212825","date":"2026-02-01T02:29:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-28T05:08:01+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-28T05:03:10+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-07T09:03:43+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of the Korean Physical Society","date":"2025-12-30T04:38:57+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-the-korean-physical-society","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Journal of the Korean Physical Society](https://link.springer.com/journal/40042)","snPcode":"40042","submissionUrl":"https://submission.springernature.com/new-submission/40042/3","title":"Journal of the Korean Physical Society","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"21c3b978-1f01-495e-b247-27d7c1fd0840","owner":[],"postedDate":"January 30th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-15T02:39:06+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-30 15:18:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8477349","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8477349","identity":"rs-8477349","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}