Flexible silicon strain gage

• US 20020179985A1
• Filed: 07/09/2002
• Published: 12/05/2002
• Est. Priority Date: 07/28/1998
• Status: Abandoned Application

• Current Assignee: Bradley J. Boggs, Christopher A. Bang, Kevin C. Stark, Marcus S. Just
• Original Assignee: Bradley J. Boggs, Christopher A. Bang, Kevin C. Stark, Marcus S. Just
• Inventors: Bang, Christopher A., Just, Marcus S., Boggs, Bradley J., Stark, Kevin C.
• Application Number:
  US10/191,176
• Publication Number:
  US 20020179985A1
• Time in Patent Office: Days
• US Class Current: 257/417
• 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 1/2293 of the semi-conductor type semi-conductor devices controllable by variations of applied mechanical force H01L29/84
• CPC Class Codes: G01L 9/0055 bonded on a diaphragm

Abstract

A generally flexible strain gage comprising a strain sensing element, and a generally flexible substrate supporting the strain sensing element. The strain sensing element is made of single crystal or polycrystalline semiconducting material. The invention also includes a method for forming a generally flexible strain gage comprising the step of selecting a wafer having a portion of a base material and portion of a single crystal or polycrystalline semiconducting material located thereon. The method further comprises the steps of etching a strain sensing element out of the semiconducting material and forming a generally flexible substrate onto said sensing element.

Claims

1. A generally flexible strain gage comprising:

a semiconducting strain sensing element having a single crystal or polycrystalline structure; and

a generally flexible substrate supporting said strain sensing element.

2. The strain gage of claim 1 wherein said strain sensing element is generally flexible.

3. The strain gage of claim 1 wherein said strain sensing element has a thickness of less than about 15 microns.

4. The strain gage of claim 1 wherein said strain sensing element is silicon.

5. The strain gage of claim 1 wherein said strain sensing element is doped silicon.

6. The strain gage of claim 1 wherein said strain sensing element has a resistance between about 100 ohms and about 10,000 ohms.

7. The strain gage of claim 1 wherein said strain sensing element has a sheet resistance between about 10 ohm/square and about 1,000 ohm/square.

8. The strain gage of claim 1 wherein said substrate is a polymer.

9. The strain gage of claim 1 wherein said substrate is polyimide.

10. The strain gage of claim 1 further comprising a first output pad electrically connected to a first end of said strain sensing element.

11. The strain gage of claim 10 wherein said first output pad is located on said substrate.

12. The strain gage of claim 11 further comprising a second output pad electrically connected to a second end of said strain sensing element.

13. The strain gage of claim 12 further comprising a first lead electrically connecting said first output pad to said strain sensing element and a second lead electrically connecting said second output pad to said strain sensing element.

14. The strain gage of claim 13 further comprising an oxide layer covering said leads, said substrate and said strain sensing element.

15. The strain gage of claim 14 wherein said pads and said leads are aluminum.

16. The strain gage of claim 1 further comprising an electronic component electrically connected to said strain sensing element, said electronic component being carried on said substrate.

18. The method of claim 17 wherein said substrate is generally flexible.

19. The method of claim 18 wherein said generally flexible substrate is polyimide, and wherein said generally flexible substrate is spun onto said wafer.

20. The method of claim 17 wherein said sensor is generally flexible.

21. The method of claim 17 further comprising the step of removing said base material after forming said substrate.

22. The method of claim 21 wherein said removing step includes removing said base material using deep reactive ion etching.

23. The method of claim 17 wherein said sensor material is a semiconducting material.

24. The method of claim 17 wherein said sensor material is a single crystal semiconductor.

25. The method of claim 17 wherein the step of forming said sensor comprises etching said sensor material.

26. The method of claim 17 wherein said sensor is a strain sensing element.

27. The method of claim 17 wherein said wafer includes an oxide layer between said base material and said sensor material.

28. The method of claim 17 further comprising the steps of fabricating microelectronic circuitry in said wafer, and electrically connecting said electronic component to said sensor.

29. The method of claim 28 wherein said electrically connecting step includes depositing metal on said wafer such that said deposited metal electrically connects said electronic component and said sensor.

17. A method for forming a sensor on a substrate, the method comprising the steps of:

selecting a wafer having a portion of base material and a portion of sensor material;

forming said sensor out of said sensor material; and

forming said substrate over said sensor.

30. A method for forming a generally flexible strain gage comprising the steps of:

selecting a wafer having a portion of a base material and portion of a single crystal semiconducting material or polycrystalline semiconducting material located thereon;

etching a strain sensing element out of said semiconducting material; and

forming a generally flexible substrate onto said sensing element.

31. The method of claim 30 wherein said strain sensing element is silicon.

32. The method claim 30 further comprising the step of etching away said base material after said forming step.

33. The method of claim 32 wherein said base material is etched away using deep reactive ion etching.

34. The method of claim 32 wherein said wafer includes an oxide layer between said base material and said semiconducting material, and wherein the method further includes the step of removing said oxide layer until said strain sensing element is exposed.

35. The method of claim 30 wherein said wafer includes an oxide layer between said base material and said semiconducting material.

36. The method of claim 30 further comprising the step of electrically connecting a first output pad to said sensing element after said etching step.

37. The method of claim 36 further comprising the step of doping a portion of said strain sensing element, and wherein said output pad is connected to said sensing element at said doped portion.

38. The method of claim 36 wherein said output pad is formed by metal sputtering, and wherein said output pad is connected to said sensing element by a metal lead.

39. The method of claim 36 wherein said wafer includes an oxide layer between said base material and said semiconducting material, and wherein the method further comprises the step of partially etching a portion of said oxide layer before forming said output pad, and wherein said output pad is formed in said partially etched portion of said oxide layer.

40. The method of claim 30 further comprising the steps of fabricating microelectronic circuitry in said wafer, and electrically connecting said microelectronic circuitry to said strain sensing element.

41. A method for forming a generally flexible strain gage comprising the steps of:

selecting a generally flexible substrate; and

mounting a generally flexible semiconducting strain sensing element on said substrate, said strain sensing element having a single crystal or polycrystalline structure.

42. The method of claim 41 further comprising the step of electrically connecting a first output pad to said strain sensing element.

43. A method for forming a sensor array comprising the steps of:

selecting a wafer having a portion of base material and a portion of sensor material;

forming a plurality of sensors out of said sensor material; and

forming said substrate over said plurality of sensors.

44. The method of claim 43 wherein each sensor has an output lead, and wherein said output leads terminate in a common area.

45. The method of claim 43 wherein each sensor has an output lead, and wherein said output leads are connected to an electronic component carried on said substrate.

46. The method of claim 43 further comprising the steps of fabricating microelectronic circuitry in said wafer before forming said sensors, and electrically connecting said component to at least one of said sensors.

48. The generally flexible sensor array of claim 47 wherein said sensors are strain gages.

49. The generally flexible sensor array of claim 48 wherein at least one of said strain gages has a single crystal silicon sensing element.

50. The generally flexible sensor array of claim 47 wherein said substrate is polyimide.

51. The generally flexible sensor array of claim 47 wherein each sensor provides an output, and wherein said sensor array further includes electronic components on said substrate for receiving said output.

47. A generally flexible sensor array for use with a specimen, the array comprising a plurality of sensors mounted on a generally flexible substrate, and wherein said substrate is shaped so as to fit around said specimen such that said sensors are located on desired locations of said specimen.