Film bulk acoustic resonators in thin LN-LT layers
Acoustic resonator devices, filter devices, and methods of fabrication are disclosed. A resonator device includes a single-crystal piezoelectric plate having a front surface and a back surface opposite the front surface, wherein the back surface is coupled to a surface of a substrate. A floating back-side conductor pattern is formed on a portion of the back surface. A front-side conductor pattern including two electrodes is formed on a portion of the front surface opposite the back-side conductor. A portion of the piezoelectric plate forms a diaphragm spanning a cavity in the substrate and the front-side conductor pattern is on the diaphragm.
1. An acoustic resonator device comprising:
a single-crystal piezoelectric plate having a front surface and a back surface opposite the front surface, wherein the back surface is coupled to a surface of a substrate;
a floating back-side conductor pattern formed on the back surface; and
a front-side conductor pattern comprising two electrodes formed on a portion of the front surface opposite the back-side conductor pattern, wherein a portion of the single-crystal piezoelectric plate forms a diaphragm spanning a cavity in the substrate and the front-side conductor pattern is on the diaphragm.
2. The device of claim 1 , wherein a radio frequency signal applied between the two electrodes excites a primary acoustic mode in the single-crystal piezoelectric plate.
3. The device of claim 1 , wherein the back-side conductor pattern is in the cavity.
4. The device of claim 1 , wherein the front-side conductor pattern comprises interleaved fingers connected to busbars of opposite polarity.
5. The device of claim 4 , wherein the interleaved fingers have a non-rectangular shape.
6. The device of claim 1 , wherein a portion of the single-crystal piezoelectric plate between the two electrodes is recessed to form a slot.
7. A filter device comprising:
a single-crystal piezoelectric plate having a front surface and a back surface opposite the front surface, wherein the back surface is coupled to a surface of a substrate;
a plurality of floating back-side conductor patterns formed on the back surface; and
a plurality of front-side conductor patterns, each consisting of two electrodes and formed on respective portions of the front surface opposite respective ones of the plurality of back-side conductor patterns, wherein each of the plurality of front conductor patterns corresponds to one of a plurality of resonators including a shunt resonator and a series resonator.
8. The device of claim 7 , wherein a radio frequency applied between the two electrodes of a respective front-side conductor pattern excites a primary acoustic mode in the single-crystal piezoelectric plate.
9. The device of claim 7 , wherein at least one of the plurality of floating back-side conductor patterns is an acoustic Bragg reflector.
10. The device of claim 9 , wherein the acoustic Bragg reflector is between the surface of the substrate and the back surface of the single-crystal piezoelectric plate.
11. The device of claim 7 , wherein a portion of the single-crystal piezoelectric plate forms at least one diaphragm spanning at least one cavity in the substrate, and at least one of the plurality of front-side conductor patterns is on a respective one of the at least diaphragm.
12. The device of claim 11 , wherein at least one of the plurality of back-side conductor patterns is in a respective one of the at least one cavity.
13. The device of claim 7 , wherein at least one of the plurality of front-side conductors comprises interleaved fingers connected to busbars of opposite polarity.
14. The device of claim 13 , wherein the interleaved fingers have a non-rectangular shape.
15. The device of claim 7 , wherein a portion of the single-crystal piezoelectric plate between the two electrodes of at least one of the plurality of front-side conductors is recessed to form a slot.
16. A method of fabricating an acoustic resonator device comprising:
coupling a back surface of a single-crystal piezoelectric plate to a substrate, the single-crystal piezoelectric plate having a front surface opposite the back surface;
forming a floating back-side conductor pattern on the back surface; and
forming a front-side conductor pattern consisting of two electrodes on a portion of the front surface opposite the back-side conductor pattern, wherein a portion of the single-crystal piezoelectric plate forms a diaphragm spanning a cavity in the substrate and the front-side conductor pattern is on the diaphragm.
17. The method of claim 16 , wherein a radio frequency signal applied between the two electrodes excites a primary acoustic mode in the single-crystal piezoelectric plate.
18. The method of claim 16 , wherein the back-side conductor pattern is in the cavity.
19. The method of claim 16 , wherein the front-side conductor pattern comprises interleaved fingers connected to busbars of opposite polarity.
20. The method of claim 19 , wherein the interleaved fingers have a non-rectangular shape.
21. The method of claim 16 , wherein a portion of the single-crystal piezoelectric plate between the two electrodes is removed to form a slot.