POLARITY DETERMINING SEED LAYER AND METHOD OF FABRICATING PIEZOELECTRIC MATERIALS WITH SPECIFIC C-AXIS

• US 20110121689A1
• Filed: 11/23/2009
• Published: 05/26/2011
• Est. Priority Date: 11/23/2009
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies Wireless IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Feng, Chris, Grannen, Kevin, Choy, John
• Granted Patent: US 9,847,768 B2
• Time in Patent Office: Days
• US Class Current: 310/357
• CPC Class Codes: C30B 23/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: H03H 9/02015 Characteristics of piezoelectric layers, e.g. cutting angles
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

An acoustic resonator comprises a first electrode, a second electrode and a piezoelectric layer disposed between the first electrode and the second electrode, and comprising a C-axis having an orientation. A polarization-determining seed layer (PDSL) is disposed beneath the piezoelectric layer, the seed layer comprising a metal-nonmetal compound. A method of fabricating a piezoelectric layer over a substrate comprises forming a first layer of a polarization determining seed layer (PDSL) over the substrate. The method further comprises forming a second layer of the PDSL over the first layer. The method further comprises forming a first layer of a piezoelectric material over the second layer of the PDSL; and forming a second layer of the piezoelectric material over the first layer of the piezoelectric material. The piezoelectric material comprises a compression axis (C-axis) oriented along a first direction.

Claims

1. An acoustic resonator, comprising:

a first electrode;

a second electrode;

a piezoelectric layer disposed between the first electrode and the second electrode, and comprising a C-axis having an orientation; and

a polarization-determining seed layer (PDSL) disposed beneath the piezoelectric layer, the seed layer comprising a metal-nonmetal compound.

2. An acoustic resonator as claimed in claim 1, wherein the PDSL terminates in a layer of the metal.

3. An acoustic resonator as claimed in claim 1, wherein the PDSL terminates in a layer of the non-metal.

4. An acoustic resonator as claimed in claim 1, wherein metal of the metal non-metal compound comprises Gallium and the non-metal comprises Nitrogen.

5. An acoustic resonator as claimed in claim 4, wherein the piezoelectric layer comprises aluminum nitride (AlN).

6. An acoustic resonator as claimed in claim 1, wherein the C-axis is a compression-positive (C_p) axis.

7. An acoustic resonator as claimed in claim 1, wherein the C-axis is a compression-positive (C_p) axis.

8. An acoustic resonator as claimed in claim 1 wherein the PDSL is a first PDSL, the piezoelectric layer is a first piezoelectric layer, and the C-axis is a first C-axis the acoustic resonator further comprising:

a second piezoelectric layer disposed over the second electrode and comprising a second C-axis; and

a second PDSL disposed between the second piezoelectric layer and the second electrode.

9. An acoustic resonator as claimed in claim 8, wherein the first C-axis is substantially antiparallel to the first C-axis.

10. An acoustic resonator as claimed in claim 8, wherein the first C-axis is substantially parallel to the first C-axis.

12. A method as claimed in claim 1, wherein the piezoelectric material is a first piezoelectric material and the PDSL is a first PDSL, the method further comprising:

forming a first film of a second PDSL;

forming a second film of the second PDSL over the first film of the second PDSL; and

forming a layer of a second piezoelectric material over the second film of the second PDSL, wherein the second piezoelectric material comprises a compression axis (C-axis) oriented along a second direction.

13. A method as claimed in claim 12, wherein the second direction is antiparallel to the first direction.

14. A method as claimed in claim 12, wherein the second direction is parallel to the first direction.

15. A method as claimed in claim 12, wherein the piezoelectric layer is AlN and the PDSL terminates in a layer of a metal.

16. A method as claimed in claim 12, wherein the piezoelectric layer is AlN and the PDSL terminates in a layer of a non-metal.

17. A method as claimed in claim 15, wherein the layer of metal comprises Gallium

18. A method as claimed in claim 16, wherein the non-metal comprises Nitrogen.

19. A method as claimed in claim 12, wherein the forming of the first layer of the PDSL and the forming of the second layer of the PDSL each comprise one of atomic layer deposition (ALD) and molecular beam epitaxy (MBE).

20. A method as claimed in claim 12, wherein the forming of the layer of the piezoelectric material comprises either atomic layer deposition (ALD) or molecular beam epitaxy (MBE), and sputter deposition.

11. A method of fabricating a piezoelectric layer over a substrate, the method comprising:

forming a first film of a polarization determining seed layer (PDSL) over the substrate;

forming a second film of the PDSL over the first film; and

forming a layer of a piezoelectric material over the second film of the PDSL, wherein the piezoelectric material comprises a compression axis (C-axis) oriented along a first direction.