SURFACE MICROMACHINED MICROPHONE WITH BROADBAND SIGNAL DETECTION

摘要

A surface micromachined microphone with a 230 kHz bandwidth. The structure uses a 2.25 μιη thick, 305 μιη radius polysilicon diaphragm suspended above an 11 μιη gap to form a variable parallel-plate capacitance. The backcavity of the microphone consists of the 11 μιη thick air volume immediately behind the moving diaphragm, and also an extended larger cavity with a radius of 504 μιη. The dynamic frequency response of the sensor in response to electrostatic signals is presented using laser Doppler vibrometry, and indicates a system compliance of 0.4 nm/Pa in the flat-band of the response. The sensor is configured for acoustic signal detection using a charge amplifier configuration, and signal to noise ratio measurements and simulations are presented herein. A resolution of 0.80 mPa/√Hz (32 dB SPL in a 1 Hz bin) is achieved in the flat-band portion of the response extending from 10 kHz to 230 kHz.