Methods of fabricating low pressure silicon transducers

• US 4,016,644 A
• Filed: 01/14/1976
• Issued: 04/12/1977
• Est. Priority Date: 03/18/1974
• Status: Expired due to Term

• Current Assignee: Kulite Semiconductor Products Inc
• Original Assignee: Kulite Semiconductor Products Inc
• Inventors: Kurtz, Anthony D.
• Primary Examiner(s): Tupman, W.
• Application Number:
  US05/648,957
• Time in Patent Office: 454 Days
• Field of Search: 29/589, 29/590, 29/583, 29/610 SG, 29/584, 29/585, 29/580, 29/591, 338/2, 338/4
• US Class Current: 438/51
• CPC Class Codes: H01L 21/78 with subsequent division of the substrate into plural individual devices cutting to change the surface-physical characteristics or shape of semiconductor bodies H01L21/304
• CPC Class Codes: H01L 2224/2919 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/8319 Arrangement of the layer connectors prior to mounting
• CPC Class Codes: H01L 2224/8382 Diffusion bonding
• CPC Class Codes: H01L 2224/83825 Solid-liquid interdiffusion
• CPC Class Codes: H01L 2224/8385 using a polymer adhesive, e.g. an adhesive based on silicone, epoxy, polyimide, polyester
• CPC Class Codes: H01L 24/29 of an individual layer connector
• CPC Class Codes: H01L 24/83 using a layer connector
• CPC Class Codes: H01L 29/84 controllable by variation of applied mechanical force, e.g. of pressure
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01015 Phosphorus [P]
• CPC Class Codes: H01L 2924/01039 Yttrium [Y]
• CPC Class Codes: H01L 2924/01074 Tungsten [W]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/0665 : Epoxy resin
• CPC Class Codes: H01L 2924/07802 : not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: Y10S 148/028 : Dicing
• CPC Class Codes: Y10S 148/135 : Removal of substrate
• CPC Class Codes: Y10T 29/42 : Piezoelectric device making
• CPC Class Codes: Y10T 29/49103 : Strain gauge making

Abstract

A low pressure transducer and methods of fabricating the same employ piezoresistive bridges deposited on or diffused within a wafer of n-type silicon, the wafer is secured to a glass sheet and is then bonded to a silicon diaphragm of a relatively large size and fabricated from a distinct piece of silicon of non-critical electrical characteristics. Methods for producing a plurality of such devices by using compatible processing steps are also provided.

Claims

1. The method of fabricating a transducer comprising the steps of:

a. diffusing a plurality of piezoresistive patterns on a surface of a single n-type silicon wafer,

b. bonding a thin glass sheet to the surface of said wafer opposite to that surface upon which said patterns are diffused,

c. separating each of said patterns to form a plurality of individual patterns, and

d. glass bonding each individual pattern on a separate diaphragm of silicon, of non-critical electrical properties as compared to said n-type wafer to form a plurality of separate diaphragm transducer structures, whereby said portion of said glass sheet on said individual pattern is bonded to said separate diaphragm of silicon.

2. The method according to claim 1 furhter comprising the step of:

a. etching an aperture in said separate silicon diaphragm prior to bonding said pattern and thence bonding said individual pattern within said etched aperture.

4. The method according to claim 1 wherein said bonding steps are accomplished by holding said parts to be bonded in intimate contact under elevated pressure and temperature and applying a potential therebetween to cause ions to move from one part to the other to provide said bond.

5. The method according to claim 1 wherein said thin glass sheet is a borosilicate glass.

6. The method according to claim 1 further comprising the steps of:

a. forming an aperture on said diaphragm and thence bonding a separate one of said cells to a separate one of said diaphragms within said aperture.

7. The method according to claim 6 wherein said aperture is formed near the outer edge of said diaphragm.

8. The method according to claim 6 wherein said diaphragm is approximately one-half inch in diameter or greater.

3. The method of fabricating a transducer, comprising the steps of:

a. diffusing a plurality of piezoresistor bridge patterns on a surface of an n-type first wafer of silicon.

b. bonding a thin glass sheet to the surface of the first wafer opposite to that surface upon which said patterns are diffused,

c. scribing each of said patterns to form a plurality of individual bridge cells,

d. cutting a plurality of diaphragms of desired thicknesses from a second wafer of silicon of non-critical electrical properties as compared to said first wafer,

e. glass bonding a separate one of said cells to a separate one of said diaphragms to form a plurality of separate transducers each including a cell and a diaphragm, whereby said portion of said glass sheets associated with said cell is bonded to said separate diaphragm.

9. A method of fabricating a low pressure transducer comprising the steps of:

a. diffusing a plurality of piezoresistive elements on a surface of a first wafer of silicon;

said silicon being of the (110) plane n-type conductivity,

b. polishing the opposite surface of said wafer of silicon to provide a smooth surface opposite to said surface containing said elements,

c. bonding a sheet of glass to said smooth surface to provide a composite assembly,

d. scribing said composite assembly to provide a plurality of individual elements from said composite assembly,

e. cutting a plurality of diaphragms from a cylindrical second wafer of silicon of a single crystal structure and of non-critical electrical properties as compared to said first wafer and each diaphragm of a diameter equal to the diameter of said cylinder and said diameter larger than any individual element,

f. glass bonding a separate one of said elements to a separate one of said diaphragms to provide a transducer, by employing the portion of said glass sheet as the bonding agent.

10. The method according to claim 9 further comprising the step of:

forming an aperture in each of said diaphragms of a dimension to accommodate said element and bonding said element within said aperture.