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US 11,469,734 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.
Claims27
A microelectromechanical systems (MEMS) device comprising:
- a structure having beams each extending in parallel along a length dimension, each of the beams having
- a respective first end that couples to a base and
- a respective second end that is free to vibrate in a direction of a second dimension which is perpendicular to the length dimension;
- wherein each of the beams has a region of maximum flexural stress adjacent the respective first end and each of the beams is characterized in the region of the maximum flexural stress by one or more layers of a first material and one or more layers of a second material, the first material having a first temperature coefficient of Young's Modulus (TCE) at an operating temperature of the MEMS device and the second material having second TCE that is opposite in sign to the first TCE at the operating temperature;
- wherein, for each respective one of the beams,
- the one or more layers of the second material in the region of the maximum flexural stress each have a length dimension parallel to the length dimension of the respective one of the beams that is greater than a thickness dimension parallel to the second dimension, and
- at least one layer of the one or more layers of the second material is sandwiched by one or more layers of the respective one of the beams, so to be covered in each direction along the thickness dimension;
- and
- wherein the second material is concentrated relative to the first material along the length dimension, each layer of the at least one layer of the second material spanning a length no more than thirty percent of and extent of the respective one of the beams along the length dimension of the respective one of the beams.
6 more elements
A microelectromechanical systems (MEMS) device comprising:
- a structure having beams each extending in parallel along a length dimension, each of the beams having
- a respective first end that couples to a base and
- a respective second end that is free to vibrate in a direction of a second dimension which is perpendicular to the length dimension;
- wherein each of the beams has a region of maximum flexural stress adjacent the respective first end and each of the beams is characterized in the region of the maximum flexural stress by one or more layers of a first material and one or more layers of a second material, the first material having a first temperature coefficient of Young's Modulus (TCE) at an operating temperature of the MEMS device and the second material having second TCE that is opposite in sign to the first TCE at the operating temperature;
- wherein, for each respective one of the beams,
- the one or more layers of the second material in the region of the maximum flexural stress each have a length dimension parallel to the length dimension of the respective one of the beams that is greater than a thickness dimension parallel to the second dimension, and
- at least one layer of the one or more layers of the second material is sandwiched by one or more layers of the respective one of the beams, so to be covered in each direction along the thickness dimension;
- and
- wherein at least one layer of the one or more layers of the second material is capped such that it is hermetically sealed relative to the first material by a capping material.
6 more elements
A microelectromechanical systems (MEMS) device comprising:
- a structure having beams each extending in parallel along a length dimension, each of the beams having
- a respective first end that couples to a base and
- a respective second end that is free to vibrate in a direction of a second dimension which is perpendicular to the length dimension;
- wherein each of the beams has a region of maximum flexural stress adjacent the respective first end and each of the beams is characterized in the region of the maximum flexural stress by one or more layers of a first material and one or more layers of a second material, the first material having a first temperature coefficient of Young's Modulus (TCE) at an operating temperature of the MEMS device and the second material having second TCE that is opposite in sign to the first TCE at the operating temperature;
- and
- wherein, for each respective one of the beams,
- the one or more layers of the second material in the region of the maximum flexural stress each have a length dimension parallel to the length dimension of the respective one of the beams that is greater than a thickness dimension parallel to the second dimension, and
- at least one layer of the one or more layers of the second material is sandwiched by one or more layers of the respective one of the beams, so to be covered in each direction along the thickness dimension;
- and
- wherein, within each respective one of the beams:
- beams,
- the second material is formed to occupy one or more slots defined within the first material, and
- a concentration of the second material relative to the first material is maximized in a region defined along the length dimension of the respective one of the beams which spans no more than thirty percent of a length of the respective one of the beams.
10 more elements
Dependencies are inferred from the claim text.