Method of providing a hydrophobic layer and a condenser microphone having such a layer

• US 6,859,542 B2
• Filed: 05/31/2001
• Issued: 02/22/2005
• Est. Priority Date: 05/31/2001
• Status: Expired

• Current Assignee: Sonion Mems A/S
• Original Assignee: Sonion Lyngby A/S
• Inventors: Larsen, Niels Bent, Rombach, Pirmin Hermann Otto, Johannsen, Ib, Mullenborn, Matthias
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): Ensey, Brian
• Application Number:
  US09/867,606
• Publication Number:
  US 20020181725A1
• Time in Patent Office: 1,363 Days
• Field of Search: 381/191, 381/113, 381/174, 381/175, 381/369, 367/181, 367/170, 361/283.1
• US Class Current: 381/174
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 31/00 Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor manufacture of microstructural arrangements of deformable or non-deformable structures in general B81C1/00182

Abstract

A method of providing at least part of a diaphragm and at least a part of a back-plate of a condenser microphone with a hydrophobic layer so as to avoid stiction between said diaphragm and said back-plate. The layer is deposited via a number small of openings in the back-plate, the diaphragm and/or between the diaphragm and the back-plate. Provides a homogeneous and structured hydrophobic layer, even to small internal cavities of the microstructure. The layer may be deposited by a liquid phase or a vapor phase deposition method. The method may be applied naturally in continuation of the normal manufacturing process.

Further, a MEMS condenser microphone is provided having such a hydrophobic layer. The static distance between the diaphragm and the back-plate of the microphone is smaller than 10 μm.

Claims

1. A condenser microphone comprising a diaphragm and a back-plate, wherein an inner surface of said diaphragm forms a capacitor in combination with an inner surface of said back-plate, said back-plate and/or said diaphragm is/are provided with a number of openings, and said inner surface of the back-plate and said inner surface of the diaphragm being provided with a hydrophobic layer, and wherein the static distance between said diaphragm and said back-plate is smaller than 10 μ

m.

2. A condenser microphone according to claim 1, wherein at least the inner surfaces of the diaphragm and the back-plate are made from a hydrophilic material.

3. A condenser microphone according to claim 1, wherein the smallest dimension of each of the openings does not exceed 10 μ

m.

4. A condenser microphone according to claim 3, wherein the smallest dimension of each of the openings does not exceed 5 μ

m.

5. A condenser microphone according to claim 4, wherein the smallest dimension of each of the openings does not exceed 1 μ

m.

6. A condenser microphone according to claim 5, wherein the smallest dimension of each of the openings does not exceed 0.5 μ

m.

7. A condenser microphone according to claim 4, wherein the smallest dimension of each of the openings is approximately 3 μ

m.

8. A condenser microphone according to claim 1, wherein the hydrophobic layer base material comprises an alkylsilane.

9. A condenser microphone according to claim 1, wherein the hydrophobic layer base material comprises a perhaloalkylsilane.

10. A condenser microphone according to claim 1, wherein the static distance between the diaphragm and the back-plate is smaller than 5 μ

m.

11. A condenser microphone according to claim 10, wherein the static distance between the diaphragm and the back-plate is smaller than 1 μ

m.

12. A condenser microphone according to claim 11, wherein the static distance between the diaphragm and the back-plate is smaller than 0.5 μ

m.

13. A condenser microphone according to claim 12, wherein the static distance between the diaphragm and the back-plate is smaller than 0.3 μ

m.

14. A condenser microphone according to claim 11, wherein the static distance between the diaphragm and the back-plate is approximately 0.9 μ

m.

15. A condenser microphone according to claim 1, wherein the hydrophobic layer has a contact angle for water being between 90°

and 130°

.

16. A condenser microphone according to claim 15, wherein the hydrophobic layer has a contact angle for water being between 100°

and 110°

.

17. A condenser microphone according to claim 1, wherein the hydrophobic layer is stable at temperatures between −

40°

C. and 130°

C.

18. A condenser microphone according to claim 17, wherein the hydrophobic layer is stable at temperatures between −

30°

C. and 110°

C.

19. A condenser microphone according to claim 1, wherein the hydrophobic layer is stable at temperatures up to at least 400°

C. for at least 5 minutes.

20. A condenser microphone comprising a diaphragm and a back-plate, wherein an inner surface of said diaphragm forms a capacitor in combination with an inner surface of said back-plate, said back-plate and/or said diaphragm is/are provided with a number of openings, and said inner surface of the back-plate and/or said inner surface of the diaphragm being provided with a hydrophobic layer having a contact angle for water being larger than 90°

, and wherein the static distance between said diaphragm and said back-plate is smaller than 10 μ

m.

21. A condenser microphone comprising:

a diaphragm;

a back-plate, wherein an inner surface of said diaphragm forms a capacitor in combination with an inner surface of said back-plate, said back-plate and/or said diaphragm being provided with a number of openings, wherein the static distance between said diaphragm and said back-plate is smaller than 10 μ

m; and

a hydrophobic layer, provided on said inner surface of the back-plate and/or on said inner surface of the diaphragm.