Silicon condenser microphone fabricated using simplified SOI processes

Abstract

A silicon condenser microphone on an SOI (silicon on insulator) substrate using only one photo mask was fabricated. This microphone consists of a diaphragm with the thickness of 10-20 μm and the diameter of 2 mm, a SiO2 insulative spacer (4 μm thick buried oxide), and a 450 μm-thick silicon back plate with the meshed structures having extremely small (60 μm) hexagonal shaped acoustic holes. The gap between the silicon diaphragm and the back plate is 4 μm, which is determined by the thickness of the buried oxide in the SOI wafer. It was found that the microphone with the diaphragm of 10μm thickness exhibited much better sensitivity. This is because the displacement of the diaphragm increases as the thickness of the diaphragm decreases.