Methods to protect silicon microstructures from the damages in deep reactive ion etching

New methods for improving the quality of the silicon deep reactive ion etching (DRIE) procedure were investigated. It suggested that a PECVD oxide layer was deposited at the silicon sidewall and a thermal oxide layer was formed at the silicon backside. Due to the silicon to silicon oxide etching selectivity (120:1-125:1), these oxide layers could protect the silicon microstructures from the damages caused by the lag and footing effects usually occurred in the basic silicon-on-glass (SOG) process. SEM microscope result confirmed that the silicon structure could endure a long time overetch and the structure surface could remain intact by the modified processes. The gyroscope device test results also were in good agreement with new process methods.