KR102091854B1 - Condensor microphone and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a condenser microphone. The condenser microphone comprises a base substrate; a membrane arranged on the base substrate; a back plate portion arranged on the membrane; an air layer arranged between the membrane and the back plate portion; and a plurality of contour-shaped protrusions protruding in the air layer toward the membrane from the back plate portion.

Description

CONDENSOR MICROPHONE AND MANUFACTURING METHOD THEREOF}

The present invention relates to a condenser microphone and a method for manufacturing the same, and more particularly, to a condenser microphone having a good vibration efficiency of a membrane vibrating by sound pressure and having excellent output voltage sensitivity, and a method for manufacturing the same.

In general, an acoustic sensor is a device that converts an acoustic signal into an electrical signal and includes a microphone.

There are many different types of microphones depending on the material and operating principle.

For example, depending on the material, it is classified into a carbon microphone, a crystal microphone, and a magnetic microphone.

In addition, depending on the operating principle, it can be divided into a dynamic microphone using an induced electromotive force by a magnetic field and a condenser microphone using a change in capacitance due to vibration of a diaphragm such as a membrane or diaphragm. have.

For portable electronic devices such as computers, mobile communication terminals, MP3 recorders, cassette recorders, camcorders, and headsets, or small electronic devices, microminiature condenser microphones such as an electret condensor microphone (ECM) microphone or a microelectromechanical system (MEMS) microphone are mainly used. .

ECM microphones use a polarized dielectric material called electret. The ECM microphone has a function of accumulating electric charge while no bias voltage is applied. The charge of the electret material is sensitive to temperature and deteriorates characteristics due to long-term drift, which degrades the sensitivity of the microphone. So, although Teflon was applied to the microphone as an electret material, the application of Teflon to a standard mass production process created many difficult problems.

On the other hand, the condenser microphone does not require an electret material, and a bias voltage may be applied to accumulate electric charges.

Condenser microphones have adequate sensing sensitivity and low sensing sensitivity depending on the temperature. Since such a condenser microphone is usually manufactured by a micro-electro-mechanical system (MEMS) process for small size and low cost mass production, the condenser microphone is also commonly referred to as a MEMS microphone.

The condenser microphone includes two flat-panel capacitances, a diaphragm and a back plate, and the two flat-panel capacitances are separated through an air gap acting as an insulating material.

A back chamber is formed on the base plate supporting the diaphragm and the back plate. A plurality of acoustic holes are formed in the back plate to serve to alleviate air damping.

The sound wave introduced through the acoustic hole of the back plate causes the diaphragm to bend, and the capacitance between the diaphragm and the back plate changes according to the change in the thickness of the air layer.

The capacitance that changes according to the change in the thickness of the air layer is converted into an appropriate electrical signal by a readout circuit configured in the condenser microphone.

Manufacturers of commercialization of microphones have been continuously improving the structure and materials of diaphragms and backplates in order to improve the sensitivity of the microphones and lower the noise level.

Condenser microphones must maintain efficient vibration of the diaphragm in order to minimize parasitic capacitance and increase the vibration efficiency of the diaphragm.

1 shows a partial structure of a conventional condenser microphone.

1, the conventional condenser microphone is located between the base substrate 10, the diaphragm 11, the back plate 12, the base substrate 10 and the back plate 12, and supports the diaphragm 11 It has an insulating connection (13a, 13a) and an air layer (14) located between the diaphragm (11) and the back plate (14).

At this time, the insulating connecting portions 13a and 13b are divided into a portion 13a positioned at the bottom and a portion 13b positioned at the top, with the diaphragm 11 as the center, as shown in FIG. 1.

The diaphragm 11 formed on the base substrate 10 has elasticity so that it can be easily vibrated in the air layer 14 and vibrates in the vertical direction to form capacitances Ce and Cc of a corresponding size between the back plate 12 and the back plate 12 do.

At this time, the vibration range of the movable diaphragm 11 is before reaching the back plate 12 (that is, before attaching it), and once the diaphragm 11 is attached to the back plate 12, the charge does not move any more. Acoustic sensors equipped with condenser microphones are damaged due to reaching the pull-in voltage state.

In order to increase the operation efficiency of the condenser microphone, the condenser microphone should maximize the capacitance between the back plate 12 and the diaphragm 11 for a voice signal and minimize the leakage capacitance.

The leakage capacitance typically generated during operation is parasitic capacitance (Cp1) generated in the insulating connection portion 13b between the back plate 12 and the diaphragm 11 and the insulation between the diaphragm 11 and the base substrate 10 And parasitic capacitance Cp2 generated in the connecting portion 13a. In addition to this parasitic capacitance, there is also a capacitance generated from a wire connecting a microphone body (not shown) and a pad formed for input / output of a signal.

Korean Patent Publication No. 10-2016-0127212 (Public Date 2016.11.03)

The problem to be solved by the present invention is to provide a condenser microphone and a manufacturing method for improving the performance of the condenser microphone by increasing the vibration efficiency of the membrane at an operating voltage.

Another problem to be solved by the present invention is to provide a condenser microphone having excellent output voltage sensitivity and a manufacturing method thereof.

The condenser microphone of the present invention for solving the above problems is provided by a base substrate, a membrane positioned on the base substrate, a back plate portion positioned on the membrane, an air layer positioned between the membrane and the back plate portion, and the back plate portion. It includes a plurality of contour projections protruding from the air layer toward the membrane.

The protrusion lengths of the plurality of contour protrusions may be the same regardless of the position.

The protrusion lengths of the plurality of contour projections may be different depending on the position.

The protruding length of the contour protrusions facing the membrane may increase as it goes from the center of the membrane to the edge.

The protruding length of the contour projection can be increased at a predetermined rate.

The density of the plurality of contour projections may be different depending on the location.

The density of the contour protrusions facing the membrane may decrease as it goes from the center of the membrane to the edge.

The back plate portion may include a first back plate in contact with the air layer and a second back plate positioned on the first back plate.

The second back plate may be made of the same material as the contour projections.

The first back plate may be made of the same material as the second back plate.

The first back plate may be made of a different material than the second back plate.

The method of manufacturing a condenser microphone according to another aspect of the present invention includes forming a membrane on a base substrate, forming a sacrificial layer on the membrane, forming a first backplate layer on the sacrificial layer, and the first bag. After depositing a resist film on the plate layer, using a mask to selectively etch the resist film to expose a portion of the first back plate layer located in the etched portion, the exposed first using the remaining resist film as a mask By removing a portion of the back plate layer, forming a first back plate having an empty portion in the form of a contour, removing the remaining resist film, etching the sacrificial layer exposed through the blank portion by a predetermined depth Forming a hole for contouring projections on the first back plate and the sacrificial layer, and Depositing a predetermined material in the above-mentioned contour-shaped projection hole and a step of forming a contour-like protrusions.

The method of manufacturing a condenser microphone according to the above feature may further include forming a second plate on the first back plate and on the contour projection.

In the forming of the second plate, the second back plate may be formed using the same material as the contour projections.

According to the features of the present invention, as a plurality of contour projections having a relatively large outer diameter and a narrow line width are provided as the center has an empty space, a phenomenon in which the vibrating membrane contacts and adheres to the back plate portion is prevented. . In addition, due to the relatively large outer diameter, damage to the membrane is prevented or minimized in contact with the contoured projections. Therefore, the life of the membrane is increased.

In addition, when a high sound pressure is applied to the condenser microphone, the contoured projection contacts the wide part of the membrane, thereby improving the durability of the condenser microphone by the buffering effect of the contoured projection.

Since the density of the plurality of contour projections decreases from the center to the edge, the buffering effect and the adhesion prevention effect of the contour projections according to the vibration pattern of the membrane are improved.

In addition, by forming the back plate portion in two layers, the support of the contour projections is improved, and the warpage phenomenon is greatly reduced.

1 is a cross-sectional view partially showing the structure of a conventional condenser microphone. Some structures are shown.
2 is an exemplary plan view of a condenser microphone for explaining the structure of a condenser microphone according to an embodiment of the present invention.
3 is a cross-sectional view of the condenser microphone shown in FIG. 2 taken along the line III-III.
4 is a schematic perspective view of a solid-line projection coupled to a second back plate in a condenser microphone according to an embodiment of the present invention.
5A to 5J are cross-sectional views taken along the line III-III of FIG. 2, sequentially showing the condenser microphone according to an exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the present invention, for the technology or configuration already known in the art

When it is determined that adding the detailed description may obscure the gist of the present invention, some of them will be omitted from the detailed description. In addition, the terms used in the present specification are terms used to properly express the embodiments of the present invention, which may vary according to persons or practices related to the field. Therefore, definitions of these terms should be made based on the contents throughout the present specification.

The terminology used herein is only to refer to a specific embodiment and is not intended to limit the invention. The singular forms used herein include plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of 'comprising' embodies certain properties, regions, integers, steps, actions, elements and / or components, and other specific properties, regions, integers, steps, actions, elements, components and / or groups. It does not exclude the existence or addition of.

Hereinafter, a condenser microphone according to an embodiment of the present invention and a method of manufacturing the same will be described with reference to the accompanying drawings.

First, the structure of a condenser microphone according to an embodiment of the present invention will be described with reference to FIGS. 2 to 4. For convenience of illustration, the illustration of the sound hole in FIG. 2 is omitted.

2 and 3, the condenser microphone of the present embodiment includes a base substrate 100, a membrane 110 positioned on the base substrate 100, a back plate portion 120 positioned on the membrane 110, and a base. The air layer 130 positioned between the substrate 100 and the back plate portion 120, and the contour protrusions protruding from the back plate portion 120 to the air layer 130, and more specifically, the concentric circular protrusions 140 ).

The base substrate 100 is made of a silicon wafer or the like.

The base substrate 100 is provided with a back chamber (ie, a cavity) 101 in which no silicon wafer is present. Therefore, the electret element is located in the back chamber 101.

The membrane 110 is a vibrating plate that vibrates according to the size of sound waves flowing into the condenser microphone, and corresponding electrical signals are generated according to the vibration of the membrane 110 according to the sound waves.

As one example, the membrane 110 has a thickness of 0.5 ~ 2.0㎛, it may be made of polysilicon (Poly Si).

If the thickness of the membrane 110 is less than 0.5㎛, the thickness of the membrane 110 is too thin, the risk of breakage is large, and when it has a thickness exceeding 2.0㎛, the vibration operation due to sound waves is disturbed.

The back plate portion 120 faces the membrane 110 with the air layer 130 interposed therebetween. Accordingly, a capacitance of a corresponding size is generated between the membrane 110 and the back plate portion 120 according to a change in the distance between the membrane 110 and the back plate portion 120 according to the vibration of the membrane 110.

The back plate portion 120 is located on the first back plate 120a and the first back plate 120a located directly above the air layer 130 and in contact with the air layer 130 and in which the contour protrusions 140 are located. It is provided with a second back plate (120b) connected to the mold projection (140).

The first back plate 120a contributes to the generation of the opposing membrane 110 and the capacitance, and the second back plate 120b serves to support the contour projections 140.

The first back plate 120a and the second back plate 120b may be made of the same material or may be made of different materials. In addition, the second back plate 120b is made of the same material as the contoured protrusions 140.

When the first back plate 120a and the second back plate 120b are made of the same material, the first back plate 120a and the second back plate 120b are made of the same material as the contour projections 140 (for example, Nitride).

However, when the first back plate 120a and the second back plate 120b are made of different materials, only the second back plate 120a is made of the same material as the contour projections 140.

As such, since the back plate portion 120 is made of two layers, the supporting force of the back plate portion 120 facing the air layer 130 is improved to prevent warpage.

In addition, due to the second back plate 120b made of the same material as the contour projections 140, the support force of the contour projections 140 increases and the contour projections 140 fall from the back plate projections 120 This is prevented.

The membrane 110 and the back plate portion 120, which sandwich the air layer 130, which is an insulating layer, may function as counter electrodes facing each other in opposite directions. In this case, a membrane electrode and a back plate electrode may be additionally provided on the membrane 110 and the back plate portion 120, respectively. A bias voltage may be applied to the membrane electrode, and the generated output voltage may be applied to the back plate electrode to allow output to the outside.

The air layer 130 is positioned between the membrane 110 and the back plate portion 120 as described above, and spaces between the membrane 110 and the back plate portion 120 by the thickness of the air layer 130.

The air layer 130 functions as a dielectric, and as described above, a capacitance of a corresponding size is generated between the membrane 110 and the back plate portion 120 according to the vibration of the membrane 110 according to sound waves.

The contoured protrusion 140 prevents a pull-in voltage state that occurs when the membrane 110 comes into contact with the back plate portion 120 when the membrane 110 vibrates, and serves for interfacial buffering.

The contour projections 140 include a plurality of contour-shaped projections, and more specifically, a contour-shaped projection 141 which is a plurality of projections in the form of concentric circles having the same center point.

Each contour protrusion 141 of this example may be made of nitride, and an empty space H14 filled with air is provided between adjacent contour protrusions 141.

Each of the contour projections 141, as shown in FIG. 3, protrudes a predetermined length from the back plate portion 120 toward the membrane 110, and is vibrated by the plurality of contour projections 141. Membrane 110 may be in contact with the contoured projection 141 facing, not the back plate portion 120.

Therefore, even during vibration, the membrane 110 does not come into contact with the back plate portion 120, so that a pull-in voltage state does not occur, thereby extending the life of the membrane 110, thereby extending the life of the condenser microphone.

In the case of FIG. 3, the protruding length of each contour protrusion 141 protruding from the lower surface of the back plate 120, more specifically, from the lower surface of the first back plate 120a toward the membrane 110 toward the membrane 110 is located. It is the same regardless.

However, the present invention is not limited thereto, and in an alternative example, the protruding lengths of the at least two contour projections 141 differ depending on the location, and accordingly, the contour projections 141 located at the center of the condenser microphone are located at the edge. The protruding length may be shorter than the contour protrusion 141.

When the protruding length differs depending on the position, the protruding length of the contour protrusion 141 may increase as it goes from the center of the condenser microphone toward the edge. At this time, the increase ratio of the protruding length may increase proportionally according to the predetermined ratio.

In general, when sound waves of the same size are introduced, the vibration width of the membrane 110 decreases from the center to the edge.

Therefore, when the protruding length of the contour projections 141 increases from the center of the condenser microphone toward the edge, the membrane 110 does not interfere with the opposing contour projections 141, and the vibration of the corresponding width is normally performed. The vibration of the membrane 110 remains symmetrical with respect to the center.

Due to this, the correct capacitance corresponding to the incoming sound wave is generated to improve the reliability of the operation of the condenser microphone, the frequency of contact with the contour protrusions 141 or the impact upon contact is alleviated, thereby damaging or damaging the membrane 110 This decreases.

In particular, since the empty space H14 positioned between the two adjacent contour projections 141 is filled with air, a buffering effect occurs when the membrane 110 hits the corresponding contour projections 141 and the membrane 110 ) Damage or breakage is further reduced.

Since the plurality of contour projections 141 are located in the form of concentric circles, the outer diameter of each contour projections 141 increases from the center to the edge.

At this time, the line width W11 of each of the contour protrusions 141, that is, the thickness is thin by maintaining a minimum of 0.2 μm, as shown in FIGS. 2 and 3, may increase from the center to the edge. However, unlike this, the line width W11 of all the contour protrusions 141 may be the same.

As such, each contour projection 141 is made of concentric circles having an empty space H14 filled with air, and thus has great durability. Due to this, breakage or breakage of the contour projections 141 due to frequent collisions with the membrane 110 is reduced.

In addition, due to the space H14 between the contoured projections 141, even if the membrane 110 contacts the contoured projections 141, the phenomenon of adhesion to the contoured projections 141 is prevented.

When the line width W11 of each contour protrusion 141 is 0.2 μm or more, the formation of the contour protrusions 141 is easy, and the risk of damage when colliding with the membrane 110 is reduced.

The plurality of contour projections 141 are located in a portion of the back plate portion 120 in which an acoustic hole (not shown) is not located. The acoustic hole is a hole through which sound waves are introduced, and is a through hole that completely penetrates the back plate portion 120.

Since the vibration of the membrane 110 is strong at the center and becomes weaker toward the edge, the density of the contour projections 141 may be different depending on the position of the facing membrane 110, for example, the contour projections 141 ) May decrease in density from the center of the membrane 110 to the edge.

Accordingly, the distance between two adjacent contour projections 141 positioned opposite the center of the membrane 110 may be narrower than the distance between two adjacent contour projections 141 positioned opposite the edge of the membrane 110. . At this time, the distance between the two adjacent contour projections 141 may change proportionally from the center of the membrane 110 toward the edge. However, unlike this, the distance between two adjacent contour protrusions 141 may be the same.

The condenser microphone of this example having such a structure, in addition to the components shown in FIGS. 2 and 3, is located on the base substrate 100 and electrically connected to an insulating connection portion and a back plate electrode to support the back plate portion 120. At least one such as an output pad for outputting a signal, a bias pad for inputting a via voltage that is electrically connected to the membrane electrode, a connection between the backplate electrode and the output pad, and a respective connector for connection between the membrane electrode and the bias pad. Additional components may be provided.

Next, a method of manufacturing a condenser microphone according to an embodiment of the present invention will be schematically described with reference to FIGS. 5A to 5J.

First, as shown in FIG. 5A, a polysilicon film is deposited on a base substrate 100 made of a silicon wafer by a CVD deposition growth method to form a membrane 110. At this time, the formed membrane 110 may have a thickness of 0.5㎛ ~ 2.0㎛.

Next, as shown in FIG. 5B, a sacrificial layer 131 is formed by growing a film having a thickness of 1.5 to 4.0 μm on the membrane 110 by thermal oxidation. At this time, the thickness of the sacrificial layer 131 may be determined according to the vibration range of the membrane 110 and the protruding length of each contour protrusion 141.

Then, as illustrated in FIG. 5C, a first back plate layer 121a made of nitride is formed on the sacrificial layer 131 using a deposition method. The thickness of the first back plate layer 121a may be 2.0 μm to 3.5 μm.

Next, as illustrated in FIG. 5D, after the resist film 151 is stacked, a portion of the exposed resist film 151 is etched by selectively masking the resist film 151 using a mask to be located at the bottom. The first back plate layer 121a is exposed.

At this time, a portion of the etched resist film 151 becomes a location where each contour projection 141 is formed.

As described above, after exposing a desired portion of the first back plate layer 121a using the resist film 151, a portion of the exposed first back plate layer 121a is exposed using the remaining resist film 151 as a mask. The first back plate 120a is formed by etching (FIG. 5E).

At this time, the first back plate 120a is provided with an empty part of a contour shape (specifically a centrifugal form) by an etching operation, and the corresponding part of the sacrificial layer 131 is exposed through the empty part.

The etchant selectively removes only a portion of the exposed first backplate layer 121a, and the exposed portion of the sacrificial layer 131 is not etched.

Then, the resist film 121 existing on the first back plate 120a is removed (FIG. 5F).

As shown in Figure 5g, by etching the sacrificial layer 131 by a predetermined depth from the surface of the exposed sacrificial layer 131, the contour line at the corresponding position of the first back plate 120a and the corresponding position of the sacrificial layer 131, respectively Forms a hole (H140) for the projection.

At this time, the depth etched from the surface of the exposed sacrificial layer 131 is preferably less than 1/2 of the total thickness of the sacrificial layer 131, and may be, for example, 0.5 μm to 1.5 μm.

When the etching depth of the sacrificial layer 131 exceeds 1/2 of the total thickness, the distance between the contour protrusions 141 and the membrane 110 is short compared to the vibration width of the membrane 110, and thus the vibration operation of the membrane 110 Adversely affects

As described above, when a plurality of contour line protrusion holes H140 are formed in the first back plate 120a and the sacrificial layer 131, nitride is placed in the plurality of contour line protrusion holes H140 through a deposition method of nitride. Filled in, the contour projections 140 having a plurality of contour projections 141 are completed (FIG. 5H).

For the deposition operation of the nitride only in the plurality of contoured projection holes H140, the first back plate 120a where the contoured projection holes H140 are not located may be masked with a mask.

Next, the second back plate 120b is formed by depositing nitride on the first back plate 120a and the contour projections 141. At this time, if the second back plate 120b is omitted, this step is omitted.

Then, the sacrificial layer 131 is selectively etched to form an air layer 130 between the membrane 110 and the first back plate 120a (FIG. 5J). If the step of forming the second back plate 120b is omitted, the process proceeds to the step of forming the air layer 130 immediately after forming the contour projections 140.

Finally, the base substrate 110 is selectively removed to form an empty space, the back chamber 101 (see FIG. 3).

In the above, embodiments of the condenser microphone of the present invention and its manufacturing method have been described. The present invention is not limited to the above-described embodiments and the accompanying drawings, and various modifications and variations will be possible from the viewpoint of those skilled in the art to which the present invention pertains. Therefore, the scope of the present invention should be defined not only by the claims of the present specification, but also by the claims and equivalents thereof.

100: base substrate 101: back chamber
110: diaphragm, membrane 120: back plate portion
120a: first back plate 120b: second back plate
121a: first plate layer 130: air layer
131: sacrificial layer 140: contour projection
141: contour projection

Claims (14)

Base substrate;
A membrane positioned on the base substrate;
A back plate portion positioned on the membrane;
An air layer located between the membrane and the back plate portion; And
A plurality of contour projections protruding from the back plate portion to the air layer toward the membrane
Including,
The back plate portion,
A first back plate in contact with the air layer; And
A second back plate located on the first back plate
Condenser microphone comprising a. According to claim 1,
The condenser microphones having the same protruding lengths of the plurality of contour projections regardless of the position. According to claim 1,
The condenser microphone having a protruding length of the plurality of contour projections differs depending on the position. According to claim 3,
The condenser microphone whose protruding length of the contour projections facing the membrane increases from the center to the edge of the membrane. According to claim 4,
The condenser microphone whose protruding length of the contour projection increases at a predetermined rate. According to claim 1,
The density of the plurality of contour projections differs depending on the location of the condenser microphone. The method of claim 6,
A condenser microphone whose density decreases as it goes from the center of the membrane to the edge, and the density of the contour projections facing it decreases. delete According to claim 1,
The second back plate is a condenser microphone made of the same material as the contour projections. The method of claim 9,
The first back plate is a condenser microphone made of the same material as the second back plate. The method of claim 9,
The first back plate is a condenser microphone made of a material different from the second back plate. Forming a membrane on the base substrate;
Forming a sacrificial layer on the membrane;
Forming a first backplate layer over the sacrificial layer;
Depositing a resist film on the first backplate layer and selectively etching the resist film using a mask to expose a portion of the first backplate layer positioned in the etched portion;
Removing a portion of the exposed first backplate layer using the remaining resist film as a mask, thereby forming a first backplate having an empty portion in a contour shape;
Removing the remaining resist film;
Etching the sacrificial layer exposed through the empty portion by a predetermined depth to form a contour hole for the first back plate and the sacrificial layer; And
Forming a contour projection by depositing a predetermined material in the contour projection hole
Method of manufacturing a condenser microphone comprising a. The method of claim 12,
And forming a second plate on the first back plate and on the contour projections. The method of claim 13,
The second plate forming step is a method of manufacturing a condenser microphone using the same material as the contour projections to form the second back plate.

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