Design of Perforated Membrane for Low-Noise Capacitive MEMS Accelerometers

We propose a design method for a thick membrane with several thousand perforations suitable for low-noise capacitive micro-electro-mechanical systems (MEMS) accelerometers. Although we have already reported that a membrane with two-step perforations shows good noise performance, it is difficult to simulate mechanical noise using a conventional method because the large number of perforations complicates the membrane structure. In this work, we assumed that the number of perforations is infinite and that there are symmetric planes between them. This assumption greatly reduces computational complexity because the simulation model is simplified in the region around a perforation. We fabricated MEMS resonators with a two-step perforated membrane and evaluated the accuracy of the simulation results. The measured Q values of the fabricated resonators were in good agreement with the calculated results. Using this design method, we optimized the structure of a membrane with two-step perforations and fabricated capacitive MEMS accelerometers that showed excellent low-noise performance (less than 15 ng/Hz1/2) and low-power consumption (20 mW).