Subminiature silicon integrated electret capacitor microphone

Microphones were prepared that use one silicon wafer to support a thin polyester diaphragm and a second to carry a Teflon or silicon dioxide electret. Subassemblies are diced from the wafer and bonded together to form complete microphones. The preamplifier circuit can be carried on either subassembly. Microphones with reasonable signal-to-noise ratios can be obtained with edge dimensions of 3 mm or less. The electroacoustic properties of prototype units are described. >