Patent ID: 11909376
Assignee: SITIME CORPORATION
Field: Basic communication processes (Electrical engineering)
Classification: CPC H | IPC H

Claim 24:
25. An integrated circuit comprising:
a microelectromechanical system (MEMS) resonator on the integrated circuit;
the MEMS resonator having a degenerately doped single-crystal silicon (SCS) layer, a piezoelectric material layer disposed on the degenerately doped SCS layer, and an electrically conductive polycrystal silicon layer disposed on the piezoelectric material layer opposite the degenerately doped SCS layer;
circuitry to sense a temperature;
circuitry to receive a signal from the MEMS resonator dependent on a resonant frequency of the MEMS resonator and to generate an output dependent on the resonant frequency and the sensed temperature, in a manner such that the output exhibits a reduced temperature dependent variation relative to temperature-dependent variation of the resonant frequency;
wherein the piezoelectric material layer has a second order temperature coefficient of frequency (TCF) and the degenerately doped SCS layer is configured to have a dopant concentration and crystal orientation relative to an axis of vibration of the resonance mode such that the degenerately doped SCS layer has a second order TCF that is opposite in sign to the second order TCF of the piezoelectric material layer; and
wherein a ratio of a thickness of the degenerately doped SCS layer to a thickness of the piezoelectric material layer is selected such that a first order TCF of the degenerately doped SCS layer is opposite in sign to a first order TCF of the piezoelectric material layer and such that an overall first order TCF of the MEMS resonator lies within a predetermined tolerance range about zero.