Patent ID: 7770279

Claim:
A method for making capacitive micromachined ultrasonic transducer devices for ultrasonic transducer use, said method comprising: providing a silicon wafer substrate; depositing a silicon oxide layer on a top surface of said substrate so as to provide dielectric insulation between the substrate and further components; providing a bottom electrode on the silicon oxide layer; providing a sacrificial layer on the bottom electrode; etching said sacrificial layer to form a structure pattern according to cell geometries; depositing first silicon nitride layer on said sacrificial layer; providing a first set of openings in said first silicon nitride layer to allow access to areas of said sacrificial layer; removing said areas of said sacrificial layer using a chemical process; providing a first top electrode pattern on said first silicon nitride layer; providing vacuum seals of said first set of openings in said first silicone nitride layer; providing a second silicon nitride layer over the first top electrode pattern; providing a second set of openings in said second silicon nitride layer to allow access to the first top electrode pattern; providing a second top electrode pattern on said second silicone nitride layer; and etching said second top electrode pattern to electrically isolate said first and second electrode patterns.