High temperature resistant solid state pressure sensor

• US 20070013014A1
• Filed: 09/19/2006
• Published: 01/18/2007
• Est. Priority Date: 05/03/2005
• Status: Abandoned Application

• Current Assignee: Rosemount Aerospace, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rosemount Aerospace, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Guo, Shuwen, Eriksen, Odd, Potasek, David
• Application Number:
  US11/523,244
• Publication Number:
  US 20070013014A1
• Time in Patent Office: Days
• US Class Current: 257/417
• CPC Class Codes: C23C 14/021 Cleaning or etching treatments
• CPC Class Codes: C23C 14/022 by means of bombardment with energetic particles or radiation
• CPC Class Codes: C23C 14/025 Metallic sublayers
• CPC Class Codes: C23C 14/0682 Silicides
• CPC Class Codes: C23C 14/5806 Thermal treatment
• CPC Class Codes: C23C 14/5846 Reactive treatment
• CPC Class Codes: C23C 14/5873 Removal of material
• CPC Class Codes: G01L 19/0061 Electrical connection means
• CPC Class Codes: G01L 19/0609 Pressure pulsation damping arrangements
• CPC Class Codes: G01L 19/147 Details about the mounting of the sensor to support or covering means
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: H01L 2224/48472 the other connecting portion not on the bonding area also being a wedge bond, i.e. wedge-to-wedge

Abstract

A harsh environment transducer including a substrate having a first surface and a second surface, wherein the second surface is in communication with the environment. The transducer includes a device layer sensor means located on the substrate for measuring a parameter associated with the environment. The sensor means including a single crystal semiconductor material having a thickness of less than about 0.5 microns. The transducer further includes an output contact located on the substrate and in electrical communication with the sensor means. The transducer includes a package having an internal package space and a port for communication with the environment. The package receives the substrate in the internal package space such that the first surface of the substrate is substantially isolated from the environment and the second surface of the substrate is substantially exposed to the environment through the port. The transducer further includes a connecting component coupled to the package and a wire electrically connecting the connecting component and the output contact such that an output of the sensor means can be communicated. An external surface of the wire is substantially platinum, and an external surface of at least one of the output contact and the connecting component is substantially platinum.

Claims

1. A harsh environment transducer comprising:

a substrate having a first surface and a second surface, wherein said second surface is in communication with the environment;

a device layer sensor means located on said substrate for measuring a parameter associated with the environment, said sensor means including a single crystal semiconductor material having a thickness of less than about 0.5 microns;

an output contact located on said substrate and in electrical communication with said sensor means;

a package having an internal package space and a port for communication with the environment, said package receiving said substrate in said internal package space such that said first surface of said substrate is substantially isolated from the environment and said second surface of said substrate is substantially exposed to the environment through said port;

a connecting component coupled to said package; and

a wire electrically connecting said connecting component and said output contact such that an output of said sensor means can be communicated, wherein an external surface of said wire is substantially platinum, and wherein an external surface of at least one of said output contact and said connecting component is substantially platinum.

2. The transducer of claim 1 wherein said external surfaces of both said output contact and said connecting component are substantially platinum.

3. The transducer of claim 1 wherein said substrate includes a generally flexible diaphragm configured to flex when exposed to a differential pressure thereacross, wherein said sensor means includes a sensing element at least partially located on said diaphragm whereby flexure of said diaphragm induces a change in an electrical property of said sensing element.

4. The transducer of claim 3 wherein said sensing element has a thickness of less than about 0.5 microns.

5. The transducer of claim 4 wherein said sensing element includes p-doped single crystal silicon.

6. The transducer of claim 5 wherein said sensing element includes piezoresistive materials arranged in a Wheatstone bridge.

7. The sensor of claim 3 wherein said diaphragm has a thickness of between about 3 and about 200 microns.

8. The transducer of claim 1 wherein said connecting component is a pin that sealingly extends through said package.

9. The transducer of claim 1 wherein said connecting component is solid platinum, or platinum-coated nickel.

10. The transducer of claim 1 wherein said package includes an internal header, and wherein said connecting component is coupled to said header.

11. The transducer of claim 10 wherein said substrate is coupled to said header at an attachment joint, and wherein said transducer is configured such that when said environment includes a fluid whose pressure is to be measured, said fluid exerts a force that causes said attachment joint to be placed in compression.

12. The transducer of claim 1 further comprising a bond securing said substrate to said package, said bond being formed by a high temperature brazing preform metal that has a liquidus temperature of between about 650°

C. and about 750°

C., and has stable mechanical properties at about 500°

C.

13. The transducer of claim 1 further comprising a bond securing said substrate to said package, wherein said bond is formed by a high temperature brazing preform material comprised of indium-copper-gold, or gold-germanium, or glass frit.

14. The transducer of claim 1 further including a thermal oxide layer covering said sensor means.

15. The transducer of claim 1 further including a cap coupled to said first surface of said substrate and generally sealingly covering at least part of said sensor means, and wherein said cap does not cover said output contact.

16. The transducer of claim 1 wherein said wire is wire bonded to said output contact and to said connecting component.

17. The transducer of claim 1 wherein said package is formed from a material having a coefficient of thermal expansion is a given direction that is within about 150% of a coefficient of thermal expansion of said substrate is said direction such that said package and said substrate are thermally compatible.

18. The transducer of claim 1 wherein said package further includes a header having a first and a second opposed face, and a hole formed therein or therethrough, and wherein said connecting component is held within said hole.

19. The transducer of claim 18 wherein said connecting component is held within said hole by a material selected from a group consisting of a high temperature brazing preform material, a hypoeutectic alloy or glass frit.

20. The transducer of claim 1 wherein said output contact includes a metallization layer, and wherein a first end of said wire is wire bonded to said metallization layer.

21. The transducer of claim 20 wherein said metallization layer includes an adhesion layer including a material selected from the group consisting of tantalum, chromium, zirconium, and hafnium, a first diffusion blocking layer of a compound selected from the group consisting of tantalum silicide, tantalum carbide, tantalum nitride and tungsten nitride, and a second diffusion blocking layer of platinum silicide.

22. The transducer of claim 20 wherein said metallization layer initially includes the following layers deposited on said substrate in succession:

a tantalum layer, a tantalum-silicide layer or a tantalum-nitride layer, and a platinum layer.

23. The transducer of claim 22 wherein said platinum layer is initially deposited to a sufficient thickness such that after annealing said metallization layer and outer surface of said metallization layer is substantially platinum.

24. The transducer of claim 1 wherein said substrate is coupled to said package such that said substrate divides said internal package space into a first internal package space that is in communication with said environment and a second internal package space is substantially sealed from the environment.

25. The transducer of claim 1 wherein said transducer can withstand, and continue functioning when exposed to, a temperature of 500 degrees Celsius.

26. The transducer of claim 1 wherein said transducer can withstand, and continue functioning when exposed to, a pressure of 600 psig.

27. A pressure sensor for use in a harsh environment comprising:

a substrate including a generally flexible diaphragm configured to flex when exposed to a differential pressure thereacross;

a sensing element at least partially located on said diaphragm whereby flexure of said diaphragm induces a change in an electrical property of said sensing element;

a package defining an internal space and receiving said substrate in said internal space such that pressure fluctuations in the environment manifest as said differential pressure; and

,

a bond between said package and said substrate formed by melting a high temperature braze material or a glass frit material.

28. The pressure sensor of claim 27 wherein said bond has a liquidus temperature of between about 650°

C. and about 750°

C., and has stable mechanical properties at about 400°

C.

29. The pressure sensor of claim 27 wherein said bond is formed by a high temperature brazing preform material comprised of indium-copper-gold, or gold-germanium, or glass frit.

30. The pressure sensor of claim 29 wherein said high temperature brazing preform material contains about 15% indium by weight.

31. The pressure sensor of claim 27 wherein said bond has stable mechanical properties at about 550°

C.

32. A pressure sensor for use in a harsh environment comprising:

a generally flexible non-metallic diaphragm configured to flex when exposed to a sufficient differential pressure thereacross; and

a semiconductive single crystal piezoelectric or piezoresistive sensing element at least partially located on said diaphragm such that said sensing element provides an electrical signal upon flexure of said diaphragm, wherein said sensor can withstand, and continue functioning when exposed to, a pressure of 600 psig and a temperature of 450°

C.

33. The sensor of claim 32 wherein said diaphragm includes a single crystal semiconductor material and has a thickness of less than about 0.5 microns.

34. The sensor of claim 32 wherein said sensor can withstand, and continue functioning when directly exposed to, combustion byproducts of an aircraft engine or turbine.

35. The sensor of claim 32 wherein said diaphragm and said sensing element are both located on, and form part of, a sensor die, and wherein said sensor die further includes an output contact located on said substrate and in electrical communication with said sensing element.

36. The sensor of claim 35 wherein said sensor die is coupled to a header and said sensor further includes a pin directly coupled to said header, and wherein said sensor further includes a wire electrically coupled to said output contact and to said pin, and wherein at least an external surface of both of said output contact and said wire is substantially platinum.

37. The sensor of claim 36 wherein said pin is directly coupled to said header by a ceramic or a ceramic glass or glass frit material.

38. The sensor of claim 35 wherein said sensor die is coupled to a header at an attachment joint, and wherein said sensor is configured such that when said sensor is exposed to a fluid whose pressure is to be measured, said fluid exerts a force that causes said attachment joint to be placed in compression.

39. The sensor of claim 35 wherein said sensor die is coupled to a header at an attachment joint, and wherein said attachment joint is made of an InCuAg brazing material, or a eutectic bonding materials, or a glass transfer tape.

40. The sensor of claim 35 wherein said sensor can withstand, and continue function when exposed to, a pressure of 4000 psig.

41. A method for forming a transducer comprising the steps of:

providing a semiconductor-on-insulator wafer including first and second semiconductor layers separated by an electrically insulating layer, wherein said first layer is formed or provided by hydrogen ion delamination of a starting wafer;

doping said first layer to form a piezoresistive film;

etching said piezoresistive film to form at least one piezoresistor;

depositing or growing a metallization layer on said semiconductor-on-insulator wafer, said metallization layer including an electrical connection portion that is located on or is electrically coupled to said piezoresistor;

removing at least part of said second semiconductor layer to form a diaphragm, with said at least part of said piezoresistor being located on said diaphragm; and

joining said wafer to a package by melting a high temperature braze material or a glass frit material.

42. A pressure sensor for use in a harsh environment comprising:

a substrate in communication with the environment, said substrate including a generally flexible diaphragm configured to flex when exposed to a sufficient differential pressure thereacross;

a sensing element at least partially located on said diaphragm such that said sensing element provides an electrical signal upon flexure of said diaphragm;

a cap configured to generally sealingly mate with said substrate and substantially cover said sensing element; and

a bond formed between said cap and said substrate by aligning said cap with said substrate and heating said cap and said substrate to a first temperature, whereby said bond that is formed after heating said cap and said substrate to said first temperature is stable at a second temperature, where said second temperature is greater than said first temperature.