Design and Fabrication of Si-Diaphragm, ZnO Piezoelectric Film-Based MEMS Acoustic Sensor Using SOI Wafers

作者：Prasad Mahanth^*; Sahula Vineet; Khanna Vinod Kumar

来源：IEEE Transactions on Semiconductor Manufacturing, 2013, 26(2): 233-241.

DOI：10.1109/TSM.2013.2238956

• Diaphragm
• silicon-on-insulator (SOI) substrate
• sound pressure level (SPL)
• thin film
• zinc oxide (ZnO) film

This paper reports a simpler technique for fabricating an microelectromechanical system acoustic sensor based on a piezoelectric zinc oxide (ZnO) thin film, utilizing silicon-on-insulator wafers. A highly c-axis-oriented ZnO film of thickness 2.4 mu m, which is covered with 0.2-mu m-thick PECVD SiO2, is sandwiched between two aluminum electrodes on a 25-mu m-thick silicon diaphragm. This diaphragm thickness has been optimized to withstand sound pressure level range of 120-160 dB. Stress distribution studies using ANSYS have been performed to determine the locations for placement of capacitor electrodes. This paper also reports a technique for the creation of a positive slope of the ZnO step to ensure proper coverage during Al metallization. In order to maximize yield, process steps have been developed to avoid the microtunnel blockage by silicon/glass particles. The packaged sensor is found to exhibit a sensitivity of 382 mu V/Pa (RMS) in the frequency range from 30 to 8000 Hz, under varying acoustic pressure.

• 出版日期2013-5