KR20140137158A - 1-chip-type MEMS microphone and method for making the 1-chip-type MEMS microphone - Google Patents

Abstract

The present invention relates to a 1-chip-type MEMS microphone and a method for manufacturing the same. The purpose of the present invention is to provide a 1-chip-type MEMS microphone and a method for manufacturing the same. The structure of an existing 1-chip-type MEMS microphone is improved, thereby reducing the number of components and processes, improving rigidity by replacing component materials, saving costs, and improving sensitivity and performance.

Description

[0001] The present invention relates to a one-chip type MEMS microphone and a method of manufacturing the same,

The present invention relates to a one-chip type MEMS microphone and a method of manufacturing the same.

Recently, researches on the technique of measuring the position of the noise source in three dimensions due to the development of the acoustic measurement technique according to the demand for reducing the noise pollution damage have been variously carried out. Especially, the device itself which directly measures the sound has been actively studied ought. Electret condenser micophone (ECM) has been widely used in acoustic measurement. However, it is difficult to install it in a desired position due to the volume of ECM due to variation and diversification of measurement environment. In addition, Technology requires a lot of microphones, but the ECM itself is a very expensive device, which also causes economic problems.

In general, MEMS (microelectromechanical system) based capacitive microphone based on MEMS (simply referred to as "MEMS microphone" hereinafter) has an advantage over the fundamental limitation of conventional ECM. MEMS microphones are mechanically or electrically biased dielectrics such as polysilicon, silicon nitride, and silicon oxide, which have reliability at temperatures of -40 ° C to + 120 ° C and are reliable for humidity and complex temperature variations. In addition, MEMS microphones using silicon substrates can withstand lead-free surface mounting temperatures above 260 ° C. This high reliability and surface mountability surpasses the existing ECM. Although ECM is only available in can-type packages, MEMS microphones can be packaged to meet the needs of the user, which is suitable for the application of microphones that are currently compact and integrated. The MEMS microphone senses the change in capacitance due to the incoming sound pressure while applying a constant direct current (DC) bias voltage between the diaphragm and the reference plate. MEMS microphones can be made smaller than most smaller ECMs and are less sensitive to mechanical vibration, temperature changes, and electromagnetic interference. These favorable characteristics are increasingly used in devices such as mobile phones, notebook computers, camcorders, and digital cameras as well as hearing aids and electronic stethoscopes.

A typical conventional MEMS microphone structure is disclosed in Korean Patent Registration No. 0737726 ("MEMS microphone packaging structure ", 2007.07.04, precedent). Generally, a MEMS microphone is composed of two substrates. More specifically, in general, currently widely used MEMS microphones include a case having one side opened and a sound hole formed on the other side, a first printed circuit board housed in a case, a MEMS die and an amplifier, and an integrated base unit And a second printed circuit board that hermetically seals the opening of the case and has an electrode formed on the back surface thereof. More specifically, a first printed circuit board is disposed on the bottom surface of the case where the sound holes are formed, a MEMS die manufactured by MEMS technology on the first printed circuit board surface for converting the voice signal into an electric signal, and an amplifier for amplifying the electric signal Respectively. The integrated base portion is provided at one side of the case to provide a conductive path for transmitting the electrical signal passed through the amplifier to the second printed circuit board. A circuit pattern is formed on a surface of the second printed circuit board in contact with the integrated base portion, and an electric signal applied from the integrated base portion is transmitted to an external device through an electrode formed on the back surface of the integrated base portion. Further, the second printed circuit board seals the opening of the case to prevent foreign matter and noise from flowing into the case. However, the MEMS microphone, which is formed by stacking two substrates in this manner, has a limitation in size that can be downsized due to the thickness of the substrate, and also has a limitation in that the number of parts and the number of processes can not be increased due to the fact that there are two substrates.

In order to solve such a problem, studies have been made on a one-chip type MEMS microphone composed of a single substrate. In the case of a single-chip MEMS microphone developed and commercialized at present, as shown in FIG. 1, A membrane 2 which is vibrated by sound pressure and which actually measures sound and a plurality of holes 31 are formed so that sound can pass therethrough so as to cover the outer side of the membrane 2 And a back plate (3) fixed on the substrate (1) by a support part (32). The membrane 2 is made of polysilicon and the backplate 3 is made of a silicon compound doped with polysilicon and the backplate 3 serves as an electrode. At this time, an air gap between the membrane (2) and the back plate (3) is 5 m or more.

The operation principle of such a one-chip type MEMS microphone is briefly described as follows. Sound is generated due to vibration of air by sound, and the membrane 2 vibrates as the sound pressure is transmitted to the membrane 2 through the hole 31 do. The vibration of the membrane 2 is transmitted to the back plate 3 serving as an electrode, and the back plate 3 transmits the electric signal to the outside to measure the sound.

However, in the conventional one-chip type MEMS microphone, since the back plate is made of a silicon material, there is a problem that the rigidity is significantly lowered. As a result, due to the vibration of the membrane due to the negative pressure, There is a problem that the measurement sensitivity is significantly lowered. Further, in manufacturing a conventional one-chip type MEMS microphone, the process is too complicated and mass production is difficult.

1. Korea Patent No. 0737726 ("MEMS microphone packaging structure", 2007.07.04)

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to improve the structure of a conventional single-chip MEMS microphone and to reduce the number of parts and processes, Chip type MEMS microphone and a method of manufacturing the same, which can improve strength and cost, and improve sensitivity and performance.

According to another aspect of the present invention, there is provided a one-chip MEMS microphone including: a substrate having an acoustic chamber at a center thereof; And is supported on the substrate 110 by a plurality of posts 121 disposed on the edge portion in a shape protruding downward and disposed on the outermost side so as to cover the upper portion of the acoustic chamber S, (120) having a plurality of bumps (122) arranged over the entire surface thereof; A thick plate 130 disposed under the diaphragm 120 to cover the upper portion of the acoustic chamber S and having a plurality of acoustic holes 131 arranged in a through hole shape over the entire surface thereof; A front electrode 141 provided on the substrate 110 to electrically contact the diaphragm 120; A rear electrode 142 disposed under the substrate 110 and in electrical contact with the rear plate 130; And the thick plate 130 is made of a metal material.

At this time, the diaphragm 120 is formed into a polygonal flat plate shape, and the corner portion is supported by the substrate 110 by the post 121, and the vertex portion is extended and fixed to the substrate 110 . At this time, the diaphragm 120 may have a spring structure at a portion where the vertex portion extends and is fixed to the substrate 110.

In addition, the method for manufacturing a one-chip type MEMS microphone according to the present invention is a method for manufacturing a single-chip MEMS microphone 100 as described above, comprising the steps of: A) depositing an oxide layer on the upper and lower sides of a substrate 110; B) removing a part of the oxide layer on the top by etching to form a groove for the post; C) a first sacrificial layer is deposited on the outer side of the oxide layers on the upper and lower sides, and a part of the first sacrificial layer on the upper side is removed by etching to form a groove for a bump and a groove for a post; D) depositing a diaphragm material on the outer side of the first sacrificial layer by ion implantation to form the diaphragm 120; E) depositing a second sacrificial layer outside the diaphragm 120; F) depositing a masking layer on the uppermost and lowermost outermost sides; G) removing a center portion of the rear surface of the substrate 110 by anisotropic etching to form an acoustic chamber S, and depositing an insulating layer on the etched surface; H) a seed layer is deposited on the insulating layer on the rear surface side of the substrate 110, and after the mold for acoustic holes is formed, electroplating is performed to form a thick plate 130 on which the acoustic holes 131 are formed; I) a front electrode 141 electrically connected to the diaphragm 120 is formed on the front surface of the substrate 110 and a rear electrode 142 electrically connected to the rear plate 130 is formed on the rear surface of the substrate 110 ); J) A portion of the first sacrificial layer, the oxide layer, and the insulating layer between the diaphragm 120 and the thick plate 130 is removed to form an air gap (not shown) between the diaphragm 120 and the thick plate 130 forming an air gap; And a control unit.

According to the present invention, unlike the conventional one-chip type MEMS microphone structure, a thick plate is formed inside the diaphragm, thereby reducing manufacturing steps compared with the conventional one. In addition, since the process step is improved by forming the thick plate on the inner side of the diaphragm, the material of the thick plate can be made of metal, unlike the conventional method. Therefore, compared with the conventional plate made of silicon, There is an economical effect that the product can be constituted.

In addition, since the plate material is made of metal, it is possible to perform the electroplating process on the plate (this process is difficult to perform due to material or structural limitations in the past), but in the present invention, Therefore, the thickness of the thick plate can be increased much more than the conventional one, and the rigidity of the thick plate can be further improved compared with the conventional one. As the rigidity of the thick plate increases, the problem of deterioration of acoustic measurement performance, which is caused by the vibration of the diaphragm being unnecessarily transmitted to the thick plate, can be greatly improved.

In addition, according to the present invention, only the vertex portion is fixed without fixing the corner portion of the diaphragm, thereby improving the flexibility of the diaphragm and greatly improving the sensitivity. In addition, by introducing a spring structure to the vertex fixing portion of the diaphragm, the flexibility of the diaphragm is maximized and the residual stress is absorbed and removed, thereby further improving the sensitivity.

Further, the present invention provides a structure in which a rear electrode is formed on a bottom surface of a substrate, and when a MEMS microphone of the present invention is disposed on another substrate, a separate electrode connection structure such as a wire is not required at all, The MEMS microphone of the present invention can be connected to the electrode only by putting it on the microphone, thereby maximizing convenience.

1 is a top view and a side sectional view of a conventional one-chip type MEMS microphone.
2 is a top view and a diagonal cross-sectional view of a one-chip MEMS microphone of the present invention.
3 is a top plan view of the diaphragm of the present invention.
4 is a top plan view of the thick plate of the present invention.
5 is a top view and a cross-sectional view of the single-chip MEMS microphone of the present invention.
FIGS. 6 and 7 illustrate steps of manufacturing a one-chip MEMS microphone of the present invention.

Hereinafter, a single-chip MEMS microphone according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a top view and a cross-sectional view of a single-chip MEMS microphone of the present invention. The one-chip type MEMS microphone of the present invention includes a substrate 110, a diaphragm 120, a thick plate 130, a front electrode 141, and a rear electrode 142 on which an acoustic chamber S is formed at a central portion The diaphragm 120 is disposed on the outermost side and the thick plate 130 is formed on the bottom of the diaphragm 120 as shown in FIG. Hereinafter, each part will be described in detail.

The diaphragm 120 is disposed outermost to cover the upper portion of the acoustic chamber S. 1, a membrane 2 (see FIG. 1) corresponding to the diaphragm 120 is disposed inside the back plate 3 (see FIG. 1) corresponding to the thick plate 130 That is, the back plate 3 is disposed on the outermost side. However, in the present invention, since the diaphragm 120 is disposed on the outermost side, the influence of the negative pressure can be better accommodated.

Particularly, in the present invention, the diaphragm 120 is partially free-floating with respect to the substrate 110. More specifically, it is as follows. FIG. 3 is a top view of the diaphragm of the present invention. As shown in FIG. 3, the diaphragm 120 has a polygonal (rectangular in FIG. 3) flat plate shape. The edge of the acoustic chamber S and the edge of the diaphragm 120 may be joined together because the acoustic chamber S formed in the central portion of the substrate 110 has a through hole. The corner portion of the diaphragm 120 is bonded to the substrate 110 as shown in FIG. 3A, so that the diaphragm 120 is not constrained, and the vertex portion is extended and fixed to the substrate 110. At this time, the diaphragm 120 is formed with a plurality of posts 121, which are disposed on the edge portion so as to protrude downward, so that the corner of the diaphragm 120 does not stick to the substrate 110. The diaphragm 120 can be maintained at an appropriate air gap with the thick plate 130 without being bonded to the substrate 110 by being supported by the posts 121. [ give. As described above, since the diaphragm 120 is minimally fixed to the substrate 120 and is almost free-floating, the acoustic measurement sensitivity can be greatly improved. In addition, as shown in FIG. 2 (B), a spring structure is formed at a portion where the vertex portion is extended and fixed to the substrate 110, so that the spring structure absorbs residual stress, 120) itself to almost zero, thereby further maximizing the acoustic measurement sensitivity.

A plurality of bumps 122 are formed on the diaphragm 120 so as to protrude downward from the diaphragm 120. The diaphragm 120 and the thick plate 130 are fixed to each other It helps prevent it. This will be described in detail later in the production method.

The thick plate 130 is formed in the form of a plate having a plurality of acoustical holes 131 arranged in the form of a through hole. FIG. 4 shows a top view of one embodiment of the thick plate 130. FIG. As shown in FIG. 2, the thick plate 130 is disposed below the vibration membrane 120 so as to cover the upper portion of the acoustic chamber S. As shown in FIG. The back plate 3 (see FIG. 1) corresponding to the thick plate 130 is formed of silicon nitride (Si ₃ ) doped with polysilicon, N ₄ ), and the like can be used instead of a silicon material. Further, according to the improved structure of the present invention and the material (replaced with a metal material), there is a problem that it is difficult to increase the thickness of the thick plate 130 It is possible to make the thickness of the thick plate 130 thicker than in the prior art. As described above, since the thick plate 130 is made of a metal material, electroplating is performed to make the thick plate 130 thicker than the conventional thick plate.

In the case of the conventional silicon material, there is a limit to increase the rigidity of the thick plate 130 because there is a restriction that the thickness thereof can not be increased beyond the limit due to process limitations as described above. Meanwhile, when the rigidity of the thick plate 130 is low, the thick plate 130 vibrates together with the diaphragm 120, which vibrates directly due to negative pressure and converts the thick plate 130 into an electrical signal. There is a problem that the noise is generated and the accuracy of the measurement signal is lowered. However, according to the present invention, as described above, by increasing the thickness of the thick plate 130 to strengthen the rigidity, the problem of shape deformation due to the external vibration can be mitigated to a great extent, You can get the effect.

In addition, since the thick plate 130 is made of a metal material, it is possible to use a material much cheaper than the conventional one, and thus the cost of the product can be further reduced.

The front electrode 141 is provided on the substrate 110 and is in electrical contact with the diaphragm 120. The rear electrode 142 is disposed under the substrate 110 to be in contact with the thick plate 130, And is electrically contacted. Chip type MEMS microphone 100 may be mounted on another substrate without requiring a separate electrode connection structure such as a wire when the one-chip type MEMS microphone 100 is connected to another substrate, Just plug it in and it will allow you to connect the electrodes right away. That is, the one-chip type MEMS microphone 100 becomes a mountable element. The one-chip type MEMS microphone 100 of the present invention greatly improves the assemblability with other substrates by the structure of the rear electrode 142.

5 is a top view and a cross-sectional view of the one-chip type MEMS microphone of the present invention, and FIGS. 6 and 7 show steps of manufacturing the one-chip type MEMS microphone of the present invention. Figs. 6 and 7 show sequentially the cross-sections A-A 'and B-B' shown in Fig. 5 at each process step. Each step will be described in more detail with reference to the drawings.

First, as shown in FIG. 6 (A), an oxide film layer is deposited on the upper and lower portions of the substrate 110. At this time, the substrate 110 is not formed with the acoustic chamber S yet. The substrate 110 may be made of silicon (Si), and the oxide layer may be made of SiO ₂ .

Next, as shown in Fig. 6 (B), a part of the oxide film layer on the top is removed by etching to form a groove for a post.

Next, as shown in FIG. 6C, a first sacrificial layer is deposited on the outer side of the oxide film layers on the upper and lower sides, and a part of the first sacrificial layer on the upper side is removed by etching, Grooves are formed. Since the bump 122 is formed over the entire surface of the diaphragm 120 as described above, the post 121 is formed only on the edge of the diaphragm 120, Only the bump grooves and the post grooves are visible in the BB 'section.

Next, as shown in FIG. 6 (D), the diaphragm material is deposited on the outer side of the first sacrificial layer in the upper portion by ion implantation to form the diaphragm 120. The diaphragm 120 may be a poly-Si material widely used as a diaphragm. The post groove and the bump groove formed in the previous step are filled with the diaphragm material so that the post 121 and the bump 122 are formed in a protruded shape. At this time, an etching process may be further performed so that a part of the material inside the posts 121 is removed as shown in the cross section taken along line B-B 'of FIG. 6 (D).

Next, as shown in Fig. 6 (E), a second sacrificial layer is deposited outside the diaphragm 120. At this time, an etching process may be further performed so that a portion of the spacer is partially removed outside the post 121, as shown in a cross section taken along line B-B 'of FIG. 6 (E).

Next, as shown in Fig. 7 (F), a masking layer is deposited on the uppermost and lowermost outermost sides. The masking layer may be silicon nitride (SiNx).

Next, as shown in FIG. 7 (G), the central portion of the rear surface of the substrate 110 is removed by anisotropic etching to form an acoustic chamber S, and an insulating layer is deposited on the etched surface. In the step of removing the center portion of the rear surface of the substrate 110, the oxide layer, which was originally deposited on the substrate 110, is exposed on the upper surface of the acoustic chamber S, And the entire surface of the substrate 110 is covered.

7 (H), a seed layer is deposited on the insulating layer on the back side of the substrate 110, and after the mold for acoustic holes is formed, electroplating is performed to form the acoustic holes 131, (130) is formed. Of course, after the thick plate 130 is formed as described above, the mold for a sound hole is removed. A spray coater can be used to form the mold for a sound hole. Conventionally, the diameter of the acoustic hole can only be reduced to about 5 탆. However, by using the method of the present invention, the diameter of the acoustic hole 131 can be reduced to about 3 탆 Can be reduced.

Next, as shown in FIG. 7 (I), a front electrode 141 electrically connected to the diaphragm 120 is formed on the front surface of the substrate 110, and the front plate 141 is formed on the rear surface of the substrate 110 130 are electrically connected to each other.

Finally, as shown in FIG. 7 (J), the first sacrificial layer, the oxide layer, and a part of the insulating layer between the diaphragm 120 and the thick plate 130 are removed. In this case, both wet etching and dry etching can be used. When the wet etching is used, the diaphragm 120 and the thick plate 130 can be adsorbed because of the surface tension. However, the bump 122 protruding from the bottom surface of the diaphragm 120 can prevent the phenomenon of adsorption. Of course, this problem is fundamentally preventable by using dry etching. The first sacrificial layer, the oxide layer, and the insulating layer are partially removed between the diaphragm 120 and the thick plate 130, thereby forming an air gap between the diaphragm 120 and the thick plate 130 air gaps are formed.

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 spirit and scope of the invention as defined by the appended claims. It goes without saying that various modifications can be made.

100: Single-chip MEMS microphone (of the present invention)
110: substrate 120: diaphragm
121: post 122: bump
130: Plate 131: Acoustic hole
141: front electrode 142: rear electrode

Claims (4)

A substrate 110 on which an acoustic chamber S is formed at the center;
And is supported on the substrate 110 by a plurality of posts 121 disposed on the edge portion in a shape protruding downward and disposed on the outermost side so as to cover the upper portion of the acoustic chamber S, (120) having a plurality of bumps (122) arranged over the entire surface thereof;
A thick plate 130 disposed under the diaphragm 120 to cover the upper portion of the acoustic chamber S and having a plurality of acoustic holes 131 arranged in a through hole shape over the entire surface thereof;
A front electrode 141 provided on the substrate 110 to electrically contact the diaphragm 120;
A rear electrode 142 disposed under the substrate 110 and in electrical contact with the rear plate 130;
, ≪ / RTI >
Wherein the thick plate (130) is made of a metal material.
The method of claim 1, wherein the diaphragm (120)
Chip type MEMS microphone according to any one of claims 1 to 3, wherein the corner portion is supported by the substrate (110) by the post (121), and the vertex portion is extended and fixed to the substrate (110).
3. The method of claim 2, wherein the diaphragm (120)
And a spring structure is formed at a portion where the vertex portion is extended and fixed to the substrate (110).
A method of manufacturing a one-chip MEMS microphone (100) according to any one of claims 1 to 3,
A) depositing an oxide layer on the top and bottom of the substrate 110;
B) removing a part of the oxide layer on the top by etching to form a groove for the post;
C) a first sacrificial layer is deposited on the outer side of the oxide layers on the upper and lower sides, and a part of the first sacrificial layer on the upper side is removed by etching to form a groove for a bump and a groove for a post;
D) depositing a diaphragm material on the outer side of the first sacrificial layer by ion implantation to form the diaphragm 120;
E) depositing a second sacrificial layer outside the diaphragm 120;
F) depositing a masking layer on the uppermost and lowermost outermost sides;
G) removing a center portion of the rear surface of the substrate 110 by anisotropic etching to form an acoustic chamber S, and depositing an insulating layer on the etched surface;
H) a seed layer is deposited on the insulating layer on the rear surface side of the substrate 110, and after the mold for acoustic holes is formed, electroplating is performed to form a thick plate 130 on which the acoustic holes 131 are formed;
I) a front electrode 141 electrically connected to the diaphragm 120 is formed on the front surface of the substrate 110 and a rear electrode 142 electrically connected to the rear plate 130 is formed on the rear surface of the substrate 110 );
J) A portion of the first sacrificial layer, the oxide layer, and the insulating layer between the diaphragm 120 and the thick plate 130 is removed to form an air gap (not shown) between the diaphragm 120 and the thick plate 130 forming an air gap;
Chip type MEMS microphone.

Images