Piezoelectric acoustic resonator with improved TCF manufactured with piezoelectric thin film transfer process

Patent metadata

Field	Value
Publication number	US-11356071-B2
Application number	US-202016893026-A
Country	US
Kind code	B2
Filing date	Jun 4, 2020
Priority date	Mar 11, 2016
Publication date	Jun 7, 2022
Grant date	Jun 7, 2022

Abstract

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. Patterned electrodes are deposited on the surface of the piezoelectric film. An etched sacrificial layer is deposited over the electrodes and a planarized support layer is deposited over the sacrificial layer. The device can include temperature compensation layers (TCL) that improve the device TCF. These layers can be thin layers of oxide type materials and can be configured between the top electrode and the piezoelectric layer, between the bottom electrode and the piezoelectric layer, between two or more piezoelectric layers, and any combination thereof. In an example, the TCLs can be configured from thick passivation layers overlying the top electrode and/or underlying the bottom electrode.

First claim

What is claimed is:

1. A method for fabricating an acoustic resonator device, the method comprising:
forming a piezoelectric film overlying a growth substrate;
forming a first electrode overlying the piezoelectric film;
forming a first passivation layer overlying the first electrode and the piezoelectric film;
forming a sacrificial layer overlying the first passivation layer, the first electrode, and the piezoelectric film;
forming a support layer overlying the sacrificial layer, the first passivation layer, the first electrode, and the piezoelectric film thereby forming a device on the growth substrate;
polishing the support layer;
forming a bonding support layer overlying a bond substrate;
flipping the device on the growth substrate and bonding the polished support layer to the bonding support layer thereby forming a bonded device;
removing the growth substrate from the bonded device;
forming a first temperature compensation layer (TCL) overlying the piezoelectric layer;
forming an electrode contact via within the piezoelectric film and the first TCL overlying the first electrode on the bonded device;
forming a second electrode layer overlying the first TCL, the piezoelectric film, and within the contact via;
etching the second electrode layer to form a top metal separated from a second electrode, wherein the top metal is physically coupled to the first electrode through the electrode contact via and the second electrode is overlying the first TCL and the piezoelectric film;
forming a first contact metal overlying the second electrode, the first TCL, and the piezoelectric film;
forming a second contact metal overlying the top metal, the first TCL, and the piezoelectric film;
forming a second passivation layer overlying the first TCL, the piezoelectric film, the second electrode, and the top metal;
forming one or more release holes within the first TCL, the piezoelectric film, and the first passivation layer overlying the sacrificial layer on the bonded device; and
removing the sacrificial layer by way of the one or more release holes to form an air cavity within the bonded device.

2. The method 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 method of claim 1 wherein the piezoelectric film is a single crystal or polycrystalline piezoelectric film that includes aluminum nitride (AlN), aluminum scandium nitride (AlScN), gallium nitride (GaN), alloys, or other epitaxial materials.

4. The method of claim 1 wherein the piezoelectric film is an upper portion of a polycrystalline piezoelectric film that includes aluminum nitride (AlN), aluminum scandium nitride (AlScN), gallium nitride (GaN), Al x Ga 1-x N alloys, or other polycrystalline epitaxial materials.

5. The method 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 first and second passivation layers, the first TCL, and the sacrificial layer include silicon nitride (SiN), silicon oxide (SiO), silicon dioxide (SiO 2 ), or other silicon materials; and
wherein the first and second contact metals include gold (Au), aluminum (Al), copper (Cu), nickel (Ni), aluminum bronze (AlCu), or other metal materials.

6. The method of claim 1 wherein the first TCL is characterized by a thickness of 50 to 2000 Angstroms.

7. The method of claim 1 wherein polishing the support layer includes a chemical-mechanical planarization (CMP) process; wherein the support layer and the bonding support layer include silicon dioxide (SiO 2 ) or other silicon materials; and wherein removing the growth substrate includes a grinding process, a blanket etching process, a film transfer process, an ion implantation transfer process, or a laser crack transfer process; and wherein the removal of the sacrificial layer includes a poly-Si etch or an a-Si etch or other etching process.

8. The method of claim 1 further comprising processing the second electrode and the top metal to form a processed second electrode and a processed top metal, wherein the processed second electrode includes an energy confinement structure.

9. The method of claim 1 further comprising processing the first electrode to form a processed first electrode, wherein the processed first electrode includes an energy confinement structure.

10. The method of claim 1 wherein forming the piezoelectric film includes forming a second TCL overlying the piezoelectric film before forming the first electrode; and
wherein forming the one or more release holes includes forming the release holes within the second TCL.

11. A method for fabricating an acoustic resonator device, the method comprising:
forming a piezoelectric film overlying a growth substrate;
forming a first temperature compensation layer (TCL) overlying the piezoelectric film;
forming a first electrode overlying the first TCL and the piezoelectric film;
forming a first passivation layer overlying the first electrode, the first TCL, and the piezoelectric film;
forming a sacrificial layer overlying the first passivation layer, the first electrode, the first TCL, and the piezoelectric film;
forming a support layer overlying the sacrificial layer, the first passivation layer, the first electrode, the first TCL, and the piezoelectric film thereby forming a device on the growth substrate;
polishing the support layer;
forming a bonding support layer overlying a bond substrate;
flipping the device on the growth substrate and bonding the polished support layer to the bonding support layer thereby forming a bonded device;
removing the growth substrate from the bonded device;
forming an electrode contact via within the piezoelectric film and the first TCL overlying the first electrode on the bonded device;
forming a second electrode layer overlying the piezoelectric film and within the contact via;
etching the second electrode layer to form a top metal separated from a second electrode, wherein the top metal is physically coupled to the first electrode through the electrode contact via and the second electrode is overlying the piezoelectric film;
forming a first contact metal overlying the second electrode and the piezoelectric film;
forming a second contact metal overlying the top metal and the piezoelectric film;
forming a second passivation layer overlying the piezoelectric film, the second electrode, and the top metal;
forming one or more release holes within the piezoelectric film and the first passivation layer overlying the sacrificial layer on the bonded device; and
removing the sacrificial layer by way of the one or more release holes to form an air cavity within the bonded device.

12. The method of claim 11 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.

13. The method of claim 11 wherein the piezoelectric film is a single crystal or polycrystalline piezoelectric film that includes aluminum nitride (AlN), aluminum scandium nitride (AlScN), gallium nitride (GaN), alloys, or other epitaxial materials.

14. The method of claim 11 wherein the piezoelectric film is an upper portion of a polycrystalline piezoelectric film that includes aluminum nitride (AlN), aluminum scandium nitride (AlScN), gallium nitride (GaN), Al x Ga 1-x N alloys, or other polycrystalline epitaxial materials.

15. The method of claim 11 wherein the first electrode, second electrode, and t

Assignees

• Akoustis Inc

Inventors

• Kim Dae Ho
• Bi Frank
• Winters Mary
• Vetury Ramakrishna
• Kochhar Abhay

Classifications

• H03H9/173

  Air-gaps · CPC title

• H03H2003/021

  the resonators or networks being of the air-gap type · CPC title

• H03H9/13

  for networks consisting of piezoelectric or electrostrictive materials (for networks using surface acoustic waves H03H9/145) · CPC title

• H03H9/177

  of the energy-trap type · CPC title

• H03H2003/0407

  Temperature coefficient · CPC title