Abstract
This study exploits the CMOS-MEMS technology to demonstrate a condenser microphone without back-plate. The reference sensing electrodes are fixed to the substrate, and thus no back-plate is required. To reduce the unwanted deformations resulted from the thin-film residual-stresses and temperature variation for the suspended CMOS-MEMS structures, the suspended acoustic diaphragm and sensing electrodes are respectively formed by the pure-dielectric and symmetric metal-dielectric layers. The design was implemented using TSMC 0.18μm 1P6M standard CMOS process, and the in-house post-CMOS releasing. Typical microphone with acoustic-diaphragm of 300μm-diameter and sensing-electrode of 50μm-long is fabricated and tested. Measurements indicate the sensitivity is -64dBV/Pa at 1kHz under 13.5V bias-voltage. The design enables the CMOS-MEMS microphone having good temperature stability between 30∼90°C.