Integrated released beam oscillator and associated methods

• US 6,124,765 A
• Filed: 10/24/1997
• Issued: 09/26/2000
• 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, Sunkara, Syama Sundar
• Primary Examiner(s): KINKEAD, ARNOLD M
• Application Number:
  US08/957,804
• Time in Patent Office: 1,068 Days
• Field of Search: 331/154, 331/156, 331/116 M, 331/47, 331/48, 331/52, 331/65, 331/183, 331/108 C, 331/176, 257/415, 73/773, 368/202, 368/155, 368/156, 968/900
• US Class Current: 331/116.00M
• CPC Class Codes: H03B 5/32 being a piezoelectric resonator selection of piezoelectric material H10N30/00
• CPC Class Codes: H03H 9/24 Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive

Abstract

An integrated oscillator and associated methods are provided for providing clock signals. The integrated oscillator preferably includes a micro-mechanical oscillating circuit for providing an oscillating clock signal. The micro-mechanical oscillating circuit preferably includes a support layer, a fixed layer positioned on a support layer, remaining portions of a sacrificial layer positioned only on portions of the fixed layer, and an oscillating layer positioned on the remaining portions of the sacrificial layer, overlying the fixed layer in spaced relation therefrom, and extending lengthwise generally transverse to a predetermined direction for defining a released beam for oscillating at a predetermined frequency. The spaced relation is preferably formed by removal of unwanted portions of the sacrificial layer. The integrated oscillator also preferably includes a clock signal controlling circuit connected to the micro-mechanical oscillating circuit for controlling the micro-mechanical oscillating circuit and for generating clock signals therefrom.

Claims

1. An integrated oscillator for providing clock signals, the integrated oscillator comprising:

micro-mechanical oscillating means for providing an oscillating clock signal, said micro-mechanical oscillating means including;

a support layer,

a fixed layer positioned on said support layer,

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

an oscillating layer positioned on said remaining portions of the sacrificial layer, overlying said fixed layer in spaced relation therefrom, and extending lengthwise generally transverse to a predetermined direction for defining a released beam for oscillating at a predetermined frequency, the spaced relation formed by removal of unwanted portions of the sacrificial layer; and

clock signal controlling means connected to said micro-mechanical oscillating means for controlling said micro-mechanical oscillating means and for generating clock signals therefrom.

2. An integrated oscillator as defined in claim 1, wherein said fixed layer comprises a fixed conductive layer and said oscillating layer comprises an oscillating conductive layer overlying said fixed conductive layer, and wherein said clock signal controlling means includes a first electrode connected to said fixed conductive layer and a second electrode connected to said oscillating conductive layer so that said fixed conductive layer and said oscillating conductive layer define two plates of a capacitor and generate an electric field therebetween when a voltage signal is applied to the first and second electrodes.

3. An integrated oscillator as defined in claim 1, wherein said clock signal controlling means includes amplitude compensating means connected to said micro-mechanical oscillating means for compensating for the amplitude variations of the predetermined oscillating frequency of said released beam over time.

4. An integrated oscillator as defined in claim 3, wherein said clock signal controlling means further includes frequency locking means connected to said amplitude compensating means for locking on the predetermined oscillating frequency of said released beam.

5. An integrated oscillator as defined in claim 4, wherein said clock signal controlling means further includes temperature compensating means connected to said frequency locking means for compensating for frequency shifting due to temperature variations and for a difference in oscillating frequency due to process variations.

6. An integrated oscillator as defined in claim 5, wherein said clock signal controlling means further includes aging compensating means connected to said temperature compensating means for compensating for frequency drift of the oscillating frequency of said released beam over time due to aging.

7. An integrated oscillator as defined in claim 2, wherein said clock signal controlling means includes a clock signal controlling circuit region, and the integrated oscillator further comprising said micro-mechanical oscillating means being positioned adjacent said clock signal controlling circuit region and transversely extending outwardly therefrom in a predetermined direction, wherein said released beam of said micro-mechanical oscillating means has a first predetermined length extending outwardly from said clock signal controlling circuit region, wherein said fixed conductive layer extends outwardly from said clock signal controlling circuit region a second predetermined length, and wherein the second predetermined length is greater than the first predetermined length.

8. An integrated oscillator as defined in claim 1, wherein said sacrificial layer includes at least one concave surface underlying said released beam.

9. An integrated oscillator as defined in claim 1, wherein said released beam includes a plurality of openings formed therein for assisting with removal of the unwanted portions of the sacrificial layer underlying said released beam, said plurality of openings extending from an upper surface of said released beam to a lower surface thereof.

10. An integrated oscillator as defined in claim 1, wherein said released beam includes laterally extending narrow portions and laterally extending wide portions integrally formed as a single layer with and extending outwardly from the narrow portions.

11. An integrated oscillator as defined in claim 1, wherein said released beam includes trimmed released portions thereof, said trimmed released portions defining peripheries of removed portions of said oscillating layer.

12. An integrated oscillator as defined in claim 1, wherein said released beam comprises a released cantilever beam.

13. An integrated oscillator as defined in claim 1, wherein said released beam comprises a released beam having a plurality of supports formed by said remaining portions of the sacrificial layer.

14. An integrated oscillator as defined in claim 2, wherein said fixed conductive layer comprises at least one of polysilicon and a metal, and wherein said released beam comprises polysilicon and a metal.

15. An integrated oscillator as defined in claim 1, wherein said micro-mechanical oscillating means further includes an insulating support layer underlying said fixed conducting layer, said insulating support layer comprising a nitride layer formed on a field oxide.

16. An integrated oscillator as defined in claim 1, wherein said sacrificial layer comprises an oxide layer.

17. An integrated oscillator for providing clock signals, the integrated oscillator comprising:

micro-mechanical oscillating means for providing an oscillating clock signal, said micro-mechanical oscillating means including;

a fixed conductive layer, and

an oscillating conductive layer overlying said fixed conductive layer in spaced relation therefrom, and extending lengthwise generally transverse to a predetermined direction for defining a released beam for oscillating at a predetermined frequency, said released beam including a plurality of openings formed therein, said plurality of openings extending from an upper surface of said released beam to a region defining the spaced relation underlying said released beam and positioned between said released beam and said fixed conductive layer, and trimmed released portions defining peripheries of removed portions of said oscillating conductive layer; and

clock signal controlling means connected to said micro-mechanical oscillating means for controlling said micro-mechanical oscillating means and for generating clock signals therefrom, said clock signal controlling means including a first electrode connected to said fixed conductive layer and a second electrode connected to said oscillating conductive layer so that said fixed conductive layer and said oscillating conductive layer define two plates of a capacitor and generate an electric field therebetween when a voltage signal is applied to the first and second electrodes.

18. An integrated oscillator as defined in claim 17, wherein said trimmed released portions form laterally extending narrow portions, and wherein said released beam further includes laterally extending wide portions integrally formed as a single layer with and extending outwardly from the laterally extending narrow portions.

19. An integrated oscillator as defined in claim 18, wherein said micro-mechanical oscillating means further includes remaining portions of a sacrificial layer positioned only on portions of said fixed conductive layer and underlying said released beam, the spaced relation between said fixed conductive layer and said oscillating conductive layer formed by removal of unwanted portions of said released beam.

20. An integrated oscillator as defined in claim 19, wherein said remaining portions define at least one support for said released beam, and wherein said trimmed released portions are positioned adjacent the at least one support to thereby inhibit said released beam from being subjected to excessive deflections and stress when forming said trimmed released portions.

21. An integrated oscillator as defined in claim 20, wherein said clock signal controlling means includes amplitude compensating means connected to said micro-mechanical oscillating means for compensating for the amplitude variations of the predetermined oscillating frequency of said released beam over time.

22. An integrated oscillator as defined in claim 21, wherein said clock signal controlling means further includes frequency locking means connected to said amplitude compensating means for locking on the predetermined oscillating frequency of said released beam.

23. An integrated oscillator as defined in claim 22, wherein said clock signal controlling means further includes temperature compensating means connected to said frequency locking means for compensating for frequency shifting due to temperature variations and for a difference in oscillating frequency due to process variations.

24. An integrated oscillator as defined in claim 23, wherein said clock signal controlling means further includes aging compensating means connected to said temperature compensating means for compensating for frequency drift of the oscillating frequency of said released beam over time due to aging.

25. An integrated oscillator as defined in claim 24, wherein said released beam comprises a released cantilever beam.

26. An integrated oscillator as defined in claim 24, wherein said released beam comprises a released beam having a plurality of supports formed by said remaining portions of the sacrificial layer.

27. An integrated oscillator as defined in claim 25, wherein said clock signal controlling means includes a clock signal controlling circuit region, and the integrated oscillator further comprising said micro-mechanical oscillating means being positioned adjacent said clock signal controlling circuit region and transversely extending outwardly therefrom in a predetermined direction, wherein said released beam of said micro-mechanical oscillating means has a first predetermined length extending outwardly from said clock signal controlling circuit region, wherein said fixed conducting layer extends outwardly from said clock signal controlling circuit region a second predetermined length, and wherein the second predetermined length is greater than the first predetermined length.

28. An integrated oscillator as defined in claim 27, wherein said sacrificial layer includes at least one concave surface underlying said released beam.

29. An integrated oscillator as defined in claim 28, wherein said fixed conducting layer comprises at least one of polysilicon and a metal.

30. An integrated oscillator as defined in claim 29, wherein said released beam comprises polysilicon and a metal.

31. An integrated oscillator as defined in claim 30, wherein said insulating support layer comprises a nitride layer formed on a field oxide, and wherein said sacrificial layer comprises an oxide layer.

32. An integrated oscillator for providing clock signals, the integrated oscillator comprising:

first and second micro-mechanical oscillating means each for providing an oscillating clock signal, each of said first and second micro-mechanical oscillating means including;

a fixed conductive layer positioned on said support layer,

remaining portions of a sacrificial layer on said fixed conductive layer, and

an oscillating conductive layer positioned on said remaining portions of the sacrificial layer, overlying said fixed conducting layer in spaced relation therefrom, and extending lengthwise generally transverse to a predetermined direction for defining a released beam for oscillating at a predetermined frequency; and

clock signal controlling means connected to said first and second micro-mechanical oscillating means for controlling each of said first and second micro-mechanical oscillating means and for generating respective clock signals therefrom, said clock signal controlling means including a first pair of electrodes respectively connected to said fixed conductive layer and said oscillating conductive layer of said first micro-mechanical oscillating means so that said fixed conductive layer and said oscillating conductive layer thereof define two plates of a capacitor and generate an electric field therebetween when a voltage signal is applied to the first pair of electrodes and a second pair of electrodes respectively connected to said fixed conductive layer and said oscillating conductive layer of said second micro-mechanical oscillating means so that said fixed conductive layer and said oscillating conductive layer thereof also define two plates of a capacitor and generate an electric field therebetween when a voltage signal is applied to the second pair of electrodes, and aging compensating means responsive to both said first and second micro-mechanical oscillating means for compensating for aging of said first micro-mechanical oscillating means by using the oscillating frequency of said second micro-mechanical means as a reference frequency.

33. An integrated oscillator as defined in claim 32, wherein said clock signal controlling means further includes first and second amplitude compensating means respectively connected to said first and second micro-mechanical oscillating means for compensating for the amplitude variations of the predetermined oscillating frequency of corresponding first and second released beams over time.

34. An integrated oscillator as defined in claim 33, wherein said clock signal controlling means further includes first and second frequency locking means respectively connected to said first and second amplitude compensating means for locking on the predetermined oscillating frequency of the corresponding first and second released beams.

35. An integrated oscillator as defined in claim 34, wherein said clock signal controlling means further includes first and second temperature compensating means respectively connected to said first and second frequency locking means for compensating for frequency shifting due to temperature variations and for a difference in oscillating frequency due to process variations.

36. An integrated oscillator as defined in claim 35, wherein said clock signal controlling means includes a clock signal controlling circuit region, and the integrated oscillator further comprising said first and second micro-mechanical oscillating means each being positioned adjacent said clock signal controlling circuit region and transversely extending outwardly therefrom in a predetermined direction, wherein said released beam of each of said first and second micro-mechanical oscillating means has a first predetermined length extending outwardly from said clock signal controlling circuit region, wherein each of said fixed conductive layers of said first and second micro-oscillating means extends outwardly from said clock signal controlling circuit region a second predetermined length, and wherein the second predetermined length is greater than the first predetermined length.

37. An integrated oscillator as defined in claim 36, wherein said sacrificial layer includes at least one concave surface underlying said released beam.

38. An integrated oscillator as defined in claim 37, wherein said released beam includes a plurality of openings formed therein for assisting with removal of the unwanted portions of the sacrificial layer underlying said released beam, said plurality of openings extending from an upper surface of said released beam to a region defining the spaced relation underlying said released beam and positioned between said released beam and said fixed conducting layer.

39. An integrated oscillator as defined in claim 38, wherein said released beam includes laterally extending narrow portions and laterally extending wide portions integrally formed as a single layer with and extending outwardly from the narrow portions.

40. An integrated oscillator as defined in claim 38, wherein said released beam includes trimmed released portions thereof, said trimmed released portions defining peripheries of removed portions of said oscillating layer.

41. An integrated oscillator as defined in claim 39, wherein said released beam comprises a released cantilever beam.

42. An integrated oscillator as defined in claim 39, wherein said released beam comprises a released beam having a plurality of supports formed by said remaining portions of the sacrificial layer.

47. An integrated oscillator as defined in claim 35, wherein said clock signal controlling means includes a clock signal controlling circuit region, and the integrated oscillator further comprising said first and second micro-mechanical oscillating means each being positioned adjacent said clock signal controlling circuit region and transversely extending outwardly therefrom in a predetermined direction, wherein each of said first and second micro-mechanical oscillating means includes a released beam having a first predetermined length extending outwardly from said clock signal controlling circuit region and a fixed conductive layer extending outwardly from said clock signal controlling circuit region a second predetermined length, and wherein the second predetermined length is greater than the first predetermined length.

48. An integrated oscillator as defined in claim 47, wherein each of said released beams includes a plurality of openings formed therein for assisting with removal of the unwanted portions of the sacrificial layer underlying said released beams, each of said plurality of openings extending from upper surfaces of said released beams to a region defining the spaced relation underlying said released beams and positioned between said released beams and said fixed conducting layers.

49. An integrated oscillator as defined in claim 48, wherein each of said released beams includes laterally extending narrow portions and laterally extending wide portions integrally formed as a single layer with and extending outwardly from the laterally extending narrow portions.

50. An integrated oscillator as defined in claim 49, wherein each of said released beam includes trimmed released portions thereof, said trimmed released portions defining peripheries of removed portions of said oscillating layer.

51. An integrated oscillator as defined in claim 47, wherein each of said released beams comprises a released cantilever beam.

52. An integrated oscillator as defined in claim 47, wherein each of said released beams comprises a released beam having a plurality of supports formed by said remaining portions of the sacrificial layer.

56. A method as defined in claim 50, wherein the step of forming the micro-mechanical oscillating region further comprises forming an insulating layer on the support prior to the step of forming the first conducting layer.

57. A method as defined in claim 56, wherein the first fixed conductive layer comprises at least one of polysilicon and a metal.

58. A method as defined in claim 57, wherein the second conductive layer comprises at least one of polysilicon and a metal.

43. An integrated oscillator for providing clock signals, the integrated oscillator comprising:

first and second micro-mechanical oscillating means each for providing an oscillating clock signal; and

clock signal controlling means connected to said first and second micro-mechanical oscillating means for controlling each of said first and second micro-mechanical oscillating means and for generating respective clock signals therefrom, said clock signal controlling means including a first pair of electrodes connected to said first micro-mechanical oscillating means, a second pair of electrodes connected to said second micro-mechanical oscillating means, and aging compensating means responsive to both said first and second micro-mechanical oscillating means for compensating for aging of said first micro-mechanical oscillating means by using the oscillating frequency of said second micro-mechanical means as a reference frequency.

44. An integrated oscillator as defined in claim 43, wherein said clock signal controlling means further includes first and second amplitude compensating means respectively connected to said first and second micro-mechanical oscillating means for compensating for the amplitude variations of the predetermined oscillating frequency of corresponding first and second released beams over time.

45. An integrated oscillator as defined in claim 44, wherein said clock signal controlling means further includes first and second frequency locking means respectively connected to said first and second amplitude compensating means for locking on the predetermined oscillating frequency of the corresponding first and second released beams.

46. An integrated oscillator as defined in claim 45, wherein said clock signal controlling means further includes first and second temperature compensating means respectively connected to said first and second frequency locking means for compensating for frequency shifting due to temperature variations and for a difference in oscillating frequency due to process variations.

53. A method of forming an integrated oscillator, the method comprising the steps of:

providing a clock signal controlling circuit region; and

forming a micro-mechanical oscillating region connected to the clock signal controlling circuit region, the micro-mechanical oscillating region being formed by at least;

forming a first fixed conductive layer of material on a support,

depositing a sacrificial layer on the first fixed conductive layer,

depositing a second conductive layer on the sacrificial layer, and

removing at least unwanted portions of the sacrificial layer underlying the second conductive layer to release the second conducting layer to thereby define a released beam overlying the fixed conducting layer for oscillating at a predetermined frequency.

54. A method as defined in claim 53, wherein the released beam forms a released cantilever beam.

55. Method as defined in claim 53, wherein the released beam forms a released beam overlying the first fixed conductive layer so as to have a configuration including at least two supports.

59. A method of forming an integrated oscillator, the method comprising the steps of:

providing a clock signal controlling circuit region; and

forming a micro-mechanical oscillating region connected to the clock signal controlling circuit region, the micro-mechanical oscillating region being formed by at least;

forming a first fixed conductive layer of material on a support,

forming a second conductive layer overlying and in spaced relation from the fixed conductive layer so as to define a released beam for oscillating at a predetermined resonant frequency, and

trimming portions of the released beam to reduce mass of the released beam so as to tune the predetermined resonant frequency thereof.

60. A method as defined in claim 59, herein the micro-mechanical oscillating region further includes forming remaining portions of a sacrificial layer on the first conductive layer and underlying the second conductive layer.

61. A method as defined in claim 60, wherein the step of forming the second conductive layer includes forming a plurality of openings extending through the second conductive layer, and the method further includes removing at least unwanted portions of the sacrificial layer underlying the second conductive layer to release the second conductive layer to thereby define the released beam overlying the fixed conductive layer.

62. A method as defined in claim 61, wherein the remaining portions of the sacrificial layer define at least one support for the released beam, and wherein the trimming step comprises laser trimming portions of the released beam adjacent the support.

63. A method as defined in claim 62, wherein the step of removing unwanted portions of the sacrificial layer comprises isotropically etching the sacrificial layer.

64. A method of forming an integrated oscillator, the method comprising the steps of:

providing first and second micro-mechanical oscillating circuits;

controlling each of the first and second micro-mechanical oscillating circuits to generate respective clock signals therefrom; and

compensating for aging of the first micro-mechanical oscillating means responsive to the oscillating frequency of the second micro-mechanical means.

65. A method as defined in claim 64, further comprising compensating for the amplitude variations of a predetermined oscillating frequency of each of the first and second micro-mechanical oscillating circuits over time.

66. A method as defined in claim 65, further comprising locking on the predetermined oscillating frequency of the first and second micro-mechanical oscillating circuits.

67. A method as defined in claim 66, further comprising compensating both for frequency shifting due to temperature variations and for a difference in oscillating frequency due to process variations.