Critical Characteristics During Silicon Deep Etching for Microelectromechanical Systems Application-Based Bosch Process

摘要

Gaseous plasma-based silicon deep dry etching is important for microelectromechanical systems device applications. In particular, a microstructure with high etch rate, high aspect ratio, and good sidewall profile with smooth surface contribute to high performance of function devices. This work presents the study of some critical characteristics, such as aspect ratio, etch rate and etched pattern angle, during silicon deep etching via the Bosch process. The influence of open critical dimension (CD) and aspect ratio on the silicon etch rate using hole pattern has been investigated in this work first. The experimental results reveal that the etch rate increases with the increase in the open CD and decreases with the increase in the aspect ratio. Furthermore, the effect of different pitch CDs with the same open CD on the etched profile is demonstrated. We find that a straight sidewall without the issue of a "U" curve could be obtained under the condition of using a small pitch CD. Finally, the influence of the proportion of deposition time during the Bosch process is presented. The experimental results indicate that both positive slopes of 89.76 degrees (trench) and 89.93 degrees (pillar) are achieved by increasing the partial deposition time compared with the as-treated negative slope of 89.82 degrees (trench) and 89.83 degrees (pillar), respectively.