Monolithic Piezoelectric Aluminum Nitride Mems-Cmos Microphone

A monolithic piezoelectric Aluminum Nitride (AlN) MEMS-CMOS microphone for high-sensitivity, low-power applications is presented. The MEMS microphone that is directly bonded to a CMOS buffer for current-to-voltage conversion consists of a circular-shaped AlN-SiO2 unimorph membrane. The radius, package dimensions, and electrode layout were optimized to maximize the MEMS sensitivity. The integrated device was fabricated by wafer-scale eutectic bonding of a 0.18 mu m CMOS buffer to the MEMS microphone. In this work, the piezoelectric microphone is formed by 1 mu m-thick AlN and 1 mu m-thick SiO2 layers and provides an average off-resonance sensitivity of 0.68 mV/Pa, a resonance frequency of 11.2 kHz, and a floor noise of 0.03 mu V/Hz.