MEMS acoustic sensor with integrated back cavity

• US 8,692,340 B1
• Filed: 03/13/2013
• Issued: 04/08/2014
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Lim, Martin, Li, Xiang, Lloyd, Stephen, Ata, Erhan Polatkan, Daneman, Michael Julian
• Primary Examiner(s): Gebremariam, Samuel
• Application Number:
  US13/800,061
• Time in Patent Office: 391 Days
• Field of Search: 257/415, 257/416, 257/417, 257/418, 257/419, 257/420
• US Class Current: 257/416
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• CPC Class Codes: B81B 2203/058 Rotation out of a plane parallel to the substrate
• CPC Class Codes: B81B 2207/012 the micromechanical device and the control or processing electronics being separate parts in the same package
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: B81B 7/0061 suitable for fluid transfer from the MEMS out of the package or vice versa, e.g. transfer of liquid, gas, sound
• CPC Class Codes: H04R 19/005 using semiconductor materials

Abstract

A MEMS device is disclosed. The MEMS device comprises a first plate with a first surface and a second surface; and an anchor attached to a first substrate. The MEMS device further includes a second plate with a third surface and a fourth surface attached to the first plate. A linkage connects the anchor to the first plate, wherein the first plate and second plate are displaced in the presence of an acoustic pressure differential between the first and second surfaces of the first plate. The first plate, second plate, linkage, and anchor are all contained in an enclosure formed by the first substrate and a second substrate, wherein one of the first and second substrates contains a through opening to expose the first surface of the first plate to the environment.

Claims

1. A MEMS device comprising;

an anchor attached to a first substrate;

a first plate with a first surface and a second surface;

a second plate with a third surface and a fourth surface, attached to the first plate; and

a linkage connecting the anchor to the first plate, where the first plate and second plate are displaced in the presence of an acoustic pressure differential between the first and second surfaces of the first plate;

wherein the first plate, the second plate, the linkage, and the anchor are contained in an enclosure formed by the first substrate and a second substrate;

wherein one of the first and second substrates contains an acoustic port to expose the first surface to the environment,

wherein at least one electrode is formed on the first substrate.

2. The MEMS device of claim 1, where each of the first and second plates comprises of a material containing silicon.

3. The MEMS device of claim 1, wherein the second plate is perforated.

4. The MEMS device of claim 1, wherein the second plate moves in an opposite direction of the first plate.

5. The MEMS device of claim 4, wherein first and second plates are torque balanced around a rotational axis.

6. The MEMS device of claim 1, wherein the second plate moves in the same direction as the first plate.

7. The MEMS device of claim 1, where the MEMS device comprises a microphone.

8. The MEMS device of claim 1, where the enclosure forms an acoustic cavity.

9. The MEMS device of claim 1, further comprising in-plane bump stops to limit lateral movement of the first and second plates.

10. The MEMS device of claim 1, further comprising a capacitor, wherein a first electrode is formed by the second plate and a second electrode is formed by a conductive layer on the first substrate.

11. The MEMS device of claim 10, wherein the second electrode comprises of aluminum.

12. The MEMS device of claim 10, wherein the second electrode is connected to an integrated circuit on the first substrate.

13. The MEMS device of claim 1, further comprising a perforated plate disposed below the first plate and covering at least a portion of the acoustic port.

14. The MEMS device of claim 1, wherein a gap is defined by a standoff etched into the second substrate.

15. The MEMS device of claim 1, further comprising an additional insulating material disposed on the second electrode.

16. The MEMS device of claim 15, the additional insulating material is extended in select portions to form bump stops.

17. The MEMS device of claim 1, wherein at least one bump stops is formed from a receded post.

18. The MEMS device of claim 1, wherein the first and second plates have uniform thickness.

19. The MEMS device of claim 1, wherein the linkage has a thickness that is substantially the same as the thickness of the first plate or the second plate.

20. The MEMS device of claim 1, wherein the first plate has a thinner portion and a thicker portion.

21. The MEMS device of claim 20, wherein the linkage has a thickness equal to the thinnest portion of the first plate.

22. The MEMS device of claim 20, the linkage having a thickness greater than the thinnest portion of the first plate.

23. The MEMS device of claim 1, wherein an air flow path is provided from the first surface to the second surface.