Piezoelectric acoustic resonator manufactured with piezoelectric thin film transfer process
A method and structure for a transfer process for an acoustic resonator device. In an example, a bulk acoustic wave resonator (BAWR) with an air reflection cavity is formed. A piezoelectric thin film is grown on a crystalline substrate. A first patterned electrode is deposited on the surface of the piezoelectric film. An etched sacrificial layer is deposited over the first electrode and a planarized support layer is deposited over the sacrificial layer, which is then bonded to a substrate wafer. The crystalline substrate is removed and a second patterned electrode is deposited over a second surface of the film. The sacrificial layer is etched to release the air reflection cavity. Also, a cavity can instead be etched into the support layer prior to bonding with the substrate wafer. Alternatively, a reflector structure can be deposited on the first electrode, replacing the cavity.
1. An acoustic resonator device comprising: a bond substrate; a bonding support layer overlying the bond substrate; a support layer overlying the bonding support layer; a reflector structure overlying the support layer, wherein the reflector structure includes at least a pair of layers having a low acoustic impedance layer and a high acoustic impedance layer; a first electrode overlying the reflector structure and a portion of the support layer; a piezoelectric film overlying the support layer, the first electrode, and the reflector structure, the piezoelectric film having an electrode contact via; a second electrode formed overlying the piezoelectric film; a top metal formed overlying the piezoelectric film, the top metal being physically coupled to the first electrode through the electrode contact via; a first contact metal formed overlying a portion of the second electrode and the piezoelectric film; a second contact metal formed overlying a portion of the top metal and the piezoelectric film; and a passivation layer formed overlying the piezoelectric film, the second electrode, and the top metal.
2. The device of claim 1 wherein the growth substrate and bond substrate includes silicon (S), silicon carbide (SiC), sapphire (Al 2 O 3 ), silicon dioxide (SiO 2 ), or other silicon materials.
3. The device of claim 1 wherein the piezoelectric film is a single crystal or polycrystalline piezoelectric film that includes aluminum nitride (AlN), gallium nitride (GaN), Al x Ga 1-x N alloys, or other epitaxial materials.
4. The device of claim 1 wherein the piezoelectric film is an upper portion of a polycrystalline piezoelectric film that includes aluminum nitride (AlN), gallium nitride (GaN), Al x Ga 1-x N alloys, or other polycrystalline epitaxial materials.
5. The device of claim 1 wherein the first electrode, second electrode, and top metal include molybdenum (Mo), ruthenium (Ru), tungsten (W), or other conductive materials, wherein the passivation layer can include silicon nitride (SiN), silicon oxide (SiOx), silicon dioxide (SiO 2 ), or other silicon materials.
6. The device of claim 1 wherein the first and second contact metals include gold (Au), aluminum (Al), copper (Cu), nickel (Ni), aluminum bronze (AlCu), or other metal materials.
7. The device of claim 1 wherein the support layer and the bonding support layer include silicon dioxide (SiO 2 ) or other silicon materials.
8. The device of claim 1 wherein at least one of the first electrode and the second electrode includes an energy confinement structure.
9. The device of claim 8 wherein the energy confinement structure is configured as a mass loaded area surrounding a resonator area of the piezoelectric film.
10. The device of claim 9 wherein the resonator area includes a region where the first electrode, the piezoelectric film, and the second electrode overlap.