Microphone and method for manufacturing same

Abstract

The present application provides a microphone and a method for manufacturing same. The microphone comprises a housing in which a cavity is formed, and a photonic crystal assembly and a photoelectric module respectively fixed in the cavity. The housing is provided with a sound inlet communicating the cavity with the outside. The photonic crystal assembly comprises a diaphragm provided in the cavity and a photonic crystal back plate fixed to the side of the diaphragm facing the photoelectric module; a gap is formed between the diaphragm and the photonic crystal back plate; and an array of through holes are provided on the photonic crystal back plate. The photoelectric module is used for emitting laser light to the diaphragm, and is further used for receiving laser light reflected back from the photonic crystal back plate and the diaphragm and performing photoelectric signal conversion processing on the received laser light. The present application provides a photonic crystal-based optical microphone, and by means of the arrangement of the photonic crystal back plate structure, the sensitivity and the signal-to-noise ratio of the microphone can be effectively improved.

Description

Microphone and method for manufacturing the same Technical Field

[0001] The present invention belongs to the technical field of photoacoustic devices, and in particular relates to a microphone and a method for manufacturing the microphone. Background Art

[0002] Mobile communication technology has developed rapidly in recent years, with consumers increasingly using mobile communication devices such as mobile phones, internet-enabled mobile phones, personal digital assistants, and other devices that communicate over dedicated communication networks. A micro-electro-mechanical system (MEMS) microphone is an electroacoustic transducer fabricated using micromachining technology. It features a small size, excellent frequency response, and low noise. As electronic devices become increasingly compact and lightweight, MEMS microphones are increasingly being used in these devices.

[0003] In related technologies, microphones include a silicon substrate and a flat-plate capacitor consisting of a polysilicon diaphragm and a silicon nitride backplate. The diaphragm and the silicon nitride backplate are opposite and separated by a certain distance. The diaphragm vibrates under the action of sound waves, causing the distance between the diaphragm and the silicon nitride backplate to change, which in turn changes the capacitance of the flat-plate capacitor, thereby converting the sound wave signal into an electrical signal. However, this type of capacitive microphone has poor sensitivity and requires a trade-off between sensitivity and operating bandwidth, making it difficult to achieve high sensitivity and high bandwidth, making it difficult to meet user needs. Technical issues

[0004] The purpose of the present application is to provide a microphone and a method for manufacturing the microphone, which can solve the problem in the related art that the microphone sensitivity and working bandwidth are in balance with each other, making it difficult to achieve high sensitivity and high bandwidth. Technical Solutions

[0005] The technical solution of this application is as follows:

[0006] On the one hand, a microphone is provided, comprising a shell forming a cavity, a photonic crystal component fixed in the cavity, and an optoelectronic module fixed in the cavity and spaced apart from the photonic crystal component; the shell has a sound inlet connecting the cavity and the outside; the photonic crystal component comprises a diaphragm arranged in the cavity and a photonic crystal backplate fixed to the diaphragm on the side facing the optoelectronic module, a gap being provided between the diaphragm and the photonic crystal backplate, and an array of through holes being provided on the photonic crystal backplate; the optoelectronic module is used to emit laser light toward the diaphragm, and is also used to receive laser light reflected back from the photonic crystal backplate and the diaphragm, and to perform optoelectronic signal conversion processing on the received laser light.

[0007] Another aspect provides a method for manufacturing a microphone, comprising the following steps:

[0008] A wafer substrate is provided, and a diaphragm is formed by etching the wafer substrate; wherein the wafer substrate includes a device layer and a base layer connected to the device layer, and the diaphragm is formed on the device layer;

[0009] Deposition processing is performed on the side of the diaphragm away from the base layer to obtain a support layer and a back plate layer; wherein one side of the support layer is connected to the device layer, and the other side is connected to the back plate layer;

[0010] etching an array of through holes on the backplane layer to form a photonic crystal structure;

[0011] The redundant materials in the base layer and the supporting layer are removed respectively to obtain a photonic crystal component. Beneficial effects

[0012] The beneficial effects of the present application are: using the principle of optical interference to detect external sound wave signals, and adjusting the band gap and transmittance of the photonic crystal by setting a through-hole array on the photonic crystal backplane, thereby significantly improving the reflectivity of the photonic crystal backplane, thereby improving the sensitivity and signal-to-noise ratio of the optical microphone. In the present application, the sensitivity of the microphone is mainly improved by means of the optical interference detection principle, so the structural design of the photonic crystal backplane can improve the working bandwidth of the microphone, thereby achieving high sensitivity and high bandwidth of the microphone, and solving the contradiction between the microphone sensitivity and bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0014] FIG1 is a cross-sectional schematic diagram of the overall structure of a microphone provided by a first embodiment of the present application;

[0015] FIG2 is a cross-sectional schematic diagram of a photonic crystal component provided in the first embodiment of the present application;

[0016] FIG3 is a schematic structural diagram of a photonic crystal backplane provided in the first embodiment of the present application;

[0017] FIG4 is a schematic diagram of a basic flow chart of a method for manufacturing a microphone provided in a second embodiment of the present application;

[0018] FIG5 is a process flow chart of a method for manufacturing a microphone provided in the second embodiment of the present application. Modes for Carrying Out the Invention

[0019] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the present application is further described below with reference to the accompanying drawings and embodiments. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0020] In the description of the embodiments of the present application, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0021] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of this application, the meaning of "plurality" is two or more, unless otherwise clearly specified.

[0022] In the embodiments of the present application, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections, electrical connections; direct connections, or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0023] As shown in Figures 1-3, in order to solve the problem of insufficient microphone sensitivity in related arts, the first embodiment of the present application provides a microphone, comprising a housing 1 having a cavity 1a, a photonic crystal component 3 fixed in the cavity 1a, and a photoelectric module 2 fixed in the cavity 1a and spaced apart from the photonic crystal component 3; the housing 1 has a sound inlet 1b connecting the cavity 1a and the outside; the photonic crystal component 3 includes a diaphragm 32 disposed in the cavity 1a and a photonic crystal backplate 31 fixed to the diaphragm 32 and facing the photoelectric module 2. There is a gap between the diaphragm 32 and the photonic crystal backplate 31, and a through-hole array 311 is provided on the photonic crystal backplate 31; the optoelectronic module 2 is used to emit laser light. After the laser light emitted by the optoelectronic module 2 reaches the photonic crystal backplate 31, part of the laser light is reflected on the photonic crystal backplate 31, and the other part of the laser light is transmitted through the photonic crystal backplate 31 and then reaches the diaphragm 32 and is reflected again. The optoelectronic module 2 is also used to receive the laser light reflected back from the photonic crystal backplate 31 and the diaphragm 32, and to perform optoelectronic signal conversion processing on the received laser light.

[0024] Specifically, when the microphone is working, the optoelectronic module 2 can emit a laser toward the photonic crystal backplate 31. After the laser (incident beam a) emitted by the optoelectronic module 2 reaches the photonic crystal backplate 31, part of the laser is reflected by the photonic crystal backplate 31 (the reflected laser is called the first reflected beam b), and the other part of the laser is transmitted through the photonic crystal backplate 31 and reaches the diaphragm 32 and is reflected again (the reflected laser is called the second reflected beam c). The first reflected beam b and the second reflected beam c will produce an interference effect during the propagation process; when the external sound wave signal is transmitted through the sound inlet 1b to the diaphragm 32, the sound wave signal causes the diaphragm 32 to vibrate, thereby changing the phase of the second reflected beam c; the effect of the sound wave signal changes the phase of the second reflected beam c, while the phase of the first reflected beam b remains unchanged, causing the phase difference between the first reflected beam b and the second reflected beam c in the coherent laser beam to change, thereby causing the interference light intensity value received by the optoelectronic module 2 to change. Therefore, the change in photocurrent detected by the optoelectronic module 2 can correspond to the detection of the sound wave signal. In a photonic crystal structure, the periodic variation in the refractive index of light creates an optical bandgap, which in turn controls the movement of light within the structure. In this embodiment, the photonic crystal backplate 31 is machined with a photonic crystal structure. By providing a through-hole array 311 on the backplate 31, the bandgap and transmittance of the photonic crystal are adjusted, significantly improving the reflectivity of the backplate 31 and, in turn, the sensitivity of the optical microphone.

[0025] In some implementations of this embodiment, the through hole array 311 includes a plurality of through holes penetrating the photonic crystal back plate 31 , and the cross-sectional shape of the through holes is at least one of circular, triangular, square, prismatic, pentagonal, and hexagonal.

[0026] Specifically, in this embodiment, the through holes can be formed by etching, that is, a through hole array 311 is etched on the photonic crystal backplane 31 to form a two-dimensional photonic crystal structure. The through holes constituting the two-dimensional photonic crystal structure can be arranged periodically or aperiodically, and the cross-sectional shape of these through holes can be a combination of one or more of circular, triangular, square, prismatic, pentagonal, and hexagonal shapes. It is understood that in other embodiments, the cross-sectional shape of the through holes can also be a trapezoidal, elongated, or even irregular shape, etc., which is not limited here.

[0027] In some implementations of this embodiment, the diaphragm 32 can be a spring-supported diaphragm 32 or a fully solid diaphragm 32. The shape of the diaphragm 32 can be square, circular, or oval. Of course, in other embodiments, the shape of the diaphragm 32 can also be a runway shape, a rounded rectangle, etc., which is not limited here. The diaphragm 32 can also be provided with corrugations, such as circular corrugations, sunburst corrugations, water corrugations, etc. These corrugations act as reinforcements, increasing the rigidity of the diaphragm 32 and the effective radiation area of ​​the diaphragm 32, while also improving the damping effect.

[0028] In some implementations of this embodiment, the photonic crystal assembly 3 further includes a support structure 33 positioned between the diaphragm 32 and the photonic crystal backplate 31. The support structure 33, the photonic crystal backplate 31, and the diaphragm 32 enclose a first sub-cavity 3a. A portion of the laser light that reaches the photonic crystal backplate 31, after being emitted and transmitted by the photonic crystal backplate 31, passes through the first sub-cavity 3a and reaches the diaphragm 32. It is then reflected by the diaphragm 32 and then sequentially passes through the first sub-cavity 3a and the photonic crystal backplate 31 to reach the optoelectronic module 2. The support structure 33 may include a first support 331 and a second support 332, each having the same thickness. The diaphragm 32 includes a middle portion and an edge portion surrounding the middle portion. The first support 331 and the second support 332 are both fixed between the edge portion of the diaphragm 32 and the photonic crystal backplate 31. The first support 331 and the second support 332 may be made of one of silicon nitride and silicon dioxide, respectively.

[0029] In some implementations of this embodiment, the photonic crystal component 3 further includes a substrate 34 fixed between the wall of the cavity 1a and the diaphragm 32 and forming a second sub-cavity 3b, and the second sub-cavity 3b connects the sound inlet 1b and the diaphragm 32. After the sound wave signal reaches the sound inlet 1b, it can reach the diaphragm 32 through the second sub-cavity 3b, causing the diaphragm 32 to vibrate. The second sub-cavity 3b can be obtained by etching the material of the substrate 34. Furthermore, in some implementations of this embodiment, the substrate 34 includes a buried oxide layer 341 connected to the diaphragm 32, and a substrate layer 342 connected to the side of the buried oxide layer 341 facing away from the diaphragm 32, and the side of the substrate layer 342 facing away from the buried oxide layer 341 is fixed to the wall of the cavity 1a. The raw material of the substrate layer 342 can be silicon. The substrate layer 342, the buried oxide layer 341, the diaphragm 32, the support structure 33, and the photonic crystal backplane 31 are integrated to form the photonic crystal assembly 3. The side of the substrate layer 342 facing away from the buried oxide layer 341 can be fixed to the housing 1 by bonding or welding. The thickness of the substrate layer 342 can be 400µm, and the thickness of the buried oxide layer 341 can be 2µm.

[0030] In some implementations of this embodiment, the optoelectronic module 2 includes an integrated circuit chip 21 fixed within the cavity 1a, a laser light source 22 electrically connected to the integrated circuit chip 21, and a light detector 23 electrically connected to the integrated circuit chip 21. The laser light source 22 and the light detector 23 are spaced apart from each other and can be fixed to a side of the cavity 1a away from the photonic crystal component 3 by bonding or welding. The laser light source 22 and the light detector 23 are electrically connected to the integrated circuit chip 21. The laser light source 22 is used to emit laser light toward the photonic crystal component 3; the light detector 23 is used to detect laser light reflected from the photonic crystal component 3. The integrated circuit chip 21 is formed with a control or central processing unit that can control the operation of the laser light source 22 and the light detector 23 and analyze and process data detected by the light detector 23.

[0031] As shown in Figures 4 and 5, the second embodiment of the present application provides a method for manufacturing a microphone, comprising the following steps:

[0032] Step S1: providing a wafer substrate, and etching the wafer substrate to form a diaphragm.

[0033] Specifically, in this embodiment, the wafer substrate may be an SOI wafer, comprising a device layer and a base layer connected to the device layer. The diaphragm is formed on the device layer. The device layer may be made of silicon. Reactive ion etching (RIE) is a highly anisotropic and selective dry etching technique. Etching is performed using molecular gas plasma in a vacuum system, utilizing ion-induced chemical reactions to achieve anisotropic etching. Specifically, the ion energy is used to form a readily etchable damage layer on the surface of the etched layer, promoting chemical reactions while also removing surface products to reveal a clean etched surface. RIE can etch materials such as silicon, silicon dioxide, semiconductor materials, and polymers. In this embodiment, RIE is used to etch the diaphragm shape into the device layer. The etching depth is equal to the thickness of the device layer, which may be 0.8µm. Furthermore, in some specific implementations of this embodiment, step S1 includes: S11, providing an SOI wafer, and performing standard RCA cleaning on the SOI wafer; S12, etching a diaphragm shape on the device layer of the SOI wafer using reactive ion etching technology.

[0034] Step S2: Deposition processing is performed on the side of the diaphragm facing away from the base layer to obtain a support layer and a back plate layer.

[0035] Specifically, one side of the support layer is connected to the device layer, and the other side is connected to the back plate layer. The support layer and the back plate layer can be formed on the side of the diaphragm away from the base layer by combining vapor deposition technology, wet etching technology, etc.

[0036] Step S3: etching a through hole array on the backplane layer to form a photonic crystal structure.

[0037] Specifically, reactive ion etching technology can be used to etch a through hole array on the back plate layer. The cross-sectional shape of the through holes in the through hole array can be circular, triangular, square, prismatic, pentagonal, hexagonal, irregular, etc.

[0038] Step S4: removing excess materials from the base layer and the support layer respectively to obtain a photonic crystal component.

[0039] Specifically, the first sub-cavity can be etched in the support layer using an etching technique, and the second sub-cavity can be etched on the base layer using an etching technique, thereby obtaining a photonic crystal component.

[0040] In this embodiment, after the photonic crystal assembly is manufactured, the method for manufacturing the microphone further includes: separately installing the photonic crystal assembly and the optoelectronic module into the cavity of the housing and fixing them to form a structurally complete microphone. The method for fixing the photonic crystal assembly and the optoelectronic module to the housing can be bonding, welding, etc., which is not limited here. When the photonic crystal assembly is applied to the microphone, the photonic crystal backplate and the diaphragm can respectively reflect the laser beam emitted by the optoelectronic module. The laser beam reflected by the photonic crystal backplate and the laser beam reflected by the diaphragm can produce an interference effect. When the external acoustic wave signal is transmitted to the diaphragm, it causes the diaphragm to vibrate. The diaphragm vibration can change the phase difference of the coherent light beam. The optoelectronic module can detect the acoustic wave signal by detecting the photocurrent corresponding to the coherent light beam, thereby realizing the function of photoacoustic conversion. In this embodiment, a photonic crystal structure is formed by etching a through-hole array on the backplate layer. The through-hole array structure is used to adjust the band gap and transmittance of the photonic crystal structure, thereby improving the reflectivity of the photonic crystal backplate and thereby improving the sensitivity of the optical microphone.

[0041] In some implementations of this embodiment, the above-mentioned step S2 includes: step S21, depositing a silicon dioxide layer on the side of the diaphragm facing away from the base layer; step S22, etching the silicon dioxide layer to form an intermediate having a gap running through the entire silicon dioxide layer; step S23, depositing silicon nitride on the gap to obtain a supporting layer; step S24, depositing silicon material on the side of the supporting layer facing away from the diaphragm to obtain a backplate layer.

[0042] Specifically, a silicon dioxide layer can be deposited on the side of the diaphragm facing away from the substrate layer using plasma-enhanced chemical vapor deposition (PECVD). This involves using microwaves or radio frequency to generate a localized plasma containing the atoms that make up the film. The plasma is highly chemically active and readily reacts, allowing the desired silicon dioxide film to be deposited on the diaphragm (device layer), facilitating the formation of the first sub-cavity between the diaphragm and the photonic crystal backplate during subsequent processing. This method offers a high deposition rate, a low base temperature, and high-quality silicon dioxide layers. The silicon dioxide layer can be obtained by wet etching, forming an intermediate with voids extending throughout the silicon dioxide layer. A silicon nitride layer can be deposited on the intermediate using vapor deposition to form a support layer. Depositing the silicon nitride layer prevents damage to the support structure formed by the silicon dioxide layer between the diaphragm and the photonic crystal backplate during subsequent processing. The backplate layer can be formed by depositing silicon or silicon nitride on the support layer using PECVD again.

[0043] In some implementations of this embodiment, the above step S4 includes: S41, etching the support layer in a BOE solution to remove excess silicon dioxide material in the support layer and form a first sub-cavity; S42, etching the base layer to form a base having a second sub-cavity to obtain a photonic crystal component.

[0044] Specifically, the silicon dioxide layer is etched in a BOE solution to release the photonic crystal backplane (forming a first sub-cavity between the backplane layer and the diaphragm). The base layer in this embodiment includes a buried oxide layer and a substrate layer. The thickness of the substrate layer can be 400µm, and the thickness of the buried oxide layer can be 2µm. The buried oxide layer is connected between the diaphragm and the substrate layer. That is, the above-mentioned wafer substrate includes a device layer, a buried oxide layer, and a substrate layer connected in sequence. Furthermore, in some specific implementations of this embodiment, step S42 includes: S421, etching the substrate layer using reactive ion etching technology; S422, etching the buried oxide layer using reactive ion etching technology to obtain a second sub-cavity that penetrates the entire base layer, thereby obtaining the desired photonic crystal component.

[0045] It should be noted that for the aforementioned method embodiments, for ease of description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that this application is not limited by the order of the actions described, because according to this application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in this specification are all preferred embodiments, and the actions and modules involved are not necessarily required by this application.

[0046] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0047] The above is only an implementation method of the present application. It should be pointed out that for ordinary technicians in this field, improvements can be made without departing from the creative concept of the present application, but these all fall within the scope of protection of the present application.

Claims

1. A microphone, comprising a housing with a cavity, a photonic crystal component fixed in the cavity, and an optoelectronic module fixed in the cavity and spaced from the photonic crystal component; the housing has a sound inlet connecting the cavity and the outside; characterized in that: The photonic crystal component includes a diaphragm arranged in the cavity and a photonic crystal backplate fixed to the diaphragm and facing the optoelectronic module. There is a gap between the diaphragm and the photonic crystal backplate, and a through-hole array is arranged on the photonic crystal backplate. The optoelectronic module is used to emit laser light toward the diaphragm, and the optoelectronic module is also used to receive laser light reflected back from the photonic crystal backplate and the diaphragm and perform optoelectronic signal conversion processing on the received laser light.

2. The microphone according to claim 1, characterized in that The through hole array includes a plurality of through holes penetrating the photonic crystal back plate, and the cross-sectional shape of the through holes is at least one of circular, triangular, square, prism, pentagonal, and hexagonal.

3. The microphone according to claim 1, characterized in that The diaphragm is one of a spring-supported diaphragm and a fully solid diaphragm, and / or the shape of the diaphragm is one of a square, a circle, and an ellipse.

4. The microphone according to claim 1, characterized in that The photonic crystal component further includes a supporting structure located between the diaphragm and the photonic crystal back plate, and the supporting structure, the photonic crystal back plate and the diaphragm enclose a first sub-cavity.

5. The microphone according to claim 1, characterized in that The photonic crystal component further comprises a substrate fixed between the wall surface of the cavity and the diaphragm, wherein the substrate forms a second sub-cavity communicating with the sound inlet and the diaphragm.

6. The microphone according to claim 5, characterized in that The substrate comprises an oxide-buried layer connected to the diaphragm and a substrate layer connected to a side of the oxide-buried layer away from the diaphragm, and a side of the substrate layer away from the oxide-buried layer is fixed to a wall surface of the cavity.

7. The microphone according to claim 1, characterized in that The optoelectronic module comprises an integrated circuit chip fixed in the cavity, a laser light source electrically connected to the integrated circuit chip, and a light detector electrically connected to the integrated circuit chip, wherein the laser light source and the light detector are arranged at intervals.

8. A method for manufacturing a microphone, characterized in that: The following steps are involved: A wafer substrate is provided, and the wafer substrate is etched to form a diaphragm; wherein the wafer substrate comprises a device layer and a base layer connected to the device layer, and the diaphragm is formed on the device layer; Deposition processing is performed on the side of the diaphragm away from the base layer to obtain a support layer and a back plate layer; wherein one side of the support layer is connected to the device layer, and the other side is connected to the back plate layer; etching a through hole array on the backplane layer to form a photonic crystal structure; The redundant materials in the base layer and the support layer are removed respectively to obtain a photonic crystal component.

9. The method for manufacturing a microphone according to claim 8, characterized in that: The step of performing deposition processing on the side of the diaphragm away from the base layer to obtain a support layer and a back plate layer comprises: Depositing a silicon dioxide layer on a side of the diaphragm facing away from the base layer; Etching the silicon dioxide layer to form an intermediate having a void penetrating the entire silicon dioxide layer; Depositing silicon nitride on the gap to obtain a supporting layer; A silicon material is deposited on a side of the support layer away from the diaphragm to obtain a back plate layer.

10. The method for manufacturing a microphone according to claim 8, characterized in that: The step of removing the redundant materials in the base layer and the support layer respectively to obtain the photonic crystal component comprises: Etching the support layer in a BOE solution to remove excess silicon dioxide material in the support layer and form a first sub-cavity; The base layer is etched to form a base with a second sub-cavity, thereby obtaining a photonic crystal component.

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