CN114390418A - MEMS electrode formation method - Google Patents

Abstract

A Micro Electro Mechanical System (MEMS) condenser microphone of the present invention includes: a base substrate; a diaphragm on the base substrate; a back plate portion on the diaphragm; a deformation preventing portion on the back plate portion; an air layer between the diaphragm and the back plate portion; and a plurality of projections projecting in the air layer from the back plate portion toward the diaphragm side.

Description

MEMS electrode formation method

technical field

The invention relates to a micro-electro-mechanical system (MEMS) condenser microphone and a method for forming a micro-electro-mechanical system electrode of the micro-electro-mechanical system condenser microphone. The invention discloses a MEMS condenser microphone with excellent sensitivity and a MEMS electrode forming method for the MEMS condenser microphone.

Background technique

In general, an acoustic sensor includes a microphone as a device for converting an acoustic signal into an electrical signal.

Microphones come in a wide variety of types, depending on the material or how they work.

For example, according to the material, it is divided into carbon microphone (carbon microphone), crystal microphone (crystal microphone), magnetic microphone (magnetic microphone) and the like.

In addition, according to the principle of operation, it can be classified into a dynamic microphone using an induced electromotive force caused by a magnetic field and a dynamic microphone using a change in capacitance caused by vibration of a vibrating plate such as a membrane or a diaphragm. condenser microphone.

In portable electronic devices or small electronic devices such as computers, mobile communication terminals, MP3 recorders, cassette tape recorders, video cameras, headsets, etc., microphones such as electret condenser microphones (ECM: Electret Condensor Microphone) or microelectromechanical systems are mainly used (Micro Electro Mechanical System) Microphones and other ultra-small condenser microphones.

ECM microphones utilize polarized dielectric substances called electrets. The ECM microphone has a function of accumulating electric charge when the bias voltage is not applied. The charge of the electret material is sensitive to temperature, and the characteristics are deteriorated by long-term drift (Long-Term Drift), reducing the sensitivity of the microphone. Therefore, the application of Teflon as an electret material to a microphone, but the application of Teflon to a standard mass production process, brings many difficulties.

Conversely, condenser microphones do not require electret substances, and only need to apply a bias voltage to allow them to accumulate charge.

The condenser microphone has a suitable sensing sensitivity and a low sensing sensitivity according to the temperature. In order to achieve small size and low-cost mass production, this kind of condenser microphone is generally manufactured through a micro-electromechanical system (MEMS) process, so the condenser microphone is also called a micro-electromechanical system microphone (MEMS microphone).

The condenser microphone includes two plate capacitors, vibrating plate and back plate, which are separated by an air gap serving as an insulating substance.

A back chamber is formed on a base substrate that supports the diaphragm and the back plate. A number of sound holes are formed on the back panel to relieve air damping.

The sound waves introduced through the sound holes of the back plate bend the diaphragm, and the capacitance between the diaphragm and the back plate changes with the thickness of the air layer.

This capacitance, which varies with the thickness of the air layer, is converted into an appropriate electrical signal by means of a readout circuit formed in the condenser microphone.

In order to improve the sensitivity of the microphone and reduce the noise level (Noise Level), the commercial microphone manufacturers are constantly improving the structure and material of the vibration plate and the back plate.

In order to minimize the parasitic capacitance and improve the vibration efficiency of the vibration plate, the condenser microphone needs to maintain the high-efficiency vibration of the vibration plate.

FIG. 1 illustrates a part of the structure of a conventional condenser microphone.

As shown in FIG. 1 , a conventional condenser microphone includes a base substrate 10 , a diaphragm 11 , a back plate 12 , insulating connection portions 13 a and 13 b located between the base substrate 10 and the back plate 12 and supporting the diaphragm 11 , and a diaphragm located on the diaphragm 11 . Air layer 14 between 11 and back plate 14 .

At this time, as shown in FIG. 1 , the insulating connection parts 13 a and 13 b are divided into a lower part 13 a and an upper part 13 b with the vibration plate 11 as the center.

The vibration plate 11 formed on the base substrate 10 has elasticity so that it can easily vibrate in the air layer 14 , vibrates in the vertical direction, and forms capacitors Ce and Cc of corresponding magnitudes between the vibration plate 11 and the back plate 12 .

At this time, the vibration range of the movable vibrating plate 11 is before touching the back plate 12 (ie, before attaching it), and once the vibrating plate 11 is attached to the back plate 12, the pull-in voltage (Pull- In Voltage) state, the sound sensor with the condenser microphone cannot perform the normal sensor function and is damaged.

In order to improve the operation efficiency of the condenser microphone, the condenser microphone needs to maximize the electrostatic capacity of the voice signal between the back plate 12 and the vibration plate 11, and minimize the leakage electrostatic capacity.

Typical leakage capacitances generated during operation include parasitic capacitance (Parasitic capacitance) Cp1 generated at the insulating connection portion 13b between the back plate 12 and the vibration plate 11 and generation at the insulating connection portion 13a between the vibration plate 11 and the base substrate 10 . The parasitic capacitance Cp2 and so on. In addition to this parasitic capacitance, there is also capacitance that occurs in wires connecting the microphone body (not shown in the figure) and the pads formed for signal input and output.

In particular, the leakage capacitance cannot be minimized, and the flat capacitance between the vibration plate (eg, diaphragm) 11 and the back plate 12 cannot be optimized, so that the problem of low performance of the condenser microphone occurs. This problem occurs because the counter electrode between the diaphragm 11 and the back plate 12 is not optimized for structural factors.

Therefore, in order to maximize the electrostatic efficiency of the counter electrode between the separator 11 and the back plate 12 , it is important to make the counter electrode a structure close to a flat shape.

prior art literature

【Patent Literature】

Korean Published Patent No. 10-2016-0127212 (Published on November 3, 2016)

SUMMARY OF THE INVENTION

technical problem to be solved

The subject to be solved by the present invention is to improve the vibration efficiency of the vibrating plate under the working voltage, thereby improving the performance of the MEMS condenser microphone.

Another problem to be solved by the present invention is to improve the sensitivity of the output voltage of the MEMS condenser microphone.

technical means

The MEMS condenser microphone of the present invention, which aims to solve the above problems, includes: a base substrate; a diaphragm on the base substrate; a back plate part on the diaphragm; a deformation preventing part , the deformation preventing portion is located on the back plate portion; an air layer, the air layer is located between the diaphragm and the back plate portion; and a plurality of protrusions, the plurality of protrusions from the back plate The plate portion protrudes in the air layer toward the diaphragm side.

The back plate portion may include a first back plate and a second back plate, the first back plate is connected to the air layer and is configured with the protrusion, and the second back plate is located on the first back plate. on the board, connected with the protrusions.

The deformation preventing portion may be arranged so that the second back plate is interposed while the first back plate is overlapped.

The first backplane may be disposed in contact with the entire lower surface of the second backplane.

The first backplane may be disposed in contact with a part of the lower surface of the second backplane.

The deformation preventing portion may also be located on the second backplane on which the first backplane is not disposed.

The second back plate may be formed of the same material as the protrusions.

The deformation preventing portion may be formed of the same material as the first back plate.

The deformation preventing portion may have the same thermal expansion coefficient as that of the first back plate.

In the first back sheet and the second back sheet, the absolute value of the difference in thermal expansion coefficient between the deformation preventing portion and the first back sheet may be small.

The plurality of protrusions may include a plurality of cylindrical protrusions.

The plurality of protrusions may further include a plurality of rod-shaped protrusions.

Another feature of the present invention is a MEMS electrode forming method for a MEMS condenser microphone, which includes: forming a diaphragm on a base substrate; forming a sacrificial layer on the diaphragm; forming a first backside on the sacrificial layer The step of the plate layer; after the photoresist film is laminated on the first back plate layer, the photoresist film is selectively etched by using a mask, so that the part of the first back plate layer located in the etched part is exposed. ; Using the remaining photoresist film as a mask, removing the exposed part of the first backplane layer to form a first backplane having a cavity portion in a cylindrical shape; removing the remaining photoresist The steps of filming; etching the sacrificial layer exposed through the cavity at a predetermined depth, and forming holes for cylindrical protrusions on the first backplane and the sacrificial layer; depositing in the holes for cylindrical protrusions A step of forming a cylindrical projection with a predetermined substance; a step of forming a second back plate on the first back plate and the projection; and a step of forming a deformation preventing portion on the second back plate.

In the step of forming the second backplane, the second backplane may be formed of the same material as the protrusion.

In the step of forming the deformation preventing portion, the deformation preventing portion may be formed of the same material as the first back plate.

In the step of forming the deformation preventing portion, the deformation preventing portion may be formed using a material having the same thermal expansion coefficient as that of the first back plate.

technical effect

According to this feature of the present invention, the cylindrical protrusion has a hollow space in the center, and thus has a relatively large outer diameter and a narrow line width. Due to this cylindrical protrusion, the diaphragm and the back plate can be prevented from vibrating. The phenomenon that the parts are in contact and fit together. In addition, due to the relatively large outer diameter, damage to the diaphragm can be prevented or minimized upon contact with the cylindrical projection. Therefore, the lifespan of the separator can be increased.

In addition, when the high sound pressure is connected to the MEMS condenser microphone, the cylindrical protrusion contacts the wider part of the diaphragm, so the durability of the MEMS condenser microphone can be improved by virtue of the buffering effect of the cylindrical protrusion.

Additionally, the density of the plurality of cylindrical protrusions gradually decreases from the center portion to the edge portion, so that the cushioning effect and the sticking prevention effect of the contoured protrusions determined by the vibration mode of the diaphragm can be improved.

In addition to the cylindrical protrusions, when the rod-shaped protrusions are additionally provided, the cylindrical protrusions and the rod-shaped protrusions can be located in the part where the sound hole is not formed, thereby improving the utilization of the space on the back plate and further improving the control of the diaphragm Effect.

Furthermore, by forming the back plate portion in two layers, the supporting force of the cylindrical protrusion can be improved, so that the bending phenomenon can be greatly reduced.

In addition, the stress (for example, at least one of thermal stress, compressive stress, and tensile stress) acting in the manufacturing process of the MEMS condenser microphone is offset by the deformation preventing portion, and the backlash caused by such stress can be greatly reduced. Plate bending phenomenon.

As described above, it is possible to prevent or reduce the warpage of the back plate portion located below the air layer that functions as a dielectric layer, so that the diaphragm electrode that functions as a counter electrode with the air layer interposed therebetween can be kept in a predetermined manner. Spacing between backplane electrodes. Therefore, the characteristic change of the MEMS condenser microphone caused by the change of the interval between the diaphragm electrode as the counter electrode and the back plate electrode due to the back plate portion bending phenomenon can be eliminated or minimized, and the characteristic of the MEMS condenser microphone can be improved.

In addition, since the bending phenomenon of the back plate portion is minimized, the electric charge generation efficiency caused by vibration of the diaphragm can be maximized, so that a high-performance MEMS condenser microphone can be fabricated.

Description of drawings

FIG. 1 is a sectional view partially illustrating the structure of a conventional MEMS condenser microphone.

FIG. 2 is an exemplary plan view of the MEMS condenser microphone for explaining the structure of the MEMS condenser microphone according to one embodiment of the present invention.

FIG. 3 is a cross-sectional view of the MEMS condenser microphone shown in FIG. 2 cut along the line III-III.

4 is a partial plan view of the MEMS condenser microphone schematically illustrating the arrangement state of sound holes and protrusions in the MEMS condenser microphone according to an embodiment of the present invention.

5a and 5b are respectively cross-sectional views of MEMS condenser microphones according to other embodiments of the present invention.

6a to 6k are cross-sectional views taken along line III-III of FIG. 2 , and are cross-sectional views illustrating the formation sequence of the MEMS condenser microphone according to an embodiment of the present invention.

7 is an exemplary plan view of a MEMS condenser microphone for explaining the structure of a MEMS condenser microphone according to another embodiment of the present invention.

FIG. 8 is a cross-sectional view showing the MEMS condenser microphone shown in FIG. 7 cut along the line III-III shown in FIG. 2 .

9 is a partial plan view of the MEMS condenser microphone schematically illustrating the arrangement of sound holes, cylindrical protrusions, and rod-shaped protrusions in the MEMS condenser microphone of the present embodiment.

reference number

100: Base substrate 101: Back chamber

110: Vibration plate, diaphragm 120: Back plate part

120a: first backplane 120b: second backplane

121a: First backing layer 125: Deformation preventing part

130: Air Layer 131: Sacrificial Layer

140: Cylinder-type protrusions 142: Rod-type protrusions

H10: Sound hole

Detailed ways

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is judged that the specific description of the known technology or configuration in the corresponding field may obscure the gist of the present invention, a part of it may be omitted in the detailed description. In addition, the terms used in the present specification are used to appropriately express the embodiments of the present invention, and may vary depending on the relevant persons in the corresponding field, conventions, and the like. Therefore, the definition of this term should be based on the entire contents of this specification.

The technical terms used herein are only used to refer to specific embodiments, and are not intended to limit the present invention. The singular form as used herein also includes the plural form, as long as the statement does not express an explicit contrary meaning. The meaning of "comprising" used in the specification is to embody specific characteristics, regions, integers, steps, actions, elements and/or components, and does not exclude other specific characteristics, regions, integers, steps, actions, elements, components and and/or the presence or addition of groups.

In addition, the following statement that the thickness, width or length of a certain component is the same means that the error in the process is taken into account, and it means that the thickness, width or length of a certain first component is the same as the thickness or width of another second component. or length, the margin of error is within 10%.

The following describes a MEMS condenser microphone and a manufacturing method thereof according to an embodiment of the present invention with reference to the accompanying drawings. The MEMS condenser microphone of this embodiment may be a condenser microphone fabricated using MEMS technology.

First, with reference to FIGS. 2 to 5 b , the structure of the MEMS condenser microphone according to an embodiment of the present invention will be described.

As shown in FIGS. 2 and 3 , the MEMS condenser microphone of this embodiment includes a base substrate 100 , a diaphragm 110 located on the base substrate 100 , a back plate portion 120 located on the diaphragm 110 , and a back plate portion 120 located on the back plate portion 120 . The deformation preventing portion 125 , the air layer 130 located between the base substrate 100 and the back plate portion 120 , and a plurality of protrusions 140 protruding from the back plate portion 120 to the air layer 130 .

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

Such a base substrate 100 is provided with a back chamber (ie, a cavity) 101 in which no silicon wafer exists. Thereby, the electret element is arranged in the acoustic chamber 101 .

The diaphragm 110 acts as a vibrating plate that vibrates according to the size of the sound wave flowing into the MEMS condenser microphone, and generates a corresponding electrical signal according to the vibration of the diaphragm 110 caused by the sound wave.

As an example, the diaphragm 110 may have a thickness of 0.5˜2.0 μm and be made of polysilicon (Poly Si).

When the thickness of the diaphragm 110 is less than 0.5 μm, the thickness of the diaphragm 110 is too thin, and the risk of breakage is high, and when the thickness exceeds 2.0 μm, the vibration operation by sound waves is hindered.

The back plate part 120 interposes the air layer 130 and faces the diaphragm 110 .

In this case, the vibration plate (for example, the diaphragm) 110 and the back plate portion 120 may function as electrodes arranged on opposite surfaces, respectively, the vibration plate 110 may function as a diaphragm electrode, and the back plate portion 120 may function as a back plate. function of the plate electrodes. At this time, the air layer 130 existing between the separator 110 and the back plate portion 120 may function as a dielectric layer.

In this embodiment, the electrodes of the MEMS condenser microphone, for example, the diaphragm electrodes and the back plate electrodes may be collectively referred to as MEMS electrodes.

With the MEMS electrodes 110 and 120 facing each other and the air layer 130 serving as a dielectric layer, as the distance between the diaphragm 110 and the back plate portion 120 changes due to the vibration of the diaphragm 110 , the distance between the diaphragm 110 and the back plate is changed. Corresponding capacitances are generated between the parts 120 .

The back plate portion 120 includes a first back plate 120a and a second back plate 120b. The first back plate 120a is located directly above the air layer 130 and is provided with a plurality of protrusions 140 that are in contact with the air layer 130. Therefore, The second backplane 120b is located on the first backplane 120a and is connected with the plurality of protrusions 140 .

The first back plate 120 a helps to generate capacitance with the opposite diaphragm 110 , and the second back plate 120 b functions to support the protrusions 140 .

As shown in FIG. 3 , the surfaces of the first backplane 120a and the second backplane 120b may have flat plate shapes as shown in FIG. 3 , and at this time, the first backplane 120a and the second backplane 120b may have flat plates shape of the electrodes.

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

When the first backplate 120a and the second backplate 120b are formed of the same material, the first backplate 120a and the second backplate 120b may be formed of the same material (eg, nitride) as the protrusions 140 .

However, when the first backplane 120a and the second backplane 120b are made of different materials, only the second backplane 120a may be made of the same material as the protrusions 140, and the first backplane 120a may contain conductive substance.

In addition, when the first backplane 120a and the second backplane 120b are made of different materials, the first backplane 120a may contain a conductive material to function as an electrode, and the second backplane 120b may be made of an insulating material.

In this way, since the back plate portion 120 is constituted by two layers, the supporting force of the back plate portion 120 facing the air layer 130 is improved, and the bending phenomenon is prevented.

In addition, due to the second back plate 120 b made of the same material as the protrusions 140 , the supporting force of the protrusions 140 is increased, thereby preventing the phenomenon that the protrusions 140 are detached from the back plate portion 120 .

In this embodiment, the second backplane 120b may be located on the upper surface of the first backplane 120a in contact with the first backplane 120a.

At this time, as shown in FIG. 3 , the first backplane 120a may be disposed in contact with the entire lower surface of the second backplane 120b.

However, as shown in FIGS. 5 a and 5 b , it may be arranged in contact with a part of the lower surface of the second back plate 120 b (for example, the central portion of the second back plate 120 b ). At this time, the second backplane 120b may be additionally located at the portion where the first backplane 120a is located, that is, not only the entire upper surface of the first backplane 120a, but also the first backplane 120a where the first backplane 120a is not disposed. on the periphery of the back plate 120a.

Therefore, in the case of FIG. 3, the formation area of the first backplane 120a and the second backplane 120b may be the same, but in the case of FIG. 5a and FIG. 5b, the formation area of the first backplane 120a may be smaller than that of the second backplane 120a. Formation area of the plate 120b.

In this embodiment, the first back plate 120a may be configured with at least one protrusion 140 as the center.

In another embodiment, the second backplane 120b may be omitted.

The deformation preventing portion 125 on the second back plate 120b may also have a flat plate shape.

The deformation preventing portion 125 may be disposed so as to overlap with the first back plate 120 a with the second back plate 120 b interposed therebetween. Therefore, the deformation preventing portion 125 can be arranged corresponding to the first back plate 120a with the second back plate 120b interposed therebetween.

Therefore, as shown in FIG. 3 and FIG. 5 a , the deformation preventing portion 125 of the present embodiment can be located on the entire upper surface of the first back plate 120 a with the second back plate 120 b interposed therebetween and located at the lower part, and has the same diameter as the first back plate 120 a. The plate 120a has the same formation area.

At this time, the deformation preventing portion 125 may have an upside-down shape with the second back plate 120b as the center.

However, as shown in FIG. 5b, when the first backplane 120a is only located on a part of the lower surface of the second backplane 120b, the deformation preventing portion 125 places the second backplane 120b therebetween, not only on the lower surface of the first backplane 120a. The upper surface may be additionally positioned on the second backplane 120b on which the first backplane 120a is not disposed.

Therefore, the deformation preventing portion 125 can be arranged on the entire upper surface of the second back plate 120b located on the first back plate 120a.

At this time, the formation area of the deformation preventing portion 125 may be larger than the formation area of the first back plate 120a.

Therefore, the deformation preventing portion 125 of the present embodiment may have the same or larger formation area as that of the first back plate 120a.

The deformation preventing portion 125 can prevent the bending phenomenon of the first back plate 120a.

The MEMS condenser microphone of this embodiment may have an air layer 130 serving as a cavity space between the first backplane 120 a and the diaphragm 110 . Therefore, since the air layer 130 serving as a cavity space, the air layer 130 located on the air layer 130 The supporting force of the first backplane 120a can only be weakened.

However, in the present embodiment, the deformation preventing portion 125 is located on the upper part of the first back plate 120a that descends toward the air layer 130 as the cavity space, and the tension of the deformation preventing portion 125 can prevent or greatly reduce the A descending phenomenon of the backplane 120a.

When manufacturing the MEMS condenser microphone, the first back plate 120a is deformed in a predetermined direction due to at least one of heat stress, compressive stress and tensile stress generated during the manufacturing process , will bend into a convex or concave shape.

Therefore, when forming the deformation preventing portion 125, the deformation preventing portion 125 may be formed in consideration of the occurrence direction of such stress, so that the tension acts in the same direction as the deformation direction of the first back plate 120a, thereby preventing or minimizing the first back plate 120a deformation.

In addition, in order to prevent the deformation of the first back plate 120b, the deformation preventing portion 125 may have the same or similar thermal expansion coefficient as the first back plate 120b, that is, the same thermal expansion coefficient within a setting error range.

When compared with the thermal expansion coefficient of the first back plate 120a and the thermal expansion coefficient of the second back plate 120b, the deformation preventing portion 125 may have the same or similar thermal expansion coefficient as the first back plate 120b compared to the second back plate 120b. Therefore, the absolute value of the difference of the thermal expansion coefficient of the deformation preventing portion 125 and the first back plate 120a may be smaller than the absolute value of the difference of the thermal expansion coefficient of the second back plate 120b.

Therefore, the deformation preventing portion 125 may be composed of the same material as the first back plate 120a, or, as already described, a material having the same or similar thermal expansion coefficient as the first back plate 120a.

In addition, the deformation preventing portion 125 may have the same or thicker thickness as that of the first back plate 120a, so that the bending phenomenon of the first back plate 120a can be suppressed more efficiently.

Such a bending phenomenon of the first back plate 120a is more likely to occur in the protrusions 140 and the periphery of the protrusions in the first back plate 120a. Therefore, when the deformation preventing portion 125 is not located on the entire upper surface of the back plate portion 120 but only on a part of the upper surface, it may be located on the central portion of the deformation preventing portion 125 where the plurality of protrusions 150 are located, and the plurality of The protrusions 150 all overlap.

As described above, with the aid of the deformation preventing portion 125 of the present embodiment, the stress (for example: at least one of thermal stress, compressive stress and tensile stress) occurring during the manufacture of the MEMS condenser microphone can be prevented or greatly reduced Therefore, the variation of the interval between the first back plate 120 a and the diaphragm 110 also does not occur or is greatly reduced.

As such a change in the interval between the first back plate 120a and the diaphragm 110 is prevented, the interval between the diaphragm electrode and the back plate electrode, which are MEMS electrodes, can also be prevented from changing. Therefore, by means of the deformation preventing portion 125, the structural deformation of the MEMS condenser microphone of the present embodiment is minimized, so that the performance of the MEMS condenser microphone can be prevented from being deteriorated.

As already described, the separator 110 and the back plate portion 120 with the air layer 130 as the insulating layer interposed therebetween may function as counter electrodes facing in opposite directions, respectively.

In this case, the diaphragm 110 and the back plate portion 120 themselves may function as diaphragm electrodes and back plate electrodes, respectively, or additional diaphragm electrodes and other diaphragm electrodes may be additionally provided on at least one of the vibrating plate (eg, diaphragm) 110 and the back plate portion 120 . at least one of the backplate electrodes. A bias voltage can be applied to the diaphragm electrode, and the output voltage can be output to the outside through the back plate electrode.

As already described, the air layer 130 is located between the diaphragm 110 and the back plate portion 120 , so that the diaphragm 110 and the back plate portion 120 are separated by a space corresponding to the thickness of the air layer 130 .

This air layer 130 functions as a dielectric. As described, the diaphragm electrode and the back plate electrode exist with the air layer 130 interposed therebetween. Therefore, with the vibration of the diaphragm 110 caused by sound waves, the diaphragm 110 and the back plate portion 120 A capacitance of corresponding size is generated between them.

The plurality of protrusions 140 are used to prevent the diaphragm 110 from being in contact with the back plate portion 120 to cause a pull-in voltage state when the diaphragm 110 vibrates, so as to play an interface buffer function.

Each protrusion 140 may all have the same shape, and may have a planar shape of a cylindrical shape having a hollow space H14 filled with air in a shape such as a circle in a central portion.

As already mentioned, such protrusions 140 may be formed of nitride as an example.

As shown in FIG. 3 , each protrusion 140 protrudes from the back plate portion 120 to the side of the diaphragm 110 by a predetermined length. With the plurality of protrusions 140, the vibrating diaphragm 110 is not in contact with the back plate portion 120, but can be It is in contact with the adjacent and opposite protrusions 140 .

Therefore, even when vibrating, the diaphragm 110 is not in contact with the back plate portion 120, and the pull-in voltage state does not occur, so that the life of the diaphragm 110 can be extended, and thus the life of the MEMS condenser microphone can also be extended.

3, from the back plate 120, more specifically, from the lower surface of the first back plate 120a toward the diaphragm 110 side to the air layer 130 side, the projection length of the projection 140 is the same regardless of the position.

However, it is not limited thereto, in an alternative embodiment, the protruding lengths of the at least two protrusions 140 may be different depending on the position, so that the protrusions 140 located at the center of the MEMS condenser microphone may be longer than the protrusions located at the edge. 140 has a short protruding length.

When the protruding length differs depending on the position, the protruding length of the protrusion 140 may gradually increase from the center portion to the edge portion side of the MEMS condenser microphone. At this time, the increase ratio of the protruding length may be proportionally increased according to a predetermined ratio.

Generally speaking, when a sound wave of the same magnitude flows, the amplitude of the diaphragm 110 decreases gradually from the center portion to the edge portion.

Therefore, when the protruding length of the protrusions 140 gradually increases from the center portion to the edge portion of the MEMS condenser microphone, the diaphragm 110 is not hindered by the opposing protrusions 140, and normally achieves a vibration action of a corresponding amplitude, so that the diaphragm 110 vibrates It can be held symmetrically about the center portion.

Thereby, an accurate capacitance corresponding to the incoming sound wave can be generated, the operation reliability of the MEMS condenser microphone can be improved, the contact frequency or impact with the protrusion 140 can be alleviated, and the damage or breakage of the diaphragm 110 can be reduced.

In particular, the cavity space H14 located at the center of each protrusion 140 is filled with air, so when the diaphragm 110 hits the corresponding protrusion 140 , a buffering effect is produced, which further reduces the damage or breakage of the diaphragm 110 .

The outer diameter D11 of each protrusion 140 can be maintained at 0.6 μm to 2.0 μm, and the inner diameter D12 can be maintained at 0.3 μm to 1.5 μm.

As described above, each protrusion 140 has a large outer diameter and has a cavity space in the central portion, so the protrusion 140 of this embodiment can have good durability. Therefore, breakage or damage of the cylindrical protrusion 140 due to frequent collision with the diaphragm 110 can be reduced.

In addition, since the line width W11 is narrow, the contact area of the cylindrical protrusion 140 in contact with the diaphragm 110 is reduced, so even if the diaphragm 110 contacts the protrusion 140 , the phenomenon of sticking to the protrusion 140 can be prevented.

If the outer diameter of the protrusions 140 is 0.6 μm or more, the range of the diaphragm 110 in contact with the protrusions 140 is increased, the impact absorption effect of the diaphragm can be improved, and the durability of the protrusions 140 can be increased. If the outer diameter of the protrusions 140 is 2.0 μm or less, a problem caused by an increase in the area where the protrusions 140 are formed can be prevented.

In addition, if the inner diameter of the protrusions 140 is 0.3 μm or more, the difficulty of forming the protrusions can be reduced, and the sticking phenomenon with the diaphragm 110 can be prevented. If the inner diameter of the protrusions 140 is 1.5 μm or less, the protrusions can be prevented. 140 line width reduction problem.

If the line width W11 of each protrusion 140 is greater than or equal to 0.2 μm, the formation of the protrusion 140 is easy, and the risk of damage to the protrusion 140 can be reduced when the protrusion 140 collides with the diaphragm 110 .

As described above, since the outer diameter (ie, the outer diameter) D11 is formed wide, the range of the diaphragm 110 that can be contacted by each unit protrusion can be enlarged.

As shown in FIG. 4 , such a plurality of protrusions 140 may be located in a portion of the back plate portion 120 where the sound hole H10 is not arranged.

The sound hole H10 is a through hole that completely penetrates the back plate portion 120 and the deformation preventing portion 125 located thereon as a hole through which the sound wave flows.

That is, the protrusions 140 are arranged around the sound hole H10 in the back plate portion 120 so as to avoid the sound hole H10. At this time, the interval between two adjacent protrusions 140 may be predetermined.

In this embodiment, as shown in FIG. 2 , the MEMS condenser microphones may be densely arranged in the center portion (ie, the center portion) of the corresponding portion (ie, the back plate portion 120 ), and may not be arranged in the MEMS condenser microphone. The edge of the condenser microphone.

However, not only the center portion of the corresponding portion of the MEMS condenser microphone, but also the protrusion 140 may be located at other portions such as the edge portion.

The vibration of the diaphragm 110 is stronger in the center and becomes weaker toward the edge, so the density of the protrusions 140 varies according to the position of the opposed diaphragm 110 . For example, the density of the protrusions 140 may decrease progressively from the center portion of the membrane 110 toward the edge portion.

Therefore, the interval between the two adjacent protrusions 140 located opposite to the center of the diaphragm 110 may be narrower than the interval between the two adjacent protrusions 140 located opposite to the edge of the diaphragm 110 . At this time, the interval between the adjacent two protrusions 140 may be changed proportionally from the center portion to the edge portion of the diaphragm 110 .

The MEMS condenser microphone of the present embodiment having such a structure may include, in addition to the constituent elements shown in FIGS. 2 and 3 , other components such as an insulating connection portion, an output pad, an offset pad, a plurality of connectors, and the like. At least one component, wherein the insulating connection portion is located on the base substrate 100 to support the back plate portion 120, the output pad is electrically connected to the back plate electrode to output an electrical signal, and the bias pad is connected to the diaphragm The electrodes are electrically connected for inputting a bias voltage, and the plurality of connectors are respectively used for the connection between the backplate electrode and the output pad and the connection between the diaphragm electrode and the bias pad.

6a to 6k , a method for forming a MEMS condenser microphone according to an embodiment of the present invention is briefly described, and more specifically, a method for forming a MEMS electrode of the MEMS condenser microphone is briefly described.

First, as shown in FIG. 6a , on the base substrate 100 composed of a silicon wafer, a polysilicon film is deposited by a CVD deposition growth method to form a diaphragm 110 . The separator 110 formed at this time may have a thickness of 0.5 μm˜2.0 μm.

Then, as shown in FIG. 6 b , a film with a thickness of 1.5 to 4.0 μm is grown on the separator 110 by a thermal oxidation method to form a sacrificial layer 131 . At this time, the thickness of the sacrificial layer 131 may be determined according to the vibration range of the diaphragm 110, the protrusion length of the cylindrical protrusion 140, and the like.

Then, as shown in FIG. 6c, a first back plate layer 121a made of nitride is formed on the sacrificial layer 131 by a deposition method. The thickness of the first backplane layer 121a may be 2.0 μm˜3.5 μm.

Then, as shown in FIG. 6d, after the photoresist film 151 is stacked, the photoresist film 151 is selectively covered with a mask, and the exposed part of the photoresist film 151 is etched so that the first The backplane layer 121a is exposed.

At this time, the portion of the etched photoresist film 151 becomes the formation position of the cylindrical bump 140 .

In this way, after using the photoresist film 151 to expose the desired part of the first backplane layer 121a, the remaining photoresist film 151 is used as a mask to etch the exposed part of the first backplane layer 121a to form a first backplane. Plate 120a (Fig. 6e).

At this time, the first back plate 120a is provided with a cylindrical cavity portion by an etching operation, and a corresponding portion of the sacrificial layer 131 is exposed through the cavity portion.

The etching solution selectively removes only the exposed portion of the first backplane layer 121a, while the exposed portion of the sacrificial layer 131 is not etched.

Then, the photoresist film 121 existing on the first back plate 120a is removed (FIG. 6f).

As shown in FIG. 6g , from the exposed surface of the sacrificial layer 131 , the sacrificial layer 131 is etched to a predetermined depth, and holes H140 for protrusions are formed in the corresponding positions of the first backplane 120 a and the corresponding positions of the sacrificial layer 131 .

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

When the etching depth of the sacrificial layer 131 exceeds 1/2 of the total thickness, the distance between the protrusions 140 and the diaphragm 110 is shorter than the amplitude of the diaphragm 110 , which adversely affects the vibration of the diaphragm 110 .

As described above, if a plurality of bump holes H140 are formed on the first backplane 120a and the sacrificial layer 131, nitride is filled in the plurality of bump holes H140 by means of nitride deposition to complete the plurality of bumps 140. (Fig. 6h).

In order to deposit the nitride only in the plurality of bump holes H140, the portion of the first back plate 120a where the bump holes H140 are not arranged may be masked with a mask.

The outer diameter D11 of each formed protrusion 140 may be 0.6˜2.0 μm, and the inner diameter D12 filled with the sacrificial layer 131 may be 0.3˜1.5 μm. In addition, the width W11 of each cylindrical protrusion 130 may be at least 0.2 μm.

Then, as shown in FIG. 6i, nitride is deposited on the first back plate 120a and on the cylindrical protrusions 140 to form the second back plate 120b. At this time, when the second back plate 120b is omitted, this step is omitted.

Then, as shown in FIG. 6j , nitride is deposited on the second back plate 120b to form the deformation preventing portion 125 . At this time, the deformation preventing portion 125 may be formed at a desired position on the upper surface of the second back plate 120b using a mask or the like.

When the second back plate 120b is omitted, the deformation preventing portion 125 may be formed by depositing nitride on the first back plate 120a. Then, the sacrificial layer 131 is selectively etched to form an air layer 130 between the diaphragm 110 and the first back plate 120a (FIG. 6k).

Finally, the base substrate 100 is selectively removed to form the acoustic chamber 101 (refer to FIG. 3 ) as a cavity space.

Then, referring to FIGS. 7 to 9 , a MEMS condenser microphone according to another embodiment of the present invention will be described.

Compared with the MEMS condenser microphone shown in FIGS. 2 to 5 b , the same reference numerals as those of FIGS. 2 to 5 b are assigned to the constituent elements of this embodiment having the same structure and performing the same functions, A detailed description thereof is omitted.

The MEMS condenser microphone of this embodiment has a structure similar to that shown in FIGS. 2 to 5 b .

That is, as shown in FIGS. 7 to 9 , the MEMS condenser microphone includes a base substrate 100 , a diaphragm 110 located on the base substrate 100 , and a backplane located on the diaphragm 110 and provided with first and second backplanes 120 a and 120 b part 120, the deformation preventing part 125 on the back plate part 120, the air layer 130 between the base substrate 100 and the back plate part 120, and a plurality of cylindrical protrusions protruding from the back plate part 120 to the air layer 130 side from 140.

However, as shown in FIGS. 8 and 9 , the MEMS condenser microphone of this embodiment further includes a plurality of bar-shaped protrusions 142 .

Therefore, in the MEMS condenser microphone of the present embodiment, a plurality of cylindrical protrusions 140 and a plurality of rod-shaped protrusions 142 are mixed in the air layer 130 .

As shown in FIG. 8 , the rod-shaped protrusions 142 protrude by a predetermined length from the surface of the first back plate 120 a toward the air layer 130 , like the cylindrical protrusions 130 .

However, unlike the cylindrical protrusions 140, the bar-shaped protrusions 142 are in the form of a bar in which a cavity space having the air layer 130 does not exist in the central portion, that is, a rod form.

The plurality of rod-shaped protrusions 142 have an outer diameter smaller than the outer diameter of the cylindrical protrusions 140, and are located where the cylindrical protrusions 140 and the sound hole H10 are not arranged.

For example, the rod-shaped protrusions 142 may be located at least one of between two adjacent cylindrical protrusions 140 , between two adjacent sound holes H10 , and a portion surrounded by the cylindrical protrusions 140 as shown in FIG. 7 . By. At this time, the interval between the adjacent two bar-shaped protrusions 142 may be predetermined or irregularly or proportionally increased.

The arrangement state of the plurality of rod-shaped protrusions 142 and the plurality of cylindrical protrusions 140 may have various forms. For example, the rod-shaped protrusions 142 may be disposed adjacent to the cylindrical protrusions 140 .

With the additional arrangement of the rod-shaped protrusions 142, the vibration of the diaphragm 110 can be adjusted uniformly, thereby improving the quality of the MEMS condenser microphone.

The spacing and position of the rod-shaped protrusions 142 can be determined according to the diameter and arrangement spacing of the sound hole H10 and the elasticity and stress of the diaphragm 110 .

The protruding length of this rod-shaped protrusion 142 is the same as that of the cylindrical protrusion 140, regardless of the position, or there are at least two rod-shaped protrusions 142 having different protrusion lengths.

When the protrusion lengths of the rod-shaped protrusions 142 are different, the protrusion length of the rod-shaped protrusions 142 arranged corresponding to the center of the diaphragm 110 may be longer than the protrusion length of the rod-shaped protrusions 142 arranged corresponding to the edge of the diaphragm 110 Out length is short. Similarly, in another embodiment, the protruding lengths of the opposite cylindrical protrusions 140 may gradually increase from the center portion to the edge portion of the diaphragm 110 . At this time, the increase ratio of the protruding length may be proportionally increased at a predetermined ratio.

The method for forming the MEMS condenser microphone of the present embodiment having the cylindrical protrusions 140 and the rod-shaped protrusions 142 in this way, more specifically, the method for forming the MEMS electrodes of the MEMS condenser microphone is the same as that shown in FIGS. 6a to 6k . The content shown is the same.

However, when the part of the photoresist film 151 exposed in FIG. 6d is etched, not only the part used as the barrel-shaped protrusion 140 but also the part used as the rod-shaped protrusion 142 is etched, and the first back plate is additionally exposed at the corresponding position In the layer 121a, when the first back plate 120a is formed, the first back plate 120a has a cylindrical cavity portion for the cylindrical protrusions 140 and a rod-shaped cavity portion for the rod-shaped protrusions.

Therefore, the sacrificial layer 131 exposed through the cylindrical cavity portion and the rod-shaped cavity portion is etched to a predetermined depth to form holes for cylindrical protrusions and holes for rod-shaped protrusions. Then, through subsequent processes, the formation of the cylindrical protrusions 140 and the rod-shaped protrusions 142 can be completed.

The embodiments of the MEMS condenser microphone and the MEMS electrode forming method for the MEMS condenser microphone of the present invention have been described above. The present invention is not limited to the above-described embodiments and drawings, and various revisions and modifications can be made from the perspective of those skilled in the art to which the present invention pertains. Therefore, the scope of the present invention should be determined not only by the claims of this specification but also by the content equivalent to the claims.

Claims (16)

1. A MEMS condenser microphone, comprising: base substrate; a diaphragm, the diaphragm is located on the base substrate; a back plate part, the back plate part is located on the diaphragm; a deformation preventing part, the deformation preventing part is located on the back plate part; an air layer located between the diaphragm and the back plate portion; and A plurality of protrusions protruding in the air layer from the back plate portion to the diaphragm side. 2. The MEMS condenser microphone of claim 1, wherein, The backplane part further includes a first backplane and a second backplane, the first backplane is connected to the air layer and is configured with the protrusion, and the second backplane is located on the first backplane on the board, connected with the protrusions. 3. The MEMS condenser microphone of claim 2, wherein, The deformation preventing portion is disposed to overlap with the first back plate with the second back plate interposed therebetween. 4. The MEMS condenser microphone of claim 3, wherein, The first backplane is disposed in contact with the entire lower surface of the second backplane. 5. The MEMS condenser microphone of claim 3, wherein, The first backplane is disposed in contact with a part of the lower surface of the second backplane. 6. The MEMS condenser microphone of claim 5, wherein, The deformation preventing portion is also located on the second backplane on which the first backplane is not disposed. 7. The MEMS condenser microphone of claim 2, wherein, The second back plate is made of the same material as the protrusions. 8. The MEMS condenser microphone of claim 2, wherein, The deformation preventing portion is made of the same material as the first back plate. 9. The MEMS condenser microphone of claim 2, wherein, The deformation preventing portion has the same thermal expansion coefficient as that of the first back plate. 10. The MEMS condenser microphone of claim 2, wherein, In the first back sheet and the second back sheet, the absolute value of the difference in thermal expansion coefficient between the deformation preventing portion and the first back sheet is small. 11. The MEMS condenser microphone of claim 1, wherein, The plurality of protrusions include a plurality of cylindrical protrusions. 12. The MEMS condenser microphone of claim 11, wherein, The plurality of protrusions also include a plurality of rod-shaped protrusions. 13. A MEMS electrode forming method for a MEMS condenser microphone, comprising: the step of forming a diaphragm on the base substrate; the step of forming a sacrificial layer on the diaphragm; the step of forming a first backplane layer on the sacrificial layer; After laminating a photoresist film on the first backplane layer, using a mask to selectively etch the photoresist film to expose the part of the first backplane layer located in the etched part; Using the remaining photoresist film as a mask to remove the exposed part of the first backplane layer to form a first backplane with a hollow cavity portion in a cylindrical shape; the step of removing the remaining said photoresist film; The step of etching the sacrificial layer exposed through the cavity at a predetermined depth, and forming holes for cylindrical protrusions on the first backplane and the sacrificial layer; A step of depositing a predetermined substance in the holes for cylindrical protrusions to form cylindrical protrusions; the step of forming a second backplane on the first backplane and on the protrusions; and The step of forming a deformation preventing portion on the second back plate. 14. The MEMS electrode forming method of the MEMS condenser microphone according to claim 13, wherein, In the step of forming the second back plate, the second back plate is formed by using the same material as the protrusion. 15. The MEMS electrode forming method of the MEMS condenser microphone according to claim 13, wherein, In the step of forming the deformation preventing portion, the deformation preventing portion is formed of the same material as the first back plate. 16. The MEMS electrode forming method of the MEMS condenser microphone according to claim 13, wherein, In the step of forming the deformation preventing portion, the deformation preventing portion is formed using a material having the same thermal expansion coefficient as that of the first back plate.

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