阅读说明：本技术 一种mems矢量传声器及其制备方法 (MEMS vector microphone and preparation method thereof ) 是由 魏晓村 刘云飞 周瑜 冯杰 于 2021-06-18 设计创作，主要内容包括：本发明公开了一种MEMS矢量传声器及其制备方法,该MEMS矢量传声器包括：基底、绝热层、导热层和敏感层；其中,所述敏感层包括：电极、加热电阻和传感电阻；在所述基底顶部开设有前后贯通的凹槽,以在所述基底的左右两侧形成两个凸台；所述绝热层分别布置在所述两个凸台上,且在所述绝热层上布置有所述电极；所述导热层被所述绝热层支撑,以悬空在所述凹槽上；所述加热电阻和传感电阻布置在所述导热层上,且所述加热电阻和传感电阻的两端分别与所述电极连接；本发明解决了现有MEMS矢量传声器因在低频和高频频带内响应特性衰减而引起的声信号在接收和后续处理上产生严重失真的技术问题。(The invention discloses an MEMS vector microphone and a preparation method thereof, the MEMS vector microphone comprises: the heat-conducting layer is arranged on the substrate; wherein the sensitive layer comprises: electrodes, heating resistors and sensing resistors; a groove which is through from front to back is formed in the top of the substrate, so that two bosses are formed on the left side and the right side of the substrate; the heat insulating layers are respectively arranged on the two bosses, and the electrodes are arranged on the heat insulating layers; the heat conduction layer is supported by the heat insulation layer to be suspended on the groove; the heating resistor and the sensing resistor are arranged on the heat conducting layer, and two ends of the heating resistor and the two ends of the sensing resistor are respectively connected with the electrodes; the invention solves the technical problem that the sound signal of the existing MEMS vector microphone generates serious distortion in receiving and subsequent processing because of the attenuation of the response characteristic in low-frequency and high-frequency bands.)

1. A MEMS vector microphone for measuring acoustic field particle velocity, comprising: the heat-conducting layer is arranged on the substrate; wherein the sensitive layer comprises: electrodes, heating resistors and sensing resistors;

a groove which is through from front to back is formed in the top of the substrate, so that two bosses are formed on the left side and the right side of the substrate; the heat insulating layers are respectively arranged on the two bosses, and the electrodes are arranged on the heat insulating layers; the heat conduction layer is supported by the heat insulation layer to be suspended on the groove; the heating resistor and the sensing resistor are arranged on the heat conducting layer, and two ends of the heating resistor and the two ends of the sensing resistor are respectively connected with the electrodes;

the heat insulating layer is used for isolating heat conduction among the substrate, the heat conducting layer and the sensitive layer;

the heat conduction layer is used for increasing heat diffusion between the heating resistor and the sensing resistor;

the heating resistor is used for forming a space temperature field under current excitation;

the sensing resistor is used for generating a temperature difference when the space temperature field is subjected to forced convection disturbance due to the fact that sound waves are introduced into the particle vibration speed, so that the resistance difference can be demodulated through the bridge circuit to measure the particle vibration speed of the sound field.

2. The MEMS vector microphone of claim 1, wherein the sensitive layer comprises: six electrodes, a heating resistor and two sensing resistors, just two sensing resistors are located heating resistor both sides.

3. The MEMS vector microphone of claim 1, wherein the temperature coefficient of resistance of the heating resistor is zero and the temperature coefficient of resistance of the sensing resistor is greater than 2000ppm/° c.

4. The MEMS vector microphone of claim 1, wherein the substrate is made of any one of the following materials: monocrystalline silicon, polycrystalline silicon, silicon oxide.

5. The MEMS vector microphone of claim 1, wherein the thermal insulation layer is made of any one of the following materials: silicon oxide, porous silicon oxide film.

6. The MEMS vector microphone of claim 1, wherein the thermally conductive layer is made of any one of the following materials: silicon carbide and graphene.

7. A method for manufacturing a MEMS vector microphone according to any of claims 1 to 6, wherein the method for manufacturing comprises:

step 1: sequentially carrying out photoetching and etching on the top surface of a silicon substrate to form porous silicon in the areas on two sides of the top surface of the silicon substrate;

step 2: depositing a silicon nitride layer on the whole area of the top surface of the silicon substrate processed in the step 1, and sequentially performing photoetching and etching to form heat insulation layers on the two side areas of the top surface of the silicon substrate;

and step 3: depositing a silicon carbide layer on the whole area of the top surface of the silicon substrate processed in the step 2, and sequentially performing photoetching and etching to form a heat conduction layer supported by the heat insulation layer on the top surface of the silicon substrate;

and 4, step 4: sputtering a titanium/platinum metal layer on the whole area of the top surface of the silicon substrate processed in the step 3, and sequentially performing photoetching and etching to form a sensitive layer on the top surface of the silicon substrate; wherein the sensitive layer comprises: the electrode is positioned on the heat insulation layer, and the heating resistor and the sensing resistor are positioned on the heat conduction layer;

and 5: and etching the silicon substrate according to the positions of the heat insulation layer and the heat conduction layer to form a groove, so that the heat insulation layer is positioned on bosses on two sides of the groove, and the heat conduction layer is suspended on the groove, thereby obtaining the MEMS vector microphone.

8. The preparation method according to claim 7, wherein the step 1 specifically comprises:

photoetching the middle area of the top surface of the silicon substrate to form an electrochemical etching mask;

and carrying out electrochemical etching on the two side areas of the top surface of the silicon substrate to form porous silicon, and cleaning the silicon substrate to remove the photoresist.

9. The preparation method according to claim 7, wherein the step 2 specifically comprises:

depositing a silicon nitride layer on the whole area of the top surface of the silicon substrate;

photoetching the middle area of the silicon nitride layer to form a dry etching mask;

etching the two side areas of the silicon nitride layer, preparing a thermal oxidation mask, and cleaning the silicon substrate to remove the photoresist;

carrying out thermal oxidation on the silicon substrate to form heat insulation layers on two side areas of the top surface of the silicon substrate;

and etching the silicon nitride layer in the middle area of the top surface of the silicon substrate, and removing the thermal oxidation mask.

10. The preparation method according to claim 7, wherein the step 3 specifically comprises:

depositing a silicon carbide layer on the whole area of the top surface of the silicon substrate;

photoetching is carried out on the silicon carbide layer to form a heat conduction layer pattern film;

etching the area, which is not covered by the heat conduction layer pattern film, in the silicon carbide layer, and cleaning the silicon substrate to remove the photoresist so as to form the heat conduction layer supported by the heat insulation layer on the top surface of the silicon substrate;

step 4, specifically comprising:

sputtering a titanium/platinum metal layer on the whole area of the top surface of the silicon substrate;

photoetching is carried out on the titanium/platinum metal layer to form a sensitive layer pattern film;

and etching the area, which is not covered by the sensitive layer pattern film, in the titanium/platinum metal layer, and cleaning the silicon substrate to remove the photoresist so as to form a sensitive layer on the top surface of the silicon substrate.

Technical Field

The invention relates to the technical field of vector microphones, in particular to an MEMS vector microphone and a preparation method thereof.

Background

An MEMS (Micro-Electro-Mechanical System) vector microphone is used for measuring the vibration velocity vector information of a sound field particle, has directivity, can suppress the influence of environmental noise when measuring an acoustic quantity, has no array aperture limitation, and is widely used for application research such as vibration and noise control, sound source target identification and positioning, and the like.

The existing MEMS vector microphone adopts a parallel platinum wire cantilever beam structure, a heat transfer medium is air, the parallel platinum wires generate heat under the excitation of a power supply when the MEMS vector microphone works to form a space temperature field, when sound waves are directly introduced into a mass point vibration velocity, the space temperature field can be disturbed, so that a tiny temperature difference is formed between the parallel platinum wires, the tiny resistance difference is converted from a thermal resistance effect, the tiny resistance difference is demodulated through a bridge circuit to obtain voltage output responding to the mass point vibration velocity, and the direct measurement of the mass point vibration velocity vector information of a sound field is realized. At present, the length of a platinum wire used in an MEMS vector microphone needs to be several millimeters, but the width and the thickness of the platinum wire are only micrometer or even submicron order, so the longitudinal and transverse dimensions of the platinum wire are nearly thousands of times different, and the preparation difficulty and the stability and the consistency are poor. In addition, in the existing MEMS vector sensor, there is a case where heat received by the platinum wire is transferred to the substrate by heat conduction, and since the change rate of the particle vibration velocity in the low frequency band is slow, more heat is dissipated into the substrate by conduction and cannot be converted into a temperature change of the platinum wire, so that the sensitivity of the MEMS vector sensor is reduced, and the sensitivity is significantly attenuated with the reduction of the frequency in the frequency band below 100 Hz. In addition, the heat transfer medium of the conventional MEMS vector sensor is air, but is limited by physical factors such as the heat conduction coefficient, the density, the specific heat capacity and the like of the air medium, the heat diffusion between the parallel platinum wires is limited, and the heat caused by particle vibration cannot be completely transferred to the platinum wires, so that the parallel platinum wires cannot effectively respond to the change of the particle vibration velocity of a high-frequency sound field, the MEMS vector sensor is caused to be in a frequency band above 1000Hz, and the sensitivity is obviously attenuated along with the increase of the frequency. The response characteristic of the MEMS vector microphone is attenuated in low and high frequency bands, which causes serious distortion of the acoustic signal in reception and subsequent processing. Therefore, how to solve the problem of inconsistent response characteristics of the existing MEMS vector microphone in the audio frequency band becomes a technical problem that needs to be solved urgently by those skilled in the art.

Disclosure of Invention

The invention aims to provide an MEMS vector microphone and a preparation method thereof, which solve the technical problem that sound signals are seriously distorted in receiving and subsequent processing caused by response characteristic attenuation of the existing MEMS vector microphone in low-frequency and high-frequency bands.

According to an aspect of the present invention, there is provided a MEMS vector microphone for measuring a sound field particle velocity, the MEMS vector microphone comprising: the heat-conducting layer is arranged on the substrate; wherein the sensitive layer comprises: electrodes, heating resistors and sensing resistors;

a groove which is through from front to back is formed in the top of the substrate, so that two bosses are formed on the left side and the right side of the substrate; the heat insulating layers are respectively arranged on the two bosses, and the electrodes are arranged on the heat insulating layers; the heat conduction layer is supported by the heat insulation layer to be suspended on the groove; the heating resistor and the sensing resistor are arranged on the heat conducting layer, and two ends of the heating resistor and the two ends of the sensing resistor are respectively connected with the electrodes;

the heat insulating layer is used for isolating heat conduction among the substrate, the heat conducting layer and the sensitive layer;

the heat conduction layer is used for increasing heat diffusion between the heating resistor and the sensing resistor;

the heating resistor is used for forming a space temperature field under current excitation;

the sensing resistor is used for generating a temperature difference when the space temperature field is subjected to forced convection disturbance due to the fact that sound waves are introduced into the particle vibration speed, so that the resistance difference can be demodulated through the bridge circuit to measure the particle vibration speed of the sound field.

Optionally, the sensitive layer includes: six electrodes, a heating resistor and two sensing resistors, just two sensing resistors are located heating resistor both sides.

Optionally, the temperature coefficient of resistance of the heating resistor is zero, and the temperature coefficient of resistance of the sensing resistor is greater than 2000 ppm/deg.c.

Optionally, the substrate is made of any one of the following materials: monocrystalline silicon, polycrystalline silicon, silicon oxide.

Optionally, the heat insulating layer is made of any one of the following materials: silicon oxide, porous silicon oxide film.

Optionally, the heat conducting layer is made of any one of the following materials: silicon carbide and graphene.

In order to achieve the above object, the present invention further provides a method for manufacturing the MEMS vector microphone described above, the method comprising:

step 1: sequentially carrying out photoetching and etching on the top surface of a silicon substrate to form porous silicon in the areas on two sides of the top surface of the silicon substrate;

step 2: depositing a silicon nitride layer on the whole area of the top surface of the silicon substrate processed in the step 1, and sequentially performing photoetching and etching to form heat insulation layers on the two side areas of the top surface of the silicon substrate;

and step 3: depositing a silicon carbide layer on the whole area of the top surface of the silicon substrate processed in the step 2, and sequentially performing photoetching and etching to form a heat conduction layer supported by the heat insulation layer on the top surface of the silicon substrate;

and 4, step 4: sputtering a titanium/platinum metal layer on the whole area of the top surface of the silicon substrate processed in the step 3, and sequentially performing photoetching and etching to form a sensitive layer on the top surface of the silicon substrate; wherein the sensitive layer comprises: the electrode is positioned on the heat insulation layer, and the heating resistor and the sensing resistor are positioned on the heat conduction layer;

and 5: and etching the silicon substrate according to the positions of the heat insulation layer and the heat conduction layer to form a groove, so that the heat insulation layer is positioned on bosses on two sides of the groove, and the heat conduction layer is suspended on the groove, thereby obtaining the MEMS vector microphone.

Optionally, step 1 specifically includes:

photoetching the middle area of the top surface of the silicon substrate to form an electrochemical etching mask;

and carrying out electrochemical etching on the two side areas of the top surface of the silicon substrate to form porous silicon, and cleaning the silicon substrate to remove the photoresist.

Optionally, step 2 specifically includes:

depositing a silicon nitride layer on the whole area of the top surface of the silicon substrate;

photoetching the middle area of the silicon nitride layer to form a dry etching mask;

etching the two side areas of the silicon nitride layer, preparing a thermal oxidation mask, and cleaning the silicon substrate to remove the photoresist;

carrying out thermal oxidation on the silicon substrate to form heat insulation layers on two side areas of the top surface of the silicon substrate;

and etching the silicon nitride layer in the middle area of the top surface of the silicon substrate, and removing the thermal oxidation mask.

Optionally, step 3 specifically includes:

depositing a silicon carbide layer on the whole area of the top surface of the silicon substrate;

photoetching is carried out on the silicon carbide layer to form a heat conduction layer pattern film;

etching the area, which is not covered by the heat conduction layer pattern film, in the silicon carbide layer, and cleaning the silicon substrate to remove the photoresist so as to form the heat conduction layer supported by the heat insulation layer on the top surface of the silicon substrate;

step 4, specifically comprising:

sputtering a titanium/platinum metal layer on the whole area of the top surface of the silicon substrate;

photoetching is carried out on the titanium/platinum metal layer to form a sensitive layer pattern film;

and etching the area, which is not covered by the sensitive layer pattern film, in the titanium/platinum metal layer, and cleaning the silicon substrate to remove the photoresist so as to form a sensitive layer on the top surface of the silicon substrate.

The MEMS vector microphone and the preparation method thereof provided by the invention solve the technical problem that the sound signal of the existing MEMS vector microphone generates serious distortion in receiving and subsequent processing due to the attenuation of the response characteristics in low-frequency and high-frequency bands. The heat insulation layer made of the material with the low heat conductivity coefficient is added between the substrate and the heat conduction layer to isolate heat conduction among the substrate, the heat conduction layer and the sensitive layer, so that the sensitivity of the MEMS vector microphone in a low-frequency band is improved. The heat conduction layer made of materials with high heat conductivity coefficients is added between the heat insulation layer and the sensitive layer to increase heat diffusion between the heating resistor and the sensing resistor, so that the sensitivity of the MEMS vector microphone in a high-frequency band is improved.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 is a schematic top view of a MEMS vector microphone according to a first embodiment;

FIG. 2 is a schematic cross-sectional view of a MEMS vector microphone according to a first embodiment;

FIG. 3(a) is a schematic cross-sectional structure diagram of step 1 of the preparation method provided in example III;

FIG. 3(b) is a schematic top view of step 1 of the preparation method provided in example III;

FIG. 4(a) is a schematic cross-sectional view of step 2 of the preparation method provided in example III;

FIG. 4(b) is a schematic top view of step 2 of the preparation method provided in example III;

FIG. 5(a) is a schematic cross-sectional view of step 3 of the preparation method provided in example III;

FIG. 5(b) is a schematic top view of step 3 of the preparation method provided in example III;

FIG. 6(a) is a schematic cross-sectional view of step 4 of the preparation method provided in example III;

FIG. 6(b) is a schematic top view of step 4 of the preparation method provided in example III;

FIG. 7(a) is a schematic cross-sectional view of step 5 of the preparation process provided in example III;

FIG. 7(b) is a schematic top view of step 5 of the preparation method provided in example III;

FIG. 8(a) is a schematic cross-sectional view of step 6 of the preparation process provided in example III;

FIG. 8(b) is a schematic top view of step 6 of the preparation method provided in example III;

FIG. 9(a) is a schematic sectional view showing step 7 of the production method provided in example III;

FIG. 9(b) is a schematic top view of step 7 of the preparation method provided in example III;

FIG. 10(a) is a schematic sectional view showing step 8 of the production process provided in example III;

fig. 10(b) is a schematic top view of step 8 of the preparation method provided in example three;

FIG. 11(a) is a schematic sectional view showing step 9 of the production process provided in example III;

fig. 11(b) is a schematic top view of step 9 of the preparation method provided in example three;

FIG. 12(a) is a schematic cross-sectional view of step 10 of the preparation method provided in example III;

fig. 12(b) is a schematic top view of step 10 of the preparation method provided in example three;

FIG. 13(a) is a schematic sectional view showing step 11 of the production method provided in example III;

fig. 13(b) is a schematic top view of step 11 of the preparation method provided in example three;

FIG. 14(a) is a schematic sectional view showing step 12 of the production method provided in example III;

fig. 14(b) is a schematic top view of step 12 of the preparation method provided in example three;

FIG. 15(a) is a schematic sectional view showing step 13 of the production method provided in example III;

fig. 15(b) is a schematic top view of step 13 of the preparation method provided in example three;

FIG. 16(a) is a schematic sectional view showing step 14 of the production method provided in example III;

fig. 16(b) is a schematic top view of step 14 of the preparation method provided in the third embodiment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

An embodiment of the present invention provides an MEMS vector microphone for measuring a particle vibration velocity of a sound field, as shown in fig. 1 and 2, the MEMS vector microphone includes: a substrate 10, a heat insulating layer 20, a heat conducting layer 30 and a sensitive layer 40; wherein the sensitive layer 40 includes: an electrode 401, a heating resistor 402, and a sensing resistor 403;

a groove which is through from front to back is formed in the top of the substrate 10, so that two bosses are formed on the left side and the right side of the substrate 10; heat insulating layers 20 are respectively arranged on the two bosses, and electrodes 401 are arranged on the heat insulating layers 20; the heat conductive layer 30 is supported by the heat insulating layer 20 to be suspended above the groove; the heating resistor 402 and the sensing resistor 403 are arranged on the heat conduction layer 30, and two ends of the heating resistor 402 and the sensing resistor 403 are respectively connected with the electrodes 401;

the heat insulating layer 20 is used for insulating heat conduction among the substrate 10, the heat conducting layer 30 and the sensitive layer 40;

the heat conductive layer 30 is used to increase heat diffusion between the heating resistor 402 and the sensing resistor 403;

the heating resistor 402 is used for forming a space temperature field under current excitation;

the sensing resistor 403 is used for generating a temperature difference when the sound wave is introduced into the particle velocity to cause the forced convection disturbance of the space temperature field, so that the resistance difference is demodulated through a bridge circuit to measure the sound field particle velocity.

Specifically, as shown in fig. 1, the sensitive layer 40 includes: the heating device comprises six electrodes 401, a heating resistor 402 and two sensing resistors 403, wherein the two sensing resistors 403 are positioned on two sides of the heating resistor 402, and two ends of the heating resistor 402 and two ends of the sensing resistors 403 are connected with the electrodes 401.

It should be noted that, in practical applications, the sensitive layer 40 at least includes a heating resistor 402 and a sensing resistor 403; preferably, the sensitive layer 40 includes a heating resistor 402 and a plurality of sensing resistors 403, but the distribution of the plurality of sensing resistors 403 is not limited to be located on two sides of the heating resistor 402.

Further, the substrate 10 is made of MEMS (micro-electromechanical systems) process materials; preferably, the substrate 10 is made of any one of the following materials: monocrystalline silicon, polycrystalline silicon, silicon oxide; the substrate 10 is provided with a groove, which can be formed by etching.

The heat insulating layer 20 is made of a material with a low heat conductivity coefficient, and has good heat insulating performance; preferably, the heat insulating layer 20 is made of any one of the following materials: silicon oxide, porous silicon oxide film.

The heat conduction layer 30 is made of a material with high heat conductivity coefficient, and has good mechanical property and high heat conductivity coefficient; preferably, the heat conductive layer 30 is made of any one of the following materials: silicon carbide, graphene; the heat conductive layer 30 has a suspended thin film structure.

The temperature coefficient of resistance of the heating resistor 402 is zero, or the temperature coefficient of resistance of the heating resistor 402 is close to zero; the heating resistor 402 may be doped with polysilicon or may be made of a resistive wire.

The sensing resistor 403 has a large temperature coefficient of resistance; preferably, the temperature coefficient of resistance of the sense resistor 403 is greater than 2000 ppm/deg.C; the sensing resistor 403 may be made of a metal material having a large temperature coefficient of resistance or polysilicon doped with a dopant.

Further, as shown in fig. 1, the operating principle of the MEMS vector microphone is as follows:

when the MEMS vector microphone works, the heating resistor 402 dissipates heat under current excitation and forms a spatial temperature field near the heat conductive layer 30; when the sound wave is introduced into the particle vibration velocity, the space temperature field is caused to generate forced convection disturbance, and the temperatures of the two sensing resistors 403 positioned at the two sides of the heating resistor 402 generate micro asymmetric temperature transformation to form a temperature difference, so that the two sensing resistors 403 generate a micro resistance difference; the micro resistance difference is demodulated through a bridge circuit, and then the vibration velocity of the sound field particle can be measured.

For a low-frequency sound field, heat conduction is a main factor causing sensitivity attenuation of the MEMS vector microphone; therefore, in the present embodiment, the heat insulating layer 20 is added between the substrate 10 and the heat conducting layer 30 to insulate the heat conduction between the substrate 10, the heat conducting layer 30 and the sensitive layer 40. The heat insulating layer 20 is made of a material with a low heat conductivity coefficient, has a good heat insulating property, and can effectively isolate heat conduction between the heat conducting layer 30 and the substrate 10, thereby reducing heat loss of the heating resistor 402 and the sensing resistor 403, and ensuring that when a mass point vibration velocity of a sound field causes heat change of a space temperature field, the sensing resistor 403 has a high temperature change after receiving the heat transferred by the space temperature field, thereby improving the sensitivity of the MEMS vector microphone in a low-frequency band and the measuring capability for the low-frequency sound field.

For a high-frequency sound field, thermal diffusion is a main factor causing sensitivity attenuation of the MEMS vector microphone; therefore, in the present embodiment, the heat conduction layer 30 is added between the heat insulation layer 20 and the sensitive layer 40 to increase the heat diffusion between the heating resistor 402 and the sensing resistor 403. The heat conduction layer 30 is made of an insulating material with a high heat conductivity coefficient, the heat conduction layer 30 has a heat conductivity coefficient higher than that of air, heat can be transferred quickly in the heat diffusion process, the heat diffusion effect between the heating resistor 402 and the sensing resistor 403 is improved, the temperature diffusion time between the heating resistor 402 and the sensing resistor 403 is shortened, and therefore the response of a space temperature field to a high-frequency sound field is improved; the temperature difference between the heating resistor 402 and the sensing resistor 403 caused by a high-frequency sound field can be increased by adding the heat conduction layer 30 between the heat insulation layer 20 and the sensitive layer 40, so that the sensitivity of the MEMS vector microphone in a high-frequency band and the measurement capability of the MEMS vector microphone for the high-frequency sound field are improved.

The existing MEMS vector microphone mostly adopts a parallel suspended filament structure, not only has high processing difficulty, but also has lower yield and consistency, is influenced by heat conduction and heat diffusion, and has inconsistent response characteristics in an audio frequency band of 0.1Hz-10 kHz; the existing MEMS vector microphone has relatively flat response characteristic only in the audio frequency band of 100Hz-1000Hz, but has the problem of response characteristic attenuation in the audio frequency band of 0.1Hz-100Hz (low frequency band) and the audio frequency band of 1000 Hz-10kHz (high frequency band), which causes serious distortion of acoustic signals on receiving and subsequent processing.

According to the MEMS vector microphone provided by the embodiment, the suspended film (namely the heat conduction layer) with high heat conductivity coefficient is supported on the heat insulation layer, so that the heat exchange between the sensing resistors is improved; the heat insulating layer with low heat conductivity coefficient is supported on the substrate to reduce the heat conduction of the heat conducting layer to the substrate, optimize the heat transfer efficiency of the sensitive structure of the vector microphone in the working process, realize the sensitization of a low frequency band and a high frequency band, have a wider flat frequency response curve and solve the problem of signal distortion caused by the unevenness of the frequency response curve.

Example two

The embodiment of the invention provides a preparation method of an MEMS vector microphone introduced in the first embodiment, which comprises the following steps:

step 1: sequentially carrying out photoetching and etching on the top surface of a silicon substrate to form porous silicon in the areas on two sides of the top surface of the silicon substrate;

specifically, step 1 includes:

step 11: photoetching the middle area of the top surface of the silicon substrate to form an electrochemical etching mask;

step 12: and carrying out electrochemical etching on the two side areas of the top surface of the silicon substrate to form porous silicon, and cleaning the silicon substrate to remove the photoresist.

Step 2: depositing a silicon nitride layer on the whole area of the top surface of the silicon substrate processed in the step 1, and sequentially performing photoetching and etching to form heat insulation layers on the two side areas of the top surface of the silicon substrate;

specifically, step 2 includes:

step 21: depositing a silicon nitride layer on the whole area of the top surface of the silicon substrate;

step 22: photoetching the middle area of the silicon nitride layer to form a dry etching mask;

step 23: etching the two side areas of the silicon nitride layer, preparing a thermal oxidation mask, and cleaning the silicon substrate to remove the photoresist;

step 24: carrying out thermal oxidation on the silicon substrate to form heat insulation layers on two side areas of the top surface of the silicon substrate;

step 25: and etching the silicon nitride layer in the middle area of the top surface of the silicon substrate, and removing the thermal oxidation mask.

And step 3: depositing a silicon carbide layer on the whole area of the top surface of the silicon substrate processed in the step 2, and sequentially performing photoetching and etching to form a heat conduction layer supported by the heat insulation layer on the top surface of the silicon substrate;

specifically, step 3 includes:

step 31: depositing a silicon carbide layer on the whole area of the top surface of the silicon substrate;

step 32: photoetching is carried out on the silicon carbide layer to form a heat conduction layer pattern film;

step 33: and etching the area, which is not covered by the heat conduction layer pattern film, in the silicon carbide layer, and cleaning the silicon substrate to remove the photoresist so as to form the heat conduction layer supported by the heat insulation layer on the top surface of the silicon substrate.

And 4, step 4: sputtering a titanium/platinum metal layer on the whole area of the top surface of the silicon substrate processed in the step 3, and sequentially performing photoetching and etching to form a sensitive layer on the top surface of the silicon substrate; wherein the sensitive layer comprises: the electrode is positioned on the heat insulation layer, and the heating resistor and the sensing resistor are positioned on the heat conduction layer;

specifically, step 4 includes:

step 41: sputtering a titanium/platinum metal layer on the whole area of the top surface of the silicon substrate;

step 42: photoetching is carried out on the titanium/platinum metal layer to form a sensitive layer pattern film;

step 43: and etching the area, which is not covered by the sensitive layer pattern film, in the titanium/platinum metal layer, and cleaning the silicon substrate to remove the photoresist so as to form a sensitive layer on the top surface of the silicon substrate.

And 5: and etching the silicon substrate according to the positions of the heat insulation layer and the heat conduction layer to form a groove, so that the heat insulation layer is positioned on bosses on two sides of the groove, and the heat conduction layer is suspended on the groove, thereby obtaining the MEMS vector microphone.

EXAMPLE III

The embodiment of the invention provides a preparation method of an MEMS vector microphone introduced in the first embodiment, which comprises the following steps:

step 1: photoetching the middle area of the top surface of the silicon substrate to form an electrochemical etching mask;

as shown in fig. 3(a) and 3(b), an electrochemical etching mask is formed in the middle region of the top surface of the silicon substrate.

Step 2: performing electrochemical etching on two side areas of the top surface of the silicon substrate to form porous silicon, and cleaning the silicon substrate to remove photoresist;

as shown in fig. 4(a) and 4(b), forming porous silicon in both side regions of the top surface of the silicon substrate, and removing the electrochemical etching mask in the middle region of the top surface of the silicon substrate;

wherein the middle region and the two side regions do not overlap, and the middle region and the two side regions constitute the entire area of the top surface of the silicon substrate.

And step 3: depositing a silicon nitride layer on the whole area of the top surface of the silicon substrate;

as shown in fig. 5(a) and 5(b), a silicon nitride layer is formed on the entire area of the top surface of the silicon substrate.

And 4, step 4: photoetching the middle area of the silicon nitride layer to form a dry etching mask;

as shown in fig. 6(a) and 6(b), a dry etching mask is formed in the middle region of the silicon nitride layer.

And 5: etching the two side areas of the silicon nitride layer, preparing a thermal oxidation mask, and cleaning the silicon substrate to remove the photoresist;

as shown in fig. 7(a) and 7(b), the silicon substrate has porous silicon in both side regions of the top surface thereof and a silicon oxide layer in the middle region of the top surface thereof.

Step 6: carrying out thermal oxidation on the silicon substrate to form heat insulation layers on two side areas of the top surface of the silicon substrate;

as shown in fig. 8(a) and 8(b), a heat insulating layer is formed at both side regions of the top surface of the silicon substrate, and a silicon oxide layer is formed at a middle region of the top surface of the silicon substrate.

And 7: etching the silicon nitride layer in the middle area of the top surface of the silicon substrate, and removing the thermal oxidation mask;

as shown in fig. 9(a) and 9(b), a heat insulating layer is formed at both side regions of the top surface of the silicon substrate, and the silicon oxide layer at the middle region of the top surface of the silicon substrate is removed.

And 8: depositing a silicon carbide layer on the whole area of the top surface of the silicon substrate; preferably, the thickness of the silicon nitride is 200 nm;

as shown in fig. 10(a) and 10(b), a silicon carbide layer is formed on the entire region of the top surface of the silicon substrate.

And step 9: photoetching is carried out on the silicon carbide layer to form a heat conduction layer pattern film;

as shown in fig. 11(a) and 11(b), a heat conductive layer pattern film is formed on the silicon carbide layer.

Step 10: etching the area, which is not covered by the heat conduction layer pattern film, in the silicon carbide layer, and cleaning the silicon substrate to remove the photoresist so as to form the heat conduction layer supported by the heat insulation layer on the top surface of the silicon substrate;

as shown in fig. 12(a) and 12(b), a heat conductive layer is formed on the top surface of the silicon substrate, and the heat conductive layer is located above the heat insulating layer.

Step 11: sputtering a titanium/platinum metal layer on the whole area of the top surface of the silicon substrate;

as shown in fig. 13(a) and 13(b), a titanium/platinum metal layer is formed on the entire area of the top surface of the silicon substrate.

Step 12: photoetching is carried out on the titanium/platinum metal layer to form a sensitive layer pattern film;

as shown in fig. 14(a) and 14(b), a sensitive layer pattern film is formed on the titanium/platinum metal layer.

Step 13: etching the area, which is not covered by the sensitive layer pattern film, in the titanium/platinum metal layer, and cleaning the silicon substrate to remove the photoresist to form a sensitive layer on the top surface of the silicon substrate; wherein the sensitive layer comprises: the electrode is positioned on the heat insulation layer, and the heating resistor and the sensing resistor are positioned on the heat conduction layer;

as shown in fig. 15(a) and 15(b), a sensitive layer is formed on the top surface of the silicon substrate, and the sensitive layer is located above the heat conductive layer.

Step 14: and etching the silicon substrate according to the positions of the heat insulation layer and the heat conduction layer to form a groove, so that the heat insulation layer is positioned on bosses on two sides of the groove, and the heat conduction layer is suspended on the groove, thereby obtaining the MEMS vector microphone.

As shown in fig. 16(a) and 16(b), a groove is formed in the silicon substrate.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.

Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner.

The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.