Method for manufacturing a semiconductor pressure sensor with single-crystal silicon diaphragm and single-crystal gage elements
AssigneeThe Foxboro Company
InventorClifford D. Fung
Life of this patent
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Abstract
A semiconductor pressure sensor utilizes single-crystal silicon piezoresistive gage elements dielectrically isolated by silicon oxide from other such elements, and utilizes an etched silicon substrate with an etch stop. P-type implants form p-type piezoresistive gage elements and form p+ interconnections to connect the sensor to external electrical devices. The diaphragm is made from epitaxially-grown single-crystal silicon. Passivation nitride can be used for additional dielectric isolation. One practice of the invention provides over-range cavity protection, and thus increased robustness, by forming an over-range stop for the diaphragm through localized oxygen ion implantation and etching.
Claims3
A method for manufacturing a semiconductor pressure sensor, said method comprising the successive steps of
- (A) providing a silicon-on-insulator wafer, said wafer including a silicon substrate, a first silicon oxide implantation for forming an etch stop, and a first surface annealed silicon,
- (B) epitaxially growing additional single-crystal silicon on said first surface silicon for forming a diaphragm with opposing first and second surfaces,
- (C) implanting oxygen ions in said additional single-crystal silicon for forming a dielectric isolator,
- (D) annealing said implanted additional single-crystal silicon thereby forming a second surface silicon on said dielectric isolator,
- (E) forming a dielectrically isolated single-crystal silicon piezoresistive gage element in said second surface silicon by boron ion implantation and etching,
- (F) forming an external connector by metal evaporation and etching, said external connector being in circuit with said gage element for providing an external electrical connection to said sensor, and
- (G) etching said substrate to said etch stop such that said diaphragm can deflect in response to a pressure difference between said first and second surfaces.
Dependencies are inferred from the claim text.