Integrated released beam, thermo-mechanical sensor for sensing temperature variations and associated methods

• US 5,917,226 A
• Filed: 10/24/1997
• Issued: 06/29/1999
• Est. Priority Date: 10/24/1997
• Status: Expired due to Term

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Chan, Tsiu Chiu, DeSilva, Melvin Joseph
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): Wille, Douglas A.
• Application Number:
  US08/957,802
• Time in Patent Office: 613 Days
• Field of Search: 257/415, 257/467, 374/187, 374/188, 374/193, 374/194, 374/195
• US Class Current: 257/415
• CPC Class Codes: G01K 5/486 using microstructures, e.g. made of silicon G01K7/015, G01K7/028, G01K7/226, G01K17/006 take precedence
• CPC Class Codes: H01H 2037/008 Micromechanical switches operated thermally

Abstract

An integrated circuit and method are provided for sensing activity such as temperature variations in a surrounding environment. The integrated released beam sensor preferably includes a switch detecting circuit region and a sensor switching region connected to the switch detecting circuit region. The sensor switching region preferably includes a fixed contact layer, a sacrificial layer on the fixed contact layer, and a floating contact on the sacrificial layer and having portions thereof overlying the fixed contact layer in spaced relation therefrom in an open switch position and extending lengthwise generally transverse to a predetermined direction. The floating contact preferably includes at least two layers of material. Each of the at least two layers have a different thermal expansion coefficient so that the floating contact displaces in the predetermined direction responsive to a predetermined temperature variation so as to contact the fixed contact layer and thereby form a closed switch position. The methods of forming an integrated sensor advantageously are preferably compatible with known integrated circuit manufacturing processes, such as for CMOS circuit manufacturing, with only slight variations therefrom.

Claims

1. An integrated cantilever sensor for sensing temperature variations in a surrounding environment, the integrated sensor comprising:

a CMOS switch detecting circuit region; and

a sensor switching region connected to and positioned adjacent said CMOS switch detecting circuit region, said sensor switching region including;

an insulating support layer,

a fixed contact layer positioned on said support layer,

remaining portions of a sacrificial layer positioned on portions of said fixed contact layer, and

a floating contact layer positioned on said remaining portions of the sacrificial layer, overlying said fixed contact layer in spaced relation therefrom in an open switch position, and extending lengthwise generally transverse to a predetermined direction for defining a released cantilever beam, the spaced relation being formed by removal of unwanted portions of the sacrificial layer, said released cantilever beam having at least two layers of material, each of the at least two layers of material having a different thermal expansion coefficient so that said released cantilever beam displaces in the predetermined direction responsive to a predetermined temperature variation so as to contact said fixed contact layer and thereby form a closed switch position, and wherein said CMOS switch detecting circuit region generates a signal responsive to contact of said released cantilever beam with said fixed contact layer.

2. An integrated sensor as defined in claim 1, wherein said fixed contact layer comprises at least one of polysilicon and a metal.

3. An integrated sensor as defined in claim 1, wherein the at least two layers of said released cantilever beam comprises polysilicon and a metal, respectively.

4. An integrated sensor as defined in claim 1, wherein each of the at least two layers of said release beam comprises at least one of the following:

polysilicon, silicon, tungsten, tungsten silicide, aluminum, titanium, titanium nitride, tantalum silicide, and tantalum nitride.

5. An integrated sensor as defined in claim 1, wherein said released cantilever beam extends outwardly from the CMOS switch detecting circuit region a predetermined length and extends outwardly beyond said sacrificial layer.

6. An integrated sensor as defined in claim 5, further comprising temperature calibrating means associated with said released cantilever beam for providing a calibrated temperature sensed by the integrated sensor.

7. An integrated sensor as defined in claim 6, wherein said temperature calibrating means includes a predetermined length of said released cantilever so as to substantially correspond to a selected temperature calibration threshold.

8. An integrated sensor as defined in claim 7, wherein the selected temperature calibration threshold is established by a portion of said fixed contact layer substantially corresponding to a region of contact of said released cantilever beam with said fixed contact layer.

9. An integrated sensor as defined in claim 6, wherein said temperature calibrating means includes providing predetermined amounts of material provided in each of the at least two layers of said released cantilever beam so that said released cantilever beam displaces to a position in contact with said fixed contact layer responsive to a calibrated predetermined temperature variation.

10. An integrated sensor as defined in claim 5, wherein the predetermined length of the outward extent of said released cantilever beam comprises a first predetermined length, wherein said fixed contact layer extends outwardly from said CMOS switch detecting circuit region a second predetermined length, and wherein the second predetermined length is greater than the first predetermined length.

11. An integrated sensor as defined in claim 1, wherein said insulating support layer comprises a nitride layer formed on a field oxide.

12. An integrated sensor as defined in claim 1, wherein said sacrificial layer comprises an oxide layer, wherein said sacrificial layer includes at least one concave surface underlying said released cantilever beam.

13. An integrated cantilever sensor for sensing temperature variations in a surrounding environment, the integrated sensor comprising:

a switch detecting circuit region; and

a sensor switching region connected to and positioned adjacent said switch detecting circuit region, said sensor switching region including;

a fixed contact layer,

remaining portions of a sacrificial layer positioned on portions of said fixed contact layer, and

a floating contact layer on said remaining portions of the sacrificial layer and having portions thereof overlying said fixed contact layer in spaced relation therefrom in an open switch position and extending lengthwise generally transverse to the predetermined direction for defining a released cantilever beam, the spaced relation being formed by removal of unwanted portions of the sacrificial layer, said released cantilever beam having at least two layers of material, each of the at least two layers of material having a different thermal expansion coefficient so that said released cantilever beam displaces in the predetermined direction responsive to a temperature variation so as to contact said fixed contact layer and thereby form a closed switch position.

14. An integrated sensor as defined in claim 13, wherein said fixed contact layer comprises at least one of polysilicon and a metal.

15. An integrated sensor as defined in claim 14, wherein the at least two layers of said cantilever beam comprises polysilicon and a metal, respectively.

16. An integrated sensor as defined in claim 13, wherein each of the at least two layers of said release beam comprises at least one of the following:

polysilicon, silicon, tungsten, tungsten silicide, aluminum, titanium, titanium nitride, tantalum, tantalum silicide, and tantalum nitride.

17. An integrated sensor as defined in claim 13, wherein said released cantilever beam extends outwardly from the switch detecting circuit region a predetermined length, and wherein said released cantilever beam has a generally uniform thickness extending substantially the entire length thereof.

18. An integrated sensor as defined in claim 14, further comprising temperature calibrating means associated with said released cantilever beam for providing a predetermined calibrated temperature sensed by the integrated sensor.

19. An integrated sensor as defined in claim 18, wherein said temperature calibrating means includes a predetermined length of said released cantilever so as to substantially correspond to a selected temperature calibration threshold.

20. An integrated sensor as defined in claim 19, wherein the selected temperature calibration threshold is established by a portion of said fixed contact layer substantially corresponding to a region of the contact of said released cantilever beam with said fixed contact layer.

21. An integrated sensor as defined in claim 18, wherein said temperature calibrating means includes predetermined amounts of material provided in each of the at least two layers of said released cantilever beam so that said released cantilever beam displaces to a position in contact with said fixed contact layer responsive to a calibrated predetermined temperature variation.

22. An integrated sensor as defined in claim 18, wherein the predetermined length of the outward extent of said released cantilever beam comprises a first predetermined length, wherein said fixed contact layer extends outwardly from said switch detecting circuit region a second predetermined length, and wherein the second predetermined length is greater than the first predetermined length.

23. An integrated sensor as defined in claim 22, wherein said sensor switching region further comprises an insulating support plate underlying said fixed contact layer, said insulating support plate comprising a nitride layer formed on a field oxide.

24. An integrated sensor as defined in claim 23, wherein said sacrificial layer comprises an oxide layer, and wherein said sacrificial layer includes at least one concave surface underlying said released cantilever beam.

25. An integrated sensor for sensing temperature variations in a surrounding environment, the integrated sensor comprising:

a switch detecting circuit region; and

a sensor switching region connected to and positioned adjacent said switch detecting circuit region, said sensor switching region including;

a fixed contact layer, and

a floating contact having portions thereof directly overlying said fixed contact layer in spaced relation therefrom in an open switch position and extending lengthwise generally transverse to the predetermined direction, said floating contact having at least two layers of material, each of the at least two layers of material having a different thermal expansion coefficient so that said floating contact displaces in the predetermined direction responsive to a predetermined temperature variation so as to contact said fixed contact layer and thereby form a closed switch position.

26. An integrated sensor as defined in claim 25, wherein said fixed contact layer comprises at least one of polysilicon and a metal.

27. An integrated sensor as defined in claim 26, wherein said floating contact comprises a released cantilever beam.

28. An integrated sensor as defined in claim 27, wherein the at least two layers of said released beam comprises at least one of polysilicon and a metal, respectively.

29. An integrated sensor as defined in claim 27, wherein each of the at least two layers of said release beam comprises at least one of the following:

silicon, tungsten, aluminum, titanium, tantalum, and nitride.

30. An integrated sensor as defined in claim 25, wherein said floating contact comprises a released beam overlying said fixed contact layer in a double support configuration.

31. An integrated sensor as defined in claim 30, wherein the at least two layers of said released beam comprises polysilicon and a metal, respectively.

32. An integrated sensor as defined in claim 30, wherein each of the at least two layers of said release beam comprises at least one of the following:

polysilicon, silicon, tungsten, tungsten silicide, aluminum, titanium, titanium nitride, tantalum silicide, and tantalum nitride.

33. An integrated sensor as defined in claim 27, wherein said floating contact extends outwardly from the switch detecting circuit region a predetermined length.

34. An integrated sensor as defined in claim 25, further comprising temperature calibrating means associated with said floating contact for providing a calibrated predetermined temperature sensed by the integrated sensor.

35. An integrated sensor as defined in claim 34, wherein said temperature calibrating means includes a predetermined length of said floating contact so as to substantially correspond to a selected temperature calibration threshold.

36. An integrated sensor as defined in claim 35, wherein the selected temperature calibration threshold is established by a portion of said fixed contact layer substantially corresponding to a region of contact of said floating contact with said fixed contact layer.

37. An integrated sensor as defined in claim 34, wherein said temperature calibrating means includes predetermined amounts of material provided in each of the at least two layers of said released cantilever beam so that said released cantilever beam displaces to a position in contact with said fixed contact layer responsive to a calibrated predetermined temperature variation.

38. An integrated sensor as defined in claim 27, wherein the predetermined length of the outward extent of said floating contact comprises a first predetermined length, wherein said fixed contact layer extends outwardly from said switch detecting circuit region a second predetermined length, and wherein the second predetermined length is greater than the first predetermined length.

39. An integrated sensor as defined in claim 25, wherein said sensor switching region further comprises an insulating support plate underlying said fixed contact layer.

40. An integrated sensor as defined in claim 25, wherein said sensor switching region further comprises a sacrificial layer positioned between said fixed contact layer and said floating contact, and wherein said sacrificial layer includes at least one concave surface underlying said floating contact.