MEMS digital-to-acoustic transducer with error cancellation

• US 6,829,131 B1
• Filed: 09/13/1999
• Issued: 12/07/2004
• Est. Priority Date: 09/13/1999
• Status: Expired due to Term

• Current Assignee: Carnegie Mellon University
• Original Assignee: Carnegie Mellon University
• Inventors: Loeb, Wayne A., Gabriel, Kaigham J., Neumann, John J. Jr.
• Primary Examiner(s): Jackson, Stephen W.
• Application Number:
  US09/395,073
• Time in Patent Office: 1,912 Days
• Field of Search: 361/115, 361/90, 361/234, 361/58, 361/160, 361/233
• US Class Current: 361/234
• CPC Class Codes: H04R 17/00 Piezoelectric transducers; Electrostrictive transducers piezoelectric or electrostrictive elements in general H10N30/00; details of piezoelectric or electrostrictive motors, generators or positioners H10N30/00
• CPC Class Codes: H04R 19/005 using semiconductor materials

Abstract

An acoustic transducer comprising a substrate; and a diaphragm formed by depositing a micromachined membrane onto the substrate. The diaphragm is formed as a single silicon chip using a CMOS MEMS (microelectromechanical systems) semiconductor fabrication process. The curling of the diaphragm during fabrication is reduced by depositing the micromachined membrane for the diaphragm in a serpentine-spring configuration with alternating longer and shorter arms. As a microspeaker, the acoustic transducer of the present invention converts a digital audio input signal directly into a sound wave, resulting in a very high quality sound reproduction at a lower cost of production in comparison to conventional acoustic transducers. The micromachined diaphragm may also be used in microphone applications.

Claims

1. A flexible diaphragm fabricated on a substrate, comprising:

a micromachined membrane fabricated on the substrate; and

a layer of material sealing said membrane.

2. The flexible diaphragm of claim 1 wherein said micromachined membrane includes a serpentine shaped spring.

3. The flexible diaphragm of claim 2 wherein said serpentine shaped spring is comprised of a plurality of alternately positioned long and short arms.

4. The flexible diaphragm of claim 3 wherein a longest side of each of said long arms is less than approximately 50 microns in length.

5. The flexible diaphragm of claim 3 wherein a maximum spacing between adjacent arms is approximately 3 microns.

6. The flexible diaphragm of claim 1 wherein said micromachined member includes a plurality of cells, each cell comprised of a plurality of serpentine shaped springs.

7. The flexible diaphragm of claim 1 wherein the substrate is selected from a group consisting of ceramic, glass, silicon, printed circuit board, and silicon-on-insulator semiconductor devices.

8. The flexible diaphragm of claim 1 wherein said layer of material is selected from a group consisting of polymer sealants.

9. The flexible diaphragm of claim 1 wherein the diaphragm is fabricated in an x-y plane and supported by the substrate so as to be free to move in a z direction.

10. The flexible diaphragm of claim 9 wherein the diaphragm is supported by the substrate such that changes in air pressure result in movement of the diaphragm.

11. The flexible diaphragm of claim 9 wherein the diaphragm is supported by the substrate such that the diaphragm moves when actuated with an electrical signal.

12. A flexible diaphragm fabricated on a substrate, comprising:

a micromachined membrane comprised of a plurality of serpentine shaped springs; and

a layer of material sealing said membrane.

13. The flexible diaphragm of claim 12 wherein each of said serpentine shaped springs is comprised of a plurality of alternately positioned long and short arms.

14. The flexible diaphragm of claim 13 wherein a longest side of each of said long arms is less than approximately 50 microns in length.

15. The flexible diaphragm of claim 13 wherein a maximum spacing between adjacent arms is approximately 3 microns.

16. The flexible diaphragm of claim 12 wherein said micromachined member includes a plurality of cells, each cell comprised of a plurality of serpentine shaped springs.

17. The flexible diaphragm of claim 12 wherein the substrate is selected from a group consisting of ceramic, glass, silicon, printed circuit board, and silicon-on-insulator semiconductor devices.

18. The flexible diaphragm of claim 12 wherein said layer of material is selected from a group consisting of polymer sealants.

19. The flexible diaphragm of claim 12 wherein the diaphragm is fabricated in an x-y plane and supported by the substrate so as to be free to move in a z direction.

20. The flexible diaphragm of claim 19 wherein the diaphragm is supported by the substrate such that changes in air pressure result in movement of the diaphragm.

21. The flexible diaphragm of claim 19 wherein the diaphragm is supported by the substrate such that the diaphragm moves when actuated with an electrical signal.

22. A combination, comprising:

a substrate;

a plurality of micromachined membranes fabricated on the substrate;

a layer of material carried by each of said membranes so as to seal said membranes to form an array of flexible diaphragms; and

a voltage source for biasing said diaphragm with respect to said substrate.

23. The combination of claim 22 wherein each of said micromachined membranes includes a serpentine shaped spring.

24. The combination of claim 23 wherein said serpentine shaped springs are each comprised of a plurality of alternately positioned long and short arms.

25. The combination of claim 24 wherein a longest side of each of said long arms is less than approximately 50 microns in length.

26. The combination of claim 24 wherein a maximum spacing between adjacent arms is approximately 3 microns.

27. The combination of claim 22 wherein each of said micromachined members includes a plurality of cells, each cell comprised of a plurality of serpentine shaped springs.

28. The combination of claim 22 wherein the substrate is selected from a group consisting of ceramic, glass, silicon, printed circuit board, and silicon-on-insulator semiconductor devices.

29. The combination of claim 22 wherein said layer of material is selected from a group consisting of polymer sealants.