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US 11,082,024 B1Granted
Temperature stable mems resonator
AssigneeSiTime Corporation
InventorsPaul M. Hagelin, Charles I. Grosjean
Life of this patent
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Abstract
A resonant member of a MEMS resonator oscillates in a mechanical resonance mode that produces non-uniform regional stresses such that a first level of mechanical stress in a first region of the resonant member is higher than a second level of mechanical stress in a second region of the resonant member. A plurality of openings within a surface of the resonant member are disposed more densely within the first region than the second region and at least partly filled with a compensating material that reduces temperature dependence of the resonant frequency corresponding to the mechanical resonance mode.
Claims20
A microelectromechanical systems (MEMS) device comprising:
- a supporting structure;
- and
- a beam having a first end and a second end, the beam connected to the supporting structure by the first end, the second end being suspended so as to be free to move relative to the supporting structure;
- the MEMS device comprising two materials, including a first material characterized by a first temperature coefficient of Young's Modulus (TCE), and a second material characterized by a second temperature coefficient of Young's Modulus (TCE), the first TCE being opposite in sign to the second TCE for at least one temperature value;
- the second material being concentrated relative to the first material at a position of maximum flexural stress of the beam when the second end moves relative to the supporting structure;
- and
- the second material having been formed in one or more slots in the beam, the second material with each of the one or more slots being encapsulated within the beam and having a thickness of no more than 0.6 microns in a direction of movement of the second end which is orthogonal to a length dimension of the beam extending between the first end and the second end.
4 more elements
A microelectromechanical (MEMS) resonator comprising:
- an anchor;
- and
- at least one beam, each beam of the at least one beam having a first end and a second end, the first end of each beam mounted relative to a handle wafer by said anchor, the second end of each beam being suspended so as to be free to move relative to the anchor;
- wherein each beam of the at least one beam comprises two materials, including a first material characterized by a first temperature coefficient of Young's Modulus (TCE), and a second material characterized by a second temperature coefficient of Young's Modulus (TCE), the first TCE being opposite in sign to the second TCE for at least one temperature value;
- the second material being concentrated relative to the first material at a position of maximum flexural stress of the beam when the second end moves relative to the supporting structure;
- wherein the MEMS resonator is characterized by a thermal coefficient of frequency (TCF) and wherein the first material and the second material are configured to have respective volumes such that, given the first TCE and the second TCE, the resonator has an overall TCF over an intended operating temperature range of the MEMS resonator that is less than |−5 ppm/° C.|;
- and
- wherein the second material having been formed in one or more slots in at least one beam of the one or more beams, the second material with each of the one or more slots being encapsulated within the at least one beam and having a thickness of no more than 0.6 microns in a direction of movement of the second end which is orthogonal to a length dimension of the at least one beam extending between the first end and the second end of the at least one beam.
5 more elements
A microelectromechanical systems (MEMS) resonator comprising:
- a beam adapted to resonate at a frequency;
- circuitry to excite vibration of the beam;
- and
- an anchor to mount the beam;
- wherein
- the beam has a first end and a second end, the beam connected to the anchor by the first end, the second end being suspended so as to be free to move relative to the anchor,
- the beam has two materials, including a first material characterized by a first temperature coefficient of Young's Modulus (TCE), and a second material characterized by a second temperature coefficient of Young's Modulus (TCE), the first TCE being opposite in sign to the second TCE for at least one temperature value, a volume of the first material relative to the second material being configured such that an overall temperature coefficient of frequency of the resonator over an intended operating range of the MEMS resonator is less than |−5 ppm/° C.|;
- the second material is concentrated relative to the first material in a region that coincides with a position of maximum flexural stress of the beam when the second end moves relative to the anchor;
- and
- the second material having been formed in one or more slots in the beam, the second material with each of the one or more slots being encapsulated within the beam and having a thickness of no more than 0.6 microns in a direction of movement of the second end which is orthogonal to a length dimension of the beam extending between the first end and the second end.
7 more elements
Dependencies are inferred from the claim text.