Piezo-on-diamond resonators and resonator systems
Disclosed are piezoelectrically-transduced micromachined bulk acoustic resonators fabricated on a polycrystalline diamond film deposited on a carrier substrate. Exemplary resonators comprise a substrate having a smooth diamond layer disposed thereon. A piezoelectric layer is disposed on the diamond layer and top and bottom electrodes sandwich the piezoelectric layer. The resonant structure comprising the diamond layer, piezoelectric layer and electrodes are released from the substrate and are free to vibrate. Additionally, one or more sensing platforms may be coupled to the substrate to form a mass sensor.
1. An acoustic resonator apparatus, comprising:
a diamond layer disposed on a substrate;
a piezoelectric layer disposed on the diamond layer; and
top and bottom electrodes sandwiching the piezoelectric layer;
wherein the diamond layer, the piezoelectric layer and the electrodes comprise a stack that is laterally and vertically released from the substrate to form a lateral extensional mode resonator that is free to vibrate relative to the substrate.
2. The apparatus recited in claim 1 wherein the substrate comprises silicon.
3. The apparatus recited in claim 1 wherein the resonator is a bulk acoustic resonator.
4. The apparatus recited in claim 1 wherein the resonator is a bulk acoustic resonator operating in its thickness, width or length extensional mode.
5. The apparatus recited in claim 1 wherein the substrate comprises silicon and silicon dioxide.
6. The apparatus recited in claim 1 wherein the diamond layer comprises a chemical vapor deposited polycrystalline diamond layer.
7. The apparatus recited in claim 1 further comprising a polished layer disposed between the diamond layer and the piezoelectric layer.
8. The apparatus recited in claim 7 wherein the polished layer compensates for the temperature coefficient of frequency of the other layers existing in the resonator composite structure.
9. The apparatus recited in claim 7 wherein the polished layer is silicon dioxide.
10. The apparatus recited in claim 1 wherein the piezoelectric layer comprises zinc oxide.
11. The apparatus recited in claim 1 wherein the piezoelectric layer comprises aluminum nitride.
12. The apparatus recited in claim 1 wherein the piezoelectric layer comprises a piezoelectric ceramic material.
13. The apparatus recited in claim 12 wherein the piezoelectric ceramic material comprises lead zirconate titanate.
14. The apparatus recited in claim 1 wherein the electrodes comprise a low resistivity metal.
15. The apparatus recited in claim 14 wherein the low resistivity metal is selected from a group including Au, Al, Pt, and Mo.
16. The apparatus recited in claim 14 wherein the low resistivity metal is deposited on either a Cr or a Ti adhesion layer.
17. The apparatus recited in claim 1 wherein the top and bottom electrodes are patterned.
18. The apparatus recited in claim 1 wherein the top electrode is patterned to provide for a two-port resonator.
19. The apparatus recited in claim 1 wherein the top electrode is patterned to excite higher order lateral bulk acoustic resonance modes of the resonant structure.
20. The apparatus recited in claim 1 further comprising one or more sensing platforms coupled to the stack to form a mass sensor.
21. The apparatus recited in claim 17 which comprises a gravimetric bio/chemical sensor.
22. The apparatus recited in claim 1 which comprises a plurality of resonator apparatus coupled together to realize a filter for RF applications.
23. The apparatus recited in claim 18 wherein the resonators are acoustically coupled.
24. The apparatus recited in claim 18 wherein the resonators are electrically coupled.