Residual Stress Evolution in Dual-Diaphragm MEMS Microphones During Fabrication and Packaging Processes

Abstract

With the rapid advancement of electronic products, the market of micro-electro-mechanical systems (MEMS) microphones has grown significantly because of their high accuracy and miniaturization. Dual-diaphragm microphones are engineered to achieve a high signal-to-noise ratio; however, their complex structure gives rise to intricate residual stress patterns within the acoustic diaphragms and significantly impacts the sensitivity of MEMS microphones. In this study, finite element modeling is employed to investigate the distribution of residual thermal stress in the two diaphragms during fabrication and packaging. Key factors, including deposition and etching temperatures, material properties, and geometric parameters, are systematically analyzed. The results show that residual thermal stresses in the diaphragms are mainly accumulated during the fabrication process of the sensor, only mildly altered by the subsequent packaging process. Selecting appropriate material properties for the sacrificial layer and lowering the deposition temperature can significantly reduce the residual thermal stress. An adhesive layer with a low modulus further helps mitigate the residual thermal stress. This work uncovers the distribution law of residual thermal stress in dual-diaphragm MEMS microphones, providing practical guidance for improving microphone sensitivity and informing device design and fabrication.