Miniature silicon condenser microphone

• US 5,870,482 A
• Filed: 02/25/1997
• Issued: 02/09/1999
• Est. Priority Date: 02/25/1997
• Status: Expired due to Term

• Current Assignee: Knowles Electronics Llc (Knowles Corporation)
• Original Assignee: Knowles Electronics Incorporated (Knowles Corporation)
• Inventors: Schafer, David E., Loeppert, Peter V.
• Primary Examiner(s): LE, HUYEN D
• Application Number:
  US08/805,983
• Time in Patent Office: 714 Days
• Field of Search: 381/170, 381/174, 381/191, 381/113, 381/116, 381/173, 29/25.41, 29/594, 367/181, 73/517 R, 73/862.59, 437/209
• US Class Current: 381/174
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• CPC Class Codes: B81B 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• CPC Class Codes: B81B 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: G01H 11/06 by electric means
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 31/006 Interconnection of transducer parts of diaphragm and outer suspension by moulding H04R31/003
• CPC Class Codes: H04R 7/16 Mounting or tensioning of diaphragms or cones

Abstract

Multiple embodiments of a solid state condenser transducer, and methods of manufacture, are disclosed. The transducer comprises a semi-conductor substrate forming a frame and having an opening, a thin-film cantilever structure forming a diaphragm extending over a portion of the opening, the structure having a proximal portion and a distal portion. The proximal portion is attached to the frame, and the distal portion extends over a portion of the frame. A variable gap capacitor having a movable plate and a fixed plate is provided, wherein the movable plate is disposed on the distal portion of the structure and the fixed plate is disposed on the frame adjacent the movable plate.

Claims

1. A solid state condensor microphone comprising:

a semi-conductor substrate forming a support structure and having an opening;

a thin-film cantilever structure forming a diaphragm responsive to fluid-transmitted acoustic pressure extending over a portion of the opening, the structure having a proximal end and a distal end, wherein the proximal end is attached to the support structure, and the distal end is detached from and extends over a portion of the support structure; and

a variable gap capacitor having a movable plate and a fixed plate, wherein the movable plate is disposed on the distal end of the structure and the fixed plate is disposed on the support structure adjacent the movable plate, wherein said condenser microphone produces an output proportional to the position of the movable plate relative to the fixed plate.

2. The transducer of claim 1 wherein said semi-conductor substrate is silicon.

3. The transducer of claim 1 wherein said proximal end of said cantilever structure is along an edge of said opening.

4. The transducer of claim 3 wherein said cantilever structure is generally in the form of a rectangle.

5. The transducer of claim 1 wherein said cantilever structure is formed of multiple layers of thin-films.

6. The transducer of claim 5 wherein said multiple layers of thin-films are quilted.

7. The transducer of claim 1 wherein said diaphragm includes means defining a pressure equalization path extending over a portion of said support structure for restricting airflow between opposing sides of the diaphragm.

8. The transducer of claim 1 including means for limiting travel of said diaphragm away from said support structure.

9. The transducer of claim 8 wherein said travel limiting means comprises means extending over said distal end of said diaphragm.

10. The transducer of claim 1 wherein said diaphragm distal end includes a vent.

11. The transducer of claim 10 wherein said vent comprises a plurality of holes extending through said distal portion.

12. A solid state condenser microphone comprising:

a silicon substrate forming a support structure and having an opening;

a multi-layer thin-film cantilever structure forming a diaphragm responsive to fluid-transmitted acoustic pressure extending over a portion of the opening, the structure having a proximal end and a distal end, wherein the proximal end is attached to the support structure, and the distal end is detached from and extends over a portion of the support structure; and

a variable gap capacitor having a movable plate and a fixed plate, wherein the movable plate is disposed on the distal end of the structure and the fixed plate is disposed on the support structure adjacent the movable plate, wherein said condenser microphone produces an output proportional to the position of the movable plate relative to the fixed plate.

13. The transducer of claim 12 wherein said proximal end of said cantilever structure is along an edge of said opening.

14. The transducer of claim 13 wherein said cantilever structure is generally in the form of a rectangle.

15. The transducer of claim 12 wherein said cantilever structure is corrugated.

16. The transducer of claim 12 wherein said diaphragm includes means defining a pressure equalization path extending over a portion of said support structure for restricting airflow between opposing sides of the diaphragm.

17. The transducer of claim 12 including means for limiting travel of said diaphragm away from said support structure.

18. The transducer of claim 17 wherein said travel limiting means comprises means extending over said distal end of said diaphragm.

19. The transducer of claim 12 wherein said diaphragm distal end includes a vent.

20. The transducer of claim 12 wherein said vent comprises a plurality of holes extending through said distal end.

21. A solid state condenser microphone comprising:

a silicon substrate support structure including a frame defining an opening and a thin-film web attached to said frame and extending across said opening;

a thin-film cantilever forming a diaphragm responsive to fluid-transmitted acoustic pressure having a central portion and a peripheral end, wherein the central portion is attached to the web, and the peripheral end is detached from and extends over a portion of the support structure; and

a variable gap capacitor having a movable plate and a fixed plate, wherein the movable plate is disposed on the peripheral end of the structure and the fixed plate is disposed on the support structure adjacent the movable plate wherein said condenser microphone produces an output proportional to the position of the movable plate relative to the fixed plate.

22. The transducer of claim 21 wherein said central portion of said cantilever structure is disposed in the center of said opening.

23. The transducer of claim 21 wherein said cantilever structure is generally in the form of a circle.

24. The transducer of claim 21 wherein said cantilever structure includes corrugations.

25. The transducer of claim 24 wherein said corrugations form concentric circles.

26. The transducer of claim 21 wherein said cantilever structure is quilted.

27. The transducer of claim 24 wherein said corrugations form generally radial lines.

28. The transducer of claim 24 wherein said corrugations form generally tangential lines.