Border ring mode suppression in solidly-mounted bulk acoustic wave resonator

• US 9,450,565 B2
• Filed: 03/12/2013
• Issued: 09/20/2016
• Est. Priority Date: 03/12/2013
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Inventors: Tajic, Alireza
• Primary Examiner(s): Summons, Barbara
• Application Number:
  US13/796,824
• Publication Number:
  US 20140273881A1
• Time in Patent Office: 1,288 Days
• Field of Search: 333/187, 333/189, 333/133
• US Class Current: 1/1
• CPC Class Codes: H03H 9/02118 of lateral leakage between adjacent resonators
• CPC Class Codes: H03H 9/131 consisting of a multilayered structure
• CPC Class Codes: H03H 9/132 characterized by a particular shape
• CPC Class Codes: H03H 9/175 Acoustic mirrors
• CPC Class Codes: H03H 9/589 Acoustic mirrors
• CPC Class Codes: H03H 9/703 Networks using bulk acoustic wave devices
• CPC Class Codes: H03H 9/706 Duplexers
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

Embodiments provide a solidly-mounted bulk acoustic wave (BAW) resonator and method of making same. In embodiments, the BAW resonator may include one or more extensions that are acoustical similar to active region components of the BAW resonator. Other embodiments may be described and claimed.

Claims

1. A solidly mounted bulk acoustic wave (BAW) resonator comprising:

a Bragg reflector;

a plurality of layers over the Bragg reflector and comprising a piezoelectric layer between a first electrode comprising tungsten and a second electrode that does not comprise tungsten;

a mass load over the plurality of layers and defining a border region within the plurality of layers and below the mass load, wherein;

an internal region is defined between the first electrode and the second electrode, within the plurality of layers and inside of the border region such that the first electrode and the second electrode reside in the internal region; and

an external region is defined within the plurality of layers and outside of the border region; and

an extension that resides against the piezoelectric layer in the external region and is directly coupled to a side edge of the second electrode, wherein acoustic impedances of the second electrode and the extension are at least similar.

2. The solidly mounted BAW resonator of claim 1 wherein an electrical response has essentially no border ring mode outside of a bandpass caused by the mass load.

3. The solidly mounted BAW resonator of claim 2 wherein the electrical response has essentially no spurious modes within the bandpass caused by lateral acoustic waves.

4. The solidly mounted BAW resonator of claim 1 wherein the first electrode extends from the internal region through the border region and into the external region and the second electrode does not extend into the external region.

5. The solidly mounted BAW resonator of claim 4 wherein the electrical response has essentially no border ring mode outside of a bandpass caused by the mass load.

6. The solidly mounted BAW resonator of claim 5 wherein an electrical response has essentially no spurious modes within the bandpass caused by lateral acoustic waves.

7. The solidly mounted BAW resonator of claim 1 wherein the first electrode comprises a tungsten layer and a non-tungsten layer such that the tungsten layer resides between the non-tungsten layer and the piezoelectric layer.

8. The solidly mounted BAW resonator of claim 7 wherein the first electrode extends from the internal region through the border region and into the external region and the second electrode does not extend into the external region.

9. The solidly mounted BAW resonator of claim 8 wherein the electrical response has essentially no border ring mode outside of a bandpass caused by the mass load.

10. The solidly mounted BAW resonator of claim 9 wherein the electrical response has essentially no spurious modes within the bandpass caused by lateral acoustic waves.

11. The solidly mounted BAW resonator of claim 1 wherein the first electrode resides between the Bragg reflector and the piezoelectric layer.

12. The solidly mounted BAW resonator of claim 1 wherein the extension comprises at least one of the group consisting of silicon oxide and hafnium oxide.

13. The solidly mounted BAW resonator of claim 1 wherein the second electrode comprises molybdenum and the extension comprises hafnium oxide.

14. The solidly mounted BAW resonator of claim 1 wherein the second electrode comprises aluminum copper and the extension comprises silicon oxide.

15. The solidly mounted BAW resonator of claim 1, wherein the acoustic impedance of the extension is between approximately 70% and approximately 130% of the acoustic impedance of the second electrode.

16. A solidly-mounted bulk acoustic wave (BAW) resonator comprising:

an internal region, a border region, and an external region;

a piezoelectric layer disposed in the internal region, the border region, and the external region;

a top electrode coupled with a first surface of the piezoelectric layer and disposed in the internal region and the border region;

a first extension coupled with the first surface of the piezoelectric layer and disposed in the external region, the first extension having an acoustic impedance that is at least similar to an acoustic impedance of the top electrode;

a bottom electrode coupled with a second surface of the piezoelectric layer, the second surface being opposite the first surface; and

a second extension directly coupled with the second surface of the piezoelectric layer and disposed in the external region, the second extension having an acoustic impedance that is at least similar to an acoustic impedance of the bottom electrode, wherein;

both the second extension and the bottom electrode include a tungsten layer and an aluminum copper layer;

the top electrode comprises aluminum copper and has a thickness of approximately 200 nanometers;

the tungsten layer has a thickness of approximately 70 nanometers; and

the aluminum copper layer has a thickness of approximately 190 nanometers.

17. The solidly-mounted BAW resonator of claim 16, wherein a difference between an anti-resonance frequency of the external region and an anti-resonance frequency of the internal active region is approximately 57 megahertz.

18. The solidly-mounted BAW resonator of claim 16, wherein a difference between a resonance frequency of the border region and a resonance frequency of the internal active region is approximately 40 megahertz and a width of the border region is approximately 2.0 microns.

19. The solidly-mounted BAW resonator of claim 16, further comprising:

a reflector having a plurality of tungsten layers disposed in silicon oxide coupled with the piezoelectric layer.

20. A solidly-mounted bulk acoustic wave (BAW) resonator comprising:

an internal region, a border region, and an external region;

a piezoelectric layer disposed in the internal region, the border region, and the external region;

a top electrode coupled with a first surface of the piezoelectric layer and disposed in the internal region and the border region;

a first extension coupled with the first surface of the piezoelectric layer and disposed in the external region, the first extension having an acoustic impedance that is at least similar to an acoustic impedance of the top electrode;

a bottom electrode coupled with a second surface of the piezoelectric layer, the second surface being opposite the first surface; and

a second extension directly coupled with the second surface of the piezoelectric layer and disposed in the external region, the second extension having an acoustic impedance that is at least similar to an acoustic impedance of the bottom electrode, wherein;

both the second extension and the bottom electrode include a tungsten layer and an aluminum copper layer;

the top electrode comprises molybdenum and has a thickness of approximately 215 nanometers;

the piezoelectric layer has a thickness of approximately 1200 nanometers;

the tungsten layer has a thickness of approximately 184 nanometers; and

the aluminum copper layer has a thickness of approximately 100 nanometers.

21. The solidly-mounted BAW resonator of claim 20, wherein a difference between an anti-resonance frequency of the external region and an anti-resonance frequency of the internal active region is approximately 196 megahertz.

22. The solidly-mounted BAW resonator of claim 20, wherein a difference between a resonance frequency of the border region and a resonance frequency of the internal active region is approximately 40 megahertz and a width of the border region is approximately 2.0 microns.

23. A solidly-mounted bulk acoustic wave resonator comprising:

an internal region, a border region, and an external region;

a piezoelectric layer disposed in the internal region, the border region, and the external region;

a top electrode coupled with a first surface of the piezoelectric layer and disposed in the internal region and the border region;

a first extension coupled with the first surface of the piezoelectric layer and disposed in the external region, the first extension having an acoustic impedance that is at least similar to an acoustic impedance of the top electrode;

a bottom electrode coupled with a second surface of the piezoelectric layer, the second surface being opposite the first surface; and

a second extension directly coupled with the second surface of the piezoelectric layer and disposed in the external region, the second extension having an acoustic impedance that is at least similar to an acoustic impedance of the bottom electrode, wherein;

both the second extension and the bottom electrode include a tungsten layer and an aluminum copper layer;

the top electrode comprises molybdenum and has a thickness of approximately 200 nanometers;

the piezoelectric layer has a thickness of approximately 1200 nanometers;

the tungsten layer has a thickness of approximately 170 nanometers;

the aluminum copper layer has a thickness of approximately 250 nanometers;

a difference between an anti-resonance frequency of the external region and an anti-resonance frequency of the internal active region is approximately 49 megahertz;

a difference between a resonance frequency of the border region and the resonance frequency of the internal active region is approximately 130 megahertz; and

a width of the border region is approximately 0.25 microns.

24. A system comprising:

a transceiver to transmit and receive radio frequency (RF) signals;

a filter coupled with the transceiver and configured to filter the RF signals provided to the transceiver;

a power amplifier coupled with the transceiver and configured to amplify the RF signals received from the transceiver;

an antenna structure to transmit and receive the RF signals over air; and

an antenna switch module to selectively couple the antenna structure with the filter and the power amplifier,

wherein the filter includes a bulk acoustic wave (BAW) resonator having;

a Bragg reflector;

a plurality of layers over the Bragg reflector and comprising a piezoelectric layer between a first electrode comprising tungsten and a second electrode that does not comprise tungsten;

a mass load over the plurality of layers and defining a border region within the plurality of layers and below the mass load, wherein;

an internal region is defined between the first electrode and the second electrode, within the plurality of layers and inside of the border region such that the first electrode and the second electrode reside in the internal region; and

an external region is defined within the plurality of layers and outside of the border region; and

an extension that resides against the piezoelectric layer in the external region and is directly coupled to a side edge of the second electrode, wherein acoustic impedances of the second electrode and the extension are at least similar.

25. The system of claim 24 wherein an electrical response of the BAW resonator has essentially no border ring mode outside of a bandpass caused by the mass load.

26. The system of claim 25 wherein an electrical response of the BAW resonator has essentially no spurious modes within a bandpass caused by lateral acoustic waves.

27. The system of claim 24 wherein the first electrode comprises a tungsten layer and a non-tungsten layer such that the tungsten layer resides between the non-tungsten layer and the piezoelectric layer.

28. The system of claim 27 wherein the first electrode extends from the internal region through the border region and into the external region and the second electrode does not extend into the external region.