Lithographically defined multi-standard multi-frequency high-Q tunable micromechanical resonators
Disclosed are micromechanical resonator apparatus having features that permit multiple resonators on the same substrate to operate at different operating frequencies. Exemplary micromechanical resonator apparatus includes a support substrate and suspended micromechanical resonator apparatus having a resonance frequency. In one embodiment, the suspended micromechanical resonator apparatus comprises a device substrate that is suspended from and attached to the support substrate, a piezoelectric layer formed on the suspended device substrate, and a plurality of interdigitated upper electrodes formed on the piezoelectric layer. In another embodiment, the suspended micromechanical resonator apparatus comprises a device substrate that is suspended from and attached to the support substrate, a lower electrode formed on the suspended device substrate, a piezoelectric layer formed on the lower electrode, and a plurality of interdigitated upper electrodes formed on the piezoelectric layer. The substrate may comprise a silicon substrate, or a semiconductor-on-insulator substrate, such as a diamond on silicon substrate. Additionally, lateral frequency-adjusting electrodes may be disposed adjacent to the resonator apparatus that are separated therefrom by a capacitive gap, and which are configured to receive a direct current voltage that adjusts the resonance frequency of the resonator apparatus.
1. A micromechanical resonator operable in a bulk acoustic mode, comprising:
a resonator apparatus suspended over a substrate, said resonator apparatus comprising a composite of a device layer and a piezoelectric stack on the device layer, said piezoelectric stack comprising a conductive metal layer on the device layer, a piezoelectric layer on the conductive metal layer and a plurality of interdigitated electrodes on the piezoelectric layer.
2. The micromechanical resonator of claim 1 , wherein said resonator apparatus is anchored to the substrate by a plurality of anchors.
3. The micromechanical resonator of claim 2 , wherein each of the plurality of interdigitated electrodes extends across a respective one of the plurality of anchors.
4. The micromechanical resonator of claim 3 , further comprising:
an excitation port on the substrate, electrically connected to a first one of the plurality of interdigitated electrodes; and
a sense port on the substrate, electrically connected to a second one of the plurality of interdigitated electrodes.
5. The micromechanical resonator of claim 3 , wherein said resonator apparatus is suspended over a cavity in the substrate; and wherein said resonator apparatus comprises an electrically insulating layer on a bottom surface of the device layer that faces the cavity.
6. The micromechanical resonator of claim 1 , wherein a pitch between said plurality of interdigitated electrodes is uniform.
7. The micromechanical resonator of claim 1 , wherein the device layer is a single crystal silicon device layer.
8. The micromechanical resonator of claim 1 , wherein the device layer comprises a material selected from a group consisting of diamond, nanocrystalline diamond, silicon carbide, silicon-germanium and gallium arsenide.
9. The micromechanical resonator of claim 1 , further comprising a pair of frequency-adjusting electrodes disposed adjacent opposite sides of said resonator apparatus and separated from the opposite sides by respective capacitive gaps.
10. The micromechanical resonator of claim 1 , wherein the piezoelectric layer comprises zinc oxide.
11. The micromechanical resonator of claim 1 , wherein the conductive metal layer comprises a composite of a gold layer and a chromium layer.