Method for making thin film bulk acoustic resonators (FBARS) with different frequencies on a single substrate and apparatus embodying the method

• US 6,617,249 B2
• Filed: 03/05/2001
• Issued: 09/09/2003
• Est. Priority Date: 03/05/2001
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Ruby, Richard C., Larson, John D. III, Bradley, Paul D.
• Primary Examiner(s): Elms, Richard
• Assistant Examiner(s): Luhrs, Michael K.
• Application Number:
  US09/799,148
• Publication Number:
  US 20020123177A1
• Time in Patent Office: 918 Days
• Field of Search: 438/131, 438/400, 438/448, 438/584, 438/689, 438/758, 438/926, 438/940, 438/942, 438/970, 438/976, 438/734, 438/714
• US Class Current: 438/689
• CPC Class Codes: H03H 2003/0428 of an electrode
• CPC Class Codes: H03H 2003/0471 of a plurality of resonators at different frequencies
• CPC Class Codes: H03H 3/04 for obtaining desired frequency or temperature coefficient
• CPC Class Codes: H03H 9/564 implemented with thin-film techniques
• CPC Class Codes: Y10S 438/926 Dummy metallization
• CPC Class Codes: Y10S 438/94 Laser ablative material removal
• CPC Class Codes: Y10S 438/942 Masking
• CPC Class Codes: Y10S 438/97 Specified etch stop material
• CPC Class Codes: Y10S 438/976 Temporary protective layer

Abstract

A method for fabricating a resonator, and in particular, a thin film bulk acoustic resonator (FBAR), and a resonator embodying the method are disclosed. An FBAR is fabricated on a substrate by introducing a mass loading top electrode layer. For a substrate having multiple resonators, the top mass loading electrode layer is introduced for only selected resonator to provide resonators having different resonance frequencies on the same substrate.

Claims

1. A method of fabricating a resonator on a substrate, the method comprising:

fabricating a bottom electrode;

fabricating a piezoelectric (PZ) layer;

fabricating a top electrode layer;

fabricating a top loading layer above a section of said top electrode layer; and

over etching the top loading layer with said top electrode layer at the same step such that the top loading layer and the top electrode layer are etched to form a top electrode.

2. The method recited in claim 1 wherein the step of over etching comprises:

masking a portion of the top loading layer;

over etching the top loading layer to remove unmasked portions of the top loading layer and portions of the top electrode layer under the unmasked portions of the top loading layer.

3. The method recited in claim 2 wherein the mask is Silicon dioxide (SiO₂).

4. The method recited in claim 1 wherein the top loading layer is approximately 100 to 1,000 Angstroms thick.

5. The method recited in claim 1 wherein the top loading layer comprises conducting material.

6. The method recited in claim 1 wherein the top loading layer comprises insulating material.

7. The method recited in claim 1 wherein the top loading layer and the top electrode comprises same material.

8. The method recited in claim 1 wherein the PZ layer comprises Aluminum Nitride (AlN).

9. The method recited in claim 1 wherein the resonator bridges a cavity formed within the substrate.

10. A method of fabricating an apparatus resonator on a substrate, the method comprising:

fabricating a first bottom electrode and a second bottom electrode;

fabricating a piezoelectric (PZ) layer over both the first and the second bottom electrodes, the PZ layer having a first portion above the first bottom electrode and a second portion above the second bottom electrode;

fabricating a top electrode layer having a first section above the first portion and a second section over the second portion;

fabricating a top loading layer above the first section; and

over etching the top loading layer such that the top loading layer and the top electrode layer are etched to form a first top electrode.

11. The method recited in claim 10 further comprising masking the top electrode layer to over etch the top loading layer.

12. The method recited in claim 11 wherein the mask is Silicon dioxide (SiO₂).

13. The method recited in claim 10 wherein the top loading layer is 100 to 1,000 Angstroms thick.

14. The method recited in claim 10 wherein the top loading layer comprises conducting material.

15. The method recited in claim 10 wherein the top loading layer comprises insulating material.

16. The method recited in claim 10 wherein the top loading layer and the top electrode layer comprises same material.

17. The method recited in claim 10 wherein the PZ layer comprises Aluminum Nitride (AlN).

18. The method recited in claim 10 wherein the resonator bridges a cavity formed within the substrate.

19. The method recited in claim 10 wherein resonant frequency of the resonator is decreased by one to six percent due to the top loading layer.