Acoustic resonator comprising acoustic reflector, frame and collar

• US 9,525,397 B2
• Filed: 02/14/2014
• Issued: 12/20/2016
• Est. Priority Date: 03/29/2011
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Inventors: Burak, Dariusz
• Primary Examiner(s): Summons, Barbara
• Assistant Examiner(s): Salazar, Jr., Jorge
• Application Number:
  US14/180,596
• Publication Number:
  US 20140232486A1
• Time in Patent Office: 1,040 Days
• Field of Search: 333/133, 333/186, 333/187, 333/188, 310/312
• US Class Current: 1/1
• CPC Class Codes: H03H 9/02102 of temperature influence cutting angles H03H9/02015
• CPC Class Codes: H03H 9/02118 of lateral leakage between adjacent resonators
• CPC Class Codes: H03H 9/132 characterized by a particular shape
• CPC Class Codes: H03H 9/171 implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
• CPC Class Codes: H03H 9/175 Acoustic mirrors
• CPC Class Codes: H03H 9/54 comprising resonators of piezoelectric or electrostrictive material H03H9/64 takes precedence

Abstract

A solidly mounted resonator (SMR) device includes an acoustic reflector having stacked acoustic reflector layer pairs, each of which includes a low acoustic impedance layer formed of low acoustic impedance material stacked on a high acoustic impedance layer formed of high acoustic impedance material. The SMR device further includes a bottom electrode disposed on the acoustic reflector, a piezoelectric layer disposed on the bottom electrode, and a top electrode disposed on the piezoelectric layer. A collar is formed outside a main active region defined by an overlap between the top electrode, the piezoelectric layer and the bottom electrode, and at least one frame is disposed within the main active region. The collar has an inner edge substantially aligned with a boundary of or overlapping the main active region, and the at least one frame has an outer edge substantially aligned with the boundary of the main active region.

Claims

1. A solidly mounted resonator (SMR) device, comprising:

an acoustic reflector disposed on a substrate, the acoustic reflector comprising a plurality of stacked acoustic reflector layer pairs, each acoustic reflector layer pair comprising a low acoustic impedance layer formed of low acoustic impedance material stacked on a high acoustic impedance layer formed of high acoustic impedance material;

a bottom electrode disposed on the low acoustic impedance layer of a top acoustic impedance layer pair of the acoustic reflector;

a piezoelectric layer disposed on the bottom electrode;

a top electrode disposed on the piezoelectric layer;

a collar formed outside a main active region defined by an overlap between the top electrode, the piezoelectric layer and the bottom electrode, the collar having an inner edge substantially aligned with a boundary of or overlapping the main active region; and

at least one frame disposed within the main active region and having an outer edge substantially aligned with the boundary of the main active region,

wherein the collar defines a collar region having a cutoff frequency that is substantially the same as a cutoff frequency of the main active region, and

wherein the collar is formed on a top surface of the top electrode and a planarization layer adjacent the top electrode or on a top surface of the bottom electrode between the bottom electrode and the piezoelectric layer.

2. The SMR device of claim 1, wherein the low acoustic impedance material comprises borosilicate glass (BSG) or tetra-ethyl-ortho-silicate (TEOS).

3. The SMR device of claim 1, wherein the collar comprises borosilicate glass, silicon dioxide, carbon-doped silicon oxide, silicon carbide, silicon nitride, aluminum oxide, aluminum nitride, zinc oxide, lead zirconium titanate, diamond, diamond-like carbon, tungsten, molybdenum or iridium.

4. The SMR device of claim 1, wherein the at least one frame comprises copper, molybdenum, aluminum, tungsten, iridium, borosilicate glass, carbon-doped silicon oxide, silicon carbide, silicon nitride, aluminum oxide, aluminum nitride, zinc oxide, lead zirconium titanate, diamond or diamond-like carbon.

5. The SMR device of claim 1, wherein the piezoelectric layer is doped with at least one rare earth element.

6. The SMR device of claim 1, wherein the low acoustic impedance material of at least one of the plurality of stacked acoustic reflector layer pairs comprises a temperature compensating material having a positive temperature coefficient for offsetting at least a portion of negative temperature coefficients of the piezoelectric layer, the bottom electrode and the top electrode.

7. A solidly mounted resonator (SMR) device, comprising:

an acoustic reflector disposed on a substrate, the acoustic reflector comprising a plurality of stacked acoustic reflector layer pairs, each acoustic reflector layer pair comprising a low acoustic impedance layer formed of low acoustic impedance material stacked on a high acoustic impedance layer formed of high acoustic impedance material;

a bottom electrode disposed on the low acoustic impedance layer of a top acoustic impedance layer pair of the acoustic reflector;

a piezoelectric layer disposed on the bottom electrode;

a top electrode disposed on the piezoelectric layer;

a collar formed outside a main active region defined by an overlap between the top electrode, the piezoelectric layer and the bottom electrode, the collar having an inner edge substantially aligned with a boundary of or overlapping the main active region, wherein at least a portion of the collar is formed on a top surface of the bottom electrode or on a top surface of the top electrode; and

at least one frame disposed within the main active region and having an outer edge substantially aligned with the boundary of the main active region,

wherein the collar defines a collar region having a cutoff frequency that is substantially the same as a cutoff frequency of the main active region, and

wherein the collar is an electrically grounded collar.

8. A solidly mounted resonator (SMR) device, comprising:

an acoustic reflector disposed on a substrate, the acoustic reflector comprising a plurality of stacked acoustic reflector layer pairs, each acoustic reflector layer pair comprising a low acoustic impedance layer formed of low acoustic impedance material stacked on a high acoustic impedance layer formed of high acoustic impedance material;

a bottom electrode disposed on the low acoustic impedance layer of a top acoustic impedance layer pair of the acoustic reflector;

a piezoelectric layer disposed on the bottom electrode;

a top electrode disposed on the piezoelectric layer;

a collar formed outside a main active region defined by an overlap between the top electrode, the piezoelectric layer and the bottom electrode, the collar having an inner edge substantially aligned with a boundary of or overlapping the main active region, wherein at least a portion of the collar is formed on a top surface of the bottom electrode or on a top surface of the top electrode; and

at least one frame disposed within the main active region and having an outer edge substantially aligned with the boundary of the main active region, wherein the at least one frame comprises a frame disposed at a bottom portion of the top electrode.

9. The SMR device of claim 8, wherein the frame disposed at the bottom portion of the top electrode comprises an add-on frame.

10. The SMR device of claim 8, wherein the frame disposed at the bottom portion of the top electrode comprises a composite frame.

11. The SMR device of claim 8, wherein the at least one frame comprises another frame disposed at one of a top portion or a bottom portion of the bottom electrode.

12. The SMR device of claim 8, wherein the piezoelectric layer is doped with at least one rare earth element.

13. The SMR device of claim 8, wherein the low acoustic impedance material of at least one of the plurality of stacked acoustic reflector layer pairs comprises a temperature compensating material having a positive temperature coefficient for offsetting at least a portion of negative temperature coefficients of the piezoelectric layer, the bottom electrode and the top electrode.

14. A solidly mounted resonator (SMR) device, comprising:

an acoustic reflector disposed on a substrate, the acoustic reflector comprising a plurality of stacked acoustic reflector layer pairs, each acoustic reflector layer pair comprising a low acoustic impedance layer formed of low acoustic impedance material stacked on a high acoustic impedance layer formed of high acoustic impedance material;

a bottom electrode disposed on the low acoustic impedance layer of a top acoustic impedance layer pair of the acoustic reflector;

a piezoelectric layer disposed on the bottom electrode;

a top electrode disposed on the piezoelectric layer;

a collar formed outside a main active region defined by an overlap between the top electrode, the piezoelectric layer and the bottom electrode, the collar having an inner edge substantially aligned with a boundary of or overlapping the main active region, wherein at least a portion of the collar is formed on a top surface of the bottom electrode or on a top surface of the top electrode; and

at least one frame disposed within the main active region and having an outer edge substantially aligned with the boundary of the main active region, wherein the at least one frame comprises a frame disposed at a bottom portion of the bottom electrode.

15. The SMR device of claim 14, wherein the piezoelectric layer is doped with at least one rare earth element.

16. The SMR device of claim 14, wherein the low acoustic impedance material of at least one of the plurality of stacked acoustic reflector layer pairs comprises a temperature compensating material having a positive temperature coefficient for offsetting at least a portion of negative temperature coefficients of the piezoelectric layer, the bottom electrode and the top electrode.

17. A solidly mounted resonator (SMR) device, comprising:

a substrate;

a distributed Bragg reflector (DBR) disposed on a top surface of the substrate, the DBR comprising a plurality of acoustic reflector layer pairs;

an acoustic stack mounted on a top surface of the DBR, the acoustic stack comprising a piezoelectric layer sandwiched between bottom and top electrode layers, and having a main active region defined by an overlap between the bottom electrode, the piezoelectric layer, and the top electrode; and

a collar arranged outside the main active region, and at least a portion of the collar being arranged outside an outer edge of the top electrode, the collar defining a collar region having a cutoff frequency that is substantially the same as a cutoff frequency of the main active region,

wherein the collar is formed on one of a top surface of the bottom electrode and a first planarization layer adjacent the bottom electrode, or a top surface of the top electrode and a second planarization layer adjacent the top electrode.

18. A solidly mounted resonator (SMR) device, comprising:

a substrate;

a distributed Bragg reflector (DBR) disposed on a top surface of the substrate, the DBR comprising a plurality of acoustic reflector layer pairs;

an acoustic stack mounted on a top surface of the DBR, the acoustic stack comprising a piezoelectric layer sandwiched between bottom and top electrode layers, and having a main active region defined by an overlap between the bottom electrode, the piezoelectric layer, and the top electrode; and

at least one frame arranged inside the main active region, an outer edge of the at least one frame substantially aligned with the boundary of the main active region,

wherein the at least one frame is in at least one of the bottom and top electrode layers, and comprises an inside electrode layer adjacent the piezoelectric layer and an outside electrode layer adjacent the inside electrode layer, the outside electrode layer being formed of a first material and the inside electrode layer being formed of the first material and a second material, wherein the first material extends from the outside electrode layer through the second material of the inside electrode layer to provide the at least one frame.

19. The SMR device of claim 18, wherein the second material has a higher sound velocity than the first material, such that the at least one frame comprises a low velocity frame.

20. The SMR device of claim 18, wherein the second material has a lower sound velocity than the first material, such that the at least one frame comprises a high velocity frame.