MEMS microphone

Abstract

A MEMS microphone, according to an embodiment of the present invention, comprises: a first substrate; a second substrate disposed on the first substrate; an adhesive layer disposed between the first substrate and the second substrate; a MEMS structure disposed on the second substrate; a signal processing element spaced apart from the MEMS structure and disposed on the second substrate; and an acoustic hole penetrating the first substrate, the adhesive layer, and the second substrate in a first direction, wherein the size of the acoustic hole formed by the first substrate and the adhesive layer is greater than the size of the acoustic hole formed by the second substrate.

Description

MEMS microphone

[0001] The present invention relates to a MEMS microphone.

[0002] Generally, audio devices generate sound by vibrating a diaphragm using electrodes, and significant advancements are being made in the field of audio equipment alongside recent technological developments. The applications of these devices are becoming increasingly diverse, such as in portable terminals and hearing aids, and as the devices in which they are applied become slimmer, the size of the audio devices themselves is also being miniaturized.

[0003] In addition, microphones utilizing MEMS (Micro Electro Mechanical Systems), a semiconductor technology, have recently been developed and are in use. MEMS is a technology that enables the fabrication of small mechanical components on the surface of silicon wafers. These MEMS microphones can be classified into electrostatic and piezoelectric types, including general capacitor types.

[0004] Recently, mobile communication terminals such as mobile phones and smartphones, as well as electronic devices like tablet PCs and MP3 players, are becoming smaller. Consequently, the components of these electronic devices are also becoming more miniaturized. Therefore, Micro Electro Mechanical System (MEMS) technology is required to overcome the physical limitations of these components.

[0005] The biggest problems with these MEMS microphones are size and noise. Since MEMS microphones are primarily used in earphones, miniaturization is a key trend for MEMS microphones in line with the trend of miniaturization in earphones connected to smartphones and the like.

[0006] In addition, as MEMS microphones become smaller, noise is generated by the connected power supply or electrical signals, and continuous efforts are needed to reduce this noise.

[0007] The technical problem that the present invention aims to solve is to provide a MEMS microphone.

[0008] To solve the above technical problem, the MEMS microphone according to the present embodiment comprises: a first substrate; a second substrate disposed on the first substrate; an adhesive layer disposed between the first substrate and the second substrate; a MEMS structure disposed on the second substrate; and a signal processing element spaced apart from the MEMS structure and disposed on the second substrate, and includes an acoustic hole penetrating the first substrate, the adhesive layer, and the second substrate in a first direction, wherein the size of the acoustic hole formed by the first substrate and the adhesive layer is larger than the size of the acoustic hole formed by the second substrate.

[0009] One surface of the second substrate may include a half-etched area in the region that overlaps with the acoustic hole formed by the first substrate and the adhesive layer in the first direction.

[0010] The second substrate includes a first pad wired to the signal processing element, and the first pad of the second substrate may be half-etched.

[0011] It includes a housing disposed on the second substrate, and among the other surfaces of the second substrate, the surface facing the inner surface of the housing may be half-etched.

[0012] The acoustic hole formed by the second substrate is circular, and the acoustic hole formed by the first substrate and the adhesive layer may be polygonal.

[0013] The length of the MEMS structure in the second direction perpendicular to the first direction may be smaller than the length of the acoustic hole formed by the first substrate and the adhesive layer in the second direction.

[0014] The acoustic hole formed by the first substrate and the adhesive layer in the first direction may include an area that does not overlap with the MEMS structure.

[0015] To solve the above technical problem, a MEMS microphone according to another embodiment of the present invention comprises: a first substrate; a second substrate disposed on the first substrate; an adhesive layer disposed between the first substrate and the second substrate; a MEMS structure disposed on the second substrate; and a signal processing element spaced apart from the MEMS structure and disposed on the second substrate, and includes an acoustic hole penetrating the first substrate, the adhesive layer, and the second substrate in a first direction, wherein the length of the acoustic hole formed by the first substrate and the adhesive layer in a second direction perpendicular to the first direction is greater than the length of the acoustic hole formed by the second substrate.

[0016] One surface of the second substrate may include a half-etched area in the region that overlaps with the acoustic hole formed by the first substrate and the adhesive layer in the first direction.

[0017] The second substrate includes a first pad wired to the signal processing element, and the first pad of the second substrate may be half-etched.

[0018] It includes a housing disposed on the second substrate, and among the other surfaces of the second substrate, the surface facing the inner surface of the housing may be half-etched.

[0019] The acoustic hole formed by the second substrate is circular, and the acoustic hole formed by the first substrate and the adhesive layer may be polygonal.

[0020] According to the embodiments, the front volume and back volume of the MEMS microphone can be increased, thereby improving the signal-to-noise ratio (hereinafter, SNR).

[0021] In addition, a bidirectional half-etching process can be applied, allowing the front volume and back volume of the MEMS microphone to be increased simultaneously without additional manufacturing costs.

[0022] Figure 1 shows a side cross-sectional view of a MEMS microphone.

[0023] Figure 2 is a top view illustrating the structure of a MEMS microphone.

[0024] FIG. 3 is a diagram illustrating the improvement of SNR performance through a MEMS microphone according to the present embodiment.

[0025] FIG. 4 is a side cross-sectional view of a MEMS microphone according to the present embodiment.

[0026] Figure 5 shows a side cross-sectional view of a MEMS microphone according to a modified example of Figure 4.

[0027] FIG. 6 shows a bottom view of a MEMS microphone according to the present embodiment.

[0028] FIG. 7 is a side cross-sectional view of a MEMS microphone according to another embodiment of the present invention.

[0029] Figure 8 shows a side cross-sectional view of a MEMS microphone according to a modified example of Figure 7.

[0030] FIG. 9 shows a bottom view of a MEMS microphone according to another embodiment of the present invention.

[0031] FIGS. 10 to 13 illustrate side cross-sectional views of a MEMS microphone according to another embodiment and a variation thereof of the present invention.

[0032] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[0033] However, the technical concept of the present invention is not limited to some of the described embodiments but can be implemented in various different forms, and within the scope of the technical concept of the present invention, one or more of the components among the embodiments may be selectively combined or substituted.

[0034] In addition, terms used in this embodiment (including technical and scientific terms) may be interpreted in a sense that is generally understood by those skilled in the art to which this embodiment belongs, unless explicitly and specifically defined otherwise. Terms that are commonly used, such as terms defined in advance, may be interpreted in consideration of their meaning in the context of the relevant technology.

[0035] Furthermore, the terms used in this embodiment are for the purpose of describing the embodiment and are not intended to limit the invention.

[0036] In this specification, the singular form may include the plural form unless specifically stated otherwise in the text, and when described as "at least one of A and B and C (or more than one)," it may include one or more of all combinations that can be formed from A, B, and C.

[0037] In addition, terms such as first, second, A, B, (a), (b), etc., may be used when describing the components of the present embodiment. These terms are used merely to distinguish the components from other components and are not intended to limit the essence, order, or sequence of the components.

[0038] And, where it is stated that a component is 'connected', 'combined', or 'connected' to another component, this may include not only cases where the component is directly 'connected', 'combined', or 'connected' to the other component, but also cases where it is 'connected', 'combined', or 'connected' due to another component located between the component and the other component.

[0039] Furthermore, when described as being formed or placed "above" or "below" each component, "above" or "below" includes not only cases where two components are in direct contact with each other, but also cases where one or more other components are formed or placed between the two components. Additionally, when expressed as "above" or "below," it may include the meaning of a downward direction as well as an upward direction relative to a single component.

[0040]

[0041] FIG. 1 is a side cross-sectional view of a MEMS microphone, FIG. 2 is a top view illustrating the structure of a MEMS microphone, FIG. 3 is a diagram for explaining the improvement of SNR performance through a MEMS microphone according to the present embodiment, FIG. 4 is a side cross-sectional view of a MEMS microphone according to the present embodiment, FIG. 5 is a side cross-sectional view of a MEMS microphone according to a modified example of FIG. 4, FIG. 6 is a bottom cross-sectional view of a MEMS microphone according to the present embodiment, FIG. 7 is a side cross-sectional view of a MEMS microphone according to another embodiment of the present invention, FIG. 8 is a side cross-sectional view of a MEMS microphone according to a modified example of FIG. 7, FIG. 9 is a bottom cross-sectional view of a MEMS microphone according to another embodiment of the present invention, FIG. 10 to FIG. 13 are side cross-sectional views of a MEMS microphone according to yet another embodiment of the present invention and a modified example thereof.

[0042] The MEMS microphone according to the present embodiment may include a first substrate (100), a second substrate (200), a MEMS structure (300), a housing (400), a signal processing element (500), and at least one capacitor (600).

[0043] The first substrate (100) is placed at the bottom of the MEMS microphone, has a plate shape, and can be electrically connected to the outside. A second substrate (200) is placed on the first substrate (100) so that the first substrate (100) and the second substrate (200) can form a single substrate unit, and the substrate unit can form an internal space together with the housing (400).

[0044] The first substrate (100) is a flexible substrate and may be a Chip on Film (COF) substrate or a flexible printed circuit board (FPCB). A Chip on Film (COF) substrate is a substrate formed by forming a circuit on a base film or mounting a component such as a chip, and has a film shape, so it is a substrate with a thickness that is considerably thinner than other substrates. By using a COF substrate as the substrate for a MEMS microphone, the thickness can be reduced compared to the case where a conventional rigid substrate is used.

[0045] The first substrate (100) is a COF substrate and may include a 2-metal COF substrate. The 2-metal COF may be formed in a structure in which a metal layer is laminated on the upper and lower surfaces of a base film so as to form a circuit or mount a device on both sides of a base film.

[0046] A flexible printed circuit board (FPCB) is a flexible circuit board that is also flexible and has a thinner thickness compared to a standard PCB board, so the thickness can be reduced by using a flexible printed circuit board as a substrate for a MEMS microphone. Other types of flexible substrates may be included. For example, the first substrate (100) may be an LCP (Liquid Crystal Polymer)-based FPCB, a PI (Polyimide)-based FPCB, or a PI-based COF, and the type of the first substrate (100) is not limited to the examples described above.

[0047] A hole (10) may be formed in the first substrate (100) at a position facing the lower part of the MEMS structure (300). The cross-sectional area of ​​the hole (10) may be circular, but is not limited thereto. Here, the hole (10) may be an acoustic hole.

[0048] The first substrate (100) may include a first pad. The first substrate (100) may have a first front pad (110) formed on its front surface to be electrically connected to a second pad of the second substrate (200) and a first rear pad (140, 150) formed to be electrically connected to a rear external configuration. That is, the first pad may include a first front pad (110) and a first rear pad (140, 150).

[0049] A plurality of first front pads (110) and a first connection circuit (120) connecting them may be formed on the front surface of the first substrate (100). Signal processing elements and capacitors may be electrically connected to the plurality of first front pads (110) and the first connection circuit (120). A plurality of first rear pads (140, 150) and a second connection circuit (not shown) may be formed on the rear surface of the first substrate (100).

[0050] The first substrate (100) may include via holes. In this case, the first substrate (100) may connect the first front pad (110) and the first rear pad (140, 150) formed on both sides through a metal layer (e.g., via) formed in the via holes. Some of the first pads may be exposed through the cavity (230) of the second substrate (200).

[0051]

[0052] The second substrate (200) is a substrate having a plate shape that is stacked to be placed on top of the first substrate (100). The second substrate (200) may include a rigid substrate, and may include, for example, a printed circuit board (PCB), a semiconductor substrate, or a ceramic substrate, a metal plate, etc. The second substrate (200) may be composed of a single layer or may be formed by stacking a plurality of substrates.

[0053] The second substrate (200) may include via holes. In this case, the second substrate (200) may connect circuits or components formed on both sides through a metal layer (e.g., via) formed in the via holes. Here, the via holes may be micro via holes and may be configured with a size of 25 μm or less.

[0054] The second substrate (200) may include an acoustic hole. The cross-sectional area of ​​the acoustic hole may be circular, but is not limited thereto. The hole formed in the second substrate (200) may be arranged to communicate with the hole formed in the first substrate (100), and a MEMS structure (300) may be arranged on the upper part of the hole communicating with the first substrate (100) and the second substrate (200).

[0055] The second substrate (200) can be electrically connected to the first substrate (100). The second substrate (200) may include a plurality of pads for electrically connecting to the first substrate (100).

[0056] The second substrate (200) may include a second pad. The second pad may include a plurality of second front pads formed on the front surface of the second substrate (200) and a plurality of second rear pads formed on the rear surface of the second substrate (200). That is, the second pad may include a second front pad (210) and a second rear pad. The second front pad (210) may be electrically connected to a signal processing element (500) and a capacitor (600), and the second rear pad may be electrically connected to the first front pad of the first substrate (100). The second rear pad of the second substrate (200) may be formed to have the same or similar shape and size as the first front pad of the first substrate (100), and may be electrically connected by being stacked so that at least a portion overlaps vertically.

[0057] The second substrate (200) may include one or more cavities (230). The second substrate (200) is placed on top of the first substrate (100), and the first substrate (100) may be exposed to the top of the second substrate (200) through the cavity (230) of the second substrate (200). The first substrate (100) may be exposed to the top of the second substrate (200) by having a first front pad (110), etc., placed in the space where the cavity (230) of the second substrate (200) is formed. In this case, since the upper surface of the first substrate (100) is positioned on the lower surface of the second substrate (200), the first front pad (110) formed on the upper surface of the first substrate (100) can be exposed to the upper surface of the second substrate (200) through the cavity (230) of the second substrate (200). The first front pad (110) of the first substrate (100) can be electrically connected to a signal processing element (500) and a capacitor (600) through the cavity (230) formed in the second substrate (200).

[0058] The second substrate (200) can be electrically connected to the signal processing element (500) and the capacitor (600). The second substrate (200) may include a plurality of pads, a plurality of connection circuits, and a plurality of vias for electrically connecting to the signal processing element (500) and the capacitor (600). The plurality of pads may overlap and contact the vias perpendicularly, or may contact an external substrate or element. The connection circuits may connect the second pads disposed on the same layer. The vias may be formed in via holes penetrating a base film or an insulating layer.

[0059] The second substrate (200) is laminated on top of the first substrate (100) so that the first substrate (100) and the second substrate (200) can form a single substrate unit. An adhesive layer (700) is disposed between the lower part of the second substrate (200) and the upper part of the first substrate (100) to bond the first substrate (100) and the second substrate (200). The adhesive layer (700) may have a shape and size corresponding to the shape and size of the first substrate (100) or the second substrate (200) as a means of bonding the first substrate (100) and the second substrate (200). The adhesive layer (700) may be made of a conductive material, but is not limited thereto and may be made of a non-conductive material.

[0060] A PSR (Photo Solder Resist) may be placed on the upper surface of the second substrate (200). The PSR is an ink used to protect and form circuits on the substrate. It is applied to the surface of the substrate and, after the circuits are formed, protects unnecessary parts to prevent corrosion or short circuits.

[0061] As the first substrate (100) and the second substrate (200) form a substrate unit, the second substrate (200) not only complements the rigidity of the first substrate (100) but also simplifies the pad design structure of the second substrate (200), and since the first substrate (100) is a flexible substrate that enables fine pitch, it is implemented to have a thinner thickness and increased fine pitch realization compared to a substrate unit using a rigid substrate where the existing pad design is performed, thereby having the effect of high freedom in circuit design.

[0062]

[0063] A housing (400), a MEMS structure (300), a signal processing element (500), and a capacitor (600) may be disposed on the second substrate (200). The capacitor (600) may be optionally disposed on the second substrate (200) as needed.

[0064] A housing (400) is a means for being placed on top of a second substrate (200) and forming a receiving space inside. The housing (400) may be formed in a cover shape with an open bottom surface, and the receiving space may be formed by the bottom surface of the housing (400) being joined to the top surface of the second substrate (200). The housing (400) and the second substrate (200) may be joined by solder being placed on top of the second substrate (200) and adhering to the bottom surface of the housing (400). Noise conditions such as SNR, PSR, and PSRR may be determined according to the size (Back Volume) of the receiving space formed inside the housing (400).

[0065] The housing (400) may be made of nickel silver or stainless steel (SUS). Nickel silver is a material containing 15-30% zinc and 10-20% nickel in copper, and allows for solder bonding without plating in its raw material state. Applying plating to the seating area of ​​the housing (400) can improve the solder bond adhesion. Ni+Au plating can be applied. Both electroless and electrolytic plating processes can be applied. Although stainless steel (SUS) contains Ni, the solder bond adhesion may decrease if plating is not performed. Therefore, plating can be applied. Unlike nickel silver, the plating adhesion on the surface of stainless steel may decrease when electroless plating is applied, so plating can be performed using an electrolytic plating process.

[0066] The MEMS structure (300) may be placed within a receiving space formed by a housing (400). The MEMS structure (300) may include a body (310), a backplate (330), and a diaphragm (320). The MEMS structure (300) may be placed on top of a second substrate (200), and the lower part of the MEMS structure (300) may be placed at a position adjacent to an acoustic hole (10) of the second substrate (200).

[0067] The body (310) is a means for forming a partition wall that surrounds the acoustic hole (10) formed in the second substrate (200). The body (310) can be coupled to the second substrate (200) so as to be electrically connected to the first substrate (100) through the second substrate (200). Additionally, an acoustic hole (360) communicating with the acoustic hole (10) can be formed in the body (310). The body (310) can be electrically connected to the second substrate (200).

[0068] An acoustic hole (360) may be formed in the body (310). When the body (310) is coupled to the second substrate (200), the acoustic hole (10) formed in the first substrate (100) and the second substrate (200) and the acoustic hole (360) of the body (310) may be arranged to communicate with each other, and thus, sound from the outside may be designed to flow in through the acoustic hole (10). The internal space formed by the acoustic hole (360) of the body (310) and the acoustic hole (10) formed in the first substrate (100) and the second substrate (200) may be referred to as a front volume (e.g., area A in FIG. 1).

[0069] The backplate (330) and the diaphragm (320) can be placed in the acoustic hole (10) formed in the body (310). The diaphragm (320) can vibrate due to the sound pressure of the sound when sound is introduced from the outside through the acoustic hole (10), and the backplate (330) can sense the acoustic signal by measuring the capacitance according to the vibration of the diaphragm (320). Although the backplate is shown as being located above the diaphragm (320) in the drawing, the diaphragm (320) may also be located above the backplate.

[0070] One or more body pads for electrical connection may be formed on the upper surface of the body (310). The body pads may be electrically connected to the backplate (330) and the diaphragm (320), and may be electrically connected to the signal processing element (500), which will be described later, via a wire. However, the connection method is merely an example, and as needed, the body pads may be placed in a form directly mounted on the pads of the second substrate (200) and electrically connected to the signal processing element (500) through a connection circuit. As the shape and material of the body pads are known technologies for electrical connection, a description thereof is omitted.

[0071] The signal processing element (500) is electrically connected to the MEMS structure (300) and can process electrical signals sensed from the MEMS structure (300). The MEMS structure (300) and the signal processing element (500) can be electrically connected through a body pad. For example, the MEMS structure (300) and the signal processing element (500) can be connected by a wire through wire bonding. As another example, the MEMS structure (300) and the signal processing element (500) can be electrically connected through a connection circuit of the second substrate (200) while mounted on the second substrate (200) in a flip-chip form. When the MEMS structure (300) and the signal processing element (500) are wire-bonded, a signal pad may be placed on the signal processing element (500) to be connected to the body pad of the MEMS structure (300) through wire bonding.

[0072] The signal processing element (500) can amplify a signal sensed from the MEMS structure (300). Here, the signal processing element (500) may include an Application-Specific Integrated Circuit (ASIC), but is not limited thereto. The signal processing element (500) may be formed as a single module or may be formed in the form of a chip. The signal processing element (500) may include an ASIC and an En-cap that coats the ASIC.

[0073] A signal processing element (500) may be placed on a second substrate (200). The signal processing element (500) may be electrically connected to a first substrate (100) through the second substrate (200). The signal processing element (500) may be placed on the second substrate (200) spaced apart from the MEMS structure (300). The signal processing element (500) may be placed in a receiving space formed inside a housing (400) spaced apart from the MEMS structure (300) and may receive a signal from the MEMS structure (300). Since signal transmission between the MEMS structure (300) and the signal processing element (500) takes place in the receiving space formed by the housing (400), external interference is reduced, and thereby noise can be reduced.

[0074] The signal processing element (500) can be electrically connected to the MEMS structure (300) and the first substrate (100). The signal processing element (500) can be electrically connected to the MEMS structure (300). The signal processing element (500) can be electrically connected to a body pad formed on the body (310) of the MEMS structure (300) by having a signal pad disposed on its upper surface. The signal pad of the signal processing element (500) and the body pad of the MEMS structure (300) can be electrically connected through wire bonding, thereby allowing the signal processing element (500) and the MEMS structure (300) to be electrically connected.

[0075] The signal processing element (500) can be electrically connected to the first substrate (100) by being electrically connected to the second substrate (200). The signal processing element (500) can be electrically connected to the second substrate (200) through wire bonding or electrically connected by being mounted on the second substrate (200) in the form of a flip chip. Since a plurality of pads are arranged on the second substrate (200), the signal processing element (500) can be electrically connected to the pads of the second substrate (200) through wire bonding or electrically connected by being mounted on the pads of the second substrate (200) in the form of a flip chip, and can be electrically connected to the first substrate (100) through the pads of the second substrate (200). The signal processed by the signal processing element (500) can be transmitted to an external location requiring the signal through one or more of the pads, connection circuits, and vias formed on the second substrate (200) and through the pads formed on the first substrate (100).

[0076] A capacitor (600) may be optionally placed on the upper part of the second substrate (200) as needed. When the capacitor (600) is placed, the performance of PSRR, which is RF-related noise, and the performance of PSR, which is power-related noise, may be improved. That is, through the capacitor (600), noise-related performance such as SNR, PSRR, and PSR can be improved. The capacitor (600) may be electrically connected to the signal processing element (500). As a result, the capacitor (600) can remove noise during the process of processing signals in the signal processing element (500).

[0077] The capacitor (600) is positioned on the upper part of the second substrate (200) and can be electrically connected to the signal processing element (500) and can be electrically connected to the first substrate (100) through the second substrate (200). The capacitor (600) can be electrically connected to the signal processing element (500) and the first substrate (100) via wires. The capacitor (600) can be electrically connected to the signal pad of the signal processing element (500) via wire bonding and can be electrically connected to the pad of the second substrate (200) via wire bonding.

[0078] However, the capacitor (600) can be electrically connected to the first substrate (100) not only by bonding via wires but also by mounting it on the second substrate (200) or the signal processing element (500) in a flip-chip form. For example, the capacitor (600) can be mounted on the second pad (210) formed on the upper part of the second substrate (200). The capacitor (600) can be mounted on the second front pad (210a) formed on the front surface (200a) of the second substrate (200). As the fine-pitch circuit implementation of the second substrate (200) becomes possible, the effect of securing mounting space for the capacitor is achieved.

[0079]

[0080] Referring to FIG. 3, the frequency band that can be covered by the MEMS microphone is the audible frequency band of 20 Hz to 20 kHz, the frequency band affected by the back volume is in the 20 Hz range, and the frequency band affected by the front volume is in the 20 kHz range. There is a limit to improving the SNR by increasing the back volume through thinning the first substrate (100) and the second substrate (200). Therefore, the present embodiment aims to improve the SNR performance by expanding the audible frequency band that can be covered by expanding the front volume of the MEMS microphone.

[0081] The front volume may refer to an internal space formed by the acoustic hole (360) of the body (310), the acoustic hole (10) formed in the first substrate (100) and the second substrate (200). The acoustic hole (10) formed in the first substrate (100) and the second substrate (200) may penetrate the first substrate (100), the adhesive layer (700), and the second substrate (200) in a first direction (z-axis direction).

[0082] Referring to FIG. 1, the size of the acoustic holes formed by the first substrate (100), the second substrate (200), and the adhesive layer (700) in the MEMS microphone was the same. In the MEMS microphone according to the present embodiment, the size of the acoustic holes formed by the first substrate (100) and the adhesive layer (700) may be larger than the size of the acoustic holes formed by the second substrate (200).

[0083] When the acoustic hole formed by the first substrate (100) and the adhesive layer (700) and the acoustic hole formed by the second substrate (200) are circular, the diameter (L2) of the acoustic hole formed by the first substrate (100) and the adhesive layer (700) may be larger than the diameter (L1) of the acoustic hole formed by the second substrate (200). In the second direction (x-axis direction) perpendicular to the first direction (z-axis direction), the length (L2) of the acoustic hole formed by the first substrate (100) and the adhesive layer (700) may be larger than the length (L1) of the acoustic hole formed by the second substrate (200).

[0084] The shape of the acoustic hole formed by the second substrate (200) may differ from the shape of the acoustic hole formed by the first substrate (100) and the adhesive layer (700). For example, the acoustic hole formed by the second substrate (200) may be circular, and the acoustic hole formed by the first substrate (100) and the adhesive layer (700) may be polygonal.

[0085] Referring to FIG. 5, one surface of the second substrate (200) may include a half-etched area (220) in a region that overlaps in a first direction (z-axis direction) with an acoustic hole formed by the first substrate (100) and the adhesive layer (700). Half etching is a process of etching a portion of the second substrate (200), which is a metal plate, to reduce its thickness, and can be implemented through a chemical method. The thickness of the half-etched area on the second substrate (200) may be smaller than the thickness of the area that is not half-etched.

[0086] In the following description, one side of the second substrate (200) may refer to the lower surface of the second substrate (200), and the other side of the second substrate (200) may refer to the upper surface of the second substrate (200). The thickness (L4) of the front volume below the lower surface of the second substrate (200) of FIG. 5, where a portion of the second substrate (200) is half-etched, may be greater than the thickness (L3) of the front volume below the lower surface of the second substrate (200) of FIG. 4, where the second substrate (200) is not half-etched.

[0087] Accordingly, the size of the front volume of the MEMS microphone (region C in FIG. 5) in which one side of the second substrate (200) is half-etched may be larger than the size of the front volume of the MEMS microphone (region B in FIG. 4) in which one side of the second substrate (200) is not half-etched. When one side of the second substrate (200) is half-etched, the front volume of the MEMS microphone can be expanded, thereby improving SNR performance.

[0088]

[0089] Referring to FIG. 6, which is a bottom view of a MEMS microphone according to the present embodiment, the rear surface of the first substrate (100) may have an area (1) where a housing (400) is placed, a first rear pad (140, 150), and an acoustic hole formed therein. The size of the acoustic hole (3) formed by the first substrate (100) and the adhesive layer (700) is formed larger than the size of the acoustic hole (2) formed by the second substrate (200), and thereby the lower surface of the second substrate (200) may be exposed.

[0090] The MEMS microphone according to the modified example of the present invention shown in FIGS. 7 to 9 can greatly expand the size of the acoustic hole formed by the first substrate (100), the second substrate (200), and the adhesive layer (700) within an area that does not interfere with the first rear pad (140, 150) formed on the rear surface of the first substrate (100).

[0091] FIG. 9 illustrates a bottom view of the MEMS microphone shown in FIG. 7 and FIG. 8. Referring to FIG. 9, the shape of the acoustic hole formed by the first substrate (100), the second substrate (200), and the adhesive layer (700) can be formed in a convex shape. The shape of the acoustic hole formed by the first substrate (100), the second substrate (200), and the adhesive layer (700) can be varied in many ways. The shape of the acoustic hole formed by the second substrate (200) may be different from the shape of the acoustic hole formed by the first substrate (100) and the adhesive layer (700). The size of the acoustic hole (3) formed by the first substrate (100) and the adhesive layer (700) is formed to be larger than the size of the acoustic hole (2) formed by the second substrate (200), and thereby the bottom surface of the second substrate (200) may be exposed.

[0092] Referring to FIGS. 7 and 8, the length in the second direction (x-axis direction) perpendicular to the first direction (z-axis direction) of the MEMS structure (300) may be smaller than the length (L5) in the second direction (x-axis direction) of the acoustic hole formed by the first substrate (100) and the adhesive layer (700). The acoustic hole formed by the first substrate (100) and the adhesive layer (700) in the first direction (z-axis direction) may include an area that does not overlap with the MEMS structure (300).

[0093] Referring to FIG. 8, one surface of the second substrate (200) may include a half-etched area (220) in a region that overlaps in a first direction (z-axis direction) with an acoustic hole formed by the first substrate (100) and the adhesive layer (700). The thickness of the half-etched area on the second substrate (200) may be smaller than the thickness of the area that is not half-etched.

[0094] The thickness (L6) of the front volume below the lower surface of the second substrate (200) of FIG. 8, in which the second substrate (200) is half-etched, may be greater than the thickness (L3) of the front volume below the lower surface of the second substrate (200) of FIG. 7, in which the second substrate (200) is not half-etched. Accordingly, the size of the front volume (region E of FIG. 8) of the MEMS microphone in which the second substrate (200) is half-etched may be greater than the size of the front volume (region D of FIG. 7) of the MEMS microphone in which the second substrate (200) is not half-etched.

[0095]

[0096] FIG. 10 is a drawing in which a half-etched area is added to a portion of the other side of the second substrate in FIG. 4, FIG. 11 is a drawing in which a half-etched area is added to a portion of the other side of the second substrate in FIG. 5, FIG. 12 is a drawing in which a half-etched area is added to a portion of the other side of the second substrate in FIG. 7, FIG. 13 is a drawing in which a half-etched area is added to a portion of the other side of the second substrate in FIG. 8, and any description of FIG. 11 to FIG. 13 that overlaps with the description of FIG. 10 is omitted.

[0097] Referring to FIGS. 10 to 13, the side of the second substrate (200) facing the inner surface of the housing (400) may include a half-etched area (230). The second substrate (200) may include a second pad (210) wire-connected to a signal processing element (500). The second pad (210) of the second substrate (200) may be half-etched. The second pad (210) of the second substrate (200) may be formed in the half-etched area (230).

[0098] The size of the back volume of the MEMS microphone (region G in FIGS. 10 to 13) in which the other side of the second substrate (200) is half-etched may be larger than the size of the back volume of the MEMS microphone in which the other side of the second substrate (200) is not half-etched (region F in FIGS. 4, 5, 7 and 8). When the other side of the second substrate (200) is half-etched, the back volume of the MEMS microphone can be expanded, thereby improving SNR performance.

[0099] The half-etching process of the metal plate can simultaneously apply bidirectional half-etching. Therefore, without additional manufacturing costs, a half-etched area can be formed on one side of the second substrate (200) and the other side of the second substrate (200) simultaneously. That is, the back volume and the front volume can be expanded simultaneously through the bidirectional half-etching process of the second substrate (200).

[0100] Those skilled in the art related to the embodiments described above will understand that they may be implemented in modified forms without departing from the essential characteristics of the description. Therefore, the disclosed methods should be considered in an illustrative rather than a restrictive sense. The scope of the invention is defined by the claims, not by the foregoing description, and all variations within the scope of equivalence should be interpreted as being included in the invention.

Claims

1. First substrate; A second substrate disposed on the first substrate; An adhesive layer disposed between the first substrate and the second substrate; A MEMS structure disposed on the second substrate; and It includes a signal processing element spaced apart from the MEMS structure and disposed on the second substrate, and The acoustic hole penetrating the first substrate, the adhesive layer, and the second substrate in a first direction is included. A MEMS microphone in which the size of the acoustic hole formed by the first substrate and the adhesive layer is larger than the size of the acoustic hole formed by the second substrate.

2. In Paragraph 1, A MEMS microphone in which one surface of the second substrate includes a half-etched area in the region overlapping in the first direction with the acoustic hole formed by the first substrate and the adhesive layer.

3. In Paragraph 1, The second substrate includes a first pad wired to the signal processing element, and The first pad of the second substrate is a MEMS microphone that undergoes half-etching treatment.

4. In Paragraph 1, It includes a housing disposed on the second substrate, and A MEMS microphone in which the surface of the other side of the second substrate facing the inner surface of the housing is half-etched.

5. In Paragraph 1, The acoustic hole formed by the second substrate is circular, and A MEMS microphone in which the acoustic hole formed by the first substrate and the adhesive layer is polygonal.

6. In Paragraph 1, A MEMS microphone in which the length in the second direction perpendicular to the first direction of the MEMS structure is smaller than the length in the second direction of the acoustic hole formed by the first substrate and the adhesive layer.

7. In Paragraph 1, A MEMS microphone in which the acoustic hole formed by the first substrate and the adhesive layer in the first direction includes an area that does not overlap with the MEMS structure.

8. First substrate; A second substrate disposed on the first substrate; An adhesive layer disposed between the first substrate and the second substrate; A MEMS structure disposed on the second substrate; and It includes a signal processing element spaced apart from the MEMS structure and disposed on the second substrate, and The acoustic hole penetrating the first substrate, the adhesive layer, and the second substrate in a first direction is included. A MEMS microphone in which the length of the acoustic hole formed by the first substrate and the adhesive layer in a second direction perpendicular to the first direction is greater than the length of the acoustic hole formed by the second substrate.

9. In Paragraph 8, A MEMS microphone in which one surface of the second substrate includes a half-etched area in the region overlapping in the first direction with the acoustic hole formed by the first substrate and the adhesive layer.

10. In Paragraph 8, The second substrate includes a first pad wired to the signal processing element, and The first pad of the second substrate is a MEMS microphone that undergoes half-etching treatment.

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