MEMS digital-to-acoustic transducer with error cancellation

• US 7,215,527 B2
• Filed: 09/20/2004
• Issued: 05/08/2007
• Est. Priority Date: 09/13/1999
• Status: Expired due to Term

• Current Assignee: Carnegie Mellon University
• Original Assignee: Carnegie Mellon University
• Inventors: Gabriel, Kaigham J., Neumann, John J. Jr.
• Primary Examiner(s): Jackson; Stephen W.
• Application Number:
  US10/945,136
• Publication Number:
  US 20050061770A1
• Time in Patent Office: 960 Days
• Field of Search: 361/233
• US Class Current: 361/233
• 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 method of fabricating a flexible diaphragm on a substrate, comprising:

forming a layer on a substrate;

forming a micromachined membrane from said layer; and

sealing said membrane.

2. The method of claim 1 wherein said forming a micromachined membrane includes etching said layer to form a serpentine spring and releasing portions of said spring from said substrate.

3. The method of claim 2 wherein said etching includes etching said layer to form a serpentine spring having a plurality of alternately positioned long and short arms.

4. The method of claim 2 wherein said etching includes etching said layer so that a longest side of each of said long arms is less than approximately 50 microns in length.

5. The method of claim 3 wherein said etching includes etching said layer so that a maximum spacing between adjacent arms is approximately 3 microns.

6. The method of claim 1 wherein said forming a micromachined membrane includes etching said layer to form a plurality of cells, each cell comprised of a plurality of serpentine spring shapes, and releasing portions of said spring shapes from said substrate.

7. The method of claim 6 wherein said releasing portions includes releasing certain of said spring shapes in their entireties.

8. The method of claim 1 wherein said sealing said membrane includes depositing one of a layer of sealant and a layer of laminating film.

9. The method of claim 8 including etching the deposited layer to achieve a desired thickness.

10. A method of fabricating a transducer, comprising:

fabricating electronics on a substrate using CMOS processes;

forming a layer on a substrate;

forming a micromachined membrane from said layer; and

sealing said membrane to form a diaphragm, said diaphragm being in communication with said electronics.

11. The method of claim 10 wherein said forming a micromachined membrane includes etching said layer to form a serpentine spring and releasing portions of said spring from said substrate.

12. The method of claim 11 wherein said etching includes etching said layer to form a serpentine spring having a plurality of alternately positioned long and short arms.

13. The method of claim 12 wherein said etching includes etching said layer so that a longest side of each of said long arms is less than approximately 50 microns in length.

14. The method of claim 12 wherein said etching includes etching said layer so that a maximum spacing between adjacent arms is approximately 3 microns.

15. The method of claim 10 wherein said forming a micromachined membrane includes etching said layer to form a plurality of cells, each cell comprised of a plurality of serpentine spring shapes, and releasing portions of said spring shapes from said substrate.

16. The method of claim 15 wherein said releasing portions includes releasing certain of said spring shapes in their entireties.

17. The method of claim 10 wherein said sealing said membrane includes depositing one of a layer of sealant and a layer of laminating film.

18. The method of claim 17 including etching the deposited layer to achieve a desired thickness.

19. The method of claim 10 additionally comprising enclosing said transducer in a housing.