CN113023664A

CN113023664A - Photoelectric detection chip and preparation method thereof

Info

Publication number: CN113023664A
Application number: CN202110227413.3A
Authority: CN
Inventors: 李刚; 胡维; 李萍萍
Original assignee: Memsensing Microsystems Suzhou China Co Ltd
Current assignee: Memsensing Microsystems Suzhou China Co Ltd
Priority date: 2021-03-01
Filing date: 2021-03-01
Publication date: 2021-06-25
Anticipated expiration: 2041-03-01
Also published as: CN113023664B

Abstract

The invention discloses a micro-electromechanical photoelectric detection chip and a preparation method thereof. The micro-electromechanical photoelectric detection chip comprises: a substrate; the air cavity is positioned on the first surface of the substrate and comprises a reticular structure film and a cavity, the reticular structure film covers the cavity, the reticular structure film is provided with at least one release hole, and the cavity is used for communicating different release holes; the suspension structure is located on the first surface of the substrate and covers the air cavity, wherein the suspension structure sequentially comprises a supporting layer and a photoelectric conversion device in the direction far away from the air cavity. The technical scheme provided by the embodiment of the invention reduces the process difficulty of the micro-electromechanical photoelectric detection chip.

Description

Photoelectric detection chip and preparation method thereof

Technical Field

The embodiment of the invention relates to the technical field of semiconductors, in particular to a photoelectric detection chip and a preparation method thereof.

Background

The Micro-Electro-Mechanical System (MEMS) photoelectric detection chip is used for absorbing an optical signal with a preset wavelength and converting the optical signal with the preset wavelength into a corresponding electrical signal, and has a wide application in the field of photoelectric detection.

The MEMS thermopile infrared sensor mostly adopts a silicon wafer back corrosion technology to form a closed membrane structure, the scheme is to design a bottom surface pattern by utilizing a double-sided exposure technology, and then a silicon substrate is etched from the back surface to further obtain the thermopile infrared chip with the closed membrane structure. Therefore, a front side release technology compatible with CMOS processes is preferred, with the front side opening releasing the support film structure. It is noted that, before the front side release technique, the thermopile pattern is completed, and during the etching process from the front side of the substrate through the opening to form the cavity, an additional protection measure is required to protect the complete structure of the device, but the damage to the thermopile pattern still occurs, which not only increases the manufacturing difficulty, but also increases the cost. In addition, due to the non-uniformity of the compressive stress of the suspended film, the front surface release usually has the problem of incomplete corrosion, which not only affects the performance of the device, but also easily causes the risk of film breakage, thereby greatly improving the difficulty of the front surface release process.

Therefore, the process difficulty is very high for obtaining the micro-electromechanical photoelectric detection chip with the quality meeting the standard.

Disclosure of Invention

In view of this, embodiments of the present invention provide a photodetection chip and a manufacturing method thereof, so as to solve the problems of film breakage and structure damage caused in the process of releasing a cavity in the prior art, and reduce the process difficulty of the micro-electromechanical photodetection chip.

The embodiment of the invention provides a micro-electromechanical photoelectric detection chip, which comprises:

a substrate;

the air cavity is positioned on the first surface of the substrate and comprises a net-shaped structure film and a cavity, the net-shaped structure film covers the cavity, at least one release hole is formed in the net-shaped structure film, and the cavity is used for communicating different release holes; the suspension structure is positioned on the first surface of the substrate and covers the air cavity, and the suspension structure sequentially comprises a supporting layer and a photoelectric conversion device in a direction far away from the air cavity.

The embodiment of the invention also provides a preparation method of the micro-electromechanical photoelectric detection chip, which comprises the following steps:

providing a substrate;

forming an air cavity on the first surface of the substrate, wherein the air cavity comprises a net-shaped structure film and a cavity, the net-shaped structure film covers the cavity, the net-shaped structure film is provided with at least one release hole, and the cavity is used for communicating different release holes;

and forming a suspension structure on the first surface of the substrate, wherein the suspension structure covers the air cavity, and the suspension structure sequentially comprises a supporting layer and a photoelectric conversion device in a direction away from the air cavity.

According to the technical scheme, the air cavity comprises the reticular structure film and the cavity body, the reticular structure film covers the cavity body, the reticular structure film is provided with at least one release hole, the cavity body is used for being communicated with different release holes, and based on the structure, etching reactants can enter the inside of the substrate from the release holes formed in the reticular structure film in the air cavity body, so that the cavity body inside the substrate is formed. Therefore, according to the technical scheme, the preparation of the air cavity can be completed firstly, and then the preparation of the suspension structure is completed, compared with the prior art, the problem that after the suspension structure is formed, an etching reactant enters the inside of the substrate from a release hole in the suspension structure is avoided, so that the air cavity is formed, and the technical problem that a photoelectric conversion device in the suspension structure is easily damaged by the etching reactant in the process of forming the air cavity is caused, so that the yield of the photoelectric conversion device in the suspension structure is improved, and the process difficulty is reduced. In addition, first aspect, based on above-mentioned structural setting, this technical scheme need not to form the release hole in suspended structure, has avoided the damage to suspended structure when forming the release hole. In the second aspect, based on the above structure, the etching reactant directly enters the substrate from the release hole formed in the mesh structure film in the air cavity, so that the substrate can be fully etched, and the technical problems that in the prior art, the etching reactant enters the substrate from the release hole in the suspension structure, the etching path is complex, and underetching or overetching exists are avoided. The third aspect, based on above-mentioned structural setting, can be at air cavity remanufacturing suspension structure after forming, avoid among the prior art etching reactant from the release hole in suspension structure get into the substrate inside, the supporting layer receives the damage, and mechanical strength descends, is not enough to support photoelectric conversion device's problem.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:

fig. 1 is a schematic structural diagram of a micro-electromechanical photodetection chip according to an embodiment of the present invention;

FIG. 2 is a top view of the film of FIG. 1 in a web configuration;

FIG. 3 is a schematic structural diagram of another microelectromechanical photoelectric detection chip according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a micro-electromechanical photodetecting chip according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a micro-electromechanical photodetecting chip according to an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a micro-electromechanical photodetecting chip according to an embodiment of the present invention;

FIG. 7 is a schematic flowchart of a method for manufacturing a micro-electromechanical photodetection chip according to an embodiment of the present invention;

FIG. 8 is a flowchart corresponding to step 120 in FIG. 7;

FIG. 9 is a schematic flowchart corresponding to step 130 in FIG. 7;

FIG. 10 is a schematic flow chart of another method for manufacturing a micro-electromechanical detection chip according to an embodiment of the present invention;

FIG. 11 is a flowchart corresponding to step 140 in FIG. 10;

fig. 12-15 are cross-sectional views corresponding to steps of a method for manufacturing a micro-electromechanical photodetection chip according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

As described in the background art, the micro electro mechanical photoelectric detection chip with quality meeting the standard is obtained by the front release technology based on the existing preparation method and the existing structural arrangement of the micro electro mechanical photoelectric detection chip, and the process difficulty is very high. The reason is that the release hole is usually arranged on the suspension structure in the existing micro-electromechanical detection chip, so that after the suspension structure is formed, an etching reactant enters the substrate from the release hole on the suspension structure, an air cavity is formed, and a photoelectric conversion device in the suspension structure is easily damaged by the etching reactant in the process of forming the air cavity.

In view of the above technical problems, an embodiment of the present invention provides the following technical solutions:

fig. 1 is a schematic structural diagram of a micro-electromechanical photodetection chip according to an embodiment of the present invention. Referring to fig. 1, the micro-electromechanical photodetection chip includes: a substrate 10; the air cavity 11 is located on the first surface 10A of the substrate 10, wherein the air cavity 11 includes a mesh-structured film 110 and a cavity 111, the mesh-structured film 110 covers the cavity 111, the mesh-structured film 110 is provided with at least one release hole 110A, and the cavity 111 is used for communicating different release holes 110A; and a suspension structure 20, the suspension structure 20 being located on the first surface 10A of the substrate 10, the suspension structure 20 covering the air cavity 11, wherein the suspension structure 20 comprises a support layer 21 and a photoelectric conversion device 22 in sequence in a direction away from the air cavity 11.

Optionally, referring to fig. 1, a cross-sectional dimension H of the release hole 110A perpendicular to the plane of the substrate 10 is greater than or equal to 10 micrometers and less than or equal to 30 micrometers, so that the etching reactant can enter the substrate 10 from the release hole 110A to form a cavity 111, and the gaseous reactant can be prevented from entering the air cavity 11 during epitaxial growth, so that the material contained in the support layer 21 cannot be formed inside the air cavity 11.

In the present embodiment, the substrate 10 may be a silicon substrate. The support layer 21 may be any one of silicon oxide, silicon nitride, and a stack of silicon oxide and silicon nitride.

Compared with the structure arrangement limited by the release holes in the suspension structure in the prior art, in the technical scheme of this embodiment, the air cavity 11 includes the mesh-structured film 110 and the cavity 111, the mesh-structured film 110 covers the cavity 111, and the mesh-structured film 110 is provided with at least one release hole 110A, the cavity 111 is used for communicating different release holes 110A, based on the above structure arrangement, the etching reactant can enter the substrate 10 from the release holes 110A arranged on the mesh-structured film 110 in the air cavity 11, so as to form the cavity 111 inside the substrate 10. Therefore, according to the technical scheme, the preparation of the air cavity 11 can be completed firstly, and then the preparation of the suspension structure 20 is completed, so that the technical problem that the photoelectric conversion device 22 in the suspension structure 20 is easily damaged by the etching reactant in the process of forming the air cavity 11 due to the fact that the etching reactant enters the substrate 10 from the release hole in the suspension structure 20 after the suspension structure 20 is formed is solved, the yield of the photoelectric conversion device 22 in the suspension structure 20 is improved, and the process difficulty is reduced. In addition, in the first aspect, based on the above structural arrangement, the technical solution does not need to form the release holes 110A in the suspension structure 20, and avoids damage to the suspension structure 20 when the release holes 110A are formed. In the second aspect, based on the above structure arrangement, the etching reactant directly enters the substrate 10 from the release hole 110A formed in the mesh-structured thin film 110 in the air cavity 11, so that the substrate 10 can be fully etched, and the technical problems that in the prior art, the etching reactant enters the substrate 10 from the release hole in the suspension structure 20, the etching path is complicated, and underetching or overetching occurs are solved. In a third aspect, based on the above structure, the suspension structure 20 may be prepared after the air cavity 11 is formed, so as to avoid the problem that in the prior art, the etching reactant enters the substrate 10 from the release hole in the suspension structure 20, the support layer 21 is damaged, the mechanical strength is reduced, and the photoelectric conversion device 22 is not sufficiently supported.

Optionally, on the basis of the above technical solution, referring to fig. 1, an inverted triangle structure 10B is disposed on a surface of the mesh-structured film 110 adjacent to the cavity 111, and a regular triangle structure 10C is disposed on a surface of the substrate 10 adjacent to the cavity 111.

Specifically, the substrate 10 is anisotropically etched by using an etching process, and different crystal planes inside the substrate 10 are etched at different speeds, so as to form the film 110 with the mesh structure including the inverted-triangular structure 10B, the substrate 10 including the regular-triangular structure 10C, and the cavity 111 located between the film 110 with the mesh structure including the inverted-triangular structure 10B and the substrate 10 including the regular-triangular structure 10C. Wherein, the two inclined planes of the inverted triangle structure 10B are different crystal planes. The two inclined planes of the regular triangle structure 10C are different crystal planes. The net-structured film 110 including the inverted triangular structure 10B has higher mechanical strength than a planar structure, and can improve stability, reliability, and durability of the net-structured film 110 for supporting the suspension structure 20. For example, the reactant of the anisotropic wet etching process may be an alkaline solution such as potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH), which has different etching rates for the two inclined surfaces of the inverted triangular structure 10B and the two inclined surfaces of the right triangular structure 10C.

Optionally, on the basis of the above technical solution, the depth of the release hole 110A is greater than or equal to 1/2 of the thickness of the substrate 10 and less than or equal to 2/3 of the thickness of the substrate 10.

Specifically, the depth of the release holes 110A is too small to be smaller than 1/2 of the thickness of the substrate 10, so that the etching reactant can enter the inside of the substrate 10 through the release holes 110A formed on the mesh-structured film 110, and the depth of the formed cavity 111 is too small, which is less effective in insulating the hot end of the thermopile 220 when the suspension structure 20 includes the thermopile 220. The increased depth of the release holes 110A may reduce heat loss, resulting in better thermal isolation of the thermopile structure 220. The depth of the release holes 110A is too great to be greater than 2/3 the thickness of the substrate 10, the substrate 10 has poor mechanical properties and is not sufficient to support the suspension structure 20.

Fig. 2 is a top view of the film of fig. 1 in a web configuration. Fig. 2 shows a top view of 6 kinds of the net-structured film 110.

Optionally, on the basis of the above technical solution, referring to fig. 2, the cross-sectional shape of the release hole 110A in the plane of the mesh-structured film 110 is a circle or a polygon.

Specifically, the etching reactant may enter the inside of the substrate 10 from the release holes 110A provided on the mesh-structured film 110 to form the cavity 111. The cross-sectional shape of the release holes 110A in the plane of the film 110 with a mesh structure is circular or polygonal, and the release holes are regular in shape and are formed by adopting an etching process.

Optionally, on the basis of the above technical solution, referring to fig. 2c and 2d, the cross-sectional shape of the release hole 110A on the plane of the mesh-structured film 110 is circular, and the release hole 110A surrounds the mesh-structured film into a plurality of concentric rings, so that the etching reactant enters the substrate 10 from the release hole 110A disposed on the mesh-structured film 110 to form a cylindrical cavity 111. Specifically, the speed of the cylindrical cavity 111 may be formed by controlling the flow rate of the etching reactant, the interval between the concentric rings, and the area of the release holes 110A.

Optionally, on the basis of the above technical solution, referring to fig. 2c, the areas of the release holes 110A are the same, specifically, the areas of the release holes 110A are the same, which reduces the difficulty in etching different release holes 110A.

Alternatively, based on the above technical solution, referring to fig. 2d, the area of the release holes 110A far from the center of the mesh-structured film 110 is smaller than the area of the release holes 110A near the center of the mesh-structured film 110. Specifically, the area of the release hole 110A far from the center of the mesh-structured film 110 is smaller than the area of the release hole 110A near the center of the mesh-structured film 110, that is, the etching rate of the etching reactant corresponding to the release hole 110A far from the center of the mesh-structured film 110 is smaller than the etching rate of the etching reactant corresponding to the release hole 110A near the center of the mesh-structured film 110, so that the etching reactant can enter the substrate 10 from the release hole 110A provided on the mesh-structured film 110, and the cavity 111 with a controllable edge shape is formed.

Optionally, on the basis of the above technical solution, referring to fig. 2b, the cross-sectional shape of the release hole 110A in the plane of the mesh-structured film 110 is a square, and the release hole 110A forms a block-shaped area in the mesh-structured film 110. The square release holes 110A have regular shapes, so that the etching reactant can enter the substrate 10 from the release holes 110A formed on the mesh-structured film 110 to form the square cavities 111. Specifically, the speed of forming the square cavity 111 can be controlled by controlling the flow rate of the etching reactant and the interval between the discharge holes 110A. The release holes 110A have the same shape, which reduces the process difficulty of etching different release holes 110A.

Alternatively, on the basis of the above technical solution, referring to fig. 2a, 2e and 2f, the cross-sectional shape of the release holes 110A on the plane of the mesh-structured film 110 is rectangular, and the adjacent release holes 110A are arranged in parallel or vertically at a predetermined interval. Specifically, fig. 2a and 2f show a top view of the mesh-structured film 110 in which adjacent release holes 110A are arranged in parallel. The rectangular release holes 110A have a regular shape, so that the etching reactant can enter the substrate 10 through the release holes 110A formed in the mesh-structured film 110 to form a square cavity 111. Specifically, the speed of forming the square cavity 111 can be controlled by controlling the flow rate of the etching reactant and the interval between the discharge holes 110A. In the top view of the film 110 with a mesh structure shown in fig. 2e, the adjacent release holes 110A are vertically arranged at a predetermined interval, so as to achieve the effect of reducing the number of the release holes 110A, thereby improving the efficiency of etching the release holes 110A.

The orientation of the release holes 110A on the plane of the reticular structure film 110 corresponds to the crystallographic orientation of the bottom silicon substrate 10, through different arrangement and combination between the adjacent release holes 110A on the reticular structure film 110, etching reactants can conveniently enter the substrate 10 from the release holes 110A arranged on the reticular structure film 110, the etching reactants effectively carry out cross etching on adjacent cavities to form a cavity 111, the maximum etching cavity effect is realized by the surface opening with the minimum area, and after the etching process and the etching process are finished, the good release performance and the mechanical integrity of the reticular structure film 110 can be ensured.

The specific structure of the suspension structure 20 in the micro-electromechanical photodetection chip is further detailed below. Fig. 3 is a schematic structural diagram of another microelectromechanical photoelectric detection chip according to an embodiment of the present invention. Referring to fig. 3, the suspension structure 20 includes: a support layer 21, the support layer 21 being located on the first surface 10A side of the substrate 10, and the support layer 21 covering the air cavity 11; a thermopile 220, the thermopile 220 being located on the surface of the support layer 21 on the side away from the air cavity 11; a passivation layer 221, wherein the passivation layer 221 is positioned on the surface of the thermopile 220 on the side far from the substrate 10; the infrared absorption layer 222 is located on a surface of the passivation layer 221, which is far away from the thermopile 220, wherein the projection of the thermopile 220 on the substrate 10 surrounds the projection of the infrared absorption layer 222 on the substrate 10, one end of the thermopile 220, which is close to the infrared absorption layer 222, serves as a hot end, one end of the thermopile 220, which is far away from the infrared absorption layer 222, serves as a cold end, the cold end of the thermopile 220 serves as an electrode, and leads an electrical signal corresponding to the infrared light signal to the second surface 10B, which is opposite to the first surface 10A, of the substrate 10 through the conductive through hole, and the infrared absorption layer 222, the passivation layer 221 and the thermopile 220 form the photoelectric.

In the present embodiment, the passivation layer 221 serves to protect the thermopile 220 and may provide a flat plane when the infrared absorption layer 222 is formed. Specifically, the infrared absorption layer 222 of the mems photodetection chip in this embodiment absorbs the infrared light signal, and the thermopile 220 converts the infrared light signal into a corresponding electrical signal. The principle in which the thermopile 220 converts an infrared light signal into a corresponding electrical signal is as follows:

based on the seebeck effect, infrared absorbing layer 222 absorbs the infrared light signal, and the hot junction and the cold junction of thermopile 220 appear temperature difference, and the hot junction of thermopile 220 is close to infrared absorbing layer 222, and its temperature is higher than the cold junction of thermopile 220, and the hot junction and the cold junction of thermopile 220 can produce thermoelectric electromotive force to realize thermopile 220 with the function of infrared light signal conversion to the signal of telecommunication that corresponds. The infrared absorption layer 222 may be a metal thin film, a porous black metal, or a thin film stacked of silicon oxide, silicon nitride, or the like.

Alternatively, referring to fig. 3, the thermopile 220 includes a first conductive layer 220A and a second conductive layer 220B made of different conductive materials, and an insulating layer 223 disposed between the first conductive layer 220A and the second conductive layer 220B, the first conductive layer 220A being located on a surface of the support layer 21 on a side away from the substrate 10, and the second conductive layer 220B being located on a surface of the insulating layer 223 on a side away from the first conductive layer 220A. One end of first conductive layer 220A near infrared absorbing layer 222 is electrically connected to one end of second conductive layer 220B near infrared absorbing layer 222 as the hot side of conductive stack 220. One end of first conductive layer 220A remote from infrared absorbing layer 222 serves as a cold side of thermopile 220 and is multiplexed as first electrode 220C of thermopile 220, and one end of second conductive layer 220B remote from infrared absorbing layer 222 serves as a cold side of thermopile 220 and is multiplexed as second electrode 220D of thermopile 220. The first electrode 220C brings an electrical signal of the first electrode 220C to the second surface 10B of the substrate 10 through the first conductive via 10C. The second electrode 220D brings an electrical signal of the second electrode 220D to the second surface 10B of the substrate 10 through the second conductive via 10D. Optionally, the micro-electromechanical photoelectric detection chip further includes a first soldering portion 12 and a second soldering portion 13, the first soldering portion 12 is electrically connected to the first conductive via 10C, and the second soldering portion 13 is electrically connected to the second conductive via 10D. The first conductive via 10C and the second conductive via 10D are filled with a conductive material 14, and an insulating material 223 is disposed between the conductive material 14 and the substrate 10. Optionally, a solder resist layer 15 is disposed on the second surface 10B of the substrate 10, and the solder resist layer 15 is provided with an opening structure exposing the first conductive via 10C and the second conductive via 10D. The first welding part 12 and the second welding part 13 can lead the thermoelectromotive force of the thermopile 220 to the second surface 10B of the substrate 10, and the microcomputer electro-optical detection chip can be electrically connected with an external device through an automatic surface mounting process. The material of the first conductive layer 220A and the material of the second conductive layer 220B are two different electrical conductors or semiconductors, such as polysilicon, aluminum metal, etc.

In order to further improve the light absorption efficiency of the near-infrared absorption layer 222 for absorbing infrared light, the embodiment of the present invention further provides the following technical solutions:

on the basis of the above technical solution, referring to fig. 3, the micro-electromechanical photodetection chip further includes: and the preset wavelength optical signal filter window 30, the preset wavelength optical signal filter window 30 being located on the surface of the suspension structure 20 on the side away from the air cavity 11, and being used for transmitting the preset wavelength optical signal and protecting the suspension structure 20 and the substrate 10.

Specifically, the preset wavelength optical signal filter window 30 has light transmittance to transmit the preset wavelength optical signal and block transmission of the non-preset wavelength optical signal, so that the transmittance of the preset wavelength optical signal is increased, and the photoelectric conversion efficiency of the micro electro mechanical system photoelectric detection chip is improved. In addition, the optical signal filter 30 with the predetermined wavelength may also be used to protect the suspension structure 20 and the substrate 10 from external force.

Optionally, the optical signal filter 30 with the wavelength of the preset wavelength and the passivation layer 221 may be bonded together through the bonding layer 40, and the suspension structure 20 and the optical signal filter 30 with the wavelength of the preset wavelength form a vacuum chamber, so that the influence of the fluctuation of the surrounding environment on the photoelectric detection performance of the photoelectric conversion device 22 in the suspension structure 20 may be reduced, and the distance between the optical signal filter 30 with the wavelength of the preset wavelength and the suspension structure 20 may be adjusted by adjusting the height of the bonding layer 40.

The specific structure of the preset wavelength optical signal filter window 30 is specifically detailed below. On the basis of the above technical solution, referring to fig. 3, the preset wavelength optical signal filter 30 includes an optical anti-reflection film layer 31, a light filtering protection layer 32 and a metal reflection layer 33, which are sequentially stacked, where the optical anti-reflection film layer 31 is used for transmitting the preset wavelength optical signal and blocking transmission of the non-preset wavelength optical signal; the light filtering protective layer 32 is used for transmitting a light signal with preset wavelength, the light filtering protective layer 32 comprises a light transmitting area 32A and a non-light transmitting area 32B surrounding the light transmitting area, the metal reflecting layer 33 is positioned on the surface of one side of the light filtering protective layer 32, which is far away from the optical antireflection film layer 31, and the metal reflecting layer 33 is positioned in the non-light transmitting area 32B; optical anti-reflection film layer 31 is adjacent to suspension structure 20.

Specifically, the optical anti-reflection film layer 31 is used for transmitting the light signals with the preset wavelength and blocking transmission of the light signals with the non-preset wavelength, so that the transmittance of the light signals with the preset wavelength is increased, and the photoelectric conversion efficiency of the micro electro mechanical system photoelectric detection chip is improved. The filter protection layer 32 is used for transmitting the optical signal with the predetermined wavelength and protecting the inner suspension structure 20 and the substrate 10. The metal reflective layer 33 is located in the non-transparent region 32B and can define a field angle of the micro-electromechanical detection chip, specifically, the metal reflective layer 33 can reflect external infrared radiation incident to the non-transparent region 32B back to the surrounding environment, define an incident light path in the range of the transparent region 32A, and then convert the incident light path into a corresponding electrical signal, so as to improve the photoelectric conversion efficiency of the micro-electromechanical photoelectric detection chip. For example, the material of the metal reflective layer 33 may be metal aluminum with good reflective performance.

On the basis of the above technical solution, referring to fig. 3, a groove 30A is formed on the surface of the light filtering protection layer 32 adjacent to the side of the optical antireflection film layer 31.

Specifically, the arrangement of the groove 30A enables the surface of the side of the filtering protective layer 32 adjacent to the optical antireflection film layer 31 to form a concave cavity structure, so that the thickness of the light-transmitting region 32A of the filtering protective layer 32 is reduced, the transmission distance of an optical signal in the filtering protective layer 32 is reduced, the loss of the optical signal is further reduced, and the transmittance of an infrared light signal is increased.

Alternatively, referring to fig. 3, the longitudinal sectional shape of the groove 30A is an inverted trapezoid. Specifically, the longitudinal section of the groove 30A is in an inverted trapezoid shape, and the side surface and the bottom surface of the groove 30A have a certain included angle, so that an optical signal reflected to the side surface of the groove 30A can be reflected back to the range of the light-transmitting area 32A, and the photoelectric conversion efficiency of the micro electro mechanical system photoelectric detection chip is improved.

Fig. 4 is a schematic structural diagram of another micro-electromechanical photodetection chip according to an embodiment of the present invention. Wherein fig. 4b is a schematic view of the structure of the preset wavelength optical signal filter 30 shown in fig. 4 a. Fig. 5 is a schematic structural diagram of another micro-electromechanical photodetection chip according to an embodiment of the present invention. Wherein fig. 5b is a schematic view of the structure of the preset wavelength optical signal filter 30 shown in fig. 5 a. Fig. 6 is a schematic structural diagram of another micro-electromechanical photodetection chip according to an embodiment of the present invention. Wherein fig. 6b is a schematic view of the structure of the preset wavelength optical signal filter 30 shown in fig. 6 a.

On the basis of the above technical solution, referring to fig. 4, 5 and 6, a fresnel diffraction structure 32C is disposed on a surface of the filtering protection layer 32 on a side away from the optical antireflection film layer 31, where the fresnel diffraction structure 32C is used for focusing a light signal with a preset wavelength on the infrared absorption layer 222.

Illustratively, referring to fig. 4, 5 and 6, the projection of the fresnel diffractive structure 32C onto the substrate 10 covers the infrared absorbing layer 222. The fresnel diffraction structure 32C is used for focusing the light signal with the preset wavelength to the infrared absorption layer 222, so that the intensity of the infrared absorption layer 222 for absorbing the infrared light signal is increased, and the photoelectric conversion efficiency of the micro-electromechanical photoelectric detection chip is improved.

Alternatively, referring to fig. 4, 5 and 6, the fresnel diffractive structure 32C includes a central region, and at least one annular slit surrounding the central region.

It should be noted that, referring to fig. 4b, the fresnel diffraction structure 32C includes a central region a, and at least one annular slit surrounding the central region, the annular slits being an annular slit b, an annular slit d, and an annular slit f, respectively. Referring to fig. 5b, the fresnel diffractive structure 32C includes a central region a, and at least one annular slit surrounding the central region, the annular slits being an annular slit b, an annular slit d, an annular slit f, and an annular slit h, respectively. Referring to fig. 6b, the fresnel diffractive structure 32C includes a central region a, and at least one annular slit surrounding the central region, the annular slits being an annular slit b, an annular slit d, an annular slit f, and an annular slit h, respectively. Wherein the radial distance of the annular slit from the central region a is related to the wavelength of the optical signal at the predetermined wavelength and the distance (focal length) from the bottom surface of the central region a to the infrared absorption layer 222.

Alternatively, referring to fig. 4, 5 and 6, the center of the annular slit coincides with the center of the central region a.

Optionally, the annular slit comprises a circular annular slit or a polygonal annular slit. That is, the slit having the circular cross-sectional shape of the annular slit is a circular annular slit. The slit with the polygonal cross section of the annular slit is a polygonal annular slit.

Optionally, the fresnel diffraction structure further includes a slit spacing region, and the slit spacing region is located between two adjacent annular slits.

Referring to fig. 4, the fresnel diffraction structure 32C further includes a slit spacing region located between two adjacent annular slits. Wherein the slit spacing region c is located between the adjacent two annular slits b and d, and the slit spacing region e is located between the adjacent two annular slits d and f. Note that the slit spacing region g is used to isolate the annular slit f.

Referring to fig. 5, the fresnel diffraction structure 32C further includes a slit spacing region located between two adjacent annular slits. Wherein the slit interval region c is located between two adjacent annular slits b and d, the slit interval region e is located between two adjacent annular slits d and f, and the slit interval region g is located between two adjacent annular slits f and h.

Note that, the fresnel diffraction structure 32C shown in fig. 4 and 6 is formed by etching the filter protection layer 32 to form an annular slit. Fig. 5 shows a fresnel diffraction structure 32C obtained by patterning and etching a metal film layer formed on the surface of the light filtering protection layer 30 on the side away from the optical antireflection film layer 31, and then etching the metal film layer.

The embodiment of the invention also provides a preparation method of the micro-electromechanical photoelectric detection chip. Fig. 7 is a schematic flow chart of a method for manufacturing a micro-electromechanical photodetection chip according to an embodiment of the present invention. Fig. 12-15 are cross-sectional views corresponding to steps of a method for manufacturing a micro-electromechanical photodetection chip according to an embodiment of the present invention. Referring to fig. 7, the preparation method of the micro-electromechanical photoelectric detection chip comprises the following steps:

step 110, providing a substrate.

Referring to fig. 12a, a substrate 10 is provided. In the present embodiment, the substrate 10 may be a single crystal silicon material.

And 120, forming an air cavity on the first surface of the substrate, wherein the air cavity comprises a net-shaped structure film and a cavity, the net-shaped structure film covers the cavity, the net-shaped structure film is provided with at least one release hole, and the cavity is used for communicating different release holes.

Referring to fig. 12b, an air cavity 11 is formed on the first surface 10A of the substrate 10, wherein the air cavity 11 includes a mesh-structured film 110 and a cavity 111, the mesh-structured film 110 covers the cavity 111, and the mesh-structured film 110 is provided with at least one release hole 110A, and the cavity 111 is used for communicating different release holes 110A.

Step 130, forming a suspension structure on the first surface of the substrate, wherein the suspension structure covers the air cavity, and the suspension structure sequentially comprises a support layer and a photoelectric conversion device in a direction away from the air cavity.

Referring to fig. 12c, a suspension structure 20 is formed on the first surface 10A of the substrate 10, the suspension structure 20 covering the air cavity 11, wherein the suspension structure 20 includes a support layer 21 and a photoelectric conversion device 22 in this order in a direction away from the air cavity 11.

Compared with the prior art that the micro-electro-mechanical-system photoelectric detection chip is formed, firstly, the substrate is provided, then the suspension structure is formed on the first surface of the substrate, the release hole is formed in the suspension structure, and finally, the etching reactant enters the substrate from the release hole in the suspension structure, so that an air cavity is formed, and the photoelectric conversion device in the suspension structure is easily damaged by the etching reactant in the process of forming the air cavity.

In the technical solution of this embodiment, the forming sequence of the air cavity 11 and the suspension structure 20 is changed, and before the suspension structure 20 is formed, the air cavity 11 is formed on the first surface 10A of the substrate 10, wherein the air cavity 11 includes a mesh-structured film 110 and a cavity 111, the mesh-structured film 110 covers the cavity 111, and the mesh-structured film 110 is provided with at least one release hole 110A, and the cavity 111 is used for communicating different release holes 110A. Therefore, according to the technical scheme, the preparation of the air cavity 11 can be completed firstly, and then the preparation of the suspension structure 20 is completed, so that the technical problem that in the process of forming the air cavity 11, the photoelectric conversion device 22 in the suspension structure 20 is easily damaged by the etching reactant due to the fact that the etching reactant enters the substrate 10 from the release hole in the suspension structure 20 after the suspension structure 20 is formed in the prior art to form the air cavity is solved, the yield of the photoelectric conversion device 22 in the suspension structure 20 is improved, and the process difficulty is reduced. In addition, in the first aspect, based on the above-described manufacturing method, the present embodiment does not need to form the release holes 110A in the suspension structure 20, and avoids damage to the suspension structure 20 when the release holes 110A are formed. In the second aspect, based on the above preparation method, the etching reactant directly enters the substrate 10 from the release hole 110A formed in the mesh-structured thin film 110 in the air cavity 11, so that the substrate 10 can be fully etched, and the technical problems in the prior art that the etching reactant enters the substrate 10 from the release hole in the suspension structure 20, the etching path is complicated, and underetching or over-etching exists are avoided. In a third aspect, based on the above manufacturing method, the suspension structure 20 may be manufactured after the air cavity 11 is formed, so as to avoid the problem that in the prior art, the supporting layer 21 is damaged and the mechanical strength is reduced, which is insufficient to support the photoelectric conversion device 22, because the etching reactant enters the substrate 10 from the release hole in the suspension structure 20.

Fig. 8 is a flowchart corresponding to step 120 in fig. 7. On the basis of the above technical solution, referring to fig. 8, the step 120 of forming an air cavity on the first surface of the substrate includes:

step 1201, a dielectric layer is formed on the first surface of the substrate.

Referring to fig. 13a, the substrate 10 may be, for example, monocrystalline silicon, and a dielectric layer 16, which may be a silicon oxide or silicon nitride layer, may be formed on the first surface 10A of the substrate 10 through a deposition process. The deposition process includes Low Pressure Chemical Vapor Deposition (LPCVD), plasma chemical vapor deposition (PECVD), or thermal oxidation process.

Step 1202, performing patterned etching on the dielectric layer to form at least one groove.

Referring to fig. 13b, the dielectric layer 16 may be patterned by photolithography, dry etching or wet etching to form a mask pattern of the mesh-structured thin film 110, including at least one groove 16A.

Step 1203, forming at least one release hole on the first surface of the substrate, wherein the release hole is communicated with the groove.

Referring to fig. 13c, a deep reactive ion silicon etching (DRIE) process may be used to etch the first surface 10A of the substrate 10, and due to the etch selectivity of the etching process to the dielectric layer 16 and the substrate 10, at least one relief hole 110A is formed, wherein the relief hole 110A communicates with the recess 16A. The size and shape of the release hole 110A may be determined according to the process and design requirements.

Step 1204, forming an air cavity on the first surface of the substrate by using an etching process, wherein the etching process comprises an anisotropic deep reactive ion etching process and/or an anisotropic wet etching process, reactants of the anisotropic deep reactive ion etching process and/or the anisotropic wet etching process enter the substrate along release holes to form the mesh-structured film and the cavity, the mesh-structured film covers the cavity, the mesh-structured film is provided with at least one release hole, and the cavity is used for communicating different release holes.

Referring to fig. 13d, an air cavity 11 is formed on the first surface 10A of the substrate 10 by using an etching process, where the etching process includes an anisotropic deep reactive ion etching process and/or an anisotropic wet etching process, reactants of the anisotropic deep reactive ion etching process and/or the anisotropic wet etching process enter the inside of the substrate 10 along the release holes 110A, a portion of the monocrystalline silicon substrate 10 under the dielectric layer 16 is etched and/or etched away to form a mesh-structured film 110 and a cavity 111, the mesh-structured film 110 covers the cavity 111, and the mesh-structured film 110 is provided with at least one release hole 110A, and the cavity 111 is used for communicating different release holes 110A. For example, the reactant of the anisotropic wet etching process may be an alkaline solution such as potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH). In the single anisotropic wet etching process, due to the anisotropy of the etching solution, the film 110 with a mesh structure forms a contraction end facing the cavity 111. When the anisotropic Deep Reactive Ion Etching (DRIE) process is used alone, the reaction ions are injected into the silicon substrate 10 through the release holes 110A for etching, and the net-structured thin film 110 and the cavity 111 can be obtained by appropriate process parameters.

Step 1205, the dielectric layer is removed.

Referring to fig. 13e, the dielectric layer 16 may be removed by a dry etching or wet etching process, so that the mesh-structured film 110 is exposed. The etching solution for wet etching may be buffered hydrofluoric acid (BOE).

Optionally, on the basis of the foregoing technical solution, the step 1204 of forming an air cavity on the first surface of the substrate by using an etching process includes:

referring to fig. 13d, the first surface 10A of the substrate 10 is anisotropically etched by using an etching process to form a mesh-structured film 110 including an inverted triangle structure 10B, a substrate 10 including a regular triangle structure 10C, and a cavity 111 located between the mesh-structured film 110 including the inverted triangle structure 10B and the substrate 10 including the regular triangle structure 10C, wherein the surface of the mesh-structured film 110 adjacent to the cavity 111 is provided with the inverted triangle structure 10B, and the surface of the substrate 10 adjacent to the cavity is provided with the regular triangle structure.

In particular, the net-structured film 110 including the inverted triangular structure 10B has higher mechanical strength than the plane structure, and can improve the stability, reliability and durability of the net-structured film 110 for supporting the suspension structure 20. For example, the reactant of the anisotropic wet etching process may be an alkaline solution such as potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH).

The following further refines the method for preparing the suspension structure 20 in the micro-electromechanical photodetection chip. Fig. 9 is a schematic flowchart corresponding to step 130 in fig. 7. On the basis of the above technical solution, referring to fig. 9, the step 130 of forming a floating structure on the first surface of the substrate includes:

step 1301, forming a supporting layer on the first surface side of the substrate, wherein the supporting layer covers the air cavity;

referring to fig. 14a, a support layer 21 is formed on the first surface 10A side of the substrate 10, and the support layer 21 covers the air cavity 11. When the substrate 10 is a single crystal silicon, the thin film layer of single crystal silicon can be formed by an epitaxial single crystal silicon process using the thin film 110 of a mesh structure as a seed crystal. Since the cross-sectional size of the release holes 110A in a plane perpendicular to the substrate 10 is 10 micrometers or more and 30 micrometers or less, it is difficult for the gaseous reactants to enter the inside of the air cavity 11 during epitaxial growth, and thus a single crystalline silicon thin film layer is not formed inside the air cavity 11, and a complete single crystalline silicon thin film layer is always obtained due to the isotropy of the deposition process. And then oxidizing the monocrystalline silicon thin film layer by a thermal oxidation process to obtain the supporting layer 21. And the thickness of the supporting layer 21 can be controlled according to the process parameters, so that the supporting layer 21 is ensured to be within a preset thickness range and to be enough to support the suspension structure 220.

Step 1302, forming a thermopile on a surface of the support layer on a side away from the air cavity.

Referring to fig. 14B and 14c, a first conductive layer 220A in the thermopile 220 is formed on the surface of the support layer 21 on the side away from the air cavity 11, and then an insulating layer 223 covering the first conductive layer 220A and a second conductive layer 220B in the thermopile 220 are sequentially formed.

And step 1303, forming a passivation layer on the surface of the thermopile on the side far away from the substrate.

Referring to fig. 14c, a passivation layer 221 is formed on the surface of the thermopile on the side away from the substrate. In the present embodiment, the passivation layer 221 serves to protect the thermopile 220 and may provide a flat plane when the infrared absorption layer 222 is formed.

And 1304, forming an infrared absorption layer on the surface of the passivation layer on the side far away from the thermopile, wherein the projection of the thermopile on the substrate surrounds the projection of the infrared absorption layer on the substrate, one end, close to the infrared absorption layer, of the thermopile serves as a hot end, one end, far away from the infrared absorption layer, of the thermopile serves as a cold end, the cold end of the thermopile serves as an electrode, an electric signal corresponding to the infrared signal is led to a second surface, opposite to the first surface, of the substrate through a conductive through hole, and the infrared absorption layer, the passivation layer and the thermopile form a photoelectric conversion.

Referring to fig. 14d, an infrared absorption layer 222 is formed on the surface of the passivation layer 221 on the side away from the thermopile 220. The projection of the thermopile 220 on the substrate 10 surrounds the projection of the infrared absorption layer 222 on the substrate 10, one end of the thermopile 220 close to the infrared absorption layer 222 is used as a hot end, one end of the thermopile 220 far from the infrared absorption layer 222 is used as a cold end, the cold end of the thermopile 220 is used as an electrode to lead an electric signal corresponding to an infrared light signal to the second surface 10B of the substrate 10 opposite to the first surface 10A through a conductive through hole, and the infrared absorption layer 222, the passivation layer 221 and the thermopile 220 form the photoelectric conversion device 22.

Optionally, referring to fig. 14e, after the step 1304, the preparation of the first soldering portion 12, the second soldering portion 13, the first conductive via 10C, the second conductive via 10D, the conductive material 14 and the solder mask layer 15 is further included. One end of the first conductive layer 220A close to the infrared absorption layer 222 and one end of the second conductive layer 220B close to the infrared absorption layer 222 are electrically connected to serve as a hot end of the conductive stack 220. One end of first conductive layer 220A remote from infrared absorbing layer 222 serves as a cold side of thermopile 220 and is multiplexed as first electrode 220C of thermopile 220, and one end of second conductive layer 220B remote from infrared absorbing layer 222 serves as a cold side of thermopile 220 and is multiplexed as second electrode 220D of thermopile 220. The first electrode 220C brings an electrical signal of the first electrode 220C to the second surface 10B of the substrate 10 through the first conductive via 10C. The second electrode 220D brings an electrical signal of the second electrode 220D to the second surface 10B of the substrate 10 through the second conductive via 10D. Optionally, the micro-electromechanical photoelectric detection chip further includes a first soldering portion 12 and a second soldering portion 13, the first soldering portion 12 is electrically connected to the first conductive via 10C, and the second soldering portion 13B is electrically connected to the second conductive via 10D. The first conductive via 10C and the second conductive via 10D are filled with a conductive material 14, and an insulating material is provided between the conductive material 14 and the substrate 10. Optionally, a solder resist layer 15 is disposed on the second surface 10B of the substrate 10, and the solder resist layer 15 is provided with an opening structure exposing the first conductive via 10C and the second conductive via 10D. The first welding part 12 and the second welding part 13 can lead the thermoelectromotive force of the thermopile 220 to the second surface 10B of the substrate 10, and the microcomputer electro-optical detection chip can be electrically connected with an external device through an automatic surface mounting process.

Fig. 10 is a schematic flow chart of another method for manufacturing a microelectromechanical photoelectric detection chip according to an embodiment of the present invention. On the basis of the above technical solution, referring to fig. 10, step 130 further includes, after forming the floating structure on the first surface of the substrate:

and 140, forming a preset wavelength optical signal filter window on the surface of the suspension structure far away from the air cavity.

Taking fig. 1 and fig. 3 as an example for illustration, a filter window 30 for a wavelength light signal of a predetermined wavelength is formed on the surface of the suspension structure 20 on the side away from the air cavity 11.

Fig. 11 is a flowchart corresponding to step 140 in fig. 10. On the basis of the above technical solution, referring to fig. 11, the step 140 of forming a filter window for a wavelength optical signal with a preset wavelength on a surface of the suspension structure on a side away from the air cavity includes:

1401, forming a preset wavelength optical signal filter window, wherein the preset wavelength optical signal filter window comprises an optical anti-reflection film layer, a filter protection layer and a metal reflection layer which are sequentially stacked, and the optical anti-reflection film layer is used for transmitting a preset wavelength optical signal and blocking transmission of a non-preset wavelength optical signal; the light filtering protective layer is used for transmitting a light signal with preset wavelength, the light filtering protective layer comprises a light transmitting area and a non-light transmitting area surrounding the light transmitting area, the metal reflecting layer is positioned on the surface of one side, away from the optical antireflection film layer, of the light filtering protective layer, and the metal reflecting layer is positioned in the non-light transmitting area.

Referring to fig. 15a, a preset wavelength optical signal filter window is formed, where the preset wavelength optical signal filter window 30 includes an optical antireflection film layer 31, a filter protection layer 32, and a metal reflection layer 33 that are sequentially stacked, where the optical antireflection film layer 31 is used to transmit a preset wavelength optical signal and block transmission of a non-preset wavelength optical signal; the filtering protection layer 32 is configured to transmit a light signal with a predetermined wavelength, the filtering protection layer 32 includes a light-transmitting region 32A and a non-light-transmitting region 32B surrounding the light-transmitting region, the metal reflective layer 33 is located on a surface of the filtering protection layer 32 on a side away from the optical anti-reflection film layer 31, and the metal reflective layer 33 is located in the non-light-transmitting region 32B.

Optionally, a groove 30A may be formed on the surface of the light filtering protection layer 32 on the side adjacent to the optical antireflection film layer 31. Specifically, the arrangement of the groove 30A enables the surface of the side of the filtering protective layer 32 adjacent to the optical antireflection film layer 31 to form a concave cavity structure, so that the thickness of the light-transmitting region 32A of the filtering protective layer 32 is reduced, the transmission distance of an optical signal in the filtering protective layer 32 is reduced, the loss of the optical signal is further reduced, and the transmittance of an infrared light signal is increased. Alternatively, the longitudinal sectional shape of the groove 30A is an inverted trapezoid. Specifically, the longitudinal section of the groove 30A is in an inverted trapezoid shape, and the side surface and the bottom surface of the groove 30A have a certain included angle, so that an optical signal reflected to the side surface of the groove 30A can be reflected back to the range of the light-transmitting area 32A, and the photoelectric conversion efficiency of the micro electro mechanical system photoelectric detection chip is improved.

Optionally, taking fig. 4, fig. 5, and fig. 6 as an example, a fresnel diffraction structure 32C may be further formed on a surface of the filtering protection layer 32 on a side away from the optical antireflection film layer 31, where the fresnel diffraction structure 32C is used to focus a wavelength signal with a preset wavelength onto the infrared absorption layer 222, so as to improve the photoelectric conversion efficiency of the micro-electromechanical photodetection chip.

And 1402, forming a preset wavelength optical signal filter window on one side of the suspension structure far away from the support layer through a wafer-level low-temperature vacuum bonding process, wherein the optical anti-reflection film layer is close to the suspension structure.

Referring to fig. 15b, a predetermined wavelength optical signal filter 30 is formed on the side of the suspension structure 20 away from the support layer 21 by a wafer-level low-temperature vacuum bonding process, wherein the optical antireflection film layer 31 is adjacent to the suspension structure 20.

Optionally, the preset wavelength optical signal filter window 30 and the passivation layer 221 may be bonded together by the bonding layer 40, the suspension structure 20 and the preset wavelength optical signal filter window 30 form a vacuum chamber, which may reduce the influence of the fluctuation of the surrounding environment on the photoelectric detection performance of the photoelectric conversion device 22 in the suspension structure 20, improve the stability of the photoelectric conversion device 22, and adjust the distance between the preset wavelength optical signal filter window 30 and the suspension structure 20 by adjusting the height of the bonding layer 40.

The technical scheme provided by the embodiment of the invention is that a cavity structure is formed by releasing from the front side, so that the problems that the corrosion window range and the thickness of the supporting film are difficult to control when corrosion is performed from the back side of a silicon wafer can be solved; on the other hand, compare with the current scheme that forms the thermopile structure at first, and release hole on the rethread supporting film structure utilizes anisotropic wet etching (KOH/TMAH etc.) technology or isotropic dry etching technology to corrode the silicon substrate and form the cavity, this patent is carried out the sculpture earlier on the silicon substrate and is formed the cavity structure, form supporting part and thermopile structure again, effectively avoided the destruction of back etching process to having the thermopile structure then, and overcome the defect of underetching and overetching, shortened the etching time greatly, reduced the technology degree of difficulty, simple and practical. In addition, in the conventional front surface cavity releasing process, the support film is easy to break due to the problems of mismatching of tensile stress and corrosive liquid. The support film prepared according to the method can not be influenced in the subsequent etching or corrosion process, and the consistency and uniformity are easy to control, so that a complete and uniform support film structure and device can be easily obtained, and the problem of film breakage possibly existing in the post-etching process is effectively avoided.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A micro-electromechanical photoelectric detection chip is characterized by comprising:

a substrate;

the air cavity is positioned on the first surface of the substrate and comprises a net-shaped structure film and a cavity, the net-shaped structure film covers the cavity, at least one release hole is formed in the net-shaped structure film, and the cavity is used for communicating different release holes;

the suspension structure is positioned on the first surface of the substrate and covers the air cavity, and the suspension structure sequentially comprises a supporting layer and a photoelectric conversion device in a direction far away from the air cavity.

2. The micro-electromechanical photoelectric detection chip as claimed in claim 1, wherein the surface of the mesh-structured film adjacent to the cavity is provided with an inverted triangle structure, and the surface of the substrate adjacent to the cavity is provided with a regular triangle structure.

3. The microelectromechanical photodetection chip of claim 1, characterized in that the depth of the release hole is greater than or equal to 1/2 of the substrate thickness and less than or equal to 2/3 of the substrate thickness.

4. The microelectromechanical photodetecting chip according to claim 1, characterized in that the cross-sectional shape of the release holes in the plane of the thin film of mesh structure is circular or polygonal.

5. The microelectromechanical photodetecting chip according to claim 4, characterized in that the cross-sectional shape of the release holes in the plane of the mesh-structured film is circular, and the release holes enclose a plurality of concentric rings in the mesh-structured film.

6. The microelectromechanical photodetecting chip according to claim 5, characterized in that the release holes have the same area;

or the area of the release holes far away from the center of the reticular structure film is smaller than that of the release holes close to the center of the reticular structure film.

7. The microelectromechanical photodetecting chip according to claim 4, characterized in that the cross-sectional shape of the release holes in the plane of the mesh-structured film is square, and the release holes enclose a block-shaped area in the mesh-structured film;

or the cross section of the release holes on the plane of the reticular structure film is rectangular, and the adjacent release holes are arranged in parallel or vertically at preset intervals.

8. The microelectromechanical photodetection chip according to claim 1, characterized in that the suspended structure comprises:

a support layer located on a first surface side of the substrate and covering the air cavity;

a thermopile on a surface of the support layer on a side away from the air cavity;

the passivation layer is positioned on the surface of one side of the thermopile far away from the substrate;

the infrared absorption layer is positioned on the surface of one side, far away from the thermopile, of the passivation layer, the projection of the thermopile on the substrate surrounds the projection of the infrared absorption layer on the substrate, one end, close to the infrared absorption layer, of the thermopile serves as a hot end, one end, far away from the infrared absorption layer, of the thermopile serves as a cold end, the cold end of the thermopile serves as an electrode, an electric signal corresponding to the infrared light signal is led to a second surface, opposite to the first surface, of the substrate through a conductive through hole, and the infrared absorption layer, the passivation layer and the thermopile form the photoelectric conversion device.

9. A preparation method of a micro-electromechanical photoelectric detection chip is characterized by comprising the following steps:

providing a substrate;

10. The method of claim 9, wherein forming an air cavity on the first surface of the substrate comprises:

forming a dielectric layer on the first surface of the substrate;

performing patterning etching on the dielectric layer to form at least one groove;

forming at least one release hole on the first surface of the substrate, wherein the release hole is communicated with the groove;

forming the air cavity on the first surface of the substrate by adopting an etching process, wherein the etching process comprises an anisotropic deep reactive ion etching process and/or an anisotropic wet etching process, reactants of the anisotropic deep reactive ion etching process and/or the anisotropic wet etching process enter the substrate along the release holes to form the mesh-structured film and the cavity, the mesh-structured film covers the cavity, the mesh-structured film is provided with at least one release hole, and the cavity is used for communicating different release holes;

and removing the dielectric layer.

11. The method of claim 10, wherein forming the air cavity on the first surface of the substrate using an etching process comprises:

adopt the etching process right the first surface of substrate carries out anisotropic sculpture to form including the network structure film of triangle structure, including the substrate of regular triangle structure and be located the network structure film including the triangle structure and cavity between the substrate including the triangle structure, wherein, the network structure film closes on the surface of cavity is provided with the triangle structure, the substrate closes on the surface of cavity is provided with regular triangle structure.

12. The method of claim 9, wherein forming the suspension structure comprises:

forming a support layer on a first surface side of the substrate, the support layer covering the air cavity;

forming a thermopile on the surface of the support layer on the side far away from the air cavity;

forming a passivation layer on the surface of the thermopile on the side far away from the substrate;

an infrared absorption layer is formed on the surface of one side, far away from the thermopile, of the passivation layer, wherein the projection of the thermopile on the substrate surrounds the projection of the infrared absorption layer on the substrate, one end, close to the infrared absorption layer, of the thermopile serves as a hot end, one end, far away from the infrared absorption layer, of the thermopile serves as a cold end, the cold end of the thermopile serves as an electrode, electric signals corresponding to the infrared light signals are led to a second surface, opposite to the first surface, of the substrate through a conductive through hole, and the infrared absorption layer, the passivation layer and the thermopile form the photoelectric conversion device.