Electrode-defined unsuspended acoustic resonator
A bulk acoustic resonator operable in a bulk acoustic mode includes a resonator body mounted to a separate carrier that is not part of the resonator body. The resonator body includes a piezoelectric layer, a device layer, and a top conductive layer on the piezoelectric layer opposite the device layer. The piezoelectric layer is a single crystal of LiNbO 3 cut at an angle of 130°±30°. A surface of the device layer opposite the piezoelectric layer is for mounting the resonator body to the carrier.
1. A bulk acoustic resonator, comprising:
a resonator body comprising:
a top conductive layer;
a piezoelectric layer located below the top conductive layer; and
a device layer of a radio frequency (RF) device below the piezoelectric layer opposite the top conductive layer,
wherein a reflectance (R) of an acoustic wave at an interface between the device layer and either the piezoelectric layer or a bottom conductive layer between the device layer and the piezoelectric layer is greater than 70%.
2. The bulk acoustic resonator of claim 1 , wherein the reflectance (R) is greater than 90%.
3. The bulk acoustic resonator of claim 1 , further comprising:
a package enclosing the resonator body,
wherein a surface of the device layer opposite the piezoelectric layer is mounted directly to an interior surface of the package.
4. The bulk acoustic resonator of claim 1 , further comprising:
a substrate having a lower acoustic impedance than an acoustic impedance of the device layer; and
a package enclosing the resonator body, wherein:
a surface of the device layer opposite the piezoelectric layer is mounted directly to the substrate; and
a surface of the substrate opposite the device layer is mounted directly to the package.
5. The bulk acoustic resonator of claim 1 , wherein the piezoelectric layer comprises one of:
(i) a single crystal of LiNbO 3 ; and
(ii) one or more of ZnO, AlN, InN, an alkali metal niobate, an alkali earth metal niobate, an alkali metal titanate, an alkali earth metal titanate, an alkali metal tantalite, an alkali earth metal tantalite, GaN, AlGaN, lead zirconate titanate (PZT), a polymer, or a doped form of any one thereof.
6. The bulk acoustic resonator according to claim 1 , wherein the device layer comprises at least one of:
(i) diamond, W, SiC, Ir, AlN, Al, Pt, Pd, Mo, Cr, Ti, Ta;
(ii) an element from one of Group 3A and 4A of the periodic table of the elements;
(iii) a transition element from one of Group 1B, 2B, 3B, 4B, 5B, 6B, 7B, and 8B of the periodic table of the elements;
(iv) ceramic;
(v) glass; and
(vi) polymer.
7. The bulk acoustic resonator of claim 1 ,
wherein a passivation layer of a dielectric material is located on one or more exterior surfaces of the bulk acoustic resonator, and
wherein the top conductive layer includes at least one pair of spaced conductive fingers.
8. The bulk acoustic resonator of claim 1 , further comprising connecting structures located at opposing sides of the resonator body.
9. The bulk acoustic resonator of claim 1 , wherein an acoustic impedance of the device layer is at least 10 6 Pa-s/m 3 .
10. The bulk acoustic resonator of claim 3 , wherein the acoustic impedance of the substrate is between 10 6 Pa-s/m 3 and 30×10 6 Pa-s/m 3 .