Silicon-mass angular acceleration sensor

• US 5,233,213 A
• Filed: 06/04/1992
• Issued: 08/03/1993
• Est. Priority Date: 07/14/1990
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Marek, Jiri
• Primary Examiner(s): MINTEL, WILLIAM A
• Application Number:
  US07/893,904
• Time in Patent Office: 425 Days
• Field of Search: 357/25, 357/26, 357/51, 357/55, 357/59, 280/735, 338/5, 73/760, 73/768, 73/777, 73/517 A, 73/517 R, 361/280, 361/283, 257/415, 257/417, 257/418, 257/419
• US Class Current: 257/415
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass

Abstract

From a silicon block or wafer a stationary frame is shaped and a seismic mass which is displaceable in rotation is mounted within the frame. The seismic mass is symmetrically suspended in the frame by two pairs of oppositely located flexible strips and either piezoresistive or capacitive detection of rotation is provided by the strips, the capacitive detection beeing provided with the help of parallel stationary electrodes connected to and insulated in the frame. In another embodiment an anchor stud in the center of the frame has two flexible interlaced spirals extending therefrom and their respective outer turns carry radial disposed masses with finger structures extending circumferentially in both directions. Stationary finger structures are provided to provide interfitting variable capacitors sensitive to rotary displacements.

Claims

1. An angular acceleration sensor produced by removal of material from a plate-shaped silicon carrier body and composed of at least a stationary frame, a displaceable seismic mass having a rest position within said frame and a plurality of flexible connection strips by which said seismic mass is suspended from said frame, all made by removal of material from said carrier body, and further comprising:

means for electrically detecting and measuring a rotary movement of said seismic mass about an axis perpendicular to a major surface of said plate-shaped carrier body.

2. The sensor of claim 1, wherein said frame is of square configuration and said seismic mass comprises a square upper surface and wherein at least one pair and not more than two pairs of said flexible strips are symmetrically disposed in said frame at opposite sides of said seismic mass and connect said seismic mass to said frame in such a way that in said rest position the edges of said square upper surface of said seismic mass are respectively parallel to two interior surfaces of said frame, said seismic mass being suspended in the middle of said frame and said flexible strips extending perpendicularly away from respective middles of sides of said upper surface of said seismic mass towards said frame.

3. The sensor of claim 1, wherein said measuring means include piezoresistances located on respective opposite side surfaces of said strips which are easily bent by said rotary motion.

4. The sensor of claim 2, wherein said measuring means include piezoresistances located on respective opposite side surfaces of said strips which are easily bent by said rotary motion.

5. The sensor of claim 1, wherein said flexible strips at least in part have a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said strips being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

6. The sensor of claim 2, wherein said flexible strips at least in part have a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said strips being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

7. The sensor of claim 3, wherein said flexible strips at least in part have a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said strips being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

8. The sensor of claim 4, wherein said flexible strips at least in part have a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said strips being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

58. The sensor of claim 1, wherein at least a portion of said seismic mass has a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said seismic mass being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

59. The sensor of claim 2, wherein at least a portion of said seismic mass has a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said seismic mass being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

60. The sensor of claim 3, wherein at least a portion of said seismic mass has a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said seismic mass being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

61. The sensor of claim 4, wherein at least a portion of said seismic mass has a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said seismic mass being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

9. An angular acceleration sensor produced by removal of material from a plate-shaped silicon carrier body composed predominantly of a plurality of layers, each predominantly of silicon, comprising first and second layers respectively distinguishable electrically from each other, and composed structurally of at least a stationary frame, a displaceable seismic mass having a rest position within said frame and a plurality of flexible connection strips by which said seismic mass is suspended from said frame, all made by removal of material from said carrier body and further comprising:

means for electrically detecting and measuring a rotary movement of said seismic mass about an axis perpendicular to a major surface of said plate-shaped carrier body.

10. The sensor of claim 9, wherein said frame is of square configuration, said seismic mass comprises a square upper surface and wherein at least one pair and not more than two pairs of said flexible strips are symmetrically disposed in said frame at opposite sides of said seismic mass and connect said seismic mass to said frame in such a way that in said rest position the edges of said square upper surface of said seismic mass are respectively parallel to two interior surfaces of said frame, said seismic mass being suspended in the middle of said frame and said flexible strips extending perpendicularly away from respective middles of sides of said upper surface of said seismic mass towards said frame.

11. The sensor of claim 9, wherein said measuring means include piezoresistances located on respective opposite side surfaces of said strips which are easily bent by said rotary motion.

12. The sensor of claim 10, wherein said measuring means include piezoresistances located on respective opposite side surfaces of said strips which are easily bent by said rotary motion.

13. The sensor of claim 9, wherein said first layer and said second layer are on opposite sides of a pn-junction of said carrier body.

14. The sensor of claim 10, wherein said first layer and said second layer are on opposite sides of a pn-junction of said carrier body.

15. The sensor of claim 9, wherein said frame, seismic mass and flexible strips are monocrystalline.

16. The sensor of claim 10, wherein said frame, seismic mass and flexible strips are monocrystalline.

17. The sensor of claim 9, wherein said first layer is a polycrystalline silicon layer and has material thereof removed between said frame and said seismic mass resulting in cavities that are open on a major surface of said plate-shaped carrier body.

18. The sensor of claim 10, wherein said first layer is a polycrystalline silicon layer and has material thereof removed between said frame and said seismic mass resulting in cavities that are open on a major surface of said plate-shaped carrier body.

19. The sensor of claim 9, further comprising at least one pair of stationary electrodes shaped out of said carrier body which electrodes respectively extend from each of two opposite sides of said frame towards said seismic mass, each said pair of stationary electrodes being parallel to one of said strips and disposed so that said one of said strips serves as a movable electrode forming a capacitor with said pair of stationary electrodes parallel thereto.

20. The sensor of claim 9, further comprising at least one pair of stationary electrodes shaped out of said carrier body which electrodes respectively extend from each of two opposite sides of said frame towards said seismic mass, each said pair of stationary electrodes being parallel to one of said strips and disposed so that said one of said strips serves as a movable electrode forming a capacitor with said pair of stationary electrodes parallel thereto.

25. The sensor of claim 9, wherein said flexible strips at least in part have a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said strips being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

26. The sensor of claim 10, wherein said flexible strips at least in part have a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said strips being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

29. The sensor of claim 9, wherein at least a portion of said seismic mass has a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said seismic mass being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

30. The sensor of claim 10, wherein at least a portion of said seismic mass has a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said seismic mass being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

35. The sensor of claim 9, further comprising at least a pair of parallel stationary electrodes shaped out of said carrier body which electrodes respectively extend from each of two opposite sides of said frame towards said seismic mass and at least a pair of parallel movable electrodes which respectively extend from each of two opposite sides of said seismic mass which sides are disposed so as to provide a capacitor on each side of said seismic mass.

36. The sensor of claim 10, further comprising at least a pair of parallel stationary electrodes shaped out of said carrier body which electrodes respectively extend from each of two opposite sides of said frame towards said seismic mass and at least a pair of parallel movable electrodes which respectively extend from each of two opposite sides of said seismic mass which sides are disposed so as to provide a capacitor on each side of said seismic mass.

39. The sensor of claim 19, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by a pn-junction.

40. The sensor of claim 20, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by a pn-junction.

43. The sensor of claim 35, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by a pn-junction.

44. The sensor of claim 36, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by a pn-junction.

47. The sensor of claim 19, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and isolation diffusions in said first layer.

48. The sensor of claim 20, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and isolation diffusions in said first layer.

51. The sensor of claim 35, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and in each case also by etched troughs penetrating fully through said first layer.

52. The sensor of claim 36, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and in each case also by etched troughs penetrating fully through said first layer.

21. An angular acceleration sensor produced by removal of material from a plate-shaped silicon carrier body composed predominantly of a first layer and a second layer, each predominantly of silicon and electrically distinguishable from each other, and an electrically insulating layer of silicon dioxide interposed between said first and second layers and composed structurally of at least a stationary frame, a displaceable seismic mass having a rest position within said frame and a plurality of flexible connection strips by which said seismic mass is suspended from said frame, all made by removal of material from said carrier body and further comprising:

means for electrically detecting and measuring a rotary movement of said seismic mass about an axis perpendicular to a major surface of said plate-shaped carrier body.

22. The sensor of claim 21, wherein said frame is of square configuration and said seismic mass comprises a square upper surface and wherein at least one pair and not more than two pairs of said flexible strips are symmetrically disposed in said frame at opposite sides of said seismic mass and connecting said seismic mass to said frame in such a way that in said rest position the edges of said square upper surface of said seismic mass are respectively parallel to two interior surfaces of said frame, said seismic mass being suspended in the middle of said frame and said flexible strips extending perpendicularly away from respective middles of sides of said upper surface of said seismic mass towards said frame.

23. The sensor of claim 21, wherein said measuring means include piezoresistances located on respective opposite side surfaces of said strips which are easily bent by said rotary motion.

24. The sensor of claim 22, wherein said measuring means include piezoresistances located on respective opposite side surfaces of said strips which are easily bent by said rotary motion.

27. The sensor of claim 21, wherein said flexible strips at least in part have a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said strips being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

28. The sensor of claim 22, wherein said flexible strips at least in part have a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said strips being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

31. The sensor of claim 21, wherein at least a portion of said seismic mass has a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said seismic mass being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

32. The sensor of claim 22, wherein at least a portion of said seismic mass has a thickness equal to the overall thickness of said silicon carrier body, the thickness dimension of said seismic mass being defined as corresponding to the thickness dimension of said plate-shaped carrier body.

33. The sensor of claim 21, further comprising at least one pair of stationary electrodes shaped out of said carrier body which electrodes respectively extend from each of two opposite sides of said frame towards said seismic mass, each said pair of stationary electrodes being parallel to one of said strips and disposed so that said one of said strips serves as a movable electrode forming a capacitor with said pair of stationary electrodes parallel thereto.

34. The sensor of claim 22, further comprising at least one pair of stationary electrodes shaped out of said carrier body which electrodes respectively extend from each of two opposite sides of said frame towards said seismic mass, each said pair of stationary electrodes being parallel to one of said strips and disposed so that said one of said strips serves as a movable electrode forming a capacitor with said pair of stationary electrodes parallel thereto.

37. The sensor of claim 21, further comprising at least a pair of parallel stationary electrodes shaped out of said plate-shaped carrier body which electrodes respectively extend from each of two opposite sides of said frame towards said seismic mass and at least a pair of parallel movable electrodes which respectively extend from each of two opposite sides of said seismic mass which respectively are disposed so as to provide a capacitor on each side of said seismic mass.

38. The sensor of claim 22, further comprising at least a pair of parallel stationary electrodes shaped out of said carrier body which electrodes respectively extend from each of two opposite sides of said frame towards said seismic mass and at least a pair of parallel movable electrodes which respectively extend from each of two opposite sides of said seismic mass which sides are disposed so as to provide a capacitor on each side of said seismic mass.

41. The sensor of claim 33, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and isolation diffusions in said first layer.

42. The sensor of claim 34, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by a pn-junction.

45. The sensor of claim 37, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and isolation diffusions in said first upper layer.

46. The sensor of claim 38, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and isolation diffusions in said first layer.

49. The sensor of claim 33, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and in each case also by etched troughs penetrating fully through said first layer.

50. The sensor of claim 34, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and in each case also by etched troughs penetrating fully through said first layer.

53. The sensor of claim 37, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and in each case also by etched troughs penetrating fully through said first layer.

54. The sensor of claim 38, wherein said flexible strips are provided only in said first layer of said plate-shaped carrier body and wherein said stationary electrodes are isolated from said frame by an insulation layer interposed between said first and second layers and in each case also by etched troughs penetrating fully through said first layer.

55. An angular acceleration sensor produced by removal of material from a plate-shaped carrier body predominantly of silicon and composed of a substrate (3), an insulation layer (5) overlying said substrate and a polycrystalline layer (2) overlying said insulation layer and further comprising:

an anchor stud (55) shaped out of said polycrystalline layer and firmly affixed to said substrate;

a pair of interlaced spirals (50,

     60) extending from said anchor stud as a mid-location, shaped out of said polycrystalline layer and unconnected with said substrate except through said anchor stud;

masses (51,

     61) shaped out of said polycrystalline layer distributed in star configuration relative to said anchor stud and each connected to an outer turn of one of said spirals;

finger structures (511,

     611) shaped out of said polycrystalline layer and extending circumferentially from each of said masses;

stationary electrodes (71) shaped out of said polycrystalline layer, connected to said substrate through said insulation layer (5) and disposed in star configuration relative to said another stud and having finger structures (711) interfitting between said finger structures of said masses; and

means (93,

     94) for electrically detecting and measuring rotary movement of said masses (51,

     61) about an axis perpendicular to a major surface of said plate-shaped carrier body.

56. The sensor of claim 55, wherein piezoresistances (111) are mounted on each of said spirals (50, 60) for sensing expansion and contraction of said spirals.

57. The sensor of claim 55, wherein said means (94) for electrically measuring rotary movement are for measuring the capacitance between said stationary electrodes and said masses (51, 61) connected to respective outer turns respectively of said spirals.