Polycrystalline silicon pressure transducer

• US 3,938,175 A
• Filed: 11/25/1974
• Issued: 02/10/1976
• Est. Priority Date: 04/24/1974
• Status: Expired due to Term

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Jaffe, James M., Seto, John Y. W.
• Primary Examiner(s): Miller, Jr., Stanley D.
• Assistant Examiner(s): Wojciechowicz, E.
• Application Number:
  US05/526,580
• Time in Patent Office: 442 Days
• Field of Search: 357/26, 357/55, 357/59
• US Class Current: 338/4
• CPC Class Codes: G01L 9/0054 integral with a semiconducting diaphragm
• CPC Class Codes: H01L 21/00 Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
• CPC Class Codes: H01L 29/84 controllable by variation of applied mechanical force, e.g. of pressure
• CPC Class Codes: Y10S 438/977 Thinning or removal of substrate
• CPC Class Codes: Y10T 29/49103 Strain gauge making

Abstract

A semiconductor pressure transducer having a polycrystalline silicon diaphragm providing an extremely pressure sensitive and temperature stable device, and a method of making the same. The polycrystalline silicon can easily be vapor deposited on an etch resistant layer covering a surface of a wafer or base, preferably monocrystalline silicon. Such vapor deposition of the polycrystalline silicon more accurately and consistently defines the thickness of the diaphragm than can be obtained by grinding or etching. A pressure responsive resistor formed in the diaphragm is automatically electrically isolated by the comparatively high resistivity of the polycrystalline silicon. Accordingly, PN junction isolation and passivating oxides on the diaphragm are not required thereby resulting in increased temperature stability.

Claims

1. A semiconductor pressure transducer having a thin vapor deposited polycrystalline silicon diaphragm providing an extremely sensitive and temperature stable device, said pressure transducer comprising:

a base member having a similar coefficient of thermal expansion to that of silicon, said base member having two major end surfaces and an aperture extending therebetween;

a layer of etch-resistant material on one of said base member end surfaces, said etch-resistant material having a crystallographic structure so as to promote vapor deposition of polycrystalline silicon thereon;

a thin, vapor deposited intrinsic polycrystalline silicon film on said etch-resistant material and covering said aperture in said base member thereby providing an extremely sensitive pressure responsive diaphragm bridging said aperture, said polycrystalline silicon diaphragm being less than about 10 microns thick and having a resistivity of at least 10⁶ ohm-centimeters, said diaphragm being free of any material having a dissimilar coefficient of thermal expansion thereby providing improved temperature stability for said pressure transducer;

a pressure responsive electronic device formed in centrally located portions of said polycrystalline silicon diaphragm wherein said device is automatically electrically isolated by the surrounding high resistivity polycrystalline silicon; and

means for making electrical connection to said pressure responsive electronic device thereby providing electrical access to said pressure transducer.

2. A semiconductor pressure transducer having a thin vapor deposited polycrystalline silicon diaphragm providing an extremely sensitive and temperature stable device, said pressure transducer comprising:

a monocrystalline silicon wafer serving as a supporting base member for said pressure transducer, said base member having two major end surfaces and an aperture extending therebetween;

an etch-resistant layer of silicon dioxide on one of said base member end surfaces, said etch-resistant layer having a crystallographic structure so as to promote vapor deposition of polycrystalline silicon thereon;

a thin, vapor deposited intrinsic polycrystalline silicon film on said etch-resistant layer and covering said aperture in said base member thereby providing an extremely sensitive pressure responsive diaphragm bridging said aperture, said polycrystalline silicon diaphragm being less than about 10 microns thick and having a resistivity of at least 10⁶ ohm-centimeters, said diaphragms being free of any material having a dissimilar coefficient of thermal expansion thereby providing improved temperature stability for said pressure transducer;

an elongated doped region formed in said polycrystalline silicon diaphragm as a diameter thereof providing a pressure responsive resistor for said pressure transducer, said resistor being electrically isolated by the surrounding high resistivity polycrystalline silicon; and

means for making electrical connection to said resistor thereby providing electrical access to said pressure transducer.