As a final project for the graduate-level course "Intro to MEMS and NEMS", I worked with a team of 5 to design the structure , sensing, and fabrication process for a MEMS microphone. The microphone required a sensitivity greater than 0.5 mV/Pa and a frequency range of 0.1-5 kHz. Our final design is described in the report below.
It was decided that capacitive microphone was the best option to meet all these requirements due to their high sensitivity and flat frequency response. Capacitive microphones consist of flexible diaphragm, a rigid backplate, and an electrode. Changes in the internal pressure of the microphone lead to changes in capacitance.
My main focus was the manufacturing process needed to produce our proposed microphone (Section III). These manufacturing techniques included silicon wafer doping, lithography, etching, and LPCVD. Additionally, I learned about multiple types of common MEMS materials such as silicon, photoresists (positive and negative), and PSG.