METHOD FOR MANUFACTURING A BAW RESONATOR WITH A HIGH QUALITY FACTOR

• US 20110080232A1
• Filed: 10/01/2010
• Published: 04/07/2011
• Est. Priority Date: 10/01/2009
• Status: Active Grant

• Current Assignee: Stmicroelectronics France (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Carpentier, Jean-Francois, Bar, Pierre, Petit, David, Joblot, Sylvain
• Granted Patent: US 8,593,234 B2
• Time in Patent Office: Days
• US Class Current: 333/187
• CPC Class Codes: H03H 2003/025 the resonators or networks comprising an acoustic mirror
• CPC Class Codes: H03H 3/02 for the manufacture of piezoelectric or electrostrictive resonators or networks H03H3/08 takes precedence
• CPC Class Codes: H03H 9/175 Acoustic mirrors
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

A method for manufacturing a bulk acoustic wave resonator, each resonator including: above a substrate, a piezoelectric resonator, and next to the piezoelectric resonator, a contact pad connected to an electrode of the piezoelectric resonator; and, between the piezoelectric resonator and the substrate, a Bragg mirror including at least one conductive layer extending between the pad and the substrate and at least one upper silicon oxide layer extending between the pad and the substrate, the method including the steps of: depositing the upper silicon oxide layer; and decreasing the thickness unevenness of the upper silicon oxide layer due to the deposition method, so that this layer has a same thickness to within better than 2%, and preferably to within better than 1%, at the level of each pad.

Claims

1. A method for manufacturing a bulk acoustic wave resonator, the method comprising:

forming a Bragg mirror on a substrate, the forming including;

forming a first conductive layer on the substrate; and

forming an upper dielectric layer on the at least one first conductive layer; and

reducing a thickness of the upper dielectric layer, the reducing including achieving less than a 2% variation in the thickness across the upper dielectric layer;

forming a piezoelectric resonator on the upper dielectric layer, the piezoelectric resonator having a first electrode; and

forming a contact pad next to the piezoelectric resonator on the upper dielectric layer, the contact pad being coupled to the first electrode of the piezoelectric resonator.

2. The method of claim 1 wherein the reducing includes achieving less than a 1% variation in the thickness in a region where the contact pad is formed.

3. The method of claim 1 wherein the reducing includes achieving less than a 1% variation in the thickness in a region where the piezoelectric resonator is formed.

4. The method of claim 1 wherein the reducing of the upper dielectric layer is performed by ion etching.

5. The method of claim 1 wherein the first conductive layer includes tungsten.

6. The method of claim 1, further comprising forming a second conductive layer superposed on the first conductive layer, the second conductive layer having an electric conductivity greater than that of the first conductive layer.

7. The method of claim 6 wherein the second conductive layer is on the substrate, the first conductive layer is on the second conductive layer, and the upper dielectric layer is on the first conductive layer.

8. The method of claim 6 wherein the second conductive layer is aluminum.

9. The method of claim 1 a layer of piezoelectric material on the first electrode and forming a second electrode on the piezoelectric material.

10. A bulk acoustic wave resonator, comprising:

a substrate;

a Bragg mirror on the substrate, the Bragg mirror having a first conductive layer on the substrate and a first dielectric layer on the first conductive layer;

a piezoelectric resonator on the first dielectric layer, the piezoelectric resonator having a first electrode;

a first contact pad adjacent the piezoelectric resonator on the first dielectric layer, the first contact pad coupled to the first electrode of the piezoelectric resonator; and

a second conductive layer between the substrate and the first conductive layer, the second conductive layer having an electric conductivity greater than that of the first conductive layer and an acoustic impedance different from that of the first conductive layer, wherein the first conductive layer and the second conductive layer extend from a first region that is between the first contact pad and the substrate to a second region that is between the piezoelectric resonator and the substrate.

11. The bulk acoustic wave resonator of claim 10 wherein the first conductive layer is tungsten and the second conductive layer is aluminum.

12. The bulk acoustic wave resonator of claim 10 wherein the piezoelectric resonator includes a piezoelectric layer on the first electrode and a second electrode on the piezoelectric layer;

a second contact pad positioned adjacent the piezoelectric resonator and coupled to the second electrode.

13. The bulk acoustic wave resonator of claim 12 wherein the first dielectric layer includes silicon dioxide.

14. The bulk acoustic wave resonator of claim 10, further comprising a second dielectric layer on the substrate, a third conductive layer on the second dielectric layer, and the second conductive layer on the third conductive layer.

15. The bulk acoustic wave resonator of claim 10, further comprising a third conductive layer on a second dielectric layer, wherein the third conductive layer and the second dielectric layer separate the first dielectric layer from the first conductive layer.

16. A device, comprising:

a substrate;

a Bragg mirror on the substrate, the Bragg mirror having a plurality of conductive layers and an upper dielectric layer, the upper dielectric layer having a thickness variation of less than 2%;

a piezoelectric resonator on the upper dielectric layer, the piezoelectric resonator having a first electrode; and

a first contact pad adjacent the piezoelectric resonator on the upper dielectric layer, the first contact pad coupled to the first electrode of the piezoelectric resonator.

17. The device of claim 16 wherein the plurality of conductive layers extends from a first region that is between the first contact pad and the substrate to a second region that is between the piezoelectric resonator and the substrate.

18. The device of claim 16 wherein a first one of the plurality of conductive layers is on the substrate, a second one of the plurality of conductive layers is on the first one, and a third one of the plurality of conductive layers is on the second one.

19. The device of claim 18 wherein the first and second one of the plurality of conductive layers extends from a first region that is between the first contact pad and the substrate to a second region that is between the piezoelectric resonator and the substrate.