Thin MEMS microphone based on package-integrated fabrication process

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Abstract
A thin capacitive-type MEMS acoustic sensor fabricated using a fully package-integrated process is presented. This sensor has a very slim thickness of 150 µm due to the elimination of the complicated back-side alignment process which requires a thickness of more than 400 µm to prevent the substrate from breaking down. In addition, a structure-based equivalent circuit modelling was performed to evaluate the characteristics of the proposed microphone. The measured initial gap was 2.8 µm, which resulted in an intrinsic capacitance of 0.89 pF and the natural frequency was 83 kHz. The sensor has an open-circuit sensitivity of −47.7 dBV/Pa at 1 kHz with 10.4 V. The modelled sensitivity shows good agreement with the measured sensitivity.