Component having a micro-mechanical microphone structure and method for producing the component

Patent metadata

Field	Value
Publication number	US-9344806-B2
Application number	US-201013388014-A
Country	US
Kind code	B2
Filing date	Jun 2, 2010
Priority date	Jul 31, 2009
Publication date	May 17, 2016
Grant date	May 17, 2016

Abstract

Measures are provided for improving the acoustic properties of a component ( 10 ) having a micromechanical microphone structure realized in a layer construction ( 20 ) over a substrate ( 1 ), and for simplifying the production method. The microphone structure of such a component ( 10 ) includes a diaphragm ( 11 ) deflectable by acoustic pressure, spanning a cavity ( 13 ) that acts as a rear-side volume in the rear side of the component, and includes a stationary, acoustically permeable counter-element ( 12 ) situated over the diaphragm ( 11 ). According to the invention, the layer construction ( 20 ) has, between the diaphragm ( 11 ) and the substrate ( 1 ), an enclosing layer ( 3 ) in which there is fashioned an acoustically transparent aperture ( 4 ). The diaphragm ( 11 ) is connected to the rear-side volume ( 13 ) via this aperture in the enclosing layer ( 3 ). Under the enclosing layer ( 3 ), the rear-side volume ( 13 ) extends laterally beyond this aperture ( 4 ).

First claim

What is claimed is:

1. A component, comprising:
a micromechanical microphone structure realized in a layer construction over a substrate, the microphone structure including:
a diaphragm that is:
arranged over, and that spans, a cavity acting as a rear-side volume in the rear side of the component; and
deflectable by acoustic pressure caused by acoustic waves entering the cavity via the diaphragm from outside the component; and

a stationary acoustically permeable counter-element that is situated over the diaphragm;

wherein:
the layer construction between the diaphragm and the substrate includes at least one enclosing layer;
an acoustically transparent aperture is configured in this enclosing layer, via which the diaphragm is connected to the rear-side volume;
the enclosing layer surrounding the aperture forms an undercutting section, which the substrate does not contact;
the rear-side volume extends under the undercutting section of the enclosing layer, laterally beyond the aperture;
a lateral width of a rear-side opening in the rear-side volume is smaller than an interior lateral width of the rear-side volume; and
the enclosing layer, when viewed in a cross-section that is in a plane parallel to a center axis of the diaphragm, includes at least one portion that, laterally in a direction towards a center axis of the diaphragm:
extends from over a top surface of the substrate towards a lateral edge of the top surface of the substrate;
continues onward to pass over the lateral edge of the top surface; and
continues onward to beyond the lateral edge of the top surface of the substrate, thereby forming the undercutting section.

2. The component of claim 1 , wherein the diaphragm is provided between the counter-element and the aperture, and wherein the diaphragm is electrically insulated against the counter-element and against the enclosing layer containing the aperture.

3. The component of claim 1 , wherein at least one of a diaphragm suspension and bypass openings are configured in the edge region of the diaphragm, and wherein the acoustically transparent aperture in the enclosing layer extends only over the closed center region of the diaphragm.

4. The component of claim 1 , wherein the acoustically transparent aperture is configured as a contiguous opening in the enclosing layer.

5. The component of claim 1 , wherein the acoustically transparent aperture is configured as a mesh structure or perforated hole structure in the enclosing layer.

6. The component of claim 5 , the diaphragm acting as a deflectable electrode, the stationary acoustically permeable counter-element including at least one counter-electrode, and arrangement being provided for applying a charge voltage between the diaphragm and the counter-electrode, wherein the mesh or perforated hole structure in the enclosing layer acts as a compensating electrode, and arrangement are provided for applying a compensating voltage between the counter-electrode and the compensating electrode.

7. The component of claim 1 , wherein the diaphragm extends over the enclosing layer laterally beyond the aperture.

8. A method for producing a component including a micromechanical microphone structure, in which a diaphragm and a stationary acoustically permeable counter-element are realized in a layer construction over a substrate, the method comprising:
defining a position, a shape, and dimensions of an acoustically transparent aperture in an enclosing layer between the substrate surface and the diaphragm layer in a front-side process;
configuring the diaphragm and the counter-element in a layer construction over the enclosing layer; and
making a cavity in the rear side of the substrate and connecting it to the microphone structure through exposure of the aperture in the enclosing layer;
wherein:
the aperture is laterally undercut, so that the rear-side volume extends laterally beyond the active diaphragm surface;
the diaphragm is:
arranged over, and spans, the cavity acting as a rear-side volume in the rear side of the component; and
deflectable by acoustic pressure caused by acoustic waves entering the cavity via the diaphragm from outside the component;

the stationary acoustically permeable counter-element is situated over the diaphragm;
the layer construction between the diaphragm and the substrate includes the enclosing layer;
the diaphragm is connected to the rear-side volume via the aperture;
the enclosing layer surrounding the aperture forms an undercutting section, which the substrate does not contact;
the rear-side volume extends under the undercutting section of the enclosing layer, laterally beyond the aperture;
a lateral width of a rear-side opening in the rear-side volume is smaller than an interior lateral width of the rear-side volume; and
the enclosing layer, when viewed in a cross-section that is in a plane parallel to a center axis of the diaphragm, includes at least one portion that, laterally in a direction towards a center axis of the diaphragm:
extends from over a top surface of the substrate towards a lateral edge of the top surface of the substrate;
continues onward to pass over the lateral edge of the top surface; and
continues onward to beyond the lateral edge of the top surface of the substrate, thereby forming the undercutting section.

9. The method of claim 8 , wherein:
at least one first electrically insulating sacrificial layer is applied onto the substrate surface and structured;
subsequently:
the enclosing layer is produced on the structured first sacrificial layer, with the first sacrificial layer separating the enclosing layer from the substrate; and
the position, geometry, and dimensions of the aperture are defined in the produced enclosing layer;

at least one second electrically insulating sacrificial layer is applied on the enclosing layer and structured;
a diaphragm layer that is electrically conductive at least in some regions is produced and structured over the second sacrificial layer;
at least one third electrically insulating sacrificial layer is applied and structured over the diaphragm layer;
a layer that is electrically conductive at least in some regions is produced over the third sacrificial layer to realize the stationary counter-element;
this conductive layer is structured in a front-side trench process, the third sacrificial layer acting as a stop layer;
a cavity is made in the rear side of the substrate to realize a rear-side volume, the first sacrificial layer in the edge region of the cavity and the second sacrificial layer in the region of the aperture acting as stop layers; and
at least the second and third sacrificial layers are removed in the diaphragm region to expose the diaphragm in the diaphragm layer between the counter-element in the conductive layer and the aperture in the enclosing layer.

10. The method of claim 8 , wherein:
at least one first electrically insulating sacrificial layer is applied onto the substrate surface;
subsequently:
the enclosing layer is produced and structured on the first sacrificial layer, with the first sacrificial layer separating the enclosing layer from the substrate; and
the aperture is produced with a defined position, geometry, and defined dimensions;

at least one second electrically insulating sacrificial layer is applied on the enclosing layer and structured;
a diaphragm layer that is electrically conductive at least in some regions is produced and structured over the second sacrificial layer;
at least one third electrically insulating sacrificial layer is applied and structured over the diaphragm layer;
a layer that is electrically conductive at least in some regions is produced over the third s

Assignees

• Reinmuth Jochen
• Bosch Gmbh Robert

Inventors

• Reinmuth Jochen

Classifications

• B81C1/00571

  Avoid or control under-cutting · CPC title

• B81C1/00182

  Arrangements of deformable or non-deformable structures, e.g. membrane and cavity for use in a transducer · CPC title

• B81B2201/0257

  Microphones or microspeakers · CPC title

• H04R19/005 Primary

  using semiconductor materials · CPC title

• H04R19/04

  Microphones (H04R19/01 takes precedence) · CPC title