MEMS capacitive microphone with various materials in acoustic plate under shock loading

Abstract

Considering shock loading on the MEMS microphone is necessary for its reliability assessment since drop of portable devices is a common situation. In this study, the stress distribution and the failures of MEMS capacitive microphone chip by TSMC 0.18 μm CMOS process, with 4 by 3 microphone array under shock loading (peak acceleration 1500 g) and shock plus static electricity loading were investigated by simulation and experiment. The results show that larger stresses occur at the corners of springs, the anchors connecting fix end and spring, the location connecting spring and acoustic plate as well as the center of silicon substrate where the same crack locations of microphone after dropping 150 times were identified. The microphone cells located at the chip center had up to 2 times higher stress at stress concentration regions when compared to the stress in those cells near the chip edge. Furthermore, the stress level under shock plus static electricity loading was higher, up to two times, than that in microphone under pure shock loading; and using polysilicon acoustic plate could ease the stress around 25% when compared with that of the original design. This study assessed the stress distribution and the failures of the MEMS capacitive microphone under various loading and valuable suggestions for the microphone design are presented.