Micro-machined pressure sensor with polymer diaphragm

• US 7,401,525 B2
• Filed: 03/23/2005
• Issued: 07/22/2008
• Est. Priority Date: 03/23/2005
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Cobianu, Cornel P., Serban, Bogdan Catalin, Gologanu, Mihai, Pavelescu, Ioan
• Primary Examiner(s): Lefkowitz; Edward
• Assistant Examiner(s): Jenkins; Jermaine
• Application Number:
  US10/907,176
• Publication Number:
  US 20060213275A1
• Time in Patent Office: 1,217 Days
• Field of Search: 73700-756, 438/47, 438/50, 438/51, 438/53, 438/99, 438/510, 438/514, 438/527, 438/528, 257/40, 257/414, 257/417
• US Class Current: 73/754
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01L 1/2287 constructional details of the strain gauges adjustable resistors H01C10/00
• CPC Class Codes: G01L 9/0052 of piezoresistive elements circuits therefor G01L9/06

Abstract

A piezoresistive pressure and/or strain sensor micro-machined primarily from plastic and/or glass. In one illustrative embodiment, the piezoresistive pressure sensor is formed on a polymer substrate. A first selectively implanted region is provided in the polymer substrate to create a piezoresistive region in the polymer substrate. A second selectively implanted region is then provided in at least part of the first selectively implanted region to modulate the electrical conductivity of the first selectively implanted region. The illustrative sensor may be selectively implanted with, for example, nitrogen to create the piezoresistive region, and boron to modulate the electrical conductivity of the piezoresistive region. Phosphorus or any other suitable material may also be used to modulate the electrical conductivity of the piezoresistive region, as desired. The piezoresistive pressure/strain sensor may be formed from a single substrate, or two or more substrates, and the resulting pressure/strain sensor may be mounted in a plastic package, if desired.

Claims

1. A piezoresistive pressure sensor comprising:

a polymer substrate;

a first implanted region of the polymer substrate having first ion implants therein, wherein the first ion implants impart piezoresistivity to the first implanted region; and

a second implanted region in the polymer substrate that includes, at least in part, the first implanted region, the second implanted region having second ion implants, wherein the second ion implants modulate the electrical conductivity of at least part of the first implanted region.

2. The piezoresistive pressure sensor of claim 1 wherein the first ion implants include nitrogen.

3. The piezoresistive pressure sensor of claim 2 wherein the second ion implants include boron.

4. The piezoresistive pressure sensor of claim 2 wherein the second ion implants include phosphorus.

5. The piezoresistive pressure sensor of claim 1 wherein the polymer substrate is a plastic.

6. The piezoresistive pressure sensor of claim 5 wherein the plastic is Kapton.

7. The piezoresistive pressure sensor of claim 5 wherein the plastic is a liquid crystal polymer.

8. The piezoresistive pressure sensor of claim 1 wherein the polymer substrate includes a front side and a back side, wherein the first and second implanted regions are on the front side of the polymer substrate.

9. The piezoresistive pressure sensor of claim 8 further comprising a cavity extending in from the back side of the polymer substrate adjacent a pressure sensor diaphragm.

10. The piezoresistive pressure sensor of claim 1 including one or more metal layers extending from the second implanted region.

11. The piezoresistive pressure sensor of claim 1 wherein at least one of the metal layers is deposited using a mask-less ink-jet printing process.

12. The piezoresistive pressure sensor of claim 1 wherein the polymer substrate is mounted to a plastic package base.

13. The piezoresistive pressure sensor of claim 1 wherein the polymer substrate includes a diaphragm region, and the second implanted region is located on at least part of the diaphragm region.

14. The piezoresistive pressure sensor of claim 13 further comprising a second substrate situated adjacent to the first substrate, wherein the second substrate includes a hole that is in registration with the diaphragm region.

15. The piezoresistive pressure sensor of claim 14 wherein the second substrate is a plastic.

16. The piezoresistive pressure sensor of claim 14 wherein the second substrate is a glass.

17. A piezoresistive pressure sensor comprising:

a polymer substrate;

a polymer layer secured relative to the polymer substrate;

a first implanted region in the polymer layer having first ion implants therein, wherein the first ion implants impart piezoresistivity to the first implanted region; and

a second implanted region in the polymer layer that includes, at least in part, the first implanted region, the second implanted region having second ion implants, wherein the second ion implants modulate the electrical conductivity of at least part of the first implanted region.

18. The piezoresistive pressure sensor of claim 17 wherein the first ion implants include nitrogen.

19. The piezoresistive pressure sensor of claim 18 wherein the second ion implants include boron.

20. The piezoresistive pressure sensor of claim 18 wherein the second ion implants include phosphorus.

21. The piezoresistive pressure sensor of claim 17 wherein the polymer substrate is a plastic.

22. The piezoresistive pressure sensor of claim 21 wherein the plastic is Kapton.

23. The piezoresistive pressure sensor of claim 21 wherein the plastic is a liquid crystal polymer.

24. The piezoresistive pressure sensor of claim 17 wherein the polymer layer is a poly styrene co-acrylonitrile 80/20 (SAN).

25. The piezoresistive pressure sensor of claim 17 wherein the polymer layer is secured to the polymer substrate via an adhesive.

26. The piezoresistive pressure sensor of claim 25 wherein the adhesive is a cyanoacrylate monomer (n-butyl cyanoacrylat), a plasticizer (dibutyl phatalate) 30% w/w, and a calixarene (4-tert-butyl-calix arene-O, O′

, O″

, O′

″

, tetraacetic acid tetraethyl ester.

27. A piezoresistive pressure sensor comprising:

a polymer substrate having a pressure sensing diaphragm region; and

a piezoresistive region extending in the diaphragm region, wherein the piezoresistive region includes first and second ion implants therein, wherein the first ion implants impart piezoresistivity to the piezoresistive region and the second ion implants effect the electrical conductivity of the piezoresistive region.

28. The piezoresistive pressure sensor of claim 27 wherein the polymer substrate is Kapton.

29. The piezoresistive pressure sensor of claim 27 wherein the polymer substrate is a liquid crystal polymer.

30. The piezoresistive pressure sensor of claim 27 wherein the first ion implants include nitrogen implants and the second ion implants include boron implants.

31. The piezoresistive pressure sensor of claim 27 wherein the first ion implants include nitrogen implants and the second ion implants include phosphorus implants.

32. A method of fabricating a piezoresistive pressure sensor having a polymer diaphragm, the method comprising the steps of:

selectively implanting a first ion implant in the polymer diaphragm to create a piezoresistive region; and

selectively implanting a second ion implant in at least a portion of the piezoresistive region to modulate the electrical conductivity of the piezoresistive region.

33. The method of claim 32 wherein the selectively implanted first ion implant and the selectively implanted second ion implant are implanted into the polymer diaphragm via ion implantation.

34. The method of claim 32 further comprising a polymer layer deposited on the polymer diaphragm, and the selectively implanted first ion implant and the selectively implanted second ion implant are implanted into the polymer layer via ion implantation.

35. The method of claim 34 wherein the polymer layer is a SAN layer.

36. The method of claim 32 wherein the first ion implant includes nitrogen, and the second ion implant includes boron.

37. The method of claim 32 wherein the first ion implant includes nitrogen, and the second ion implant includes phosphorous.

38. A piezoresistive pressure sensor comprising:

a polymer sensor having a piezoresistive region, the piezoresistive region including first ion implants therein, wherein the first ion implants impart piezoresistivity to the piezoresistive region, the piezoresistive region further having second ion implants therein, wherein the second ion implants modulate the electrical conductivity of at least part of the piezoresistive region; and

a polymer package substrate, wherein the polymer sensor is secured to the polymer package substrate via an adhesive.

39. The piezoresistive pressure sensor of claim 38 wherein the adhesive includes calixarene.

40. The piezoresistive pressure sensor of claim 38 wherein the first ion implants and the second ion implants are provided by ion implantation.