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, the support layer having an air cavity;
a first electrode overlying the air cavity and a portion of the support layer, the first electrode being recessed in the support layer;
a first passivation layer overlying the support layer and being physically coupled to the first electrode;
a piezoelectric film overlying the support layer, the first electrode, and the air cavity, 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 second 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 include 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; and wherein the first and second passivation layers can include silicon nitride (SiN), silicon oxide (SiO), 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.
11. The device of claim 1 , wherein all of the first electrode is recessed in the support layer.