Bulk acoustic wave resonator with piezoelectric layer comprising lithium niobate or lithium tantalate

Patent metadata

Field	Value
Publication number	US-10164605-B2
Application number	US-201615006724-A
Country	US
Kind code	B2
Filing date	Jan 26, 2016
Priority date	Jan 26, 2016
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

A bulk acoustic wave (BAW) resonator includes a substrate defining a cavity, a bottom electrode disposed over the substrate and the cavity, a piezoelectric layer disposed on the bottom electrode, and a top electrode disposed on the piezoelectric layer. The piezoelectric layer includes polycrystalline lithium niobate (LN) material or polycrystalline lithium tantalite (LT) material. The BAW resonator may further include an encapsulant layer formed on side and top surfaces of the piezoelectric layer. The encapsulant layer is configured to protect the LN material or the LT material of the piezoelectric layer from a release solvent previously applied to sacrificial material within the cavity in the substrate.

First claim

The invention claimed is:

1. A bulk acoustic wave (BAW) resonator, comprising:
a substrate defining a cavity;
a bottom electrode disposed over the substrate and the cavity;
a piezoelectric layer disposed over the bottom electrode, the piezoelectric layer comprising polycrystalline lithium niobate (LN) material;
a top electrode disposed over the piezoelectric layer; and
an encapsulant layer formed over side and top surfaces of the piezoelectric layer, the encapsulant layer being configured to protect the LN material from a release solvent previously applied to sacrificial material within the cavity in the substrate.

2. The BAW resonator of claim 1 , wherein the polycrystalline LN is formed of crystal columns substantially aligned in parallel to each other.

3. The BAW resonator of claim 2 , wherein each of the LN crystal columns has a c-axis oriented substantially perpendicular to a top surface of the bottom electrode.

4. The BAW resonator of claim 1 , wherein at least one of the bottom electrode and the top electrode comprises multiple conductive layers, a first conductive layer being disposed adjacent to the piezoelectric layer and having a first acoustic impedance, and a second conductive layer being disposed adjacent to the first conductive layer and having a second acoustic impedance greater than the first acoustic impedance.

5. The BAW resonator of claim 1 , further comprising:
at least one lateral performance enhancement feature in at least one of the bottom electrode or the top electrode.

6. The BAW resonator of claim 5 , wherein the at least one lateral performance enhancement feature comprises at least one of an air-bridge or an air-wing.

7. The BAW resonator of claim 5 , wherein the at least one lateral performance enhancement feature comprises one of an inner frame or an outer frame.

8. A bulk acoustic wave (BAW) resonator, comprising:
a substrate defining a cavity;
a bottom electrode disposed over the substrate and the cavity;
a piezoelectric layer disposed over the bottom electrode, the piezoelectric layer comprising polycrystalline lithium tantalate (LT) material; and
a top electrode disposed over the piezoelectric layer; and
an encapsulant layer formed over side and top surfaces of the piezoelectric layer, the encapsulant layer being configured to protect the LT material from a release solvent previously applied to sacrificial material within the cavity in the substrate.

9. The BAW resonator of claim 8 , wherein each of the polycrystalline LT is formed of crystal columns substantially aligned in parallel to each other.

10. The BAW resonator of claim 9 , wherein each of the LT crystal columns has a c-axis oriented substantially perpendicular to a top surface of the bottom electrode.

11. The BAW resonator of claim 8 , wherein at least one of the bottom electrode and the top electrode comprises multiple conductive layers, a first conductive layer being disposed adjacent to the piezoelectric layer and having a first acoustic impedance, and a second conductive layer being disposed adjacent to the first conductive layer and having a second acoustic impedance greater than the first acoustic impedance.

12. The BAW resonator of claim 8 , further comprising:
at least one lateral performance enhancement feature in at least one of the bottom electrode or the top electrode.

13. The BAW resonator of claim 12 , wherein the at least one lateral performance enhancement feature comprises at least one of an air-bridge or an air-wing.

14. The BAW resonator of claim 12 , wherein the at least one lateral performance enhancement feature comprises one of an inner frame or an outer frame.

15. A bulk acoustic wave (BAW) resonator, comprising:
a substrate defining a cavity;
a bottom electrode disposed over the substrate and the cavity;
a piezoelectric layer disposed over the bottom electrode, the piezoelectric layer comprising one or polycrystalline lithium niobate (LN) material or polycrystalline lithium tantalate (LT) material;
a top electrode disposed over the piezoelectric layer; and
an encapsulant layer formed on the piezoelectric layer, the encapsulant layer comprising a dielectric material resistant to release solvent for releasing sacrificial material.

16. The BAW resonator of claim 15 , where the dielectric material comprises one of silicon carbide (SiC) or non-etchable boron-doped silicon glass (NEBSG).

17. The BAW resonator of claim 15 , where the dielectric material is resistant to release solvent comprising hydrofluoric acid.

18. The BAW resonator of claim 15 , wherein at least one of the bottom electrode and the top electrode comprises multiple conductive layers, a first conductive layer being disposed adjacent to the piezoelectric layer and having a first acoustic impedance, and a second conductive layer being disposed adjacent to the first conductive layer and having a second acoustic impedance greater than the first acoustic impedance.

19. The BAW resonator of claim 15 , further comprising:
at least one lateral performance enhancement feature in at least one of the bottom electrode or the top electrode.

Assignees

• Avago Technologies General Ip
• Avago Tech Int Sales Pte Lid

Inventors

• Burak Dariusz
• Grannen Kevin J
• Choy John

Classifications

• H03H9/175 Primary

  Acoustic mirrors · CPC title

• H03H3/04

  for obtaining desired frequency or temperature coefficient · CPC title

• H03H9/173

  Air-gaps · CPC title

• H03H2003/0428

  of an electrode · CPC title

• H03H9/02118

  of lateral leakage between adjacent resonators · CPC title