One-step silicon substrate through-wafer etching process for high precision MEMS application

In order to get a low mechanical noise and high sensitivity, warpage during fabrication process which comes from the mismatching of thermal expansion between different materials is considered as a major issue for high precision measurement MEMS devices. For the purpose of warpage reduction, we proposed a one-step silicon substrate through-wafer etching process. The process is composed of a normal DRIE (Deep Reactive Ion Etching) process for an etching depth of 450μm and an optimized low frequency etching process for the residual silicon (50μm) removal. The deformation was suppressed within 2μm for a spring-mass structure with dimension of 20mm×26mm, which will be very attractive for nano-g MEMS accelerometer application.