Bulk acoustic wave resonators having convex surfaces, and methods of forming the same
Bulk acoustic wave (BAW) resonators having convex surfaces, and methods of forming the same are disclosed. An example BAW resonator includes a first electrode, a piezoelectric layer formed on the first electrode, the piezoelectric layer having a convex surface, and a second electrode formed on the convex surface. An example integrated circuit (IC) package includes a BAW resonator disposed in the IC package, the BAW resonator including a piezoelectric layer having a convex surface.
1. A bulk acoustic wave (BAW) resonator comprising:
a substrate configured to have a first planar surface and a second planar surface, the second planar surface opposite the first planar surface, the first planar surface configured to be disposed on an integrated circuit;
a first electrode configured to have a third planar surface, a fourth planar surface, a first planar surface end, and a second planar surface end, the third planar surface opposite the fourth planar surface, the third planar surface spanning between the first planar surface end and the second planar surface end, wherein the third planar surface, the first planar surface end, and the second planar surface end are configured to be disposed on the second planar surface of the substrate;
a piezoelectric layer disposed on the first electrode, the piezoelectric layer having a convex surface; and
a second electrode disposed on the convex surface.
2. The BAW resonator of claim 1 , wherein the convex surface reduces a spurious mode and confines a main mode in a central portion of the BAW resonator.
3. The BAW resonator of claim 1 , wherein the piezoelectric layer has a planar surface opposite the convex surface.
4. The BAW resonator of claim 1 , wherein the substrate is configured to support the BAW resonator.
5. The BAW resonator of claim 1 , wherein the piezoelectric layer includes a thin film of at least one of aluminum nitride or zinc oxide.
6. The BAW resonator of claim 1 , wherein the convex surface reduces a leakage of acoustic energy out from the BAW resonator.
7. The BAW resonator of claim 6 , wherein the reduction of the leakage of the acoustic energy increases a quality factor of the BAW resonator.
8. An integrated circuit (IC) package comprising:
a bulk acoustic wave (BAW) resonator disposed in the package, the BAW resonator including:
a substrate configured to have a first planar surface and a second planar surface, the second planar surface opposite the first planar surface, the first planar surface configured to be disposed on an integrated circuit;
an electrode configured to have a third planar surface, a fourth planar surface, a first planar surface end, and a second planar surface end, the third planar surface opposite the fourth planar surface, the third planar surface spanning between the first planar surface end and the second planar surface end, wherein the third planar surface, the first planar surface end, and the second planar surface end are configured to be disposed on the second planar surface of the substrate; and
a piezoelectric layer disposed on the fourth planar surface of the electrode, the piezoelectric layer having a convex surface.
9. The IC package of claim 8 , wherein the BAW resonator is a thin-film BAW resonator.
10. The IC package of claim 8 , the convex surface formed using at least one of shaped lithography, or gray-scale lithography.
11. The IC package of claim 8 , wherein the substrate is to support the BAW resonator.
12. The IC package of claim 8 , wherein the piezoelectric layer includes aluminum nitride.
13. The IC package of claim 8 , wherein the piezoelectric layer is plano-convex.