BAW STRUCTURE WITH REDUCED TOPOGRAPHIC STEPS AND RELATED METHOD

• US 20100231329A1
• Filed: 09/12/2008
• Published: 09/16/2010
• Est. Priority Date: 10/18/2007
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Inventors: Butler, Jeffrey A., Barber, Bradley P., Carpenter, Craig E.
• Granted Patent: US 8,514,033 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

Abstract

According to one embodiment, a method of forming a segment of a layer of material, where the segment of the layer of material has at least one tapered sidewall, is disclosed, where the method includes forming a mask over the layer of material. The method includes etching the mask and the layer of material in an etch process by controlling an etch rate of the mask and an etch rate of the layer of material so as to form the segment of the layer of material with the at least one tapered sidewall. A first etch chemistry is used to etch the mask and a second etch chemistry is used to etch the layer of material. The etch rates of the mask and the layer of material can be controlled by controlling a ratio of the first and second etch chemistries. The method can be utilized to fabricate BAW structures.

Claims

1. A method of forming at least one tapered sidewall in a segment of a layer of material in a semiconductor die, said method comprising steps of:

forming a mask over said layer of material and causing said mask to have at least one tapered sidewall;

etching said mask and said layer of material in an etch process by controlling an etch rate of said mask and an etch rate of said layer of material so as to form said segment of said layer of material having said at least one tapered sidewall.

2. The method of claim 1, wherein a first etch chemistry is used to etch said mask and a second etch chemistry is used to etch said layer of material in said etch process.

3. The method of claim 2, wherein said etch rate of said mask and said etch rate of said layer of material are controlled by controlling a ratio of said first etch chemistry to said second etch chemistry.

4. The method of claim 2, wherein a ratio of said first etch chemistry to said second etch chemistry is controlled in said etch process so as to cause said etch rate of said mask to be approximately equal to said etch rate of said layer of material.

5. The method of claim 1, wherein a slope of said at least one tapered sidewall can be controlled by controlling an initial slope of at least one sidewall of said mask.

6. The method of claim 1, wherein said mask comprises photoresist.

7. A method of forming a bulk acoustic wave (BAW) structure, said method comprising steps of:

forming a mask over a metal layer and causing said mask to have at least one tapered sidewall;

etching said mask and said metal layer in an etch process by controlling an etch rate of said mask and an etch rate of said metal layer so as to form a lower electrode of said BAW structure with at least one tapered sidewall;

forming a piezoelectric layer of said BAW structure over said lower electrode.

8. The method of claim 7, wherein a first etch chemistry is used to etch said mask and a second etch chemistry is used to etch said metal layer in said etch process.

9. The method of claim 8, wherein said etch rate of said mask and said etch rate of said metal layer are controlled by controlling a ratio of said first etch chemistry to said second etch chemistry.

10. The method of claim 7, wherein a slope of said at least one tapered sidewall can be controlled by controlling an initial slope of at least one sidewall of said mask.

11. The method of claim 7 further comprising a step of forming an acoustic mirror structure prior to said step of forming said mask over said metal layer, wherein said acoustic mirror comprises a plurality of metal segments.

12. The method of claim 11, wherein at least one of said plurality of metal segments has tapered sidewalls.

13. The method of claim 7, wherein a ratio of said first etch chemistry to said second etch chemistry is controlled in said etch process so as to cause said etch rate of said mask to be approximately equal to said etch rate of said metal layer.

14. A bulk acoustic wave (BAW) structure comprising:

a lower electrode situated over a substrate, said lower electrode having at least one tapered sidewall;

a piezoelectric layer situated over said lower electrode;

an upper electrode situated over said piezoelectric layer;

an acoustic mirror situated between said lower electrode and said substrate, wherein said acoustic mirror comprises a plurality of metal segments, wherein at least one of said plurality of metal segments has tapered sidewalls.

15. The BAW structure of claim 14, wherein each of said plurality of metal segments has tapered sidewalls.

16. The BAW structure of claim 14, wherein each of said plurality of metal segments has tapered sidewalls, and wherein each of said tapered sidewalls has a slope substantially equal to a slope of said at least one tapered sidewall of said lower electrode.