The Novel Sensitivity Improved Surface Micromachined MEMS Microphone with the Center-Hole Membrane

Abstract

We present a new capacitive type surface micromachined MEMS microphone with improved sensitivity and frequency response. In contrast to the bulk micromachined MEMS microphones, the surface MEMS microphone shows advantages of CMOS compatibility and no backside etching process [1]. However, the shallow back chamber depth and the small sensing gap of the surface MEMS microphone increase the air damping on the sensing membrane and reduce the overall sensitivity. In this paper, we proposed the center-hole membrane. The proposed center-hole on the sensing membrane reduces the air damping at the center and increases the membrane displacement. The fabricated surface MEMS microphone with center-hole membrane shows an improved sensitivity and frequency response. The displacement of center-hole membrane is increased to 168% for 500μm diameter membrane and 172% for 700μm diameter membrane at 10kHz, with an equivalent acoustic pressure of 1Pa and a bias of 6V.