Bulk acoustic wave resonators having convex surfaces, and methods of forming the same
In bulk acoustic wave (BAW) resonators having convex surfaces, 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 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 having opposite first and second surfaces;
a first electrode having opposite third and fourth surfaces, a first edge and a second edge, in which the third surface spans between the first edge and the second edge, and the third surface and the first and second edges are on the second surface;
a piezoelectric layer on the first electrode, the piezoelectric layer having a convex surface; and
a second electrode on the convex surface.
2. The BAW resonator of claim 1 , wherein the convex surface is configured to: reduce a spurious mode; and confine a main mode in a central portion of the BAW resonator.
3. The BAW resonator of claim 1 , wherein the piezoelectric layer has a surface opposite the convex surface.
4. The BAW resonator of claim 1 , wherein the substrate supports the BAW resonator.
5. The BAW resonator of claim 1 , wherein the piezoelectric layer includes a film of at least one of aluminum nitride or zinc oxide.
6. The BAW resonator of claim 1 , wherein the convex surface is configured to reduce a leakage of acoustic energy from the BAW resonator.
7. The BAW resonator of claim 6 , wherein the convex surface is configured to increase a quality factor of the BAW resonator by reducing the leakage of the acoustic energy from the BAW resonator.
8. An integrated circuit (IC) comprising:
a bulk acoustic wave (BAW) resonator, the BAW resonator including:
a substrate having opposite first and second surfaces;
an electrode having opposite third and fourth surfaces, a first edge and a second edge, in which the third surface spans between the first edge and the second edge, and the third surface and the first and second edges are on the second surface; and
a piezoelectric layer on the fourth surface, the piezoelectric layer having a convex surface.
9. The IC of claim 8 , wherein the BAW resonator is a thin-film BAW resonator.
10. The IC of claim 8 , wherein the convex surface is formed using at least one of shaped lithography or gray-scale lithography.
11. The IC of claim 8 , wherein the substrate supports the BAW resonator.
12. The IC of claim 8 , wherein the piezoelectric layer includes aluminum nitride.
13. The IC of claim 8 , wherein the piezoelectric layer is plano-convex.
14. The IC of claim 8 , wherein the convex surface is configured to: reduce a spurious mode; and confine a main mode in a central portion of the BAW resonator.
15. The IC of claim 8 , wherein the piezoelectric layer has a surface opposite the convex surface.
16. The IC of claim 8 , wherein the piezoelectric layer includes a film of at least one of aluminum nitride or zinc oxide.
17. The IC of claim 8 , wherein the convex surface is configured to reduce a leakage of acoustic energy from the BAW resonator.
18. The IC of claim 17 , wherein the convex surface is configured to increase a quality factor of the BAW resonator by reducing the leakage of the acoustic energy from the BAW resonator.
19. The IC of claim 8 , wherein the electrode is a first electrode, and the IC further comprises a second electrode on the convex surface.
20. The BAW resonator of claim 1 , wherein the BAW resonator is a thin-film BAW resonator.
21. The BAW resonator of claim 1 , wherein the convex surface is formed using at least one of shaped lithography or gray-scale lithography.
22. The BAW resonator of claim 1 , wherein the piezoelectric layer includes aluminum nitride.
23. The BAW resonator of claim 1 , wherein the piezoelectric layer is plano-convex.