ACOUSTIC RESONATOR HAVING TEMPERATURE COMPENSATION

• US 20140225682A1
• Filed: 02/14/2013
• Published: 08/14/2014
• Est. Priority Date: 02/14/2013
• 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, CHOY, John, GRANNEN, Kevin J.
• Granted Patent: US 9,484,882 B2
• Time in Patent Office: Days
• US Class Current: 333/187
• CPC Class Codes: H03H 9/02102 of temperature influence cutting angles H03H9/02015
• CPC Class Codes: H03H 9/0211 of reflections
• CPC Class Codes: H03H 9/02118 of lateral leakage between adjacent resonators
• CPC Class Codes: H03H 9/173 Air-gaps
• CPC Class Codes: H03H 9/175 Acoustic mirrors

Abstract

An acoustic resonator structure comprises a substrate having an air cavity, an acoustic stack disposed over the substrate and comprising a piezoelectric material disposed between a first electrode and a second electrode, and an acoustic reflector disposed over the substrate and comprising a single pair of acoustic impedance layers configured to reflect acoustic waves produced by vibration of the acoustic stack, wherein at least one of the acoustic impedance layers comprises a temperature compensating material.

Claims

1. An acoustic resonator structure, comprising:

a substrate having an air cavity;

an acoustic stack disposed over the substrate and comprising a piezoelectric material disposed between a first electrode and a second electrode; and

an acoustic reflector disposed over the substrate and comprising a single pair of acoustic impedance layers configured to reflect acoustic waves produced by vibration of the acoustic stack, wherein at least one of the acoustic impedance layers comprises a temperature compensating material.

2. The acoustic resonator structure of claim 1, wherein the temperature compensating material comprises a form of undoped or doped silicon oxide.

3. The acoustic resonator structure of claim 2, wherein another one of the acoustic impedance layers comprises a high acoustic impedance material selected from a group consisting of tungsten, molybdenum, iridium, copper, aluminum, diamond, diamond-like carbon, aluminum oxide, silicon nitride, aluminum nitride, zinc oxide and silicon carbide.

4. The acoustic resonator structure of claim 1, wherein the acoustic reflector is disposed on the substrate between the air cavity and the acoustic stack.

5. The acoustic resonator structure of claim 1, wherein the acoustic stack is disposed on the substrate between the air cavity and the acoustic reflector.

6. The acoustic resonator structure of claim 4, wherein the first electrode is disposed between the acoustic reflector and the piezoelectric layer, and the acoustic resonator structure further comprises a frame disposed around an active region of the acoustic stack between the second electrode and the piezoelectric layer.

7. The acoustic resonator structure of claim 6, wherein the frame is an add-on frame or a composite frame.

8. The acoustic resonator structure of claim 4, wherein the first electrode is disposed between the acoustic reflector and the piezoelectric layer, and the acoustic resonator structure further comprises a frame disposed around an active region of the acoustic stack between the first electrode and the acoustic reflector.

9. The acoustic resonator structure of claim 4, further comprising first and second frames connected to the acoustic stack in a side by side configuration, wherein the first frame is disposed in a first frame region and is configured to shift a cutoff frequency of the first frame region in a first direction, and wherein the second frame is disposed in a second frame region and is configured to shift a cutoff frequency of the second frame region in a second direction opposite the first direction.

10. The acoustic resonator structure of claim 9, wherein the first electrode is disposed between the acoustic reflector and the piezoelectric layer, and the first and second frames are connected to one of the first and the second electrodes.

11. The acoustic resonator structure of claim 10, wherein each of the first and second frames is one of an add-on and a composite frame.

12. The acoustic resonator structure of claim 1, wherein each of the acoustic impedance layers has a thickness in a range of approximately an eighth to a half of a wavelength of a resonance frequency of the acoustic stack.

13. The acoustic resonator structure of claim 1, wherein the acoustic impedance layer comprising the temperature compensating material has a thickness approximately equal to an eighth wavelength of a resonance frequency of the acoustic stack.

14. The acoustic resonator structure of claim 4, wherein a first layer among the single pair of acoustic impedance layers is formed adjacent to the substrate and a second layer among the single pair of acoustic impedance layers comprises the temperature compensating material, wherein the first layer is etched in a region over the air cavity such that a portion of the second layer is exposed to the air cavity.

15. An acoustic resonator structure, comprising:

a substrate having an air cavity;

an acoustic stack disposed over the substrate and comprising a piezoelectric material disposed between a first electrode and a second electrode; and

an acoustic reflector disposed over the substrate and comprising a single acoustic impedance layer formed of a temperature compensating material and configured to reflect acoustic waves produced by vibration of the acoustic stack.

16. The acoustic resonator structure of claim 15, wherein the single acoustic impedance layer is formed between the substrate and the acoustic stack.

17. The acoustic resonator structure of claim 15, wherein the acoustic stack is formed between the substrate and the single acoustic impedance layer.

18. The acoustic resonator structure of claim 15, wherein the temperature compensating layer comprises a form of undoped or doped silicon oxide.

19. The acoustic resonator structure of claim 16, further comprising a frame disposed around an active region of the acoustic stack and between the single acoustic impedance layer and the second electrode.

20. The acoustic resonator structure of claim 19, further comprising another frame disposed around the active region of the acoustic stack and between the single acoustic impedance layer and the second electrode, in a side by side configuration with the frame.