KR101887537B1 - Acoustic sensor and manufacturing method thereof - Google Patents

Abstract

The present invention relates to an acoustic sensor and a method of manufacturing the same. More specifically, the present invention relates to an acoustic sensor and a method of manufacturing the same, wherein a plurality of depressions are formed between the rim An opening is formed between the depression and the rim, so that the flatness, ductility and vibration efficiency of the diaphragm are good.

Description

TECHNICAL FIELD [0001] The present invention relates to an acoustic sensor,

The present invention relates to an acoustic sensor in which a diaphragm (membrane or diaphragm) vibrating by a negative pressure has good vibration efficiency at an operating voltage and excellent sensitivity of an output voltage and a method of manufacturing the same.

Generally, an acoustic sensor includes a microphone as an apparatus for converting an acoustic signal into an electrical signal. Microphones are available in a wide variety of materials, depending on the material and operating principle. Depending on the material, it can be classified into a carbon microphone, a crystal microphone, and a magnetic microphone. Depending on the operation principle, it can be classified into a dynamic microphone using an induced electromotive force by a magnetic field and a condenser microphone using a capacitance change due to vibration of the membrane.

2. Description of the Related Art Micro condenser microphones such as ECM (Electret Condenser Microphone) and MEMS (Micro Electro Mechanical System) microphones are mainly used in portable or small electronic devices such as computers, mobile communication terminals, MP3 sound recorders, cassette recorders, camcorders and headsets. The ECM microphone uses a polarizable dielectric material called an electret. The ECM microphone has a function of accumulating charge while the bias voltage is not applied. Electronic charge of the electret material is sensitive to temperature and deteriorates microphone sensitivity due to long-term drift. So, applying Teflon as an electret material to microphones, but applying Teflon to standard mass production processes has created many difficult problems.

On the other hand, a condenser microphone does not require an electret material, but a bias voltage may be applied to accumulate electric charges. Condenser microphones have appropriate sensitivity and low sensitivity to temperature. Because it is usually manufactured by MEMS (Micro-Electro-Mechanical System) process for small size and low cost mass production, condenser microphone is sometimes referred to as MEMSZ microphone.

The condenser microphone includes two plate capacitances: a diaphragm (membrane or diaphragm) and a back plate, and the two plate capacitances are separated through an air gap acting as an insulating material. A back chamber is formed on the base substrate supporting the diaphragm (membrane or diaphragm) and the back plate. A plurality of acoustic holes are formed on the back plate to reduce air damping. The sound waves introduced through the acoustic holes of the back plate cause the diaphragm (membrane or diaphragm) to bend, and the capacitance between the diaphragm (membrane or diaphragm) and the back plate changes with the change of the air gap. A readout circuit is constructed to appropriately change the capacitance change by an electrical signal. Microphone commercialization manufacturers have continued to improve the structure and materials of diaphragms (membranes or diaphragms) and backplates to improve sensitivity and reduce noise levels.

The condenser microphone (or MEMS microphone) must maintain efficient vibration of the diaphragm (membrane or diaphragm) to minimize the parasitic capacitance and increase the vibration efficiency of the diaphragm (membrane or diaphragm).

1A and 1B show a structure of a base board 100, a vibration plate 110 and a back plate 120 of a conventional condenser microphone (or MEMS microphone).

1A shows a contact portion 111B formed on a part of the diaphragm 110 and a side wall A3 of the contact portion 111B is bent so that the diaphragm 110 formed on the base substrate 100 can easily vibrate. However, when the area of the contact portion 111B of the diaphragm 110 is narrow, the vibration of the diaphragm 110 causes the contact portion 111B to be lifted off and the side wall A3 of the contact portion 111B to be deformed have.

The structure of the partial contact type diaphragm is as follows. 1) When there is a problem in stiffness, the vibration width of the diaphragm 110 becomes narrow. 2) When the contact area of the diaphragm contact portion is narrow, And 3) the membrane electrode 112 and the counter electrode 122 of the back plate 120 are abnormally close to each other due to a narrow air gap between the diaphragm and the back plate.

Referring to FIG. 1B, a condenser microphone (or a MEMS microphone) needs to maximize the capacitance between the back plate 120 and the diaphragm 110 with respect to voice signals, and to minimize the leakage capacitance. The leakage capacitance typically generated during operation is determined by the parasitic capacitance CP1 generated in the insulating connection portion 130B between the back plate 120 and the diaphragm 110 and the insulation between the diaphragm 110 and the base substrate 100 And a parasitic capacitance (CP2) generated in the connection part 130A. In addition, there is an unnecessary capacitance generated in the wire connecting the microphone body and the pad. It is important to maximize the flat plate capacitance Cmic between the back plate 120 and the diaphragm 110 through design and process improvement as much as possible. However, when the membrane 110 vibrates as shown in FIG. 1B, There is a difference in capacitance by position due to the deviation. That is, since the capacitance Cc of the central portion and the capacitance Ce of the peripheral portion are not the same, the sensitivity of the output voltage is decreased. Therefore, it is important to keep the central portion capacitance Cc and the peripheral portion capacitance Ce as close to each other as possible.

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

In order to solve the conventional problems, the present invention provides an acoustic sensor including a condenser microphone having a flatness, ductility, and vibration efficiency of a diaphragm at an operating voltage and a method of manufacturing the same.

The present invention also provides an acoustic sensor including a condenser microphone having excellent sensitivity of an output voltage and a method of manufacturing the same.

According to an aspect of the present invention, there is provided an acoustic sensor comprising: a base substrate having a back chamber formed therein; A plurality of depressions formed between the membrane electrode and the rim are spaced apart from each other in a strip shape when viewed from above, and a plurality of depressions are formed on the first sacrificial layer formed on the surface of the base substrate, A diaphragm having protrusions on the bottoms of the plurality of depressions, and an opening formed between the plurality of depressions and the rims; A connector formed on a surface of the diaphragm and connected to a pad for a bias voltage; An edge is fixed to the connector and the second sacrificial layer formed on the surface of the first sacrificial layer, and an opposite electrode facing the membrane electrode of the diaphragm and an air gap is formed in the central region, A back plate having a central region, a plurality of acoustical holes formed at regular intervals between the counter electrode and the frame, and a plurality of microprojections formed around the acoustic holes formed between the counter electrode and the frame; And a connector connected to the pad for output voltage formed between the back plate and the second sacrificial layer and preventing the membrane electrode of the diaphragm and the opposing electrode of the back plate from approaching abnormally when the diaphragm vibrates In order to prevent the diaphragm from separating from the base substrate by pressing the diaphragm when the diaphragm vibrates, a center region where the counter electrode is formed is formed with an annular projection surrounding the periphery of the plurality of acoustic holes. And the plurality of fine projections are formed between the counter electrode and the plurality of acoustic holes formed between the edges.

Further, in the acoustic sensor according to the present invention, the annular protrusion of the back plate has annular protrusions formed around the acoustic holes existing in the regions where the opposite electrodes are formed, and correspond to each acoustic hole of the center region formed with the opposite electrodes, And only one acoustic hole is formed at the center and the edge of the central region where the counter electrodes are formed.

In addition, the acoustic sensor according to the present invention is characterized in that the diaphragm is formed with a plurality of vent holes formed so that openings of the diaphragm are spaced apart from each other. The acoustic sensor according to the present invention is characterized in that the diaphragm is formed with a plurality of slits which are formed so that the openings of the diaphragm are spaced apart from each other. In one example, a plurality of slits formed in the first depression of the diaphragm are formed adjacent to each other with a straight slit and a refractive slit. The refraction type slit includes a first rectilinear section, a first bend section connected to the first rectilinear section, a second bend section connected to the first bend section, and a second rectilinear section connected to the second bend section .

According to another aspect of the present invention, there is provided a method of manufacturing an acoustic sensor, comprising the steps of: a) forming a first sacrificial layer on a surface of a base substrate, selectively etching the first sacrificial layer to expose a surface of the base substrate, ; ≪ / RTI > b) forming a membrane layer on the surface of the first sacrificial layer on which the plurality of annular annular patterns are formed by chemical vapor deposition, wherein depressions are formed in the plurality of annular annular patterns, and openings are formed between the rims of the membrane layers and depressions ; ≪ / RTI >

c) forming a membrane electrode and a pad for a bias voltage on the surface of the membrane layer, and then forming a second sacrificial layer; forming a counter electrode on the second sacrificial layer to face the pad for the output voltage and the membrane electrode, and forming a backplate layer on the counter electrode and the second sacrificial layer through a deposition process; e) applying a resist to the backplate layer, forming a plurality of annular etches in regions where the counter electrodes are formed through selective resistor patterning, and forming a plurality of protrusion-type etches in the remaining regions;

f) forming a plurality of annular protrusions and a plurality of fine protrusions on the back plate layer having the annular etch portion and the protrusion type etch portion by a deposition process, applying a resist to the back plate layer having the plurality of annular protrusions and the plurality of fine protrusions Forming an acoustic hole between the plurality of annular projections and between the plurality of microprojections through selective resistor patterning;

g) forming an air gap between the back plate layer and the membrane layer in which the acoustic holes are formed; h) etching the inside of the base substrate to form a back chamber, and then removing a back chamber and a first sacrificial layer existing under the membrane layer, wherein the annular protrusion And the micro protrusions are formed between the plurality of acoustic holes formed in the remaining area.

According to the above configuration, the acoustic sensor and the method of manufacturing the same according to the present invention have the following effects.

First, a plurality of depressed portions are formed between the rim of the diaphragm and the membrane electrode so as to be spaced apart from each other in a strip shape when viewed from above, and protrusions are formed on the bottoms of the depressions, and openings are formed between the plurality of depressions and the rims, The flatness, ductility and vibration efficiency of the diaphragm are good.

Second, since the annular protrusion is formed around the acoustic hole of the counter electrode formed on the back plate, it is possible to prevent the membrane electrode of the diaphragm and the counter electrode of the back plate from approaching abnormally when the diaphragm vibrates.

Thirdly, since the plurality of slits are spaced apart from the plurality of depressed portions and the rim, the vertical vibration can be improved by increasing the flexibility in the vertical direction when the diaphragm vibrates, and the post-packing sensitivity Improvement is possible. In particular, a ventilation effect capable of improving the low frequency can be obtained.

Fourth, when the diaphragm vibrates, the micro projection of the back plate presses the diaphragm, thereby preventing the diaphragm from being detached from the base substrate. Especially, when the diaphragm is vibrated by pressing the diaphragm, the sensitivity of the output voltage is excellent by increasing the capacitance of the plate by minimizing the difference in capacitance by position due to the deviation of the vibration surface.

Fifth, an opening is formed between the rim of the diaphragm and a plurality of depressions, so that the air discharge accumulated in the air gap can be easily adjusted.

Sixth, the diaphragm has a plurality of vent holes spaced at a certain distance from the outermost depressed portion of the plurality of depressions, thereby achieving a ventilation effect capable of improving the low frequency.

Figs. 1A and 1B show a structure of a base board, a vibration plate and a back plate of a conventional condenser microphone (or a MEMS microphone).
FIG. 2 is a diagram illustrating a structure of a condenser microphone included in an acoustic sensor according to an embodiment of the present invention. Referring to FIG.
3 is an exemplary diagram illustrating a structure of a condenser microphone included in an acoustic sensor according to another embodiment of the present invention.
4 to 7 are diagrams for explaining a diaphragm structure of a condenser microphone included in an acoustic sensor according to the present invention.
8A to 8H are views for explaining a process of manufacturing a condenser microphone included in an acoustic sensor according to the present invention.
Fig. 9 is an exemplary view for explaining another condenser microphone. Fig.
10 is an exemplary view for explaining another condenser microphone.
11 is an exemplary view for explaining another condenser microphone.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

The acoustic sensor according to the present invention includes a condenser microphone having a base substrate on which a back chamber is formed, the diaphragm and the back plate. On the surface of the diaphragm is formed a connector to be connected to a pad for a bias voltage, and a connector to be connected to a pad for an output voltage is formed on the back plate. The acoustic sensor according to the present invention improves the structure of the diaphragm and the back plate to realize a condenser microphone.

As shown in Fig. 2, the membrane electrode 112 is formed in the center region of the diaphragm 110, and the ring-shaped concave-convex portions 113A and 113B are repeatedly formed. The ring-like concave and convex portions 113A and 113B are manufactured in consideration of both the flatness and ductility of the diaphragm 110 and improve the efficiency of vibration when the diaphragm 110 vibrates. The structure of the diaphragm 110 will be described later with reference to Figs.

 The back plate 120 is located on the top of the diaphragm 110. The back plate 120 is formed with a counter electrode 122 facing the membrane electrode 112 of the diaphragm 110 and an air gap. The back plate 120 has a plurality of acoustic holes 123 formed at regular intervals between the center region where the counter electrode 122 is formed, the counter electrode 122 and the rim. As shown in FIG. 2, the back plate 120 has a plurality of fine protrusions 125A and 125B formed around the acoustic hole 123 formed between the counter electrode 122 and the rim. An annular projection 126C is formed around the acoustic hole 124B in the center region where the counter electrode 122 is formed.

The annular protrusion 126C formed around the acoustic hole 124B is shorter than the fine protrusions 125A and 125B. The annular projection 126C serves to prevent the membrane electrode 112 of the diaphragm 110 from abnormally approaching the counter electrode 122 of the back plate 120 when the diaphragm 110 vibrates. The width of the annular projection 126C is larger than the acoustic hole, for example, in the range of 0.5 to 5.0 mu m, more preferably 0.8 to 3.0 mu m. The fine protrusions 125A and 125B prevent the diaphragm 110 from separating from the base substrate by pressing the diaphragm 120 when the diaphragm 110 vibrates.

2, the annular protrusion 126C formed in the region of the counter electrode 122 may be symmetrically formed around the center of the counter electrode 122 and around the acoustic hole at the rim of the counter electrode 122, for example. As another example, as shown in FIG. 3, the annular projection 126C formed in the region of the counter electrode 122 may be formed with an annular projection radially around the acoustic hole existing in the region where the counter electrode 122 is formed. Referring to FIG. 3, a connecting portion 126D connecting the plurality of annular protrusions 126C may be formed. The connecting portion 126D increases the durability of the plurality of annular projections 126C.

Hereinafter, the structure of the diaphragm 110 will be described in detail with reference to FIGS. 4 to 7 show a cross-sectional view of the diaphragm 110 and a top view.

4, the diaphragm 110 is formed such that a plurality of depressions 111C1, 111C2, and 111C3 are spaced apart from each other in a band shape when viewed from the top, and a plurality of depressions 111C1, 111C2, and 111C3 are formed with protrusions C1, C2, and C3, respectively. The widths of the plurality of depressions 111C1, 111C2, and 111C3 are implemented to have different values D1, D2, and D3. The widths of the depressions 111C1, 111C2, and 111C3 are formed to be relatively small as the depression is formed close to the membrane electrode 112. [ This is to keep the vibrating effect of the diaphragm 110 at the maximum at the outer side and at the inner side so as to keep the central capacitance and the peripheral capacitance as close as possible.

5, the diaphragm 110 has a plurality of depressions 111C1 ', 111C2', and 111C3 'having the same width, and a plurality of depressions 111C1', 111C2 ', and 111C3' (350) is formed. By forming the openings 350, it is possible to easily adjust the air discharge accumulated in the air gap.

As shown in FIG. 5, the openings 350 may be embodied as a plurality of slits 351 and 352 spaced apart from each other. The plurality of slits may be formed such that the linear slit 351 and the refractive slit 352 are adjacent to each other. The refraction type slit 352 includes a first rectilinear section, a first bent section connected to the first rectilinear section, a second bent section connected to the first bent section, and a second rectilinear section connected to the second bent section, And the like.

By forming the plurality of slits 351 and 352, the vertical vibration can be improved by increasing the flexibility in the vertical direction when the diaphragm 110 vibrates, and the post-packing sensitivity can be improved by acting as a discharge passage for negative pressure . In particular, a ventilation effect capable of improving the low frequency can be obtained.

As another example, the openings 350 may be embodied as a plurality of ventilation holes H1 formed to be spaced apart from each other as shown in FIG. As shown in FIG. 7, the opening 350 may be formed in the outermost depression 111C3 'of the depressions 111C1', 111C2 ', and 111C3' As shown in Fig.

8A to 8H are views for explaining a process of manufacturing a condenser microphone included in an acoustic sensor according to the present invention.

First, as shown in FIG. 8A, a first sacrificial layer 131 is formed on the surface of the base substrate 100. Thereafter, the first sacrificial layer 131 is selectively etched to expose the surface of the base substrate 100 to form a plurality of annular annular patterns, and the first sacrificial layer having the plurality of annular annular patterns formed thereon is subjected to chemical vapor deposition Thereby forming a membrane layer (Fig. 8B).

Referring to FIG. 8B, depressions 111C1 ', 111C2', and 111C3 'are formed in the plurality of annular ring patterns, respectively. The depressions 111C1 ', 111C2', 111C3 'are formed in a strip shape when viewed from above. An opening 350 may be formed between the rim of the membrane layer 110 and depressions 111C1 ', 111C2', 111C3 '. The openings 350 may be formed as a plurality of slits 351 and 352 that are spaced apart from each other. Then, a membrane electrode 112 and a pad 114B for a bias voltage are formed on the surface of the membrane layer 110. Referring to FIG. 8C, a connector 1141 is formed on the pad 114B for a bias voltage, and a second sacrificial layer 132 is formed.

8D, the counter electrode 122 is formed on the second sacrificial layer 132 so as to face the pad 1140 for output voltage and the membrane electrode 112, and the counter electrode 122 and the second sacrificial layer 132 to form a backplate layer 120 through a deposition process. Thereafter, a plurality of annular etching portions are formed in regions where the counter electrodes 122 are formed through selective resist patterning after the resist 136 is applied to the backplate layer 120, and a plurality of projection type etching portions are formed in the remaining regions do.

Referring to FIG. 8E, a plurality of annular protrusions 126C and a plurality of fine protrusions 1260C are formed on a back plate layer 120 having an annular etch portion and a protruded etch portion through a deposition process.

8F, a resist is applied to a back plate layer 120 having a plurality of annular protrusions 126C and a plurality of fine protrusions 1260C, and a plurality of annular protrusions 126C and a plurality And an acoustic hole 121 is formed between the micro-protrusions 1260C.

Referring to FIG. 8G, an air gap is formed between the back plate layer 120 having the acoustic holes 121 and the membrane layer 110 by wet etching or vapor-phase etching.

Referring to FIG. 8H, a back chamber 101 is formed by etching the inside of the base substrate 100, and then a back chamber 101 and a first The sacrificial layer 131 is removed.

Fig. 9 is an exemplary view for explaining another condenser microphone. Fig. The condenser microphone according to Fig. 9 is manufactured according to the procedure of Figs. 8A to 8H described above. However, the plurality of fine protrusions 1260C are inserted into the depressions 111C1 ', 111C2', 111C3 'of the diaphragm 110 so as to have a length.

10 is an exemplary view for explaining another condenser microphone. The condenser microphone according to Fig. 10 is manufactured according to the procedure of Figs. 8A to 8H described above. However, an opening is formed between the concave portions 111C1 ', 111C2', 111C3 'and the rim with a predetermined distance therebetween.

11 is an exemplary view for explaining another condenser microphone. The condenser microphone according to Fig. 11 is manufactured according to the procedure of Figs. 8A to 8H described above. However, an opening is formed between the concave portions 111C1 ', 111C2', 111C3 'and the rim with a predetermined distance therebetween. However, a plurality of vent holes may be formed in the outermost depression 111C3 'of the depressions 111C1', 111C2 ', 111C3' so as to be spaced apart from each other by a predetermined distance.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims. Accordingly, the true scope of the present invention should be determined only by the appended claims.

100: Base substrate
101: back chamber
110: diaphragm, membrane layer
112: membrane electrode
120: Back Plate
121: Acoustic hole
122: opposing electrode
123, 124B: Acoustic hole
126C: annular projection
1260C:
126D: Connection
131: first sacrificial layer
132: second sacrificial layer
136: resist layer
113A and 113B:
1140: Pad for output voltage
1141: Pads for bias voltage
114A, 114B: connector
C1, C2, C3:
111C1, 111C2, 111C3:
111C1 ', 111C2', 111C3 ': ring-shaped depressions
H1, H2: Ventilation holes
133: Air gap

Claims (15)

A base substrate on which a back chamber is formed;
A plurality of depressions formed between the membrane electrode and the rim are spaced apart from each other in a strip shape when viewed from above, and a plurality of depressions are formed on the first sacrificial layer formed on the surface of the base substrate, A diaphragm having protrusions on the bottoms of the plurality of depressions, and an opening formed between the plurality of depressions and the rims;
A connector formed on a surface of the diaphragm and connected to a pad for a bias voltage;
An edge is fixed to the connector and the second sacrificial layer formed on the surface of the first sacrificial layer, and an opposite electrode facing the membrane electrode of the diaphragm and an air gap is formed in the central region, A back plate having a central region, a plurality of acoustical holes formed at regular intervals between the counter electrode and the frame, and a plurality of microprojections formed around the acoustic holes formed between the counter electrode and the frame;
And a connector formed between the back plate and the second sacrificial layer and connected to the pad for the output voltage,
In order to prevent the membrane electrode of the diaphragm and the opposing electrode of the back plate from approaching abnormally when the diaphragm is vibrated, an annular projection is formed in the central region where the counter electrode is formed to surround the plurality of acoustic holes And,
In order to prevent the diaphragm from separating from the base substrate by pressing the diaphragm when the diaphragm is vibrating, the plurality of microprojections are arranged between the counter electrode and the plurality of acoustic holes formed between the opposing electrodes , ≪ / RTI >
Wherein the acoustic sensor comprises: The method according to claim 1,
The plurality of annular projections are interconnected by a connecting portion,
The opening of the diaphragm
A plurality of ventilation holes formed to be spaced apart from each other,
Wherein the acoustic sensor comprises: The method according to claim 1,
The plurality of annular projections are interconnected by a connecting portion,
The opening of the diaphragm
A plurality of slits formed so as to be spaced apart from each other,
Wherein the acoustic sensor comprises: The method of claim 3,
The plurality of slits may include a plurality of slits,
The linear slit and the refracting slit are formed adjacent to each other,
The refractive slit
A first linear portion, a first bend portion connected to the first straight portion, a second bend portion connected to the first bend portion, and a second straight portion connected to the second bend portion,
Wherein the acoustic sensor comprises: The method according to claim 1,
The diaphragm includes:
The width of the plurality of depressed portions being different from each other,
Wherein the acoustic sensor comprises: The method according to claim 1,
The diaphragm includes:
A plurality of vent holes are formed at a predetermined distance in the outermost depression of the plurality of depressions,
Wherein the acoustic sensor comprises: The method according to claim 1,
Wherein the annular protrusions correspond one by one for each acoustic hole in the central region where the counter electrode is formed,
Wherein the acoustic sensor comprises: The method according to claim 1,
The annular protrusions corresponding to only one acoustic hole formed at the center and the edge of the central region where the counter electrode is formed,
Wherein the acoustic sensor comprises: The method according to any one of claims 1 to 8,
The back plate includes:
Wherein the plurality of micro-projections are formed to have a length to be inserted into a depression of the diaphragm,
Wherein the acoustic sensor comprises: a) forming a first sacrificial layer on a surface of a base substrate, selectively etching the first sacrificial layer to expose a surface of the base substrate to form a plurality of annular ring patterns;
b) forming a membrane layer on the surface of the first sacrificial layer on which the plurality of annular annular patterns are formed by chemical vapor deposition, wherein depressions are formed in the plurality of annular ring patterns, and an opening is formed between the rim of the membrane layer and the depressions ; ≪ / RTI >
c) forming a membrane electrode and a pad for a bias voltage on the surface of the membrane layer, and then forming a second sacrificial layer;
forming a counter electrode on the second sacrificial layer to face the pad for the output voltage and the membrane electrode, and forming a backplate layer on the counter electrode and the second sacrificial layer through a deposition process;
e) applying a resist to the backplate layer, forming a plurality of annular etches in the regions where the counter electrodes are formed through selective resistor patterning, and forming a plurality of protrusion-type etches in the remaining regions;
f) forming a plurality of annular protrusions and a plurality of fine protrusions on the back plate layer having the annular etch portion and the protrusion type etch portion by a deposition process, applying a resist to the back plate layer having the plurality of annular protrusions and the plurality of fine protrusions Forming an acoustic hole between the plurality of annular projections and between the plurality of microprojections through selective resistor patterning;
g) forming an air gap between the back plate layer and the membrane layer in which the acoustic holes are formed;
h) etching the inside of the base substrate to form a back chamber, and then removing a back chamber and a first sacrificial layer existing under the membrane layer,
The annular projection is formed to surround the periphery of the acoustic hole,
Wherein the fine protrusions are disposed between a plurality of acoustic holes formed in the remaining region,
Wherein the acoustic sensor is formed of a metal. The method of claim 10,
The step b)
A plurality of vent holes formed in the membrane layer so that openings of the membrane layer are spaced apart from each other,
Wherein the acoustic sensor is formed of a metal. The method of claim 10,
The step b)
A plurality of slit-like steps in which openings of the membrane layer are spaced apart from each other,
Wherein the acoustic sensor is formed of a metal. The method of claim 12,
The plurality of slits may include a plurality of slits,
The linear slit and the refracting slit are formed adjacent to each other,
The refractive slit
A first linear portion, a first bend portion connected to the first straight portion, a second bend portion connected to the first bend portion, and a second straight portion connected to the second bend portion,
Wherein the acoustic sensor is formed of a metal. The method of claim 10,
The step b)
The width of the plurality of depressed portions being different from each other, and the width being relatively small as the membrane electrode is formed,
Wherein the acoustic sensor is formed of a metal. The method of claim 10,
The step b)
Wherein a plurality of vent holes are spaced apart from each other by a predetermined distance in an outermost depression of the plurality of depressions,
Wherein the acoustic sensor is formed of a metal.

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