Integrated sensor having plurality of released beams for sensing acceleration

• US 6,058,778 A
• Filed: 10/24/1997
• Issued: 05/09/2000
• 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): CHAPMAN JR, JOHN E
• Application Number:
  US08/957,809
• Time in Patent Office: 928 Days
• Field of Search: 73/514.01, 73/514.16, 73/514.35, 73/514.36, 73/514.38, 73/510, 73/651, 200/61.48, 200/61.51, 257/415, 257/417
• US Class Current: 73/514.16
• CPC Class Codes: B81B 2201/014 having a cantilever fixed on one side connected to one or more dimples
• CPC Class Codes: B81C 1/00246 Monolithic integration, i.e. micromechanical structure and electronic processing unit are integrated on the same substrate
• CPC Class Codes: B81C 2203/0735 Post-CMOS, i.e. forming the micromechanical structure after the CMOS circuit
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/135 by making use of contacts which are actuated by a movable inertial mass
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

An integrated circuit and method are provided for sensing activity such as acceleration in a predetermined direction of movement. The integrated released beam sensor preferably includes a switch detecting circuit region and a sensor switching region connected to and positioned adjacent the switch detecting circuit region. The sensor switching region preferably includes a plurality of floating contacts positioned adjacent and lengthwise extending outwardly from said switch detecting circuit region for defining a plurality of released beams so that each of said plurality of released beams displaces in a predetermined direction responsive to acceleration. The plurality of released beams preferably includes at least two released beams lengthwise extending outwardly from the switch detecting circuit region to different predetermined lengths and at least two released beams lengthwise extending outwardly from the switch detecting circuit region to substantially the same predetermined lengths. The methods of forming an integrated sensor advantageously are preferably compatible with know integrated circuit manufacturing processes, such as for CMOS circuit manufacturing, with only slight variations therefrom.

Claims

1. An 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 plurality of floating contacts positioned adjacent and lengthwise extending outwardly from said switch detecting circuit region for defining a plurality of released beams so that each of said plurality of released beams displaces in a predetermined direction responsive to acceleration, said plurality of released beams including at least two released beams lengthwise extending outwardly from said switch detecting circuit region to different predetermined lengths and at least two released beams lengthwise extending outwardly from said switch detecting circuit region to substantially the same predetermined lengths, each of said plurality of released beams comprising a integrally monolithic material having a generally uniform thickness extending substantially the entire length thereof,

at least one fixed contact layer underlying said plurality of released beams, and

remaining portions of at least one sacrificial layer positioned between said at least one fixed contact layer and each of said plurality of released beams, each of said plurality of released beams being positioned in spaced relation from said at least one fixed contact layer in a normally open position, the spaced relation forming by removal of unwanted portions of the sacrificial layer, and each of said plurality of released beams contacting said at least one fixed contact layer responsive to acceleration in a predetermined direction to form a closed switch position.

2. An integrated sensor as defined in claim 1, wherein said switch detecting circuit region generates a signal responsive to the contact of said at least one of said plurality of released beams with said at least one fixed contact layer.

3. An integrated sensor as defined in claim 2, wherein said sensor switching region further comprises at least one insulating support plate underlying said at least one fixed contact layer.

4. An integrated sensor as defined in claim 3, wherein said remaining portions of the at least one sacrificial layer includes at least one concave surface underlying each of said plurality of released beams.

5. An integrated sensor as defined in claim 4, wherein said at least one fixed contact layer comprises polysilicon or a metal.

6. An integrated sensor as defined in claim 1, wherein said sensor switching region further comprises a plurality of fixed contact layers each underlying a corresponding one of said plurality of released beams, and wherein each of said plurality of released beams contacts the corresponding respective one of said plurality of fixed contact layers responsive to acceleration in a predetermined direction so as to form a closed switch position, and wherein said switch detecting circuit region is responsive to the contact of each of said plurality of released beams with each of said plurality of fixed contact layers.

7. An integrated sensor as defined in claim 6, wherein said sensor switching region further comprises at least one insulating support layer underlying at least one of said plurality of fixed contact layers and a plurality of insulating layers each positioned between an adjacent pair of the plurality of fixed contact layers for insulating each of said plurality of fixed contact layers from another one of said plurality of fixed contact layers.

8. An integrated sensor as defined in claim 7, wherein said sensor switching region further comprises remaining portions of at least one sacrificial layer positioned between each of said plurality of fixed contact layers and each of said plurality of released beams, wherein each of said plurality of released beam is positioned in spaced relation from a corresponding one of said plurality of fixed contact layers in a normally open position, the spaced relation forming by removal of unwanted portions of the at least one sacrificial layer, and wherein each of said plurality of released cantilever beams contacts said at least one fixed contact layer responsive to acceleration in a predetermined direction to form a closed switch position.

9. An integrated sensor as defined in claim 8, wherein each of said plurality of fixed contact layers comprises at least one of polysilicon and a metal.

10. An integrated sensor as defined in claim 1, wherein at least one of said plurality of released beams comprises a released cantilever beam.

11. An integrated sensor as defined in claim 10, wherein said released cantilever beam comprises polysilicon.

12. An integrated sensor as defined in claim 1, wherein at least one of said plurality of released beams comprises a released beam having a configuration including at least two supports having thicker portions of the same material forming the released beam positioned at opposing ends thereof.

13. An integrated sensor as defined in claim 12, wherein said released beam comprises polysilicon or a metal.

14. An integrated sensor as defined in claim 1, further comprising acceleration calibrating means associated with said plurality of released beams for providing a plurality of calibrated accelerations sensed by the integrated sensor, said acceleration Calibrating means including different predetermined length of each of said plurality of released beams so as to substantially correspond to a plurality of different preselected calibration threshold regions.

15. An integrated sensor as defined in claim 14, wherein said sensor switching region further includes at least one fixed contact layer underlying said plurality of released beams, and wherein each of the plurality of selected acceleration calibration threshold regions comprises a portion of said at least one fixed contact layer substantially corresponding to a region of contact of at least one of said plurality of released beams with said at least one fixed contact layer.

16. An integrated sensor as defined in claim 15, wherein the predetermined lengths of the outward extent of said plurality of released beams comprise a first plurality of predetermined lengths, wherein said at least one fixed contact layer extends outwardly from said switch detecting circuit region a second predetermined length, and wherein the second predetermined length is greater than at least one of the first plurality of predetermined lengths.

17. An 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 plurality of floating contacts positioned adjacent and lengthwise extending outwardly from said switch detecting circuit region for defining a plurality of released beams so that each of said plurality of released beams displaces in a predetermined direction responsive to acceleration, said plurality of released beams including at least two released beams lengthwise extending outwardly from said switch detecting circuit region to different predetermined lengths and at least two released beams lengthwise extending outwardly from said switch detecting circuit region to substantially the same predetermined lengths, each of said plurality of relesed beams comprising an integrally monolithic material having a generally uniform thickness extending substantially the entire length thereof.

18. An integrated sensor as defined in claim 17, wherein said sensor switching region further comprises at least one fixed contact layer underlying said plurality of released beams, and wherein at least one of said plurality of released beams contacts said at least one fixed contact layer responsive to acceleration in a predetermined direction so as to form a closed switch position, and wherein said switch detecting circuit region generates a signal responsive to the contact of said at least one of said plurality of released beams with said at least one fixed contact layer.

19. An integrated sensor as defined in claim 18, wherein said sensor switching region further comprises at least one insulating layer underlying said at least one fixed contact layer.

20. An integrated sensor as defined in claim 19, wherein said sensor switching region further comprises remaining portions of a sacrificial layer positioned between said at least one fixed contact layer and each of said plurality of released beams, wherein each of said plurality of released beam is positioned in spaced relation from said at least one fixed contact layer in a normally open position, the spaced relation forming by removal of unwanted portions of the sacrificial layer, and wherein each of said plurality of released beams contacts said at least one fixed contact layer responsive to acceleration in a predetermined direction to form a closed switch position.

21. An integrated sensor as defined in claim 20, wherein said at least one fixed contact layer comprises polysilicon go a metal.

22. An integrated sensor as defined in claim 17, wherein said sensor switching region further comprises a plurality of fixed contact layers each underlying a corresponding one of said plurality of released beams, and wherein each of said plurality of released beams contacts the corresponding respective one of said plurality of fixed contact layers responsive to acceleration in a predetermined direction so as to form a closed switch position, and wherein said switch detecting circuit region is responsive to the contact of each of said plurality of released beams with each of said plurality of fixed contact layers.

23. An integrated sensor as defined in claim 22, wherein said sensor switching region further comprises at least one insulating support layer underlying at least one of said plurality of fixed contact layers and a plurality of insulating layers each positioned between an adjacent pair of the plurality of fixed contact layers for insulating each of said plurality of fixed contact layers from another one of said plurality of fixed contact layers.

24. An integrated sensor as defined in claim 23, wherein said sensor switching region further comprises remaining portions of at least one sacrificial layer positioned between each of said plurality of fixed contact layers and each of said plurality of released beams, wherein each of said plurality of released beam is positioned in spaced relation from a corresponding one of said plurality of fixed contact layers in a normally open position, the spaced relation forming by removal of unwanted portions of the at least one sacrificial layer, and wherein each of said plurality of released beams contacts said at least one fixed contact layer responsive to acceleration in a predetermined direction to form a closed switch position.

25. An integrated sensor as defined in claim 24, wherein each of said plurality of fixed contact layers comprises polysilicon or a metal, and wherein said remaining portions of the at least one sacrificial layer includes at least one concave surface underlying each of said plurality of released beams.

26. An integrated sensor as defined in claim 17, wherein at least one of said plurality of released beams comprises a released cantilever beam.

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

28. An integrated sensor as defined in claim 17, wherein at least one of said plurality of released beams comprises a released beam having a configuration including at least two supports having thicker portions of the same material forming the released beam positioned at opposing ends thereof.

29. An integrated sensor as defined in claim 28, wherein said released beam comprises polysilicon or a metal.

30. An integrated sensor as defined in claim 17, further comprising acceleration calibrating means associated with said plurality of released beams for providing a plurality of calibrated accelerations sensed by the integrated sensor, said acceleration calibrating means including a predetermined length of each of said plurality of released beams so as to substantially correspond to a plurality of preselected calibration threshold regions.

31. An integrated sensor as defined in claim 30, wherein said sensor switching region further includes at least one fixed contact layer underlying said plurality of released beams, and wherein each of the plurality of selected acceleration calibration threshold regions comprises a portion of said at least one fixed contact layer substantially corresponding to a region of contact of at least one of said plurality of released beams with said at least one fixed contact layer.

32. An integrated sensor as defined in claim 31, wherein the predetermined lengths of the outward extent of said plurality of released beams comprise a first plurality of predetermined lengths, wherein said at least one fixed contact layer extends outwardly from said switch detecting circuit region a second predetermined length, and wherein the second predetermined length is greater than at least one of the first plurality or predetermined lengths.