Acoustic devices using an AIGaN piezoelectric region

• US 20070139141A1
• Filed: 12/20/2005
• Published: 06/21/2007
• Est. Priority Date: 12/20/2005
• Status: Active Grant

• Current Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Johnson, Noble, Kneissl, Michael, Knollenberg, Clifford
• Granted Patent: US 7,528,681 B2
• Time in Patent Office: Days
• US Class Current: 333/191
• CPC Class Codes: H03H 3/02 for the manufacture of piezoelectric or electrostrictive resonators or networks H03H3/08 takes precedence
• CPC Class Codes: H03H 9/0542 consisting of a lateral arrangement H03H9/0566 takes precedence
• CPC Class Codes: H03H 9/172 Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
• CPC Class Codes: H03H 9/587 Air-gaps
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

Provided is a method of forming an acoustic based device, including forming an AlGaN region having a first surface and a second surface. A first electrode is deposited on the first surface of the AlGaN region, and then a second electrode is deposited on a second surface of the AlGaN-region. In another aspect of the present application, the AlGaN region is formed by an epitaxial layer overgrowth process.

Claims

1. A method of forming an acoustical device arrangement, comprising:

providing a substrate having a first surface and a second surface;

providing a sacrificial layer on at least a portion of the first surface of the substrate;

growing a piezoelectric region on the first surface of the first substrate by epitaxial layer overgrowth, the piezoelectric region formed over at least a portion of the sacrificial layer, wherein growth of the piezoelectric region is at least in part perpendicular to the first surface of the substrate;

etching the piezoelectric region to define a first portion of the piezoelectric region, having a polar axis perpendicular to the first surface of the substrate, the etching used to define the portion of the piezoelectric region employing a photolithographic pattern arrangement, wherein the thickness of the piezoelectric portion is determined by use of the photolithographic pattern arrangement;

forming a first electrode on a first side of the first portion of the piezoelectric region;

forming a second electrode on a second side of the first portion of the piezoelectric region; and

removing the sacrificial layer.

2. The method according to claim 1, wherein the piezoelectric region is a grown single crystal AlGaN material.

3. The method according to claim 1, wherein the piezoelectric region is a grown polycrystalline AlGaN material.

4. The method according to claim 1, wherein

the etching of the piezoelectric region further includes etching to define a second portion of the piezoelectric region, having a crystal growth pattern at least in part perpendicular to the first surface of the substrate, the etching used to define the first and the second portions of the piezoelectric regions by employing a photolithographic pattern arrangement, wherein thicknesses of the first and second piezoelectric portions are determined by use of the photolithographic pattern arrangement;

and

the forming steps further include,

forming a first electrode on a first side of the second piezoelectric region, and

forming a second electrode on a second side of the second piezoelectric region.

5. The method according to claim 4, wherein the acoustical device arrangement includes at least two separately and simultaneously formed acoustical devices.

6. The method according to claim 5, wherein the acoustical device arrangement includes at least two acoustical devices, each operational in at least one of a bulk resonant mode and a shear wave resonant mode.

7. The method according to claim 5, wherein a thickness of the first piezoelectric portion is different from a thickness of the second piezoelectric portion.

8. The method according to claim 7, wherein the first piezoelectric portion and the second piezoelectric portion resonate at frequencies different from each other.

9. A method of forming an acoustical device comprising:

providing a first substrate having a first surface and a second surface;

growing a piezoelectric region having a first surface and a second surface, the piezoelectric region located on the first surface of the first substrate, wherein the first surface of the piezoelectric region and the first surface of the substrate are in direct contact;

depositing a first electrode layer on a second surface of the piezoelectric region;

performing a laser lift-off process to break a bond between the first surface of the first substrate and the first surface of the single crystal to separate the first substrate and the piezoelectric region; and

depositing a second electrode layer on the first surface of the piezoelectric region.

10. The method according to claim 9, wherein the piezoelectric region is a grown single crystal material.

11. The method according to claim 9, wherein the piezoelectric region is a grown polycrystalline material.

12. The method according to claim 9, wherein the lift-off process includes,

emitting, from a radiation source, a radiation beam through the first substrate to an attachment interface formed by the first substrate and the single crystal, wherein the first substrate is substantially transparent at the wavelength of the radiation beam, and the radiation beam generates sufficient absorbed energy at the interface to break the attachment.

13. The method according to claim 12, further including trimming the piezoelectric region to cause the piezoelectric region to resonate at a desired frequency.

14. The method according to claim 12, wherein following the step of depositing the first electrode, providing a gap forming arrangement on the same side as the first electrode.

15. The method according to claim 14, wherein prior to performing the liftoff process, bonding the gap forming arrangement to a second substrate.

16. The method according to claim 9, wherein the acoustical device is operational in at least one of a bulk resonant mode and a shear wave resonant mode.

17. An acoustical device, comprising:

an AlGaN region having a first surface and a second surface;

a first electrode deposited on the first surface of the AlGaN region;

a second electrode deposited on the second surface of the AlGaN region;

a first air or vacuum interface associated with at least a portion of the first surface of the AlGaN region and the first electrode; and

a second air or vacuum interface associated with at least a portion of the second surface of the AlGaN region and the second electrode.

18. The device according to claim 17, wherein the acoustical device is operational in at least one of a bulk resonant mode and a shear wave resonant mode.

19. The device according to claim 17, wherein the AlGaN region is a single crystal AlGaN region.

20. The device according to claim 17, wherein the AlGaN region is a polycrystalline AlGaN region.

21. The method according to claim 17, wherein the AlGaN region may be selected from a variety of AlGaN material types, having different values, from each other, of at least one of the Al and Ga components, and wherein In may be used during growth and incorporated in the AlGaN region.