MEMS microphone with reduced parasitic capacitance

• US 9,382,109 B2
• Filed: 11/14/2011
• Issued: 07/05/2016
• Est. Priority Date: 11/14/2011
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: Epcos AG (TDK Corporation)
• Inventors: Johansen, Leif Steen, Ravnkilde, Jan Tue, Rombach, Pirmin Hermann Otto, Rasmussen, Kurt
• Primary Examiner(s): Nguyen, Cuong Q
• Assistant Examiner(s): Kim, Tong-Ho
• Application Number:
  US13/261,875
• Publication Number:
  US 20140346620A1
• Time in Patent Office: 1,695 Days
• Field of Search: 257/416, 438/53, 428/131
• US Class Current: 1/1
• CPC Class Codes: B81B 3/0086 Electrical characteristics, e.g. reducing driving voltage, improving resistance to peak voltage
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: B81C 1/00698 Electrical characteristics, e.g. by doping materials
• CPC Class Codes: H04R 1/222 for microphones H04R1/24, H04R1/26 take precedence
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 2201/003 Mems transducers or their use of the electrostatic type H04R19/005
• 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
• CPC Class Codes: H04R 31/006 Interconnection of transducer parts of diaphragm and outer suspension by moulding H04R31/003

Abstract

A MEMS microphone has reduced parasitic capacitance. The microphone includes a trench electrically separating an acoustically active section of a backplate from an acoustically inactive section of the backplate.

Claims

1. A MEMS microphone, comprising:

an acoustically active region;

a rim region surrounding the acoustically active region;

a membrane in a membrane layer, the membrane having a section in the acoustically active region and a section in the rim region;

a first backplate in a first backplate layer, the first backplate having a section in the acoustically active region and a section in the rim region; and

a first trench that electrically separates the membrane section of the rim region from the membrane section of the acoustically active region and/or the first backplate'"'"'s section of the rim region from the first backplate'"'"'s section of the acoustically active region, wherein a resistance between the separated regions is 10GΩ

or more.

2. The MEMS microphone of claim 1, where the first backplate further comprises:

a first backplate isolation layer; and

a first conductive backplate layer arranged between the first backplate isolation layer and the membrane;

wherein the first backplate isolation layer mechanically connects the first conductive backplate layer'"'"'s section of the acoustically active region to the microphone.

3. The MEMS microphone of claim 1, further comprising a first anchor element in the rim region of an anchor layer, where the anchor layer is arranged between the first backplate and the membrane.

4. The MEMS microphone of claim 3, comprising:

a first backplate isolation layer;

a first conductive backplate layer; and

a substrate on which the membrane is arranged.

5. The MEMS microphone of claim 4, wherein the substrate comprises Si;

wherein the membrane comprises polycrystalline Si;

wherein the anchor layer comprises SiO₂;

wherein the first conductive backplate layer comprises polycrystalline Si; and

wherein the first backplate isolation layer comprises silicon rich silicon nitride.

6. The MEMS microphone of claim 1, further comprising a second backplate, wherein the second backplate comprises a second backplate isolation layer and a second conductive backplate layer, and wherein the second conductive backplate layer is arranged between the second backplate isolation layer and the membrane.

7. The MEMS microphone of claim 6, further comprising an isolation element in the rim region of the second conductive backplate layer, wherein the isolation element separates the second conductive backplate layer of the acoustically active region from the second conductive backplate layer of the rim region.

8. The MEMS microphone of claim 1, wherein the membrane further comprises a first membrane isolation layer, a second membrane isolation layer and a conductive membrane layer arranged between the first and second membrane isolation layers, wherein a second trench electrically separates the conductive membrane layer'"'"'s section of the rim region from the conductive membrane layer'"'"'s section of the acoustically active region.

9. The MEMS microphone of claim 1, wherein the first trench separates the membrane section of the rim region from the membrane section of the acoustically active region.

10. The MEMS microphone of claim 1, wherein the first trench separates the first backplate'"'"'s section of the rim region from the first backplate'"'"'s section of the acoustically active region.

11. The MEMS microphone of claim 1, wherein the first trench both separates the membrane section of the rim region from the membrane section of the acoustically active region and the first backplate'"'"'s section of the rim region from the first backplate'"'"'s section of the acoustically active region.

12. A method for manufacturing a MEMS microphone, the method comprising:

providing a substrate;

structuring a membrane on the substrate, the membrane having a section in an acoustically active region and a section in a rim region;

depositing an anchor layer onto the membrane;

depositing a backplate layer onto the anchor layer;

structuring a backplate and an anchor element, the backplate having a section in the acoustically active region and a section in the rim region; and

structuring a trench in the backplate such that a central section of the backplate is electrically separated from a rim sided section of the backplate and a resistance between the central section of the backplate and the rim sided section is 10GΩ

or more.

13. The method of claim 12,

wherein the substrate comprises Si;

wherein the membrane comprises polycrystalline Si; and

wherein the anchor layer comprises SiO₂.