Microelectromechanical resonator
In a MEMS device having a substrate and a moveable micromachined member, a mechanical structure secures the moveable micromachined member to the substrate, thermally isolates the moveable micromachined member from the substrate and provides a conduction path to enable heating of the moveable micromachined member to a temperature of at least 300 degrees Celsius.
1. A microelectromechanical system (MEMS) resonator comprising:
a layer of degenerately-doped polycrystalline silicon;
a layer of degenerately-doped single-crystal silicon; and
a layer of piezoelectric material sandwiched between the degenerately-doped polycrystalline silicon layer and the degenerately-doped single-crystal silicon layer.
2. The MEMS resonator of claim 1 wherein the layer of piezoelectric material comprises aluminum nitride.
3. The MEMS resonator of claim 1 wherein the degenerately-doped single-crystal silicon layer is at least 10 times thicker than the layer of piezoelectric material.
4. The MEMS resonator of claim 1 wherein the layers of degenerately-doped polycrystalline silicon, degenerately-doped single-crystal silicon and piezoelectric material form a resonator body and one or more tethering structures that mechanically couple the resonator body to anchoring points within a field area.
5. The MEMS resonator of claim 4 wherein the layer of degenerately-doped polycrystalline silicon comprises a first electrode within the resonator body and a first conductive path within each of the one or more tethering structures to enable the first electrode to be electrically coupled, through at least one of the tethering structures, to a first node of a voltage source external to the resonator.
6. The MEMS resonator of claim 5 wherein the layer of degenerately-doped single-crystal silicon comprises a second electrode within the resonator body and a second conductive path within each of the one or more tethering structures to enable the second electrode to be electrically coupled to a second node of the voltage source external to the resonator such that a voltage generated by the voltage source yields an electrostatic potential across the layer of piezoelectric material.
7. The MEMS resonator of claim 5 wherein the one or more tethering structures comprise at least two tethering structures that enable the first electrode to be coupled between the first node of the voltage source external to the resonator and a second node of the voltage source external to the resonator such that a potential difference is applied across the first electrode.
8. The MEMS resonator of claim 5 wherein the first electrode is patterned to form a resistive region with sufficient resistance to heat the resonator body to a temperature of at least 300 degrees Celsius when a current is conducted through the resistive region.
9. The MEMS resonator of claim 5 wherein the one or more tethering structures thermally isolate the resonator body from the anchoring points and exhibit sufficient electrical resistivity to enable heating of the resonator body to a temperature of at least 300 degrees Celsius when a joule heating current is conducted through the one or more tethering structures.
10. The MEMS resonator of claim 5 wherein the one or more tethering structures comprise two tethering structures coupled to the first electrode at opposite sides of the resonator body.