For the ASE process, systematical experiments are designed to study the effects under various parameters. Silicon etching rate about 3 μm/min and perpendicularity about 90±0.5° are reached in this study. In addition, sidewall roughness can be down to 10 nm rms and process can maintain at high etching rate about 2.5 μm/min. These achievements can be widely used in MEMS applications like optical devices, microfluidic applications, micro-actuators, and micro-sensors.