MEMS MICROPHONE WITH CAVITY AND METHOD THEREFOR

• US 20100276767A1
• Filed: 04/29/2009
• Published: 11/04/2010
• Est. Priority Date: 04/29/2009
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Liu, Lianjun, Mitchell, Douglas G.
• Granted Patent: US 8,158,492 B2
• Time in Patent Office: Days
• US Class Current: 257/419
• CPC Class Codes: H01L 29/84 controllable by variation of applied mechanical force, e.g. of pressure
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H01L 2924/30105 Capacitance
• CPC Class Codes: H01L 2924/3025 Electromagnetic shielding
• CPC Class Codes: H04R 19/005 using semiconductor materials

Abstract

A device comprises a substrate, a micro electro-mechanical systems (MEMS) structure, and a dielectric film. The substrate has a first side and a second side, the second side opposite the first side. The MEMS structure is formed on the first side of the substrate. The cavity is formed in the substrate directly opposite the MEMS structure. The cavity has an opening formed on the second side. The dielectric film is attached to the second side of the substrate and completely covering the opening. In one embodiment, the MEMS structure is a diaphragm for a microphone. Another embodiment includes a method for forming the device.

Claims

1. A device comprising:

a substrate having a first side and a second side, the second side opposite the first side;

a micro electro-mechanical systems (MEMS) structure formed on the first side of the substrate, and a cavity formed in the substrate directly opposite the MEMS structure, the cavity having an opening formed on the second side; and

a dielectric film attached to the second side of the substrate and completely covering the opening.

2. The device of claim 1, wherein the MEMS structure includes a diaphragm for a microphone.

3. The device of claim 1, wherein the substrate comprises silicon.

4. The device of claim 1, wherein the substrate is a semiconductor wafer.

5. The device of claim 1, wherein the dielectric film comprises a photosensitive dielectric film.

6. The device of claim 5, wherein the photosensitive dielectric film includes a scribe street formed therein.

7. The device of claim 1, further comprising a metal layer formed on the dielectric film.

8. The device of claim 7, wherein the metal layer comprises aluminum.

9. A method comprising:

providing a substrate having a first side and a second side, the second side opposite the first side;

forming a micro electro-mechanical system (MEMS) structure on the first side of the substrate;

forming a cavity in the substrate directly opposite the MEMS structure, the cavity having an opening on the second side; and

attaching a dielectric film to the substrate and completely covering the opening.

10. The method of claim 9, further comprising:

forming a scribe street in the dielectric film to expose a predetermined portion of the second side of the substrate;

forming a metal layer over dielectric film and over the second side of the substrate in the scribe street; and

forming a cut in the substrate in the scribe street.

11. The method of claim 10, further comprising forming a bond pad on the first side of the substrate.

12. The method of claim 10, wherein forming a metal layer further comprises forming a metal layer in electrical contact with the substrate.

13. The method of claim 9, wherein forming the MEMS structure further comprises forming a MEMS microphone diaphragm.

14. The method of claim 9, wherein forming the MEMS structure in a polysilicon layer on the first side of the substrate.

15. The method of claim 9, wherein attaching the dielectric film to the substrate further comprises attaching a photosensitive dielectric film having an adhesive on one side.

16. The method of claim 15, further comprising photo exposing the photosensitive dielectric film to a radiation to remove the dielectric film from over a predetermined scribe street of the substrate.

17. A method comprising:

providing a substrate having a first side and a second side, the second side opposite the first side;

forming a micro electro-mechanical system (MEMS) microphone diaphragm on the first side of the substrate;

forming a cavity in the substrate directly opposite the MEMS microphone diaphragm, the cavity having an opening on the second side;

attaching a photosensitive dielectric film to the substrate, the photosensitive dielectric film completely covering the opening;

exposing a predetermined portion of the photosensitive dielectric film to a radiation to remove a first portion of the photosensitive dielectric film from over the substrate in the predetermined portion and to leave a second portion of the photosensitive dielectric film over the opening; and

forming a metal layer over the second portion of photosensitive dielectric film and contacting the substrate at the predetermined portion.

18. The method of claim 17, wherein providing the substrate further comprises providing a silicon wafer.

19. The method of claim 17, further comprising forming a bond pad on the first side of the substrate.

20. The method of claim 17, wherein forming the MEMS microphone diaphragm further comprises forming the MEMS microphone diaphragm in a polysilicon layer on the first side of the substrate.