KR101877838B1 - MEMS Microphone Device And MEMS Microphone Module Comprising The Same - Google Patents

Abstract

There is provided a MEMS microphone element and a MEMS microphone module of a solid conduction type in which the inflow of external pollutants and the inflow of ambient noise are suppressed. A MEMS microphone module according to the present invention includes: a printed circuit board; A MEMS microphone element mounted on one surface of the printed circuit board; And a housing enclosing the MEMS microphone element together with the printed circuit board to form an internal space separated from an external space, wherein the MEMS microphone element comprises: a back plate fixed to the printed circuit board or the housing; A diaphragm which vibrates relative to the back plate; And a cavity formed on the opposite side of the back plate with the diaphragm interposed therebetween, the cavity being blocked by the printed circuit board or the housing and blocking the sound pressure transmission path to the outside through the air.

Description

[0001] The present invention relates to a MEMS microphone device and a MEMS microphone module including the MEMS microphone device.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MEMS (Micro Electro Mechanical System) microphone, and more particularly, to a MEMS microphone element and a module that provide an acoustic signal according to vibration.

Generally, a microphone is a device that converts voice or sound into electrical signals. A microphone is also an essential element for transmitting voice or sound through a communication device, or for amplifying a specific range of voice or sound and processing it into a necessary form. Here, the voice refers to the sound that the person puts in the voice with meaning, and the sound means the sound that is perceived audibly including the voice.

In order to be recognized as a good microphone, excellent sensitivity and operability for voice / sound signals to be converted into electrical signals, and excellent reliability in the use environment are required. In recent years, there has been an increasing demand for microphones such as mobile communication devices and headsets and hearing aids as accessories thereof. As a microphone suitable for miniaturization, a MEMS microphone can be mentioned. Since the MEMS microphone is formed through a thin film process in which elements for sensing sound such as a vibration membrane and a back plate are formed on a silicon substrate, it is possible to reduce the size of the microphone and improve the productivity by automation Do.

Until recently, research on MEMS microphones has been proceeding with resistance type, Piezo type, and condenser type. Particularly, research and development have been proceeded on a capacitor-type MEMS microphone centered on a voice frequency band having excellent stability and frequency characteristics of a converted sound field. The condenser type MEMS microphone has a pair of conductive films arranged opposite to each other. One of them constitutes a vibrating membrane which vibrates in response to a signal such as a back plate, which is a fixed electrode, and the other, a signal such as voice. The condenser type MEMS microphone utilizes a phenomenon in which the electrostatic capacity between the diaphragm and the back plate, which is installed with an air gap of several mu m to several tens of micrometers apart, is changed according to the vibration of the diaphragm by voice / sound Thereby generating an electrical signal.

The conventional condenser type MEMS microphone module generally includes a printed circuit board and an MEMS microphone element mounted on the printed circuit board and an IC component (generally, ASIC, Application Specific Integrated Circuit) for driving the MEMS microphone element. The MEMS microphone device includes a printed circuit board and a housing made of a metal or a synthetic resin to cover and protect the MEMS microphone element and the IC component therein. At least one of the printed circuit board and the housing is provided with an opening through which air is transmitted from the outside of the printed circuit board and the housing to the diaphragm inside the housing through the air.

These openings have been recognized as indispensable elements for receiving acoustic input. However, on the other hand, the mechanical stability of the above-mentioned diaphragm may be deteriorated. Since the diaphragm of the MEMS microphone has a very thin thickness and is easily affected by contaminants entering through the opening. Also, the opening may be a path through which unnecessary ambient noises are introduced through the vibration of the air.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a MEMS microphone device and a MEMS microphone module including the MEMS microphone device, A microphone element, and a MEMS microphone module.

In order to solve the above-described problems, a MEMS microphone module according to the present invention includes: a printed circuit board; A MEMS microphone element mounted on one surface of the printed circuit board; And a housing enclosing the MEMS microphone element together with the printed circuit board to form an internal space separated from an external space, wherein the MEMS microphone element comprises: a back plate fixed to the printed circuit board or the housing; A diaphragm which vibrates relative to the back plate; And a cavity formed on the opposite side of the back plate with the diaphragm interposed therebetween, the cavity being blocked by the printed circuit board or the housing and blocking the sound pressure transmission path to the outside through the air.

Wherein the diaphragm and the back plate each have a diaphragm electrode and a counter electrode opposed to each other with an air gap therebetween, and the printed circuit board on which the backplate is fixed, or between the housing and the counter electrode, ≪ / RTI >

Wherein the MEMS microphone element comprises: a first substrate portion having the diaphragm and defining a cavity that is a void space corresponding to a planar shape of the diaphragm electrode by forming a peripheral portion of the diaphragm; A second substrate portion having the back plate; And a gap forming joint joining the first substrate portion and the second substrate portion to each other such that the diaphragm and the backplate face each other and forming an air gap between the diaphragm and the backplate .

In the above-mentioned MEMS microphone element, the gap forming joint is sandwiched between a first peripheral metal pattern of the first substrate portion and a second peripheral metal pattern of the second substrate portion to have a thickness corresponding to the air gap, Wherein the first peripheral metal pattern is formed of the same metal layer as the vibrating film electrode on the periphery of the vibrating film electrode formed on the vibrating film and the second peripheral metal pattern is formed on the periphery of the counter electrode formed on the backplate, May be formed of the same metal layer as the counter electrode.

Wherein the first substrate portion and the second substrate portion are multi-layer structures each having at least one thin film laminated on a silicon base substrate, the second substrate portion includes a metal layer forming the counter electrode and the second peripheral metal pattern, All of the layers except for the contacted surface may be uniformly formed in a plane.

The first peripheral metal pattern may be disposed so as to overlap the peripheral portion of the cavity in a plan view.

On the other hand, the MEMS microphone element can be bonded to one surface of the printed circuit board and the other surface to the inner surface of the housing.

A MEMS microphone device according to an aspect of the present invention includes: a diaphragm having a diaphragm electrode on one surface thereof; A cavity formed on the opposite side of the diaphragm electrode with the diaphragm interposed therebetween in a shape corresponding to a planar shape of the diaphragm electrode; And a counter electrode facing the vibrating membrane electrode with a predetermined air gap interposed therebetween, and a back plate opposite the counter electrode filled with a solid material.

The MEMS microphone device may include a first substrate portion having the diaphragm and defining a cavity that is a void space corresponding to a planar shape of the diaphragm electrode by forming a peripheral portion of the diaphragm; A second substrate portion having the back plate; And a gap forming joining portion joining the first substrate portion and the second substrate portion to each other such that the diaphragm and the back plate face each other and forming an air gap between the diaphragm and the back plate. have.

Wherein the gap forming joint is interposed between a first peripheral metal pattern of the first substrate portion and a second peripheral metal pattern of the second substrate portion to bond the first peripheral metal pattern and the second peripheral metal pattern to a thickness corresponding to the air gap, The pattern is formed of the same metal layer as the vibrating film electrode on the periphery of the vibrating film electrode formed on the vibrating film, and the second surrounding metal pattern is formed on the periphery of the counter electrode formed on the back plate as a metal layer May be formed.

The MEMS microphone device according to the present invention and the MEMS microphone module including the MEMS microphone device according to the present invention can prevent the inflow of external pollutants from the source to improve the reliability of the product even in a severe use environment and minimize the inflow of noise by air vibration Thereby eliminating noise other than the effective signal transmitted by the solid conduction, thereby providing a high-quality signal even in an environment with high noise.

1 shows a state in which a housing is opened in a MEMS microphone module according to an embodiment of the present invention.
2 shows an internal structure of a MEMS microphone module according to an embodiment of the present invention.
FIG. 3 illustrates a first substrate portion manufacturing process of a MEMS microphone device according to an embodiment of the present invention.
4 illustrates a second substrate portion manufacturing process of a MEMS microphone device according to an embodiment of the present invention.
5 shows a MEMS microphone element formed by combining a first substrate portion according to the process of FIG. 3 and a second substrate portion according to the process of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below can be modified in various ways, and the scope of the present invention is not limited to the following embodiments. The embodiments of the present invention are provided to clearly convey the technical idea of the present invention to those skilled in the art.

1 shows a state in which a housing is opened in a MEMS microphone module according to an embodiment of the present invention.

The MEMS microphone module according to the present embodiment includes a printed circuit board 20, a MEMS microphone element 10 mounted on one side of the printed circuit board, and the MEMS microphone element 10 And a housing 40 surrounding the outer space to define an inner space separated from the outer space. An IC component 30 for driving the MEMS microphone device 10 may be mounted on the surface of the printed circuit board 20 together with the MEMS microphone device 10 in the housing 40. A plurality of electrode pads 21 are provided on one surface of the printed circuit board 20 and the IC components 30 are electrically connected to the plurality of electrode pads 21 and the plurality of lead wires 22 Or may be wire-bonded through the wire. The MEMS microphone device 10 may also be wire-bonded through the IC component 30 and the lead wire 22m.

The MEMS microphone device 10 may be bonded to at least one of the printed circuit board 20 and the housing 40. According to the present embodiment, the MEMS microphone element 10 is adhered to the printed circuit board 20 with epoxy or the like, but the present invention is not limited thereto. For example, if the surface mounting is performed on the printed circuit board according to the position of the output terminal electrode of the MEMS microphone element, soldering bonding is performed, so that separate adhesion may be unnecessary. In addition, some of the other surfaces that are not bonded to the printed circuit board 20 may be bonded to the housing 40.

Unlike the conventional MEMS microphone module, the printed circuit board 20 and the housing 40 do not have openings for transmitting sound including sound propagated through the air to the internal space. The MEMS microphone module according to the present embodiment is configured such that the vibration that generates sound including sound is transmitted to the MEMS microphone device through solid conduction. These configuration features will be described in more detail below.

2 shows an internal structure of a MEMS microphone module according to an embodiment of the present invention.

The MEMS microphone element 10 viewed through the center section thereof includes a back plate 12 fixed to the printed circuit board 20 and a diaphragm 14 which vibrates relative to the back plate 12 ) And formed on the opposite side of the back plate (12) with the diaphragm (14) interposed therebetween. The housing (40) is closed by a part of the housing (40) And a cavity 16 in which a sound pressure transmission path to the outside is blocked. The cavity 16 functions as a resonant acoustic chamber in a corresponding structure of a conventional MEMS microphone module, but has a limited function as a structure that allows the diaphragm 14 to vibrate in a direction perpendicular to its plane .

 A cavity peripheral portion defining the cavity 16, which is an empty space of a certain type, may be bonded to the housing 40. As a concrete example, it can be bonded with an adhesive such as epoxy. Such a structure assists vibration transmitted from the outside to the housing 40 as a sound source to be transmitted to the diaphragm 14 through solid conduction.

A diaphragm electrode 114m is disposed on the diaphragm 14 opposite to the cavity 16. The diaphragm electrode 114m constitutes a variable capacitor. On one surface of the diaphragm 14 opposite to the diaphragm 14, a counter electrode 124c, which is another electrode constituting the variable capacitor, is disposed with an air gap 15 therebetween. The two electrodes may be formed of a metal pattern formed by patterning a metal thin film. A first peripheral metal pattern 114g and a second peripheral metal pattern 124g are formed on the periphery of the vibrating membrane electrode 114m and the periphery of the counter electrode 124c, 15 may be provided on the outer circumferential surface. The gap forming junction 115 may be formed of a bonding material having a low vibration damping ratio, for example, a metallic bonding material, so that solid conduction of vibration can be performed between the back plate 12 and the vibrating film 14.

In the MEMS microphone module according to the present embodiment, the MEMS microphone element 10 includes a first substrate portion 11 that constitutes the diaphragm 14 and a peripheral portion of the cavity 16, And a second substrate portion constituting the second substrate portion 12. (In the present embodiment, the back plate 12 and the second substrate portion are referred to in the functional and structural aspects only, and are substantially the same. Therefore, the same reference numerals will be used for the second substrate portion in the following description. ) The first substrate portion 11 and the second substrate portion 12 are multilayer structures in which at least one thin film is laminated on the silicon base substrates 111 and 121, respectively. The detailed lamination structure will be described later do.

Hereinafter, a process for manufacturing a MEMS microphone device according to the above-described embodiment will be described. The process to be described is only one example, and there is no reason why the MEMS microphone device according to the present invention should be construed as being manufactured by the following process. However, the structure of the above-mentioned MEMS microphone device can be understood more clearly through the process.

FIG. 3 illustrates a first substrate portion manufacturing process of a MEMS microphone device according to an embodiment of the present invention.

First, silicon oxide (SiO2) layers 112a and 112b are formed as dry-etching masking materials on both sides of a silicon base substrate 111, as shown in FIG. 3A. Next, silicon nitride (SiNx) layers 113a and 113b are formed on both sides of the silicon nitride (SiNx) layer to form a nonmetallic thin film portion of the diaphragm, as shown in FIG. 3 (b). The silicon nitride layers 113a and 113b are preferably formed to have a low residual stress to improve durability of the diaphragm due to repetitive vibration.

Next, as shown in FIG. 3C, a conductive metal layer 114 is laminated on the silicon nitride layer 113a, and the metal layer 114 is patterned to form a metal pattern having a predetermined planar shape A first peripheral metal pattern 114g extending in the form of a narrow band is formed on the membrane electrode 114m and its periphery. At this time, the metal layer 114 may be formed of a metal having high electrical conductivity such as Ti, Au, Cu, Al, Pt, or Sn, or an alloy thereof.

Then, as shown in FIG. 3D, a first metal bonding material pattern 115a having a predetermined thickness is formed on the first peripheral metal pattern 114g. The first metal bonding material pattern 115a may be, for example, a thin film pattern of a metallic bonding material suitable for eutectic bonding, and its thickness may be about 1/2 of the air gap described above.

3 (e), the rear surface of the first substrate portion 11 is etched using a reactive ion etching (DRIE) method to form the diaphragm 14 , That is, a cavity 16 extending from the diaphragm 14 to the opposite surface of the diaphragm electrode 114m is formed. The planar shape of the cavity 16 may be similar to the planar shape of the diaphragm electrode 114m and may be formed wider than the area of the diaphragm electrode 114m.

FIG. 3 (f) shows a view of the first substrate portion 11 formed through the above process from above the vibrating membrane electrode 114m. Accordingly, the first peripheral metal pattern 114g and the first metal bonding material pattern 115a can be seen in a planar form. In the present embodiment, the diaphragm electrode 114m and the first peripheral metal pattern 114g are connected to each other by a conductive metal pattern. The diaphragm electrode 114m and the output terminal portion Reference numeral 114e) for electrical connection.

4 illustrates a second substrate portion manufacturing process of a MEMS microphone device according to an embodiment of the present invention.

The second substrate portion, like the first substrate portion, also utilizes a silicon wafer as a base substrate. Silicon nitride (Si 3 N 4) layers 123 a and 123 b are formed on both sides of the silicon base substrate 121 as shown in FIG. 4 (a). The silicon nitride layers 123a and 123b are used as a wet etching masking layer.

Next, as shown in FIG. 4 (b), a conductive metal layer 124 is laminated on the silicon nitride layer 123a on one side and patterned to form a counter electrode 124c pattern and a second peripheral electrode pattern 124g do. The metal layer 124 is the same as the metal layer 114 of the first substrate portion. Next, a second metal bonding material pattern 115b is formed on the second peripheral metal pattern 124g. The second metal bonding material pattern 115b may be a thin film pattern of a metallic bonding material suitable for eutectic bonding, and the thickness thereof may be about 1/2 of the air gap described above.

4D is a view of the second substrate portion 12 viewed from the side of the counter electrode 124c and shows the pattern of the counter electrode 124c and the second peripheral metal pattern 124g formed in the above- Shape. The counter electrode 124c is formed so that most of its area overlaps with the above-mentioned diaphragm electrode 114m in a plan view. However, the counter electrode 124c may extend to a portion where the second peripheral metal pattern 124g is not formed, and configure the output terminal 124e. As a result, the counter electrode 124c and its output terminal 124e are electrically connected to each other in the same metal layer, and the aforementioned vibrating membrane electrode (see 114m of FIG. 3 (f)) and its output terminal 114e are electrically connected Are electrically connected to each other through a first peripheral metal pattern 114g, a first metal bonding material pattern 115a, a second metal bonding material pattern 115b, and a second peripheral metal pattern 124g.

5 shows a MEMS microphone element formed by combining a first substrate portion according to the process of FIG. 3 and a second substrate portion according to the process of FIG.

As shown in the figure, the first substrate portion 11 having the diaphragm 14 and the second substrate portion 12 as a back plate are aligned and bonded to each other using a matching aligner. The bonding process can be performed according to the eutectic bonding method as described above. The eutectic bonding temperature depends on the kind of the bonding material. For example, the bonding may be performed at a temperature of about 300 ° C lower than the melting temperature of the first and second metal bonding materials 115a and 115b. The above-described process is advantageous in accurately controlling the air gap 15.

The condenser type MEMS microphone element converts the mechanical vibration of the diaphragm 14 into an electrical signal by detecting a change in capacitance between the diaphragm electrode and the counter electrode with the air gap 15 interposed therebetween. The MEMS microphone device according to the first embodiment has a direct effect of vibrating the diaphragm 14 not by the negative pressure transmitted through the air in the cavity 16 but through the second substrate 12 or the first substrate 11, Mechanical vibrations transmitted in a manner that is not known. In other words, an electrical signal is generated through relative oscillation of the diaphragm 14 due to inertia with respect to the back plate 12. To this end, it is preferable that the back plate 12 is filled with a solid material without a space at the bottom of the counter electrode.

10: MEMS microphone element
11: first substrate part 12: second substrate part
14: diaphragm 15: air gap
16: cavity 20: printed circuit board
30: IC component 40: housing
114m: diaphragm electrode 114g: first peripheral metal pattern
115: gap forming junction 124c: counter electrode
124g: second peripheral metal pattern

Claims (10)

Printed circuit board;
A housing defining an inner space separated from an outer space together with the printed circuit board; And
And a MEMS microphone element fixed to one surface of the printed circuit board covered with the housing or to the housing,
The MEMS microphone device includes:
A back plate fixed to one surface of the printed circuit board or to the housing;
A diaphragm which vibrates relative to the back plate; And
And a cavity formed on an opposite side of the back plate with the diaphragm interposed therebetween, the cavity being blocked by the printed circuit board or the housing and blocking a sound pressure transmission path to the outside through the air,
Wherein the diaphragm and the back plate each have a diaphragm electrode and a counter electrode opposed to each other with an air gap therebetween,
Wherein the back plate is fixed to the printed circuit board or between the housing and the counter electrode,
MEMS microphone module.
delete The method according to claim 1,
The MEMS microphone device includes:
A first substrate portion having the diaphragm and defining a cavity which is an empty space in a shape corresponding to a planar shape of the diaphragm electrode by forming a peripheral portion of the diaphragm;
A second substrate portion having the back plate; And
And a gap forming joint joining the first substrate portion and the second substrate portion to each other such that the diaphragm and the backplate face each other and forming an air gap between the diaphragm and the backplate.
MEMS microphone module. The method of claim 3,
The gap forming joint is interposed between a first peripheral metal pattern of the first substrate portion and a second peripheral metal pattern of the second substrate portion to bond the first peripheral metal pattern and the second peripheral metal pattern to a thickness corresponding to the air gap,
Wherein the first peripheral metal pattern is formed of the same metal layer as the vibrating film electrode on the periphery of the vibrating film electrode formed on the vibrating film,
Wherein the second peripheral metal pattern is formed in the peripheral portion of the counter electrode formed on the back plate and formed of the same metal layer as the counter electrode,
MEMS microphone module. 5. The method of claim 4,
Wherein the first substrate portion and the second substrate portion are multilayer structures each having at least one thin film laminated on a silicon base substrate,
Wherein the second substrate portion is formed by forming all the layers except the metal layer forming the counter electrode and the second peripheral metal pattern and the surface in contact therewith uniformly in a planar manner,
MEMS microphone module. 5. The method of claim 4,
Wherein the first peripheral metal pattern is disposed so as to overlap the periphery of the cavity in a plan view,
MEMS microphone module. The method according to claim 1,
Wherein the MEMS microphone element has one surface bonded to the surface of the printed circuit board and the other surface bonded to the inner surface of the housing,
MEMS microphone module. delete delete delete

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