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US 12,492,120 B2Granted
MEMS resonator
AssigneeSiTime Corporation
InventorsCharles I. Grosjean, Nicholas Miller, Paul M. Hagelin, Ginel C. Hill, Joseph C. Doll
Life of this patent
Estimating the term…
Abstract
Multiple degenerately-doped silicon layers are implemented within resonant structures to control multiple orders of temperature coefficients of frequency.
Claims26
A method of fabricating an integrated circuit, the method comprising:
- forming a microelectromechanical systems (MEMS) device so as to have a first layer of silicon, a second layer of silicon, and a layer of piezoelectric material;
- wherein:
- at least one of the first layer of silicon or the second layer of silicon is both degenerately doped and to serve as an electrode during operation of the MEMS device;
- the MEMS device has a body that is to deflect or vibrate during operation of the integrated circuit, the body having a shape that is symmetric about at least one anchor point of the MEMS device;
- the MEMS device is to, during operation of the integrated circuit, output a signal representing sensed deflection or vibration of the body;
- a ratio between (1) a thickness of the piezoelectric material, and (2) a thickness of at least one of the first layer of silicon or the second layer of silicon is selected such that a maximum variation of vibration frequency of the body, within a predetermined temperature range, lies within a threshold, and such that a nonlinear contribution of the piezoelectric material to variation in the vibration frequency is of opposite polarity relative to a nonlinear contribution of the one of the first layer of silicon or the second layer of silicon to variation in the vibration frequency, for a majority of the predetermined temperature range;
- and
- forming further comprises encapsulating the MEMS device within the integrated circuit;
- and
- subjecting the MEMS device to a post-encapsulation tuning process, in which the body is heated, and in which the deflection or vibration of the body is measured, so as to adjust, dependent on the tuning process, at least one temperature-dependent characteristic of the MEMS device.
7 more elements
A method of fabricating an oscillator integrated circuit, the method comprising:
- forming a microelectromechanical systems (MEMS) resonator so as to have a body having a first layer of silicon, a second layer of silicon, and a layer of piezoelectric material;
- wherein:
- at least one of the first layer of silicon or the second layer of silicon is both degenerately doped and to serve as an electrode during operation of the MEMS device;
- the body that is to deflect or vibrate during operation of the integrated circuit, the body having a shape that is symmetric about at least one anchor point of the MEMS device;
- the MEMS device is to, during operation of the integrated circuit, output a signal representing sensed deflection or vibration of the body;
- a ratio between (1) a thickness of the piezoelectric material, and (2) a thickness of at least one of the first layer of silicon or the second layer of silicon is selected such that a maximum variation of vibration frequency of the body, within a predetermined temperature range, lies within a threshold, and such that a nonlinear contribution of the piezoelectric material to variation in the vibration frequency is of opposite polarity relative to a nonlinear contribution of the one of the first layer of silicon or the second layer of silicon to variation in the vibration frequency, for a majority of the predetermined temperature range;
- and
- forming further comprises encapsulating the MEMS device within the integrated circuit;
- and
- subjecting the MEMS device to a post-encapsulation tuning process, in which the body is heated, and in which the deflection or vibration of the body is measured, so as to adjust, dependent on the tuning process, at least one temperature-dependent characteristic of the MEMS device.
7 more elements
Dependencies are inferred from the claim text.