Improvement of Damping Analysis for MEMS Acoustic Membranes

Because of small size and low cost, MEMS microphones are prevalent in portable electronic devices. However, their system performance is significantly affected by air damping and the corrugated structure for residual stress reduction also leads to non-uniform damping effects. Based on the governing equations of squeeze film and MEMS flexible acoustic membrane with corrugated structure, the finite-element model of MEMS microphone system is constructed. The model is validated by theory and coupled multi-physics analysis is developed. According to simulation results, air damping of the acoustic membrane with corrugated structure is higher than the non-corrugated one. Change of the air gap by residual stress will increase air damping dramatically. Besides, maximum air damping pressure occurs under corrugated structure and the center of membrane. Therefore, enlarging the area of holes underneath can effectively improve the performance of MEMS microphones.