The Effect of Design Parameters on Static and Dynamic Behaviors of the MEMS Microphone

This paper describes the effect of design parameters of MEMS capacitive microphone on the static and dynamic behaviors. The aim is to develop the microphones with high sensitivity and flat frequency response. The high sensitivity can be obtained by changing the initial stress of diaphragm,
σ_r
, diaphragm size,
a
, diaphragm thickness,
t
, back plate thickness,
h
, air gap thickness,
d
, back plate hole radius,
r
, surface area fraction occupied by the holes,
α.
, and bias voltage. The equivalent electrical circuit method has been used to predict the structure behaviors and the microphone performance. The optimized structure has a diaphragm thickness of 0.8 μm, a diaphragm area of 2.43 mm
²
, an air gap of 4.0 μm and a 1.0 μm thick back plate with acoustical ports. The device shows maximum sensitivity of 47.9mV/Pa, with a high frequency response extending to 18kHz.