Mems Microphone, Production Method and Method for Installing

• US 20080279407A1
• Filed: 11/06/2006
• Published: 11/13/2008
• Est. Priority Date: 11/10/2005
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: Epcos AG (TDK Corporation)
• Inventors: Pahl, Wolfgang
• Granted Patent: US 8,229,139 B2
• Time in Patent Office: Days
• US Class Current: 381/355
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• CPC Class Codes: B81B 7/0064 for protecting against electromagnetic or electrostatic interferences
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/49109 outside the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 2225/49 Reducing the effects of electromagnetic noise on the functioning of hearing aids, by, e.g. shielding, signal processing adaptation, selective (de)activation of electronic parts in hearing aid

Abstract

A microphone in a miniaturized form is described herein. The microphone includes a flat carrier substrate having a first recess extending through the carrier substrate. The microphone includes a first electro-acoustic transducer on a first surface of the carrier substrate and at least partially overlapping the first recess. The microphone also includes a cap on a second surface opposite the first surface having a tight seal with the second surface and spanning the first recess. The cap includes at least one metallic layer for electromagnetic shielding.

Claims

1. A microphone in a miniaturized form, comprising:

a flat carrier substrate having a first recess extending through the carrier substrate,

a first electro-acoustic transducer on a first surface of the carrier substrate and at least partially overlapping the first recess, and

a cap on a second surface opposite the first surface, the cap being configured to form a tight seal with the second surface and span the first recess, the cap comprising at least one metallic layer for electromagnetic shielding.

2. The microphone of claim 1, wherein the first electro-acoustic transducer comprises a micro-electromechanical system (MEMS) component on a silicon wafer.

3. The microphone of claim 1, wherein the cap comprises a multi-layer structure, wherein an outmost layer of the multi-layer structure comprises the metallic layer.

4. The microphone of claim 3, wherein an innermost layer of the cap comprises a plastic film.

5. The microphone of claim 1, further comprising solderable contacts electrically connected to one or more terminals of the first electro-acoustic transducer and/or one or more integrated components on the first surface of the carrier substrate.

6. The microphone of claim 1, further comprising at least one electrical component electrically connected to the first electro-acoustic transducer and selected from the group consisting of an impedance transducer, amplifier, low-pass filter, signal processor, A/D converter, and fuse component, the at least one electrical component being on the second surface of the carrier substrate under the cap.

7. The microphone of claim 1, wherein the carrier substrate comprises at least one metallization layer including electrical connection lines.

8. The microphone of claim 7, wherein the carrier substrate comprises a multi-layered structure that includes at least one additional metallization layer, wherein the metallization layers are separated by one or more electrically insulating layers and connections between the metallization layers by via contacts form circuitry.

9. The microphone of claim 1, wherein the first electro-acoustic transducer includes at least one piezoelectric layer comprising transducer electrodes for electrically converting sound signals.

10. The microphone of claim 1, further comprising a shielding layer comprising metal on the first surface of the carrier substrate and on parts of the first electro-acoustic transducer.

11. The microphone of claim 1, further comprising a second electro-acoustic transducer above a second recess on the first surface of the carrier substrate.

12. The microphone of claim 11, wherein each of the first and the second electro-acoustic transducers has a body comprising crystalline silicon and having on its surface away from the first surface of the carrier substrate, a sound entrance opening closed with a porous, metallized membrane.

13. A method for fabricating an encapsulated microphone, the method comprising:

providing a carrier substrate having a first surface and a second surface, the first surface opposite the second surface,

depositing and structuring a reactive layer on the second surface of the carrier substrate,

applying at least one encapsulation layer above the reactive layer and the carrier substrate to form a tight seal with the carrier substrate around the reactive layer,

generating a recess extending through the carrier substrate up to the reactive layer from the first surface of the carrier substrate,

removing the reactive layer to form a cantilevered cap by the one or more encapsulation layers, and

arranging an electro-acoustic transducer above the recess.

14. The method of claim 13, wherein the reactive layer comprises a photo-structured resist layer and wherein removing the reactive layer comprises dissolving the reactive layer by a solvent through the recess.

15. The method of claim 13, further comprising, before depositing the reactive layer, depositing at least one electrical component on the second surface of the carrier substrate under the cap.

16. The method of claim 13, wherein the encapsulation layer comprises at least one metallic layer.

17. The method of claim 13, further comprising depositing a plastic film directly onto the reactive layer through lamination.

18. The method of claim 16, wherein the metallic layer comprises

a base metallization layer vapor-deposited or sputtered on the reactive layer, and the method further comprises reinforcing the layer using a solution in a galvanic or current-less deposition method.

19. The method of claim 13, wherein the method is performed on a panel and the method generates a plurality of caps on a first surface of a large surface-area carrier substrate and a corresponding number of electro-acoustic transducers on a second surface of the carrier substrate.

20. The method of claim 13, wherein arranging an electro-acoustic transducer comprises soldering or affixing the electro-acoustic transducer with a conductive adhesive.

21. The method of claim 13, further comprising, subsequent to arranging an electro-acoustic transducer, vapor-depositing or sputtering metal on the first surface of the carrier substrate, wherein at least one sound entrance opening of the electro-acoustic transducer is covered prior to vapor-depositing or sputtering the metal on the first surface of the carrier substrate.

22. The method of claim 21, wherein the sound entrance opening is covered on a panel by placing or shaking spheres comprising glass or another dielectric material adapted to the size of the sound entrance opening.

26. The method of claim 17, wherein the metallic layer comprises a base metallization layer vapor-deposited or sputtered on the plastic film above the reactive layer, and the method further comprises reinforcing the layer using a solution in a galvanic or current-less deposition method.

23. A method for installing a microphone in a printed-circuit board, the method comprising:

providing a printed circuit board with an opening holding an electro-acoustic transducer

providing a microphone, the microphone comprising;

a flat carrier substrate having a first recess extending through the carrier substrate,

the electro-acoustic transducer on a first surface of the carrier substrate and at least partially overlapping the first recess, and

a cap on a second surface opposite the first surface, the cap being configured to form a tight seal with the second surface and span the first recess, the cap comprising at least one metallic layer for electromagnetic shielding; and

soldering or affixing the carrier substrate having the cap and the electro-acoustic transducer to the printed-circuit board, such that the transducer projects into the opening and a plurality of solderable contacts of the microphone on the first surface of the carrier substrate are electrically connected to corresponding contacts on a surface of the printed-circuit board.

24. The method of claim 23, wherein an interior of the opening in the printed-circuit board is laminated with metal.

25. The method of claim 23, further comprising a sealing material in a gap between the electro-acoustic transducer and the inner wall of the opening.