Improvements on Breakdown Characteristics of FS- IGBT with Multi-Field Limited Ring Terminal Structure

Improvements on Breakdown Characteristics of FS- IGBT with Multi-Field Limited Ring Terminal Structure | 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 Article Improvements on Breakdown Characteristics of FS- IGBT with Multi-Field Limited Ring Terminal Structure Lijun Zhang, Wenpei Li, Mengmeng Li, Yongshun Wang, Junqiang Fan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7053465/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The proper termination structure of the device can effectively improve the voltage capacity of IGBT. The phenomenon of electric field concentration can be reduced, and the breakdown voltage be increased, by using field limit multi-ring terminal structure. A physical model for silicon-based field cut-off IGBT with the field limited multi-ring structure was established. The dependence of the breakdown voltage on the structural geometric dimensions and the drift region doping concentration were simulated based on numerical simulation software in this paper. The surface electric field intensity and distribution when breakdown occurs was extracted by adjusting the ring spacing, and the breakdown mechanism was analyzed in depth. The breakdown voltage increases with the increase in number of field-limited rings and its doping concentration. It firstly increases and then decreases with the increase in junction depth of the field limited ring. The optimum technological parameters were obtained by comparing and analyzing, the number of field-limited rings N = 110, the doping concentration of field limited rings N Pj =6×10 17 cm -3 , its junction depth H n =2 µm, the doping concentration of drift region N d =1.6×10 13 cm -3 , for which the maximum breakdown voltage of V B =4518 V, and the stability and reliability of the devices are improved. Physical sciences/Energy science and technology Physical sciences/Engineering Physical sciences/Physics IGBT field limited ring doping concentration drift region breakdown voltage surface field Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 1. Introduction With the developments of power electronic technologies, high power insulated gate bipolar transistors (IGBT) are widely applied in many regions such as aerospace industry, smart power grid, consumer electronics, automotive electronics and rail transit, becoming one of the main power semiconductor devices [ 1 ]. IGBT device is mainly comprised of basic primitive cell and terminations, in which field concentration may occur due to small curvature radius of depletion region a t cell edge [ 2 ], resulting in decrease of breakdown voltage at edge region. The local location electric field concentration at cell edge can be reduced by reasonable termination configuration, decreasing field peak value of chief junction, and further alleviating field concentration. Thus, the reliability and breakdown characteristics are improved [ 3 ]. At present, there are many termination configuration techniques such as field limited ring (FLR) [ 4 – 5 ], field plate (FP), floating field ring (FFR), junction termination expansion (JTE), variation in doping (VLD), positive and negative oblique angle shape (OAS), and their combination [ 6 – 8 ]. The fabrication process of IGBT is very complicated, and the production cost is very high. In order achieve high voltage capacity, low conduction voltage drop and turn-off loss, the field limited rings and field plate were usually used, due to its simple process and excellent compatibility with IGBT [ 9 ]. In recent years, many structures of field limited rings were proposed. In order alleviate field concentration, a method of counter doping (CD) introduced in the junction termination extension (JTE) region to create a multizone termination was represented [ 10 ]. This method greatly reduces the sensitivity of breakdown voltage (BV) to JTE doses and surface charges. The field intensity high peak at edge was divided into many low peaks, effectively alleviating field concentration. A novel edge termination structure with Four-Region Multistep Field Limiting Rings (FRM-FLRs) is proposed [ 11 ], exhibiting a good blocking performance. This structure with FRM-FLRs decreases the sensitivity of the interface charges, which greatly improves the reliability of the device at the off-state. A novel termination configuration was designed by forming many p-type doping regions in silicon planar gate FS-IGBT in this paper, called multi-field limited ring structure [ 12 ]. The dependence of device breakdown characteristics on the number of field limited rings, geometrical dimensions of device structure and technology process parameters were simulated and analyzed in depth. The structure and performance parameters were improved according to the electric field distribution and its peak value when breakdown occurs. The maximum breakdown voltage of V B =4518 V, and the stability and reliability of the devices were much improved. 2. Device structure and physical model 2.1. Structure of field limited rings The high voltage the device withstood when breakdown occurs was reduced gradually by ring dividing and s haring, therefore, the breakdown voltage was much increased. The designed field limited ring structure in IGBT device was shown in Fig. 1 . When a voltage was inversely biased to the main junction, a depletion layer was formed around PN junction. With the increase in inverse voltage, the depletion layer becomes wider. When the biased inverse voltage increased to a certain value, the depletion layer extends to the ring, dividing a part of inverse voltage. The concentration phenomenon of electric field at the edge of main junction was alleviated. Thus, the breakdown voltage can be improved by increasing the number of field-limited rings and the ring spacing. 2.2. Structure description The traditional field stop insulated gate bipolar transistor (FS-IGBT), called T-IGBT, was illustrated in Fig. 2(a), the designed novel IGBT with multi-ring for limiting electric field, called M-IGBT in Fig. 2(b). Compared with T-IGBT, many field-limited rings were formed by doping p + impurities on epitaxial layer in MF-IGBT, resulting in electric field redistribution at the surface of device in blocking state. This new device structure has many advantages such as steady internal electric field, low leakage current, high breakdown voltage, easy depletion for drift region. The doping concentration in drift region may be increased for the structure to further reduce conduction resistance. The geometrical and process parameters were designed based on the operation mechanism of devices as follows: length of drift region L d (µm) = 1250, thickness of drift region H d (µm) = 400, gate oxide thickness H OX (µm) = 0.05, drift region doping concentration N d (cm -3 ) = 2×10 13 . The important process parameters such as number of rings N R , junction depth of ring H n (µm), doping concentration of rings N p (cm -3 ), spacing between two rings W n (µm) and width of ring W(µm) were optimized by simulation experiments and analysis in depth in next sections. 3 Simulation experiments The planar gate FS-IGBT device with many field limited rings was designed simulated based on numerical simulation software Silvaco TCAD. Many factors that may influence device performance were taken into full account. The dependence of electrical performance of devices on doping concentrations, electric field distribution in horizontal and vertical directions was analyzed in depth. The breakdown voltage characteristics of the designed devices were analyzed simulated based on many theoretical models, such as impact ionization (IMPACT SELB), mobility (CVT), Shockley recombination (SRH), band gap narrowing (BGN), Auger recombination (AUGER) and carrier mobility (FLDMOB) [ 13 – 15 ]. The equation group of continuity, Poisson and drift-diffusion models were solved by using Gummel and Newton iterative algorithm [ 16 ]. 4 Simulation and discussion 4.1. Breakdown characteristics For voltage capacity of 3300 V, the doping concentration N d of drift region can be estimated with empirical formula: V B =5.34×10 13 N d -3/4 (1) The acquired doping concentration of drift region was N d =1.65×10 13 cm -3 for breakdown voltage 3960 V of traditional T-IGBT according to (1). The I-V characteristics of T-IGBT was shown in Fig. 3 (a). When the collector voltage increases to 3854 V, the avalanche breakdown occurs, the collector current quickly increases suddenly. The simulation result shows traditional T-IGBT structure did not achieve desired objective. Therefore, in order to improve the breakdown voltage, the novel structure with many field limited rings and simulation model were used to further ensure reliability. The threshold voltage was 5.3 V as indicated in transfer characteristics of MF-IGBT as shown in Fig. 3 (b). 4.2. Dependence of breakdown characteristics on the number of rings The voltage capacity of silicon device IGBT with termination configuration has been improved by the increase in number of field limited rings, as the electric field concentration around the main junction was mitigated due to the field redistribution. The field limited rings were arranged at a distance W n between two rings, with equal increment for next one, W n was determined by the expression (2), W n (µm) = D+(N-1)d (2) Where, W n is the spacing of Nth ring, d is the spacing increment, D is the distance between main junction and first ring. With the increase in ring spacing, the influence of ring number on the breakdown characteristics was shown in Fig. 4 . The breakdown voltage of designed MF-IGBT increases with the increase in ring number. The maximum voltage 4365 V of MF-IGBT is 32% higher than 3300 V of traditional T-IGBT. The voltage capacity and reliability of devices can be improved by increasing the number of rings. With the increase in number of rings, the variation in breakdown voltage shows a trend of first increasing and then decreasing, as shown in Fig. 5. When the number of field limited rings is 80, the breakdown reaches maximum value. 4.3. Influence of ring number N on electric field distribution In order to further investigate the influencing mechanism of ring number N on breakdown voltage, it is necessary to analyze the relationship between electric field concentration at surface and ring number N. The electric field distributions along longitudinal direction and on device surface corresponding maximum breakdown voltage of MF-IGBT were shown in Fig. 6(a) and (b), respectively. With the gradual increase of ring number N, many peaks of electric field were generated that may partially counteract surface electric field and alleviate concentration of surface electric field. Therefore, the electric field endurance capacity of drift region was enhanced, increasing breakdown voltage. When the number of rings N saturates, the electric field distributes uniformly on the surface, and the voltage capacity tend towards steady finally. Therefore, the influence of both geometrical and technological parameters on breakdown performance was analyzed in depth for given length of the drift region and N = 80. 4.4. Dependence of breakdown performance on junction depth of rings It is necessary to consider the effect of junction depth on breakdown characteristics when the field limited rings were formed in the drift region. For given doping concentration of drift region N d =1.6×10 13 cm -3 , concentration of field limited rings N Pj =6× 17 cm -3 and ring width W = 3 µm, the depth of junction H n increases from 1 µm to 2.8 µm in numerical simulation process. With the increase of H n , the breakdown voltage V B increases firstly, and reaches the maximum value at H n =2 µm, then decreases as indicated in Fig. 7 . The dependence of breakdown voltage on junction depth H n was shown in Fig. 8. With the increase of junction depth H n , the breakdown voltage V B increases to the maximum value, then decreases. 4.5. Dependence of breakdown performance on doping concentration of rings The influence of different doping concentration of field limited rings on breakdown performance of devices was shown in Fig. 9 . Given the doping concentration of drift region N d =1.6×10 13 cm -3 and junction depth of rings H n =2 µm, the doping concentration of field limited rings varies from N Pj 从0.6×10 17 cm -3 to 11×10 17 cm -3 in numerical simulation. With the increase in doping concentration of rings N Pj , the breakdown voltage increases, and reaches the maximum value at N Pj =11×10 17 cm -3 . It can be seen from Fig. 10 V B that with the increase in doping concentration N P of rings, the breakdown voltage V B increases gradually. The breakdown values 4121 V, 4345 V and 4372 V are corresponding to the doping concentrations N Pj =1.0×10 17 , 6×10 17 and 11×10 17 cm -3 , respectively. 4.6. Influence of doping concentration N Pj on surface field distribution The field distribution profile at surface of device, as the doping concentration N Pj increases from 0.6×10 17 cm -3 to 11×10 17 cm -3 , was shown in Fig. 11 . Many peaks of electric field were induced by field limited rings, and the peak value increases with increase on N Pj . Compared with traditional T-IGBT, the surface field distribution in drift region of MF-IGBT is more uniform, and has higher capacity of electric field. 4.7. Influence of Nd on breakdown voltage The most part of inversely applied voltage at blocking state was undertaken by the drift region, prohibiting the current from flowing through, and the depletion region extends main in this region. The doping concentration of drift region affects the voltage capability of IGBT in blocking state. It also can control the flowing condition of electrons and holes, affecting conduction and blocking performances of devices. With the increase in doping concentration of drift region, the field intensity in this region was enhanced. When the field intensity approaches or reaches the critical value, the breakdown phenomenon may occur. Given the doping concentration N Pj =6×10 17 cm -3 , junction depth H n =2 µm of field limited rings, and other parameters remaining constant in the simulation process, let the doping concentration N d increase from 1.5×10 13 cm -3 to 2.5×10 13 cm -3 , the simulated results were shown in Fig. 12 . It can be seen from this result that when the doping concentration of drift region was N d =1.5×10 13 cm -3 , the breakdown voltage V B reaches its maximum value. With the increase of doping concentration of drift region, the breakdown voltage decreases linearly as show N d - V B characteristics in Fig. 13. The surface field distribution for doping concentration N d from 1.5×10 13 cm -3 to 2.5×10 13 cm -3 and N = 90, when breakdown occurs was shown in Fig. 14 . With the increase of distance from field peak to emitter, the surface field intensity of IGBT structure with different ring spacings increases to the maximum value and then decreases. With increase in doping concentration N d , the field distributes more uniformly. 4.8. Impact of thickness of drift region on breakdown The thickness of drift region is an important parameter that influences breakdown performance. The thicker drift region can provide large enough space for depletion layer extension, decreasing field intensity. However, the too large thickness of drift region may result in high switching loss, due to large resistance in conduction state. Given doping concentration of rings N Pj =6×10 17 cm -3 , junction depth H n =2 µm and doping concentration of drift region N d =1.6×10 13 cm -3 , let thickness of drift region H d increase from 350 µm to 450 µm, and other parameters remain constant in numerical simulation. The dependence of breakdown characteristics on thickness of drift region H d was shown in Fig. 15 . V B reaches its maximum when H d =450 µm. With the increase in thickness of drift region, the breakdown voltage increases linearly shown in Fig. 16. 4.9. Influence of thickness H d of drift region on surface field distribution In order to understand the influence of thickness of drift region on breakdown voltage, the distribution of field intensity peaks when breakdown occurs was shown as Fig. 17 . Given the drift region H d increase from 350 µm to 450 µm and N = 100 in the numerical simulation. With the increase in distance from field peak to the emitter of device, the surface field intensity increases to the maximum then decreases, and it tends towards uniform distribution. 5. Results The influence of both geometrical structure and technological process parameters, including doping concentration of rings, number N, junction depth, doping concentration of drift region and its thickness, on breakdown characteristics of FS-IGBT with structure of field limited ring was researched in depth in this paper. The dependence of breakdown voltage on surface field distribution was analyzed deeply. With the increase of number of rings, the breakdown voltage increases to its maximum and then tends towards saturation. It increases with increase in doping concentration of field limited rings for given number of rings. The breakdown voltage increases to its maximum and then decreases with the increase of junction depth of field limited rings while the doping concentration remains constant. For given junction depth of rings, the breakdown voltage decreases gradually with the increase in doping concentration of drift region. It increases with the increase of thickness of drift region for constant doping concentration of field limited rings. The spaces between rings were so designed linearly that the electric field of device distributes more uniformly. The maximum breakdown voltage V B =4518 V was acquired for optimum parameters N = 110, N Pj =6×10 17 cm -3 , H n =2 µm, N d =1.6×10 13 cm -3 . Declarations Funding Declaration The work was supported by a grant from the National Natural Science Foundation of China (Grant No: 6136606), awarded to Dr. Yongshun Wang. Author Contributions Statement Author Lijun Zhang was mainly responsible for data collection and the selection of research plans, determining the research direction and key points of the paper. Author Wenpei Li was mainly in charge of the research. After confirming the data, simulation experiments were carried out to obtain data graphs, and then data analysis was performed and the paper was written. Author Mengmeng Li was mainly responsible for data modification and proofreading, and analyzed the feasibility of the data. Author Yongshun Wang was mainly responsible for the revision of the paper writing. Author Junqiang Fan was mainly responsible for the final revision of the paper, modifying the details to ensure the overall value of the paper. All authors reviewed the manuscript. Author Contribution Author Lijun Zhang was mainly responsible for data collection and the selection of research plans, determining the research direction and key points of the paper.Author Wenpei Li was mainly in charge of the research. After confirming the data, simulation experiments were carried out to obtain data graphs, and then data analysis was performed and the paper was written.Author Mengmeng Li was mainly responsible for data modification and proofreading, and analyzed the feasibility of the data.Author Yongshun Wang was mainly responsible for the revision of the paper writing.Author Junqiang Fan was mainly responsible for the final revision of the paper, modifying the details to ensure the overall value of the paper.All authors reviewed the manuscript. Acknowledgments The work was supported by a grant from the National Natural Science Foundation of China (Grant No: 6136606), awarded to Dr. Yongshun Wang. Data Availability All data generated or analysed during this study are included in this published article References Han, L. et al. A review of SiC IGBT: models, fabrications, characteristics, and applications[J]. IEEE Trans. Power Electron. 36 (2), 2080–2093 (2020). Tang, G. et al. 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Design and optimization of four-region multistep field limiting rings for 10kV 4H-SiC IGBTs[C]//2018 14th IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT). IEEE, : 1–3. (2018). Liu, Y. et al. 10kV 4H-SiC IGBT based on the multi-floating-zone junction terminal extension (MFZ-JTE) structure[C]//2021 IEEE International Conference on Integrated Circuits, Technologies and Applications (ICTA). IEEE, : 90–91. (2021). Hu, R. et al. An improved composite JTE termination technique for ultrahigh voltage 4H-SiC power devices[C]//2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSL China: IFWS). IEEE , : 18–21. (2019). Wang, Y. et al. Process optimization for improving the threshold voltage distribution of 3300V IGBT platform[C]//2020 4th IEEE Electron Devices Technology & Manufacturing Conference (EDTM). IEEE, : 1–4. (2020). Wei, J. et al. Gate structure design of SiC trench IGBTs for injection-enhancement effect[J]. IEEE Trans. Electron. Devices . 66 (7), 3034–3039 (2019). Ma, C. et al. Design and optimization of 6.5 kV SiC MOSFET device termination check for updates[C]//The Proceedings of 2023 4th International Symposium on Insulation and Discharge Computation for Power Equipment (IDCOMPU2023): Volume IV. Springer Nature, 1103: 367. (2023). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. 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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-7053465","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":486754394,"identity":"747e95a2-d8c0-4b4c-8dd1-dbaedc69bb1b","order_by":0,"name":"Lijun Zhang","email":"","orcid":"","institution":"Lanzhou Jiaotong University","correspondingAuthor":false,"prefix":"","firstName":"Lijun","middleName":"","lastName":"Zhang","suffix":""},{"id":486754397,"identity":"bfb49f54-0cfe-4929-81dd-4e4c41d2198f","order_by":1,"name":"Wenpei 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10:40:41","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":29171,"visible":true,"origin":"","legend":"\u003cp\u003eDependence of breakdown voltage \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e on N\u003c/p\u003e","description":"","filename":"Fig.5.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/5c3392c82d69aaa317db227d.png"},{"id":87018758,"identity":"328e4c81-4d05-4f25-bd51-154786862399","added_by":"auto","created_at":"2025-07-18 10:40:41","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":77361,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of electric field corresponding maximum breakdown voltage: (a)along the longitudinal direction; (b) on device surface\u003c/p\u003e","description":"","filename":"Fig.6.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/e2cc7373b4920855a6319cdb.png"},{"id":87018768,"identity":"59330ffc-8172-4b1c-a29f-2a1bcd7929ad","added_by":"auto","created_at":"2025-07-18 10:40:41","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":55536,"visible":true,"origin":"","legend":"\u003cp\u003eInfluence of N on \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e for different junction depth \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Fig.7.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/b093873c950a8273c035dfdb.png"},{"id":87018771,"identity":"9700033b-798c-44b2-b1fb-eae3cffadaba","added_by":"auto","created_at":"2025-07-18 10:40:41","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":30976,"visible":true,"origin":"","legend":"\u003cp\u003eDependence \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e on \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Fig.8.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/4cfd18c8f33a9c9570c04dbf.png"},{"id":87018800,"identity":"8501092a-2c87-4d02-a952-ae8420a9e95d","added_by":"auto","created_at":"2025-07-18 10:40:42","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":65297,"visible":true,"origin":"","legend":"\u003cp\u003eBreakdown characteristics for different\u003cem\u003e N\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Fig.9.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/6717a2f364e9525ec6b5d977.png"},{"id":87020075,"identity":"a6a795b2-c551-479f-aa7f-d116c783990e","added_by":"auto","created_at":"2025-07-18 10:56:41","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":29950,"visible":true,"origin":"","legend":"\u003cp\u003eVariations of \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e with \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Fig.10.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/c3f1853890085810c95d5993.png"},{"id":87018760,"identity":"2fea92d1-a376-44bb-baff-81c5897791ea","added_by":"auto","created_at":"2025-07-18 10:40:41","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":101186,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of surface electric field at blocking state for different \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Fig.11.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/bce8dbcfb0858103b871c9c3.png"},{"id":87018781,"identity":"898ea5f3-4330-4189-b237-283a92bd8ca0","added_by":"auto","created_at":"2025-07-18 10:40:42","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":68116,"visible":true,"origin":"","legend":"\u003cp\u003eBreakdown characteristics for different \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Fig.12.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/c3a79ed0d0c0efcc6ec416d6.png"},{"id":87019254,"identity":"3969e194-e331-45e5-9f5f-3df3ad2a2fa6","added_by":"auto","created_at":"2025-07-18 10:48:41","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":27735,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e-\u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e characteristics\u003c/p\u003e","description":"","filename":"Fig.13.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/c63f19f76a0bb626d595efe1.png"},{"id":87018783,"identity":"827afb4d-81ce-45b8-adaa-4f1c85dd5dce","added_by":"auto","created_at":"2025-07-18 10:40:42","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":100136,"visible":true,"origin":"","legend":"\u003cp\u003eSurface field distribution in blocking state for different \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Fig.14.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/3e7bc0d6b2eb279c1ddf3889.png"},{"id":87019256,"identity":"f237ed3c-aee3-4d6d-afbd-03ead70a1168","added_by":"auto","created_at":"2025-07-18 10:48:41","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":54153,"visible":true,"origin":"","legend":"\u003cp\u003ebreakdown characteristics for different\u003cem\u003e H\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Fig.15.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/0adb6fb7e9a628a87d3e9a12.png"},{"id":87019257,"identity":"931785dc-c313-41f5-84a3-5fd247dc24a7","added_by":"auto","created_at":"2025-07-18 10:48:42","extension":"png","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":26438,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eH\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e-\u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e characteristics different \u003cem\u003eH\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Fig.16.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/084ecbbc7cf7b7fa0ca0bf45.png"},{"id":87020076,"identity":"da3e20c9-d83b-4273-ab06-00a1d323872a","added_by":"auto","created_at":"2025-07-18 10:56:42","extension":"png","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":85104,"visible":true,"origin":"","legend":"\u003cp\u003eSurface field distribution in blocking state for\u003c/p\u003e","description":"","filename":"Fig.17.png","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/5b38d757593d9e9ab6678f9d.png"},{"id":101999569,"identity":"62dd3f74-63b9-4478-8110-90b071ded8d8","added_by":"auto","created_at":"2026-02-06 01:39:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1790228,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7053465/v1/1c923b12-3d45-4bcf-8bb2-59e18e736e40.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Improvements on Breakdown Characteristics of FS- IGBT with Multi-Field Limited Ring Terminal Structure","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eWith the developments of power electronic technologies, high power insulated gate bipolar transistors (IGBT) are widely applied in many regions such as aerospace industry, smart power grid, consumer electronics, automotive electronics and rail transit, becoming one of the main power semiconductor devices [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. IGBT device is mainly comprised of basic primitive cell and terminations, in which field concentration may occur due to small curvature radius of depletion region a t cell edge [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], resulting in decrease of breakdown voltage at edge region. The local location electric field concentration at cell edge can be reduced by reasonable termination configuration, decreasing field peak value of chief junction, and further alleviating field concentration. Thus, the reliability and breakdown characteristics are improved [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. At present, there are many termination configuration techniques such as field limited ring (FLR) [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], field plate (FP), floating field ring (FFR), junction termination expansion (JTE), variation in doping (VLD), positive and negative oblique angle shape (OAS), and their combination [\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The fabrication process of IGBT is very complicated, and the production cost is very high. In order achieve high voltage capacity, low conduction voltage drop and turn-off loss, the field limited rings and field plate were usually used, due to its simple process and excellent compatibility with IGBT [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn recent years, many structures of field limited rings were proposed. In order alleviate field concentration, a method of counter doping (CD) introduced in the junction termination extension (JTE) region to create a multizone termination was represented [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. This method greatly reduces the sensitivity of breakdown voltage (BV) to JTE doses and surface charges. The field intensity high peak at edge was divided into many low peaks, effectively alleviating field concentration. A novel edge termination structure with Four-Region Multistep Field Limiting Rings (FRM-FLRs) is proposed [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], exhibiting a good blocking performance. This structure with FRM-FLRs decreases the sensitivity of the interface charges, which greatly improves the reliability of the device at the off-state.\u003c/p\u003e\u003cp\u003eA novel termination configuration was designed by forming many p-type doping regions in silicon planar gate FS-IGBT in this paper, called multi-field limited ring structure [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The dependence of device breakdown characteristics on the number of field limited rings, geometrical dimensions of device structure and technology process parameters were simulated and analyzed in depth. The structure and performance parameters were improved according to the electric field distribution and its peak value when breakdown occurs. The maximum breakdown voltage of \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e=4518 V, and the stability and reliability of the devices were much improved.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"2. Device structure and physical model","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n\u003ch2\u003e2.1. Structure of field limited rings\u003c/h2\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\n\u003cp\u003eThe high voltage the device withstood when breakdown occurs was reduced gradually by ring dividing and s haring, therefore, the breakdown voltage was much increased. The designed field limited ring structure in IGBT device was shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. When a voltage was inversely biased to the main junction, a depletion layer was formed around PN junction. With the increase in inverse voltage, the depletion layer becomes wider. When the biased inverse voltage increased to a certain value, the depletion layer extends to the ring, dividing a part of inverse voltage. The concentration phenomenon of electric field at the edge of main junction was alleviated. Thus, the breakdown voltage can be improved by increasing the number of field-limited rings and the ring spacing.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n\u003ch2\u003e2.2. Structure description\u003c/h2\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\n\u003cp\u003eThe traditional field stop insulated gate bipolar transistor (FS-IGBT), called T-IGBT, was illustrated in Fig.\u0026nbsp;2(a), the designed novel IGBT with multi-ring for limiting electric field, called M-IGBT in Fig.\u0026nbsp;2(b). Compared with T-IGBT, many field-limited rings were formed by doping p\u003csup\u003e+\u003c/sup\u003e impurities on epitaxial layer in MF-IGBT, resulting in electric field redistribution at the surface of device in blocking state. This new device structure has many advantages such as steady internal electric field, low leakage current, high breakdown voltage, easy depletion for drift region. The doping concentration in drift region may be increased for the structure to further reduce conduction resistance. The geometrical and process parameters were designed based on the operation mechanism of devices as follows: length of drift region \u003cem\u003eL\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e (\u0026micro;m)\u0026thinsp;=\u0026thinsp;1250, thickness of drift region \u003cem\u003eH\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e(\u0026micro;m)\u0026thinsp;=\u0026thinsp;400, gate oxide thickness \u003cem\u003eH\u003c/em\u003e\u003csub\u003eOX\u003c/sub\u003e(\u0026micro;m)\u0026thinsp;=\u0026thinsp;0.05, drift region doping concentration \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e(cm\u003csup\u003e-3\u003c/sup\u003e)\u0026thinsp;=\u0026thinsp;2\u0026times;10\u003csup\u003e13\u003c/sup\u003e. The important process parameters such as number of rings \u003cem\u003eN\u003c/em\u003e\u003csub\u003eR\u003c/sub\u003e, junction depth of ring \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e (\u0026micro;m), doping concentration of rings \u003cem\u003eN\u003c/em\u003e\u003csub\u003ep\u003c/sub\u003e(cm\u003csup\u003e-3\u003c/sup\u003e), spacing between two rings \u003cem\u003eW\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e(\u0026micro;m) and width of ring W(\u0026micro;m) were optimized by simulation experiments and analysis in depth in next sections.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003c/div\u003e"},{"header":"3 Simulation experiments","content":"\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe planar gate FS-IGBT device with many field limited rings was designed simulated based on numerical simulation software Silvaco TCAD. Many factors that may influence device performance were taken into full account. The dependence of electrical performance of devices on doping concentrations, electric field distribution in horizontal and vertical directions was analyzed in depth. The breakdown voltage characteristics of the designed devices were analyzed simulated based on many theoretical models, such as impact ionization (IMPACT SELB), mobility (CVT), Shockley recombination (SRH), band gap narrowing (BGN), Auger recombination (AUGER) and carrier mobility (FLDMOB) [\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The equation group of continuity, Poisson and drift-diffusion models were solved by using Gummel and Newton iterative algorithm [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"4 Simulation and discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e4.1. Breakdown characteristics\u003c/h2\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eFor voltage capacity of 3300 V, the doping concentration \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e of drift region can be estimated with empirical formula:\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e=5.34\u0026times;10\u003csup\u003e13\u003c/sup\u003e \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e\u003csup\u003e-3/4\u003c/sup\u003e (1)\u003c/p\u003e\n \u003cp\u003eThe acquired doping concentration of drift region was \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=1.65\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e for breakdown voltage 3960 V of traditional T-IGBT according to (1). The I-V characteristics of T-IGBT was shown in Fig. 3 (a). When the collector voltage increases to 3854 V, the avalanche breakdown occurs, the collector current quickly increases suddenly. The simulation result shows traditional T-IGBT structure did not achieve desired objective. Therefore, in order to improve the breakdown voltage, the novel structure with many field limited rings and simulation model were used to further ensure reliability. The threshold voltage was 5.3 V as indicated in transfer characteristics of MF-IGBT as shown in Fig. 3 (b).\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e4.2. Dependence of breakdown characteristics on the number of rings\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eThe voltage capacity of silicon device IGBT with termination configuration has been improved by the increase in number of field limited rings, as the electric field concentration around the main junction was mitigated due to the field redistribution. The field limited rings were arranged at a distance \u003cem\u003eW\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e between two rings, with equal increment for next one, \u003cem\u003eW\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e was determined by the expression (2),\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eW\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e(\u0026micro;m)\u0026thinsp;=\u0026thinsp;D+(N-1)d (2)\u003c/p\u003e\n \u003cp\u003eWhere, \u003cem\u003eW\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e is the spacing of Nth ring, d is the spacing increment, D is the distance between main junction and first ring. With the increase in ring spacing, the influence of ring number on the breakdown characteristics was shown in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. The breakdown voltage of designed MF-IGBT increases with the increase in ring number. The maximum voltage 4365 V of MF-IGBT is 32% higher than 3300 V of traditional T-IGBT. The voltage capacity and reliability of devices can be improved by increasing the number of rings. With the increase in number of rings, the variation in breakdown voltage shows a trend of first increasing and then decreasing, as shown in Fig. 5. When the number of field limited rings is 80, the breakdown reaches maximum value.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e4.3. Influence of ring number N on electric field distribution\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eIn order to further investigate the influencing mechanism of ring number N on breakdown voltage, it is necessary to analyze the relationship between electric field concentration at surface and ring number N. The electric field distributions along longitudinal direction and on device surface corresponding maximum breakdown voltage of MF-IGBT were shown in Fig. 6(a) and (b), respectively. With the gradual increase of ring number N, many peaks of electric field were generated that may partially counteract surface electric field and alleviate concentration of surface electric field. Therefore, the electric field endurance capacity of drift region was enhanced, increasing breakdown voltage. When the number of rings N saturates, the electric field distributes uniformly on the surface, and the voltage capacity tend towards steady finally. Therefore, the influence of both geometrical and technological parameters on breakdown performance was analyzed in depth for given length of the drift region and N\u0026thinsp;=\u0026thinsp;80.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e4.4. Dependence of breakdown performance on junction depth of rings\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eIt is necessary to consider the effect of junction depth on breakdown characteristics when the field limited rings were formed in the drift region. For given doping concentration of drift region \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=1.6\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e, concentration of field limited rings \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e=6\u0026times;\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e and ring width W\u0026thinsp;=\u0026thinsp;3 \u0026micro;m, the depth of junction \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e increases from 1 \u0026micro;m to 2.8 \u0026micro;m in numerical simulation process. With the increase of \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e, the breakdown voltage \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e increases firstly, and reaches the maximum value at \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e=2 \u0026micro;m, then decreases as indicated in Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e. The dependence of breakdown voltage on junction depth \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e was shown in Fig. 8. With the increase of junction depth \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e, the breakdown voltage \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e increases to the maximum value, then decreases.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e4.5. Dependence of breakdown performance on doping concentration of rings\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eThe influence of different doping concentration of field limited rings on breakdown performance of devices was shown in Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e. Given the doping concentration of drift region \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=1.6\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e and junction depth of rings \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e=2 \u0026micro;m, the doping concentration of field limited rings varies from \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e从0.6\u0026times;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e to 11\u0026times;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e in numerical simulation. With the increase in doping concentration of rings \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e, the breakdown voltage increases, and reaches the maximum value at \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e=11\u0026times;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e. It can be seen from Fig. 10 \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e that with the increase in doping concentration \u003cem\u003eN\u003c/em\u003e\u003csub\u003eP\u003c/sub\u003e of rings, the breakdown voltage \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e increases gradually. The breakdown values 4121 V, 4345 V and 4372 V are corresponding to the doping concentrations \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e=1.0\u0026times;10\u003csup\u003e17\u003c/sup\u003e, 6\u0026times;10\u003csup\u003e17\u003c/sup\u003eand 11\u0026times;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e\u003csub\u003e,\u003c/sub\u003e respectively.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e4.6. Influence of doping concentration N\u003csub\u003ePj\u003c/sub\u003e on surface field distribution\u003c/h2\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eThe field distribution profile at surface of device, as the doping concentration \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e increases from 0.6\u0026times;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e to 11\u0026times;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e, was shown in Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e. Many peaks of electric field were induced by field limited rings, and the peak value increases with increase on \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e. Compared with traditional T-IGBT, the surface field distribution in drift region of MF-IGBT is more uniform, and has higher capacity of electric field.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e4.7. Influence of Nd on breakdown voltage\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eThe most part of inversely applied voltage at blocking state was undertaken by the drift region, prohibiting the current from flowing through, and the depletion region extends main in this region. The doping concentration of drift region affects the voltage capability of IGBT in blocking state. It also can control the flowing condition of electrons and holes, affecting conduction and blocking performances of devices. With the increase in doping concentration of drift region, the field intensity in this region was enhanced. When the field intensity approaches or reaches the critical value, the breakdown phenomenon may occur.\u003c/p\u003e\n \u003cp\u003eGiven the doping concentration \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e=6\u0026times;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e, junction depth \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e=2 \u0026micro;m of field limited rings, and other parameters remaining constant in the simulation process, let the doping concentration \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e increase from 1.5\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e to 2.5\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e, the simulated results were shown in Fig. \u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e. It can be seen from this result that when the doping concentration of drift region was \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=1.5\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e, the breakdown voltage \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e reaches its maximum value. With the increase of doping concentration of drift region, the breakdown voltage decreases linearly as show \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e-\u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e characteristics in Fig. 13.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eThe surface field distribution for doping concentration \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e from 1.5\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e to 2.5\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e and N\u0026thinsp;=\u0026thinsp;90, when breakdown occurs was shown in Fig. \u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e. With the increase of distance from field peak to emitter, the surface field intensity of IGBT structure with different ring spacings increases to the maximum value and then decreases. With increase in doping concentration \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e, the field distributes more uniformly.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e4.8. Impact of thickness of drift region on breakdown\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eThe thickness of drift region is an important parameter that influences breakdown performance. The thicker drift region can provide large enough space for depletion layer extension, decreasing field intensity. However, the too large thickness of drift region may result in high switching loss, due to large resistance in conduction state.\u003c/p\u003e\n \u003cp\u003eGiven doping concentration of rings \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e=6\u0026times;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e, junction depth \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e=2 \u0026micro;m and doping concentration of drift region \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=1.6\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e, let thickness of drift region \u003cem\u003eH\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e increase from 350 \u0026micro;m to 450 \u0026micro;m, and other parameters remain constant in numerical simulation. The dependence of breakdown characteristics on thickness of drift region \u003cem\u003eH\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e was shown in Fig. \u003cspan class=\"InternalRef\"\u003e15\u003c/span\u003e. V\u003csub\u003eB\u003c/sub\u003e reaches its maximum when \u003cem\u003eH\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=450 \u0026micro;m. With the increase in thickness of drift region, the breakdown voltage increases linearly shown in Fig. 16.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e4.9. Influence of thickness H\u003csub\u003ed\u003c/sub\u003e of drift region on surface field distribution\u003c/h2\u003e\n \u003cp\u003eIn order to understand the influence of thickness of drift region on breakdown voltage, the distribution of field intensity peaks when breakdown occurs was shown as Fig. \u003cspan class=\"InternalRef\"\u003e17\u003c/span\u003e. Given the drift region \u003cem\u003eH\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e increase from 350 \u0026micro;m to 450 \u0026micro;m and N\u0026thinsp;=\u0026thinsp;100 in the numerical simulation. With the increase in distance from field peak to the emitter of device, the surface field intensity increases to the maximum then decreases, and it tends towards uniform distribution.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"5. Results","content":"\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe influence of both geometrical structure and technological process parameters, including doping concentration of rings, number N, junction depth, doping concentration of drift region and its thickness, on breakdown characteristics of FS-IGBT with structure of field limited ring was researched in depth in this paper. The dependence of breakdown voltage on surface field distribution was analyzed deeply. With the increase of number of rings, the breakdown voltage increases to its maximum and then tends towards saturation. It increases with increase in doping concentration of field limited rings for given number of rings. The breakdown voltage increases to its maximum and then decreases with the increase of junction depth of field limited rings while the doping concentration remains constant. For given junction depth of rings, the breakdown voltage decreases gradually with the increase in doping concentration of drift region. It increases with the increase of thickness of drift region for constant doping concentration of field limited rings. The spaces between rings were so designed linearly that the electric field of device distributes more uniformly. The maximum breakdown voltage \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e=4518 V was acquired for optimum parameters N\u0026thinsp;=\u0026thinsp;110, \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e =6\u0026times;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e, \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e=2 \u0026micro;m, \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e =1.6\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cb\u003eFunding Declaration\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe work was supported by a grant from the National Natural Science Foundation of China (Grant No: 6136606), awarded to Dr. Yongshun Wang.\u003c/p\u003e\u003cp\u003e\u003ch2\u003eAuthor Contributions Statement\u003c/h2\u003e\u003cp\u003eAuthor Lijun Zhang was mainly responsible for data collection and the selection of research plans, determining the research direction and key points of the paper.\u003c/p\u003e\u003cp\u003eAuthor Wenpei Li was mainly in charge of the research. After confirming the data, simulation experiments were carried out to obtain data graphs, and then data analysis was performed and the paper was written.\u003c/p\u003e\u003cp\u003eAuthor Mengmeng Li was mainly responsible for data modification and proofreading, and analyzed the feasibility of the data.\u003c/p\u003e\u003cp\u003eAuthor Yongshun Wang was mainly responsible for the revision of the paper writing.\u003c/p\u003e\u003cp\u003eAuthor Junqiang Fan was mainly responsible for the final revision of the paper, modifying the details to ensure the overall value of the paper.\u003c/p\u003e\u003cp\u003eAll authors reviewed the manuscript.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAuthor Lijun Zhang was mainly responsible for data collection and the selection of research plans, determining the research direction and key points of the paper.Author Wenpei Li was mainly in charge of the research. After confirming the data, simulation experiments were carried out to obtain data graphs, and then data analysis was performed and the paper was written.Author Mengmeng Li was mainly responsible for data modification and proofreading, and analyzed the feasibility of the data.Author Yongshun Wang was mainly responsible for the revision of the paper writing.Author Junqiang Fan was mainly responsible for the final revision of the paper, modifying the details to ensure the overall value of the paper.All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e\u003cp\u003eThe work was supported by a grant from the National Natural Science Foundation of China (Grant No: 6136606), awarded to Dr. Yongshun Wang.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data generated or analysed during this study are included in this published article\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHan, L. et al. 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(2020).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWei, J. et al. Gate structure design of SiC trench IGBTs for injection-enhancement effect[J]. \u003cem\u003eIEEE Trans. Electron. Devices\u003c/em\u003e. \u003cb\u003e66\u003c/b\u003e (7), 3034\u0026ndash;3039 (2019).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMa, C. et al. Design and optimization of 6.5 kV SiC MOSFET device termination check for updates[C]//The Proceedings of 2023 4th International Symposium on Insulation and Discharge Computation for Power Equipment (IDCOMPU2023): Volume IV. Springer Nature, 1103: 367. (2023).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"IGBT, field limited ring, doping concentration, drift region, breakdown voltage, surface field","lastPublishedDoi":"10.21203/rs.3.rs-7053465/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7053465/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe proper termination structure of the device can effectively improve the voltage capacity of IGBT. The phenomenon of electric field concentration can be reduced, and the breakdown voltage be increased, by using field limit multi-ring terminal structure. A physical model for silicon-based field cut-off IGBT with the field limited multi-ring structure was established. The dependence of the breakdown voltage on the structural geometric dimensions and the drift region doping concentration were simulated based on numerical simulation software in this paper. The surface electric field intensity and distribution when breakdown occurs was extracted by adjusting the ring spacing, and the breakdown mechanism was analyzed in depth. The breakdown voltage increases with the increase in number of field-limited rings and its doping concentration. It firstly increases and then decreases with the increase in junction depth of the field limited ring. The optimum technological parameters were obtained by comparing and analyzing, the number of field-limited rings N\u0026thinsp;=\u0026thinsp;110, the doping concentration of field limited rings \u003cem\u003eN\u003c/em\u003e\u003csub\u003ePj\u003c/sub\u003e=6\u0026times;10\u003csup\u003e17\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e, its junction depth \u003cem\u003eH\u003c/em\u003e\u003csub\u003en\u003c/sub\u003e=2 \u0026micro;m, the doping concentration of drift region \u003cem\u003eN\u003c/em\u003e\u003csub\u003ed\u003c/sub\u003e=1.6\u0026times;10\u003csup\u003e13\u003c/sup\u003e cm\u003csup\u003e-3\u003c/sup\u003e, for which the maximum breakdown voltage of \u003cem\u003eV\u003c/em\u003e\u003csub\u003eB\u003c/sub\u003e=4518 V, and the stability and reliability of the devices are improved.\u003c/p\u003e","manuscriptTitle":"Improvements on Breakdown Characteristics of FS- IGBT with Multi-Field Limited Ring Terminal Structure","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-18 10:40:36","doi":"10.21203/rs.3.rs-7053465/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d13c0298-4c73-49eb-a432-6401eb41eb7a","owner":[],"postedDate":"July 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":51675260,"name":"Physical sciences/Energy science and technology"},{"id":51675262,"name":"Physical sciences/Engineering"},{"id":51675264,"name":"Physical sciences/Physics"}],"tags":[],"updatedAt":"2026-02-06T01:38:59+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-18 10:40:36","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7053465","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7053465","identity":"rs-7053465","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}