High Reflectivity Distributed Bragg Reflector Based on Silicon-Rich SiNx-SiOy at 80 °C Pecvd

This study investigates the mechanical an optical characteristics of silicon nitride thin films deposited with PECVD at 80 °C for tunable SiNx-SiOy based MEMS cavities. By varying the deposition parameters using SiH4 and N2 as precursor gases for SiNx thin films allows to tune the refractive index to a value as high as of 2.398±0.013 at an extinction coefficient of only 0.011, an excellently low surface roughness of only 0.41 nm and a compressive stress about 140 MPa. We deposited a 6.5 layer pairs of SiNx/SiOy distributed Bragg reflector (DBR) micro-electro-mechanical system (MEMS) mirror that covers the whole 1300 and 1550 nm range. Cavity architectures were fabricated in the clean room providing a variety of cavity lengths between 0.615 µm and 2.85 µm. These lengths were then simulated in order to estimate the Young´s Modulus of SiNx, obtaining values from 56-92 GPa.