Fabrication Process Of A Capacitive Microphone With p++ Diaphragm And Silicon Bonded Top-Plate

Abstract

This paper purposes a very simple and reliable fabrication process foar a silicon capacitive microphone, the two electrodes of the condenser microphone are: a thin p++ silicon membrane fabricated using an optimized diffusion process, and a thick -30 μm - top electrode, processed also on a silicon wafer. Isolating and metal layers assure the gap between those two eletrodes. The bonding between electrode's wafers is performed using an Au-Si eutectic wafer-to-wafer bonding techniques. The thinning of top-electrode was made in the same step of the process as the etching of silicon diaphragm. The concept of fabrication process was to avoid the sticking of thin diaphragm to top electrode during different wet process. Different design with different size of diaphragm was fabricated using this process. The resulting capacitance was in the range of 1.85-3.5 pF.