Infrared micro-bolometer detector and design method, manufacturing method and system thereof

Abstract

An infrared microbolometer detector (100), and a design method, manufacturing method and system thereof, comprising: a first substrate, a detector readout circuit (106), a microbolometer microelectromechanical system structure (105) and a pixel-level metasurface layer (102), the pixel-level metasurface layer (102) comprising a plurality of pixel-level metasurface minimum cells (304), the size M of the pixel-level metasurface minimum unit (304) meets the following conditions: M < lambda / 2nmeta, A is the wavelength of incident light, and nmeta is the refractive index of the pixel-level metasurface layer (102). The size of each pixel-level metasurface minimum unit (304) is smaller than the wavelength of incident light, the incident light can be finely distinguished, the distinguished incident light is converged into a specific micro-bolometer micro electro mechanical system structure (105) so that a detector reading circuit (106) can read the distinguished incident light, and finally a finer infrared image is obtained.

Description

Infrared microbolometer detector and design method, manufacturing method and system thereof Technical Field

[0001] The present invention relates to the field of infrared detection, and in particular to an infrared microbolometer detector and a design method and a manufacturing method thereof, and an infrared microbolometer system. Background Art

[0002] In recent years, color infrared thermal imaging has become a new research hotspot. Traditional infrared thermal imaging involves focusing infrared light emitted by an object through a lens and receiving it on an infrared focal plane detector (FAPOD), ultimately producing a grayscale, monochromatic infrared image. However, a grayscale, monochromatic infrared image represents the combined effect of incident light across a wide wavelength band. For example, a type of FAPOD, such as a microbolometer, typically produces a grayscale image containing all the information from long-wave infrared light in the 8-14 micron (μm) band. Because grayscale, monochromatic infrared images represent the combined effect of incident light across a wide wavelength band, the detailed information contained is very limited. Therefore, a key technology of the new generation of FAPODs is to separate infrared light of different wavelengths and direct them onto different pixels, enabling multispectral or multi-polarization imaging, and then generating a color infrared image through RGB rendering.

[0003] However, existing color infrared focal plane detectors are primarily cooled detectors based on mercury cadmium telluride (HgCdTe) materials. These detectors can only distinguish between broad wavelengths, such as short-wave infrared, medium-wave infrared, and long-wave infrared, and have difficulty distinguishing finer spectral bands. This fails to meet the demand for more refined infrared images.

[0004] Summary of the Invention

[0005] In view of this, the purpose of the present application is to provide an infrared microbolometer detector and a design method and a manufacturing method thereof, wherein the infrared microbolometer detector can distinguish finer spectral segments, and the infrared image detected can have higher fineness.

[0006] To achieve the above objectives, this application has the following technical solutions:

[0007] The present invention provides an infrared microbolometer detector, comprising:

[0008] a first substrate and a detector readout circuit and a microbolometer microelectromechanical system structure sequentially disposed on one side of the first substrate;

[0009] a pixel-level metasurface layer, disposed on a side of the microbolometer MEMS structure away from the first substrate;

[0010] The pixel-level metasurface layer includes a plurality of pixel-level metasurface minimum units, and the size M of the pixel-level metasurface minimum unit satisfies the following conditions:

[0011]

[0012] The λ is the wavelength of incident light, and the n meta is the refractive index of the pixel-level metasurface layer.

[0013] The present invention provides a method for designing an infrared microbolometer detector, including:

[0014] Randomly generate a pixel-level metasurface unit and simulate to obtain a function value of a first heuristic function of the pixel-level metasurface unit, where the first heuristic function represents an imaging effect of the pixel-level metasurface unit, and the pixel-level metasurface unit includes a plurality of pixel-level metasurface minimum units;

[0015] Modifying the shape of at least one of the pixel-level hypersurface minimum units using a simulated annealing algorithm, and simulating to obtain a function value of a first heuristic function of the modified pixel-level hypersurface unit;

[0016] Repeating the step of modifying the shape of at least one of the pixel-level hypersurface minimum units using a simulated annealing algorithm until a pixel-level hypersurface unit corresponding to an extreme point of a first heuristic function is determined, and determining the pixel-level hypersurface unit corresponding to the extreme point of the first heuristic function as an optimal hypersurface unit;

[0017] Arranging the optimal metasurface units in a periodic manner to form a pixel-level metasurface layer;

[0018] Simulating the pixel super surface layer to obtain a function value of a second heuristic function of the pixel super surface layer, where the second heuristic function represents an imaging effect of the pixel super surface layer;

[0019] Modifying the shape of at least one of the pixel-level hypersurface minimum units using a simulated annealing algorithm, and simulating to obtain a function value of a second heuristic function of the modified pixel-level hypersurface unit;

[0020] Repeat the step of modifying the shape of at least one of the pixel-level hypersurface minimum units using the simulated annealing algorithm until the pixel-level hypersurface layer corresponding to the extreme point of the second heuristic function is determined, and determine the pixel-level hypersurface layer corresponding to the extreme point of the second heuristic function as the optimal hypersurface layer.

[0021] The present invention provides a method for manufacturing an infrared microbolometer detector, comprising:

[0022] forming a detector readout circuit and a microbolometer microelectromechanical system structure on the first substrate in sequence;

[0023] A pixel-level metasurface layer is formed on a side of the microbolometer MEMS structure away from the first substrate, wherein the pixel-level metasurface layer includes a plurality of pixel-level metasurface minimum units, and a size M of the pixel-level metasurface minimum unit satisfies the following conditions:

[0024]

[0025] The λ is the wavelength of incident light, and the n meta is the refractive index of the pixel-level metasurface layer.

[0026] An embodiment of the present application provides an infrared microbolometer system, characterized by comprising an infrared lens, a shutter plate, and the infrared microbolometer detector described in any one of the above embodiments.

[0027] An embodiment of the present application provides an infrared microbolometer detector, characterized by comprising: a first substrate, a detector readout circuit and a microbolometer microelectromechanical system structure sequentially arranged on one side of the first substrate, a pixel-level metasurface layer arranged on a side of the microbolometer microelectromechanical system structure away from the first substrate, the pixel-level metasurface layer including a plurality of pixel-level metasurface minimum units, and a size M of the pixel-level metasurface minimum unit satisfying the following conditions:

[0028]

[0029] Where λ is the wavelength of incident light, n meta is the refractive index of the pixel-level metasurface layer. The pixel-level metasurface layer provided in the embodiment of the present application includes a plurality of pixel-level metasurface minimum units, each of which is smaller than the wavelength of the incident light. This enables fine differentiation of the incident light and converges the differentiated incident light into a specific microbolometer microelectromechanical system structure so that the detector readout circuit can read the incident light and ultimately obtain a more refined infrared image. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] FIG1 shows a schematic diagram of a refrigerated detector based on mercury cadmium telluride material;

[0032] FIG2 shows a schematic cross-sectional structure diagram of an infrared microbolometer detector provided in an embodiment of the present application;

[0033] FIG3 shows a side cross-sectional view of an infrared microbolometer detector provided in an embodiment of the present application;

[0034] FIG4 shows a schematic diagram of a partial structure of an infrared microbolometer detector provided in an embodiment of the present application;

[0035] FIG5 shows a schematic diagram of an equivalent pixel of a detector provided in an embodiment of the present application;

[0036] FIG6 shows a schematic diagram of a partial structure of another infrared microbolometer detector provided in an embodiment of the present application;

[0037] FIG7 shows a schematic diagram of a local structure of a pixel-level metasurface layer provided in an embodiment of the present application;

[0038] FIG8 shows a schematic diagram of the local structure of various pixel-level metasurface minimum units provided in an embodiment of the present application;

[0039] FIG9( a ) shows a schematic diagram of a pixel-level metasurface layer provided in an embodiment of the present application;

[0040] FIG9( b ) shows a schematic diagram of another pixel-level metasurface layer provided in an embodiment of the present application;

[0041] FIG10( a ) shows a functional schematic diagram of an infrared microbolometer detector provided in an embodiment of the present application;

[0042] FIG10( b ) shows a functional schematic diagram of another infrared microbolometer detector provided in an embodiment of the present application;

[0043] FIG10( c ) shows a functional schematic diagram of another infrared microbolometer detector provided in an embodiment of the present application;

[0044] FIG10( d ) shows a functional schematic diagram of another infrared microbolometer detector provided in an embodiment of the present application;

[0045] FIG11 is a schematic diagram showing a partial structure of the infrared microbolometer detector shown in FIG10 ;

[0046] FIG12 shows a schematic cross-sectional structure diagram of another infrared microbolometer detector provided in an embodiment of the present application;

[0047] FIG13 shows a bonding diagram of an infrared microbolometer detector provided in an embodiment of the present application;

[0048] FIG14 shows a flow chart of a design method for an infrared microbolometer detector provided in an embodiment of the present application;

[0049] FIG15 shows a flow chart of another method for designing an infrared microbolometer detector provided in an embodiment of the present application;

[0050] FIG16( a ) shows a rendering of a manufacturing process of an infrared microbolometer detector provided in an embodiment of the present application;

[0051] FIG16( b ) shows an effect diagram of a manufacturing process of another infrared microbolometer detector provided in an embodiment of the present application;

[0052] FIG16( c ) shows an effect diagram of a manufacturing process of another infrared microbolometer detector provided in an embodiment of the present application;

[0053] FIG17( a ) shows a simulation schematic diagram of an infrared microbolometer detector provided in an embodiment of the present application;

[0054] FIG17( b ) shows the simulation effect diagram of FIG17( a );

[0055] FIG18 shows a flow chart of a method for manufacturing an infrared microbolometer detector provided in an embodiment of the present application;

[0056] FIG19 shows a flow chart of a method for manufacturing a pixel-level metasurface layer provided in an embodiment of the present application;

[0057] FIG20 shows a flow chart of another method for manufacturing a pixel-level metasurface layer provided in an embodiment of the present application;

[0058] FIG21 is a flow chart showing another method for manufacturing a pixel-level metasurface layer provided in an embodiment of the present application;

[0059] FIG22 shows a schematic structural diagram of an infrared microbolometer system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0060] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below with reference to the accompanying drawings.

[0061] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0062] Secondly, this application is described in detail with reference to schematic diagrams. When describing the embodiments of this application, for ease of explanation, cross-sectional views of device structures may be partially enlarged and not to scale. Furthermore, these schematic diagrams are merely illustrative and should not limit the scope of protection of this application. Furthermore, in actual production, three-dimensional dimensions, including length, width, and depth, should be included.

[0063] In recent years, color infrared thermal imaging has become a new research hotspot. Traditional infrared thermal imaging involves focusing infrared light emitted by an object through a lens and receiving it on an infrared focal plane detector (FAPOD), ultimately producing a grayscale, monochromatic infrared image. However, a grayscale, monochromatic infrared image represents the combined effect of incident light across a wide wavelength band. For example, a type of FAPOD, such as a microbolometer, typically produces a grayscale image containing all the information from long-wave infrared light in the 8-14 micron (μm) band. Because grayscale, monochromatic infrared images represent the combined effect of incident light across a wide wavelength band, the detailed information contained is very limited. Therefore, a key technology for the new generation of FAPODs is to separate infrared light of different wavelengths or polarization states and apply them to separate pixels, achieving multispectral and multipolarization imaging, and then generating a color infrared image through RGB rendering.

[0064] However, existing color infrared focal plane detectors are primarily based on cooled HgCdTe (HgCdTe) materials, as shown in Figure 1. These HgCdTe-based detectors utilize vertically distributed infrared absorption regions across different wavelength bands to achieve multispectral imaging. The substrates used for these detectors are expensive, the wafers are small, and they are highly toxic, making them unsuitable for large-scale production. Furthermore, the stacked distribution of the absorption regions makes it difficult to control doping during the manufacturing process and ensure doping stability within the wafer and between wafer batches. Furthermore, the etching process can cause significant material damage. These process issues can lead to reduced detection quantum efficiency and wavelength shift. Furthermore, HgCdTe-based cooled detectors must operate at extremely low temperatures to maintain sufficiently low dark current, requiring cooling equipment such as Dewar flasks, further increasing system costs. Furthermore, HgCdTe-based detectors are typically only able to distinguish between broad wavelengths such as the shortwave infrared (SWIR), midwave infrared (MWIR), and longwave infrared (LWIR), and struggle to distinguish finer spectral segments. This fails to meet the demand for more refined infrared images.

[0065] Based on this, an embodiment of the present application provides an infrared microbolometer detector, comprising: a first substrate, a detector readout circuit and a microbolometer microelectromechanical system structure sequentially arranged on one side of the first substrate, a pixel-level metasurface layer, arranged on a side of the microbolometer microelectromechanical system structure away from the first substrate, the pixel-level metasurface layer including a plurality of pixel-level metasurface minimum units, and a size M of the pixel-level metasurface minimum unit meeting the following conditions:

[0066]

[0067] Where λ is the wavelength of incident light, n meta is the refractive index of the pixel-level metasurface layer. The pixel-level metasurface layer provided in the embodiment of the present application includes a plurality of pixel-level metasurface minimum units, each of which is smaller than the wavelength of the incident light. This enables fine differentiation of the incident light and converges the differentiated incident light into a specific microbolometer microelectromechanical system structure so that the detector readout circuit can read the incident light and ultimately obtain a more refined infrared image.

[0068] In order to better understand the technical solutions and technical effects of the present application, specific embodiments will be described in detail below with reference to the accompanying drawings.

[0069] Referring to Figures 2 and 3, Figure 2 shows a schematic cross-sectional view of an infrared microbolometer detector according to an embodiment of the present application, and Figure 3 shows a side cross-sectional view of an infrared microbolometer detector according to an embodiment of the present application. The infrared microbolometer detector according to an embodiment of the present application is capable of fine-grained spectral differentiation, particularly in the long-wave infrared band, specifically within the 8-14 μm wavelength range, enabling color infrared imaging or polarized infrared imaging.

[0070] The infrared microbolometer detector 100 provided in the embodiment of the present application includes: a first substrate, and a detector readout integrated circuit (ROIC) 106 and a microbolometer microelectromechanical system structure 105 sequentially arranged on one side of the first substrate.

[0071] As a possible implementation, the first substrate is a wafer, and the detector readout circuit 106 may be a complementary metal oxide semiconductor (CMOS) circuit that has been integrated on the first substrate to form a detector readout circuit wafer.

[0072] A microbolometer MEMS structure 105 is provided on a side of the detector readout circuit 106 away from the first substrate, for receiving incident light and converting it into an electrical signal for transmission to the detector readout circuit 106. The microbolometer MEMS structure 105 may also be referred to as a microbolometer MEMS structure.

[0073] The infrared microbolometer detector 100 provided in the embodiment of the present application includes: a pixel-level metasurface layer 102, which is arranged on a side of the microbolometer microelectromechanical system structure 105 away from the first substrate.

[0074] The pixel-level metasurface layer 102 includes a plurality of pixel-level metasurface minimum units 304. Referring to FIG4 , the size M of the pixel-level metasurface minimum unit 304 satisfies the following conditions:

[0075]

[0076] Where λ is the wavelength of incident light, n meta is the refractive index of the pixel-level metasurface layer.

[0077] It can be seen that in the embodiment of the present application, the size M of the pixel-level metasurface minimum unit 304 is smaller than the wavelength of the incident light. When the size of each pixel-level metasurface minimum unit is smaller than the wavelength of the incident light, it is possible to achieve fine differentiation of the incident light, and the differentiated incident light can be converged into a specific micro-bolometer microelectromechanical system structure so that the detector readout circuit can read it and ultimately obtain a more refined infrared image.

[0078] In practical applications, the size M of the smallest unit 304 of the pixel-level metasurface can be much smaller than the wavelength of the incident light, for example, less than one tenth of the wavelength of the incident light.

[0079] The pixel-level supersurface layer 102 provided in the embodiment of the present application is different from the current traditional supersurface layer. The size M of the pixel-level supersurface minimum unit 304 provided in the embodiment of the present application can be smaller than the period U of the traditional supersurface layer. traditional restrictions.

[0080] The period U of the conventional metasurface layer traditional The restrictions are as follows:

[0081]

[0082] Wherein, NA is the numerical aperture, and the inequality related to the numerical aperture in the above formula means that the traditional metasurface layer needs to meet the Nyquist sampling critical condition. The inequality related to the refractive index of the pixel-level metasurface layer means that the traditional metasurface layer needs to meet the condition of no second-order diffraction under the condition of oblique incident light. However, since the size M of the pixel-level metasurface minimum unit 304 provided in the embodiment of the present application is not restricted by this condition, the pixel-level metasurface layer 102 provided in the embodiment of the present application can allow high-order diffraction, so that when the pixel-level metasurface layer 102 is designed, the size M of the pixel-level metasurface minimum unit 304 can be regulated without restrictions, and M can be much smaller than the size of the minimum unit of the traditional metasurface layer.

[0083] In an embodiment of the present application, in a direction perpendicular to the first substrate, the detector readout circuit 106 and the microbolometer microelectromechanical system structure 105 include a plurality of detector unit pixels 303, N detector unit pixels 303 constitute one detector equivalent pixel 302, the pixel-level metasurface layer includes a plurality of pixel-level metasurface units 301, and the plurality of pixel-level metasurface units 301 include a plurality of pixel-level metasurface minimum units 304, wherein N is a positive integer, and the pixel-level metasurface unit 301 and the detector equivalent pixel 303 have the same size and correspond one to one, as shown in FIG4 .

[0084] That is, N detector unit pixels 303 are defined as one detector equivalent pixel 302. The value of N can be determined based on actual needs. Specifically, the detector equivalent pixel 302 can include four detector unit pixels 303, as shown in FIG5(a), nine detector unit pixels 303, as shown in FIG5(b), or one detector unit pixel 303, as shown in FIG5(e). The detector unit pixels 303 can be arranged to form a rectangle, a vertical line, or a horizontal line, as shown in FIG5(a)-FIG5(e).

[0085] The pixel-level metasurface unit 301 is located directly above the detector equivalent pixel 302. The side lengths of the pixel-level metasurface unit 301 in the X and Y directions are equal to the side lengths of the detector equivalent pixel 302, and the structures of the two are aligned along the optical axis Z, that is, perpendicular to the direction of the first substrate, as shown in Reference 4.

[0086] In this way, the pixel-level metasurface unit 301 and the detector equivalent pixel 303 have the same size and a one-to-one correspondence. This allows the output light of the pixel-level metasurface unit 301 to, ideally, only act on the detector equivalent pixel 302 directly below the metasurface. The pixel-level metasurface unit 301 and the detector equivalent pixel 302 below have a corresponding infrared feature relationship. For example, after infrared light passes through the pixel-level metasurface layer 102, infrared light of different wavelengths is focused onto specific detector unit pixels 303 below. Each detector unit pixel 303 corresponds to a specific wavelength band. Referring to Figure 6, incident infrared light of 8-14 μm, after passing through the pixel-level metasurface layer 102, is divided into three infrared light beams: 8-10 μm infrared light, 10-12 μm infrared light, and 12-14 μm infrared light. These three beams are incident on the detector unit pixels 303 of the corresponding wavelength bands. This ultimately achieves fine differentiation of the incident light and enables color infrared imaging.

[0087] In an embodiment of the present application, the pixel-level metasurface layer 102 includes at least a metasurface substrate 201 and a metasurface column layer 202. The metasurface column layer 202 is disposed on a side of the metasurface substrate 201 away from the first substrate, as shown in FIG4 . Specifically, the material of the metasurface substrate 201 can be silicon or germanium, and the material of the metasurface column layer 202 can also be silicon or germanium.

[0088] In an embodiment of the present application, if the material of the metasurface substrate 201 and the material of the metasurface column layer 202 are silicon, the reflectivity of the interface between silicon and air is relatively high for infrared light, and the metasurface column layer 202 can reduce infrared reflection and increase transmittance, thereby achieving the effect of enhancing the transmittance of infrared light on the basis of realizing the function of distinguishing spectral segments by utilizing the pixel-level metasurface layer 102.

[0089] In an embodiment of the present application, the pixel-level super-surface layer 102 may include a coating layer 203, which is located at least on one side of the super-surface column layer 202 away from the super-surface substrate 201, for protecting the super-surface column layer 202 and increasing the transmittance of infrared light. Specifically, the material of the coating layer 203 can be zinc sulfide (ZnS) or magnesium fluoride (MgF2) or other materials with high transmittance in the infrared and a large refractive index. The coating layer 203 can be uniformly or non-uniformly covered on the side wall of the super-surface column layer 202, as shown in Figure 7, and the coating layer 203 may not cover the side wall of the super-surface column layer 202.

[0090] In an embodiment of the present application, the metasurface column layer 202 includes a plurality of convex structures, and the pixel-level metasurface minimum unit (Minimum Meta-surface Cell) 304 may include a flat cell (Flat Cell) 305 and a convex unit 306, wherein the convex unit 306 has a convex structure, as shown in FIG8 . That is, inside the pixel-level metasurface unit 301, it can be divided into a plurality of pixel-level metasurface minimum units 304 of equal area according to the specific design, and the pixel-level metasurface minimum unit 304 can have two types of flat units 305 and convex units 306. The convex unit 306 has a convex structure above the metasurface substrate 201, and the flat unit 305 does not have a convex structure above the metasurface substrate 201. The shape of the convex structure on the convex unit 306 can be a completely filled rectangular column, or an elliptical or rounded rectangular column or other arbitrary columnar structure. The convex structure in the embodiment of the present application is not limited to the shape shown in FIG8 , and can be arbitrarily modified to meet the purpose of using the pixel-level metasurface layer 102 to distinguish spectral segments in the present application.

[0091] In the embodiment of the present application, the height H of the protruding structure approximately satisfies the following conditions:

[0092]

[0093] Among them, n i is the refractive index of the incident medium, λ is the wavelength of the incident light, n meta is the refractive index of the pixel-level metasurface layer. That is, the height H of the metasurface column layer 202 mainly depends on the wavelength λ of the incident infrared spectrum and the refractive index n of the pixel-level metasurface layer. meta . Usually in air environment, n i =1, specifically, the height H of the protruding structure may be 6-8 um.

[0094] In an embodiment of the present application, the internal graphics of the pixel-level supersurface unit 301 may not be periodic, that is, the arrangement of the pixel-level supersurface minimum unit 304 may be non-periodic. For example, the entire pixel-level supersurface layer 102 can be composed of a long-range periodic structure of a pixel-level supersurface unit 301, as shown in Figure 9 (a), all of which are composed of a pattern (Pattern) A, that is, the pixel-level supersurface unit 301 is periodic, and the pixel-level supersurface minimum unit 304 is not periodic. For another example, the entire pixel-level supersurface layer 102 may not be periodic at all, as shown in Figure 9 (b), the pixel-level supersurface unit 301 is composed of different patterns, and the size of the pixel-level supersurface minimum unit 304 in each pixel-level supersurface unit 301 may also be different, that is, the pixel-level supersurface unit 301 is not periodic, and the pixel-level supersurface minimum unit 304 is not periodic either. The entire pixel-level supersurface layer 102 is not periodic at all.

[0095] That is to say, different sizes can be designed for the pixel-level metasurface minimum unit 304 at different positions of the entire pixel-level metasurface layer 102, so that local optimization can be achieved by changing the minimum size of the pixel-level metasurface minimum unit 304 at a specific position. Specifically, when the incident light is incident, there are certain differences in the conditions of the incident light, for example, the incident angle of the incident light of each pixel-level metasurface minimum unit 304 is different. At the pixel-level metasurface minimum unit 304 near the optical axis, the incident light is closer to vertical incidence, while the pixel-level metasurface minimum unit 304 away from the optical axis has a larger angle of incidence. Since the pixel-level metasurface layer 102 has a worse dispersion effect on infrared light with a larger incident angle, these positions with poor dispersion effects can be additionally optimized by changing the minimum size of the pixel-level metasurface minimum unit 304 to improve the imaging effect of the infrared microbolometer detector.

[0096] In the embodiments of the present application, multiple functions of the infrared microbolometer detector can be achieved by changing the shape of the protruding structure or the size of the smallest unit of the pixel-level metasurface. The multiple functions include at least dispersion refraction, narrowband filtering, polarization refraction, and local focusing, which are described in detail below:

[0097] The first possible function is dispersive refraction. As shown in Figure 10(a), incident infrared light of different wavelengths is refracted at specific angles and converged onto specific detector unit pixels 303. The three detector unit pixels 303 at the bottom of Figure 10(a) correspond to wavelengths of 8-10 μm, 10-12 μm, and 12-14 μm, respectively. After passing through the pixel-level metasurface layer 102, the incident infrared light of different wavelengths is refracted directly above the corresponding detector unit pixels 303.

[0098] The second possible function is narrowband filtering. As shown in Figure 10(b), the pixel-level metasurface layer 102 has different reflectivities for incident infrared light of different wavelengths, allowing only narrowband infrared light of a specific wavelength to pass through. Unlike dispersive refraction, the pixel-level metasurface layer 102 reflects all of the infrared wavelengths that are not permitted to pass through. Taking the 8-10 μm detector unit pixel 303 as an example, infrared light of all other wavelengths, including those less than 8 μm and those greater than 10 μm, will be reflected by the pixel-level metasurface layer 102. Only infrared light with a wavelength of 8-10 μm passes through the pixel-level metasurface layer 102 and irradiates the detector unit pixel 303.

[0099] The third possible function is polarization refraction, as shown in Figure 10(c). This refraction produces specific angles of refraction for incident infrared light of different polarization states, converging them onto specific detector unit pixels 303. In Figure 10(c), incident infrared light of vertical polarization, horizontal polarization, and circular / elliptically polarized polarization produces different refraction angles after passing through the pixel-level metasurface layer 102. Infrared light of different polarization states is refracted directly onto the corresponding detector unit pixel 303.

[0100] The fourth possible function is local focusing, as shown in Figure 10 (d), which focuses the incident infrared light onto a specific detector unit pixel 303, no longer distinguishing between wavelength and polarization state, but converging the incident light onto the central area of ​​the microbolometer MEMS structure 105. In traditional infrared microbolometer detectors, infrared light will irradiate the gaps between the detector unit pixels 303 or the bridge legs of the microbolometer MEMS structure. These infrared lights cannot be converted into heat signals and are therefore wasted. However, in an embodiment of the present application, the pixel-level metasurface layer 102 can converge the infrared light into the central infrared absorption area 111 of the detector unit pixel 303, as shown in Figure 11, to increase the infrared absorption efficiency. Pixel-level focusing can improve the infrared light utilization rate of the infrared microbolometer detector.

[0101] In practical applications, when implementing the dispersion refraction function, the pixel-level metasurface layer 102 will refract infrared light of a specific wavelength across the entire surface onto specific detector unit pixels 303, thereby achieving higher efficiency and light energy utilization. When implementing the narrowband filtering function, the pixel-level metasurface layer 102 generally has better wavelength selectivity and stronger out-of-band infrared light suppression. When implementing the polarization refraction function, the pixel-level metasurface layer 102 will refract infrared light of a specific polarization state across the entire surface onto specific detector unit pixels 303, thereby achieving higher efficiency and light energy utilization compared to traditional solutions using polarizers.

[0102] In the embodiment of the present application, the size of the detector unit pixel 303 is approximately 8-14um, which is relatively close to the wavelength of long-wave infrared light. Therefore, if a traditional metasurface layer is used, only a small number of protrusion structures can be formed in the traditional metasurface unit corresponding to a detector unit pixel 303. However, in actual applications, the more protrusion structures arranged in the unit pixel, the more fine phase control can be achieved. Therefore, the total area of ​​the traditional metasurface layer must be larger than several hundred times the unit pixel area, so that enough protrusion structures can be arranged to achieve specific functions. However, the size of the pixel-level metasurface minimum unit 304 in the pixel-level metasurface layer 102 provided in the embodiment of the present application is much smaller than the wavelength of the incident infrared light, which means that a large number of protrusion structures can be arranged in the pixel-level metasurface unit 301 corresponding to a detector equivalent pixel 302, realizing specific functions within a limited area, which greatly reduces the total area compared to the traditional metasurface layer.

[0103] In an embodiment of the present application, the infrared microbolometer detector may include a wafer-level packaging cover 103, as shown in FIG2 or FIG12. Wafer-level packaging cover 103 is disposed on a side of the microbolometer MEMS structure 105 away from the first substrate to form a vacuum-tight environment and protect the microbolometer MEMS structure 105.

[0104] The pixel-level super-surface layer 102 may be disposed on the surface of the wafer-level packaging cover 103 or may not be disposed on the surface of the wafer-level packaging cover 103 , as described in detail below:

[0105] As a possible implementation method, the pixel-level metasurface layer 102 can be provided on one side surface of the wafer-level packaging cover 103, which can be either the inner surface or the outer surface, as shown in Figure 2. In other words, the pixel-level metasurface layer 102 can be integrated into the wafer-level packaging cover 103. Such a structure can facilitate the alignment of the pixel-level metasurface layer 102 and the microbolometer microelectromechanical system structure 105 when the wafer-level packaging cover 103 is bonded to the first substrate. In addition, the pixel-level metasurface layer 102 is usually provided at the focal plane position of the incident infrared lens, so the position of the pixel-level metasurface layer 102 requires relatively precise control. Setting the pixel-level metasurface layer 102 on the wafer-level packaging cover 103 can ensure accurate positioning.

[0106] As another possible implementation, the pixel-level metasurface layer 102 may not be disposed on the surface of the wafer-level packaging cover 103, but may be disposed on the side of the wafer-level packaging cover 103 away from the first substrate. Specifically, the pixel-level metasurface layer 102 may be disposed on the surface of an independent metasurface optical element 110, and the metasurface optical element 110 is disposed on the side of the wafer-level packaging cover 103 away from the first substrate. The pixel-level metasurface layer 102 may be disposed on the side of the metasurface optical element 110 away from the first substrate, as shown in FIG12 .

[0107] In practical applications, the infrared microbolometer detector may include an infrared anti-reflection layer 104, which is used to increase the transmittance of infrared light and improve the final imaging effect. Specifically, the infrared anti-reflection layer 104 can be enhanced by optical coating methods or by forming an additional pixel-level metasurface layer for enhanced transmittance.

[0108] As a possible implementation method, the infrared transmittance-enhancing layer 104 is arranged on the side of the pixel-level supersurface layer 102 away from the first substrate, and can also be arranged on the side of the pixel-level supersurface layer 102 close to the first substrate.

[0109] As an example, the infrared transmittance-enhancing layer 104 is arranged on the side of the pixel-level super-surface layer 102 away from the first substrate, specifically, it can be the two side surfaces of the wafer-level packaging cover 103, wherein the pixel-level super-surface layer 102 can be set on the side close to the first substrate, and the infrared transmittance-enhancing layer 104 can be set on the side away from the first substrate.

[0110] As another example, the infrared transmittance-enhancing layer 104 is arranged on the side of the pixel-level supersurface layer 102 close to the first substrate. Specifically, the infrared transmittance-enhancing layer 104 is arranged between the pixel-level supersurface layer 102 and the micro-bolometer microelectromechanical system structure 105, as shown in Figure 2.

[0111] As another example, the infrared anti-reflection layer 104 is provided on the side of the pixel-level metasurface layer 102 close to the first substrate, and specifically can be the two side surfaces of the wafer-level packaging cover 103, wherein the side away from the first substrate can be provided with the pixel-level metasurface layer 102, and the side close to the first substrate can be provided with the infrared anti-reflection layer 104. As another possible implementation, the infrared anti-reflection layer 104 can be provided on a side surface of the metasurface optical element 110 close to the first substrate and / or on a side surface of the wafer-level packaging cover 103, as shown in FIG12 .

[0112] In an embodiment of the present application, the first substrate has a bonding ring 403 and an auxiliary positioning mark 404. As shown in FIG13 , the bonding ring 403 surrounds the microbolometer MEMS structure 105. The size of the bonding ring 403 is the same as that of the wafer-level package cover 103. The auxiliary positioning marks 404 are located on both sides of the bonding ring 403. The height of the auxiliary positioning mark 404 is greater than the height of the bonding ring 403. The auxiliary positioning marks 404 are used to assist the wafer-level package cover 103 and the bonding ring 403 in a one-to-one correspondence when the wafer-level package cover 103 and the first substrate are bonded. That is, during the bonding process, after the first substrate and the wafer-level package cover 103 come into contact, a high pressure is applied, which may cause a horizontal offset. For ordinary bonding, since it does not involve alignment between pixels, a larger offset is tolerable. However, since the pixel-level super-surface layer 102 needs to be aligned with the corresponding microbolometer MEMS structure 105 below it, a larger bonding offset will greatly affect the imaging quality. Therefore, auxiliary positioning marks 404 can be made on both sides of the bonding ring 403 surrounding the microbolometer MEMS structure 105. The auxiliary positioning marks 404 can be higher than the bonding ring 403 by a certain distance. In this way, during the bonding process, the upper wafer-level packaging cover 103 can be embedded in the structure of the auxiliary positioning marks 404, thereby preventing or reducing bonding deviation to the greatest extent.

[0113] Specifically, the auxiliary positioning marks 404 can be shaped like rectangles, rounded rectangles, circles, or other shapes. Each auxiliary positioning mark 404 is spaced equidistantly from the bonding ring 403. The spacing between the auxiliary positioning marks 404 determines the size of the bonding offset. If the spacing is too large, the maximum allowable bonding offset will be too high. If the spacing is too small, contact may be lost during bonding. As an example, the spacing between the auxiliary positioning marks 404 and the bonding ring 403 is 0.5 to 2 μm.

[0114] The present invention provides an infrared microbolometer detector, comprising: a first substrate, a detector readout circuit and a microbolometer microelectromechanical system structure sequentially arranged on one side of the first substrate, and a pixel-level metasurface layer arranged on a side of the microbolometer microelectromechanical system structure away from the first substrate. The pixel-level metasurface layer includes a plurality of pixel-level metasurface minimum units, and the size M of the pixel-level metasurface minimum unit satisfies the following conditions:

[0115]

[0116] Where λ is the wavelength of incident light, n metais the refractive index of the pixel-level metasurface layer. The pixel-level metasurface layer provided in the embodiment of the present application includes a plurality of pixel-level metasurface minimum units, each of which is smaller than the wavelength of the incident light. This enables fine differentiation of the incident light and converges the differentiated incident light into a specific microbolometer microelectromechanical system structure so that the detector readout circuit can read the incident light and ultimately obtain a more refined infrared image.

[0117] Based on the infrared microbolometer detectors provided in the above embodiments, the present invention also provides a design method for an infrared microbolometer detector. Referring to FIG14 , which is a flow chart of a design method for an infrared microbolometer detector provided in the present invention, the method includes the following steps:

[0118] S101, randomly generate a pixel-level hypersurface unit and simulate to obtain the function value of a first heuristic function (Heuristic Function) of the pixel-level hypersurface unit.

[0119] S102, using a simulated annealing algorithm to modify the shape of at least one of the pixel-level hypersurface minimum units, and simulating to obtain a function value of a first heuristic function of the modified pixel-level hypersurface unit.

[0120] S103, repeatedly using the simulated annealing algorithm to modify the shape of at least one of the pixel-level hypersurface minimum units until the pixel-level hypersurface unit corresponding to the extreme point of the first heuristic function is determined, and the pixel-level hypersurface unit corresponding to the extreme point of the first heuristic function is determined as the optimal hypersurface unit.

[0121] S104: Arrange the optimal metasurface units in a periodic manner to form a pixel-level metasurface layer.

[0122] S105 , simulating the pixel supersurface layer to obtain a function value of a second heuristic function of the pixel supersurface layer, where the second heuristic function represents an imaging effect of the pixel supersurface layer.

[0123] S106, using a simulated annealing algorithm to modify the shape of at least one of the pixel-level hypersurface minimum units, and simulating to obtain a function value of a second heuristic function of the modified pixel-level hypersurface unit.

[0124] S107, repeatedly using the simulated annealing algorithm to modify the shape of at least one of the pixel-level hypersurface minimum units until the pixel-level hypersurface layer corresponding to the extreme point of the second heuristic function is determined, and the pixel-level hypersurface layer corresponding to the extreme point of the second heuristic function is determined as the optimal hypersurface layer.

[0125] In the embodiments of the present application, the design method of the infrared microbolometer detector focuses on the design method of the pixel-level metasurface layer. The pixel-level metasurface layer can be divided into two parts: the pixel-level metasurface unit design and the overall design of the pixel-level metasurface layer. The following is a detailed introduction:

[0126] For the design of pixel-level metasurface units, first randomly generate pixel-level metasurface units and simulate to obtain the function value of the first heuristic function H1 of the pixel-level metasurface unit. Among them, the first heuristic function H1 represents the imaging effect of the pixel-level metasurface unit, and the pixel-level metasurface unit includes multiple pixel-level metasurface minimum units. The shape of at least one pixel-level metasurface minimum unit is randomly modified using a simulated annealing algorithm, for example, the flat or convex state of the pixel-level metasurface minimum unit 304 is modified, and simulation software such as finite time domain difference (FDTD) / finite element method (FEM) is called to simulate and obtain the function value of the first heuristic function H1 of the modified pixel-level metasurface unit, that is, the first heuristic function H1 is used to quantify the difference in imaging effects. Repeat the steps of modifying the shape of at least one pixel-level hypersurface minimum unit using the simulated annealing algorithm until the pixel-level hypersurface unit corresponding to the extreme point of the first heuristic function H1 is determined, and the pixel-level hypersurface unit corresponding to the extreme point of the first heuristic function H1 is determined as the optimal hypersurface unit, that is, the simulated annealing algorithm is continuously iterated to finally find an extreme point of the first heuristic function H1, which is the optimal result of the pixel-level hypersurface unit.

[0127] For the overall design of the pixel-level metasurface layer, the optimal metasurface units are arranged in a periodic pattern to form a pixel-level metasurface layer. Simulation software such as finite time-domain difference (FDTD) and finite element method (FEM) are used to simulate the pixel-level metasurface layer to obtain the function value of the second heuristic function H2 of the pixel-level metasurface layer. The second heuristic function H2 represents the imaging effect of the pixel-level metasurface layer. The simulated annealing algorithm is used to randomly modify the shape of at least one pixel-level metasurface minimum unit. This can be generalized to all pixel-level metasurface minimum units with equivalent excitation conditions. The function value of the second heuristic function H2 of the modified pixel-level metasurface unit is simulated and obtained, that is, the difference in imaging effect is quantified using the second heuristic function H2. The step of modifying the shape of at least one pixel-level metasurface minimum unit using the simulated annealing algorithm is repeated until the pixel-level metasurface layer corresponding to the extreme value of the second heuristic function H2 is determined. The pixel-level metasurface layer corresponding to the extreme value of the second heuristic function H2 is determined as the optimal metasurface layer. In other words, the simulated annealing algorithm is continuously iterated to finally find an extreme value of the second heuristic function H2, which is the optimal result of the entire pixel-level metasurface.

[0128] As an example, the design method of the pixel-level metasurface layer can refer to the figure shown in Figure 15. First, the simulated annealing algorithm is used to optimize the metasurface unit: an initial random metasurface unit is generated, and simulation initialization is performed, and the parameters of the minimum metasurface unit are defined, such as the size M and the type K. It is judged whether the final annealing temperature of the simulated annealing algorithm is reached. If so, the parameters M and K are redefined to achieve a better convergence effect. If not, an approximate unit of the simulated annealing algorithm is generated, and the process simulation algorithm is used to modify the unit structure model. The unit structure model is imported into the simulation software, and the simulation conditions are updated, such as boundary addition, incident angle of infrared light, etc. The FDTD / FEM algorithm is used for simulation, and the first heuristic function H is used. 1(x) evaluates the simulation results, defines the imaging effect (performance) parameter as H1(new)-H1(old), and determines whether the performance parameter is greater than 0. If so, accept the new approximate unit. If not, if the Metropolis criterion is met, accept the new approximate unit, and determine whether the simulation of the new approximate unit can find the maximum value of H1(x) and whether the algorithm converges. If not, lower the current annealing temperature, change the performance parameter, and repeat the step of determining whether the final annealing temperature of the simulated annealing algorithm is reached. If so, save the current hypersurface unit and periodically copy the hypersurface unit to fill the entire pixel area.

[0129] Then the simulated annealing algorithm is used to optimize the entire metasurface: the simulation is initialized, the parameters of the local metasurface minimum unit are defined, such as size M and type K, and whether the final annealing temperature of the simulated annealing algorithm is reached. If so, the parameters M and K are redefined to achieve better convergence. If not, the simulated annealing algorithm approximate local unit is generated, and all the structural equivalent metasurface units found are replaced with the generated approximate units. The unit structure model is imported into the simulation software, and the simulation conditions are updated, such as boundary addition, incident angle of infrared light, etc. The FDTD / FEM algorithm is used for simulation, and the simulation results are evaluated using the second heuristic function H2(x). The performance parameter is H2(new)-H2(old). Determine whether the performance parameter is greater than 0. If so, accept the new approximate unit. If not, if the Metropolis criterion is met, accept the new approximate unit. Determine whether the simulation of the new approximate unit can find the maximum value of H2(x) and whether the algorithm converges. If not, lower the current annealing temperature, change the performance parameter, and repeat the step of determining whether the final annealing temperature of the simulated annealing algorithm is reached. If so, save the complete hypersurface result to obtain the final optimized surface.

[0130] In the embodiments of the present application, since the critical dimensions of the smallest unit of the pixel-level metasurface are very small, the imperfections of the lithography and etching processes will be very obvious during the actual manufacturing process. If the lithography plate is strictly implemented according to the design dimensions, the structure and design of the pixel-level metasurface finally manufactured will have large errors. Some of these errors are caused by uneven light field distribution during lithography, as shown in Figure 16 (a), some are caused by uneven etching depth due to the load effect during etching, as shown in Figure 16 (b), and some sidewall tilt and scallop effects are caused by gas circulation in the deep reactive ion etching (DRIE) etching process, as shown in Figure 16 (c). Among them, the photolithography plate can be compensated to a certain extent through technologies such as optical proximity correction (OPC), but the graphic structure made by the final process is only improved, and it cannot be completely consistent with the design and the actual structure. In order to reduce the deviation of the structure obtained by design and manufacturing, the embodiment of the present application can obtain the actual process parameters of the minimum unit of the pixel-level metasurface before simulating the first heuristic function of the pixel-level metasurface unit or before simulating the pixel metasurface layer to obtain the second heuristic function of the pixel metasurface layer, and adjust the shape of the minimum unit of the pixel-level metasurface according to the actual process parameters.

[0131] Specifically, referring to the design flow chart shown in FIG15 , the design method provided in the embodiment of the present application provides step 131, which can modify the current structural model according to the process simulation. This step 131 will modify the original ideal design model into a structure closer to the actual process manufacturing, so that the simulation results are more accurate. The model modification parameters are mainly obtained based on process experience, as shown in FIG17 . In FIG17 (a), the rectangular column is mainly modified into a rounded rectangular column, and the inclination angle of the column side wall is adjusted from the ideal 90° to 89.3~89.6°, and the specific value depends on the size of the rounded rectangular column. According to the local density of the surrounding lithographic patterns, the height of the rounded rectangular column is adjusted, and a scallop pattern is added to the side wall. FIG17 (b) is a schematic diagram of the simulation adjustment.

[0132] In an embodiment of the present application, in the design method of the pixel-level metasurface layer, the simulated annealing algorithm is also improved. When the final annealing temperature is reached, if it still does not converge, the size of the pixel-level metasurface minimum unit is further reduced, and the iterative step 132 is repeated, as shown in Figure 15. The advantage of reducing the size of the pixel-level metasurface minimum unit is that it increases the design variables of the pixel-level metasurface, making it easier to achieve convergence to the design requirements. That is to say, when the local heuristic function does not converge, the size of the pixel-level metasurface minimum unit is further reduced to increase the range of the design variables, improve the optical performance of the metasurface and promote algorithm convergence. However, the smaller the size of the pixel-level metasurface minimum unit, the higher the difficulty of process manufacturing. Therefore, a design method can be used to obtain a pixel-level metasurface minimum unit size that is adaptive to design requirements, which can relax the process difficulty to the maximum extent while meeting the design requirements.

[0133] This method of designing the minimum unit size of an adaptive pixel-level metasurface is characterized in that the pixel-level metasurface layer generated can have local optimization and non-periodicity of the entire non-pixel metasurface layer. Specifically, when the incident light is incident, there are certain differences in the conditions of the incident light, for example, the incident angle of each pixel-level metasurface minimum unit is different. For the pixel-level metasurface minimum unit near the optical axis, the incident light is closer to vertical incidence, while the pixel-level metasurface minimum unit away from the optical axis has a larger incident angle. Since the pixel-level metasurface layer has a worse dispersion effect for infrared light with a larger incident angle, these locations with poor dispersion effects can be additionally optimized by changing the minimum size of the pixel-level metasurface minimum unit to improve the imaging effect of the infrared microbolometer detector.

[0134] The pixel-level metasurface layer proposed in the embodiment of the present application can obtain simulation results including 2nd and higher-order diffraction using simulation software such as FEM or FDTD, and then heuristically find the most suitable structure of the pixel-level metasurface layer through the simulated annealing algorithm, so that the designed pixel-level metasurface layer can allow high-order diffraction, so the size of the minimum unit of the pixel-level metasurface can be much smaller than the size of the minimum unit of the traditional metasurface layer.

[0135] In practical applications, the multiple functions of infrared microbolometer detectors can be realized by modifying the definition of the heuristic function to achieve different structural designs for the pixel-level metasurface layer.

[0136] Based on the infrared microbolometer detector provided in the above embodiment, the present application also provides a method for manufacturing an infrared microbolometer detector. Referring to FIG18 , there is shown a flow chart of a method for manufacturing an infrared microbolometer detector provided in the present application embodiment. The method includes the following steps:

[0137] S201 , forming a detector readout circuit and a microbolometer micro-electromechanical system structure on the first substrate in sequence.

[0138] S202: Form a pixel-level metasurface layer on a side of the microbolometer MEMS structure away from the first substrate.

[0139] In an embodiment of the present application, to form an infrared microbolometer detector, a detector readout circuit 106 and a microbolometer microelectromechanical system structure 105 may be sequentially formed on a first substrate.

[0140] As a possible implementation, the first substrate is a wafer, and the detector readout circuit 106 may be a CMOS circuit that has been integrated on the first substrate to form a detector readout circuit wafer 406, as shown in FIG13 .

[0141] A microbolometer MEMS structure 105 is formed on the detector readout circuit 106. The microbolometer MEMS structure 105 is used to receive incident light and convert it into an electrical signal for transmission to the detector readout circuit 106. The microbolometer MEMS structure 105 may also be called a microbolometer MEMS structure.

[0142] A pixel-level metasurface layer is then formed on the microbolometer MEMS structure 105 .

[0143] The pixel-level metasurface layer includes multiple pixel-level metasurface minimum units, and the size M of the pixel-level metasurface minimum unit meets the following conditions:

[0144]

[0145] Where λ is the wavelength of incident light, n meta is the refractive index of the pixel-level metasurface layer.

[0146] In the embodiment of the present application, a wafer-level packaging cover 103 may be formed on the microbolometer MEMS structure 105 to form a vacuum airtight environment to protect the microbolometer MEMS structure 105 .

[0147] The pixel-level super-surface layer 102 may be disposed on the surface of the wafer-level packaging cover 103 or may not be disposed on the surface of the wafer-level packaging cover 103 , as described in detail below:

[0148] As a possible implementation, the pixel-level metasurface layer 102 can be provided on one side surface of the wafer-level packaging cover 103, which can be either the inner surface or the outer surface, as shown in FIG2 . In other words, the pixel-level metasurface layer 102 can be integrated into the wafer-level packaging cover 103 to form a pixel-level metasurface packaging cover wafer (ROIC wafer) 405. As shown in FIG13 , one side surface of the wafer-level packaging cover 103 can be etched to form the pixel-level metasurface layer 102.

[0149] When bonding pixel-level metasurface packaging cover wafer 405 and detector readout circuit wafer 406, it is necessary to align pixel-level metasurface layer 102 and microbolometer MEMS structure 105, achieving alignment much smaller than the pixel size. Specifically, an alignment machine or bonding machine with infrared alignment capabilities can be used, and alignment patterns 401 provided on pixel-level metasurface packaging cover wafer 405 and alignment patterns 402 provided on detector readout circuit wafer 406 can be used to assist in alignment.

[0150] During the bonding process, after the pixel-level metasurface packaging cover wafer 405 and the detector readout circuit wafer 406 come into contact, a higher pressure is applied, which may cause a horizontal offset, so that the offset between the two wafers will be further increased. For ordinary bonding, since it does not involve alignment between pixels, a larger offset is tolerable. However, since the pixel-level metasurface layer 102 needs to be aligned with the corresponding micro-bolometer micro-electromechanical system structure 105 below it, a larger bonding offset will greatly affect the imaging quality. Therefore, auxiliary positioning marks 404 can be made on both sides of the bonding ring 403 surrounding the micro-bolometer micro-electromechanical system structure 105. The auxiliary positioning marks 404 can be higher than the bonding ring 403 by a certain distance. In this way, during the bonding process, the upper wafer-level packaging cover 103 can be embedded in the structure of the auxiliary positioning marks 404 to prevent or reduce the bonding offset to the greatest extent.

[0151] That is to say, a bonding ring 403 and an auxiliary positioning mark 404 can be formed on the first substrate. Specifically, the bonding ring 403 and the auxiliary positioning mark 404 can be formed on the detector readout circuit wafer 406. Referring to Figure 13, the bonding ring 403 surrounds the micro-bolometer microelectromechanical system structure 105. The size of the bonding ring 403 is the same as the size of the wafer-level packaging cover 103. The auxiliary positioning mark 404 is located on both sides of the bonding ring 403. The height of the auxiliary positioning mark 404 is greater than the height of the bonding ring 403. Subsequently, the bonding ring 403 and the auxiliary positioning mark 404 can be used to bond the wafer-level packaging cover 103 and the first substrate in the direction of the pixel-level supersurface layer away from the first substrate.

[0152] The following is a detailed description of the process flow for forming a pixel-level metasurface package cover wafer, as shown in Figure 19. It includes 16 steps:

[0153] 1. Clean the substrate. The substrate material can be silicon or germanium.

[0154] 2. Photolithography or nano-imprinting to form a photoresist layer (photolithography or Nano-imprint), the pattern shape of the photoresist layer is the pattern shape of the pixel-level metasurface layer to be formed.

[0155] 3. Deep silicon etching (DRIE), that is, using the photoresist layer to etch the substrate to form a super-surface column layer of the pixel-level super-surface layer.

[0156] 4. Strip the photoresist.

[0157] 5. Forming a protective layer (PECVD SiN as a protective layer), specifically using a PECVD process. The protective layer can specifically be an oxide layer or silicon nitride (SiN). The protective layer is used to protect the formed super surface column layer.

[0158] 6. Flip the wafer and sputter bonding metal.

[0159] 7. Form a BSA photolithography mark, the pattern of which is the pattern of the bond and metal structure.

[0160] 8. Etch the bonding metal layer to pattern the bonding metal layer.

[0161] 9. Strip photoresist.

[0162] 10. Form a photolithography cavity layer to facilitate subsequent cavity formation.

[0163] 11. Etching to form a cavity (DRIE cavity)

[0164] 12. Optionally, an optical anti-reflection coating or a pixel-level metasurface anti-reflection layer (coating or metasurface) can be formed in the cavity.

[0165] 13. Optionally, a getter can be deposited in the cavity.

[0166] 14. Strip photoresist.

[0167] 15. Remove the protective layer (remove SiN).

[0168] 16. ROIC wafer bonding (pixel-level ultra-surface packaging cover wafer bonding).

[0169] As another possible implementation, the pixel-level metasurface layer 102 may not be provided on the surface of the wafer-level packaging cover 103, but may be provided on the side of the wafer-level packaging cover 103 away from the first substrate. Specifically, the pixel-level metasurface layer 102 may be provided on the surface of an independent metasurface optical element 110, the metasurface optical element 110 is provided on the side away from the first substrate of the wafer-level packaging cover 103, and the pixel-level metasurface layer 102 may be provided on the side surface of the metasurface optical element 110 away from the first substrate, as shown in FIG12 . In other words, the metasurface optical element 110 may be formed first, and then one side surface of the metasurface optical element 110 may be etched to form the pixel-level metasurface layer 102.

[0170] In practical applications, the infrared microbolometer detector may include an infrared anti-reflection layer, which is used to increase the transmittance of infrared light and improve the final imaging effect. Specifically, the infrared anti-reflection layer can be enhanced by optical coating, as shown in Figure 20, or an additional pixel-level metasurface layer can be formed to enhance the transmittance, as shown in Figures 19 or 21.

[0171] In practical applications, when the pixel-level metasurface layer 102 is formed on the surface of the metasurface optical element 110, an infrared anti-reflection layer may also be formed on the other side of the metasurface optical element 110. The details are as follows:

[0172] In the first possible implementation, the infrared anti-reflection layer is enhanced by optical coating. When a pixel-level metasurface layer is formed on one side of the metasurface optical element, an optical coating is performed on the other side of the metasurface optical element to form an infrared anti-reflection layer. Referring to Figure 20, the process flow includes seven steps:

[0173] 1. Clean the substrate. The substrate material can be silicon or germanium.

[0174] 2. Photolithography or nano-imprinting to form a photoresist layer (photolithography or Nano-imprint), the pattern shape of the photoresist layer is the pattern shape of the pixel-level metasurface layer to be formed.

[0175] 3. Deep silicon etching (DRIE), that is, using the photoresist layer to etch the substrate to form a super-surface column layer of the pixel-level super-surface layer.

[0176] 4. Strip the photoresist.

[0177] 5. Forming a protective layer (PECVD SiN as a protective layer), specifically using a PECVD process. The protective layer can specifically be an oxide layer or silicon nitride (SiN). The protective layer is used to protect the formed super surface column layer.

[0178] 6. Flip the wafer and form an infrared anti-reflection layer (Flip the wafer and coating).

[0179] 7. Remove the protective layer (remove SiN).

[0180] The second possible implementation method is to use an additional pixel-level metasurface layer to enhance the infrared reflectivity. When the pixel-level metasurface layer is formed on one side of the metasurface optical element, the infrared reflectivity layer is etched on the other side of the metasurface optical element. As shown in Figure 21, the process flow includes 8 steps:

[0181] 1. Clean the substrate. The substrate material can be silicon or germanium.

[0182] 2. Photolithography or nano-imprinting to form a photoresist layer (photolithography or Nano-imprint), the pattern shape of the photoresist layer is the pattern shape of the pixel-level metasurface layer to be formed.

[0183] 3. Deep silicon etching (DRIE), that is, using the photoresist layer to etch the substrate to form a super-surface column layer of the pixel-level super-surface layer.

[0184] 4. Strip the photoresist.

[0185] 5. Forming a protective layer (PECVD SiN as a protective layer), specifically using a PECVD process. The protective layer can specifically be an oxide layer or silicon nitride (SiN). The protective layer is used to protect the formed super surface column layer.

[0186] 6. Flip the wafer and perform photolithography or nano-imprinting to form a photoresist layer on the other side. The pattern of the photoresist layer is the pattern of the infrared anti-reflection layer to be formed.

[0187] 7. Deep silicon etching (DRIE), that is, using the photoresist layer to etch the substrate to form an infrared anti-reflection layer.

[0188] 4. Strip the photoresist.

[0189] 9. Remove the protective layer (remove SiN).

[0190] It can be seen from this that when forming the manufacturing process of the pixel-level supersurface layer, the manufacturing process of forming the infrared anti-reflection layer can also be added, so that the pixel-level supersurface layer and the infrared anti-reflection layer can be formed in the same series of processes, reducing the overall process steps.

[0191] Based on the infrared microbolometer detectors provided in the above embodiments, embodiments of the present application also provide an infrared microbolometer system. FIG22 shows a schematic structural diagram of an infrared microbolometer system provided in embodiments of the present application. The infrared microbolometer system provided in embodiments of the present application includes an infrared lens 101, a shutter plate 107, and any of the infrared microbolometer detectors provided in the above embodiments.

[0192] Specifically, the infrared microbolometer system may further include a ceramic tube holder 108 and a plastic housing 109 .

[0193] When the pixel-level metasurface layer 102 is integrated into the wafer-level packaging cover 103, after the pixel-level metasurface packaging cover wafer 405 and the detector readout circuit wafer 406 are bonded, they can be divided into separate infrared microbolometer detectors, and then finally form an infrared microbolometer system.

[0194] In actual applications, the wafer-level packaging cover and the infrared anti-reflection layer are located at the focal plane of the infrared lens. After the incident infrared light is imaged at the focal plane by the infrared lens, the infrared light of the local area pixels passes through the pixel-level metasurface layer, producing different wavelength deflection or polarization refraction effects, and irradiates different detector unit pixels. Finally, the infrared light with different wavelength information or different polarization information is mapped into RGB color infrared images through the micro-bolometer micro-electromechanical system structure and detector readout circuit.

[0195] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0196] The descriptions of the processes or structures corresponding to the above figures have different emphases. For parts that are not described in detail in a certain process or structure, please refer to the relevant descriptions of other processes or structures.

[0197] The above is only a preferred embodiment of the present application. Although the present application has been disclosed as a preferred embodiment, it is not intended to limit the present application. Any technician familiar with the art can use the above-disclosed methods and technical contents to make many possible changes and modifications to the technical solution of the present application without departing from the scope of the technical solution of the present application, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application are still within the scope of protection of the technical solution of the present application.

[0198] Based on the implementation methods provided in the above aspects, this application can also be further combined to provide more implementation methods.

Claims

1. An infrared microbolometer detector, characterized in that, Comprising: A first substrate, a detector readout circuit, and a microbolometer microelectromechanical system structure sequentially disposed on one side of the first substrate; A pixel-level metasurface layer disposed on the side of the microbolometer microelectromechanical system structure away from the first substrate; The pixel-level metasurface layer includes a plurality of pixel-level metasurface minimum units, and the size M of the pixel-level metasurface minimum unit satisfies the following conditions: where λ is the wavelength of the incident light, and n meta is the refractive index of the pixel-level metasurface layer.

2. The infrared microbolometer detector according to claim 1, wherein, In the direction perpendicular to the first substrate, the detector readout circuit and the microbolometer microelectromechanical system structure include a plurality of detector unit pixels, and N of the detector unit pixels form 1 detector equivalent pixel. The pixel-level metasurface layer includes a plurality of pixel-level metasurface units, and the plurality of pixel-level metasurface units include a plurality of the pixel-level metasurface minimum units, where N is a positive integer; The pixel-level metasurface units and the detector equivalent pixels have the same size and correspond to each other one by one.

3. The infrared microbolometer detector according to claim 1, wherein, The pixel-level metasurface layer at least includes a metasurface substrate and a metasurface pillar layer, and the metasurface pillar layer is disposed on the side of the metasurface substrate away from the first substrate.

4. The infrared microbolometer detector according to claim 3, characterized in that, The metasurface pillar layer includes a plurality of protruding structures, the pixel-level metasurface minimum unit includes a flat unit and a protruding unit, and the protruding unit has the protruding structure.

5. The infrared microbolometer detector according to claim 4, characterized in that, The height H of the protruding structure approximately satisfies the following conditions: Said n i is the refractive index of the incident medium.

6. The infrared microbolometer detector according to any one of claims 1-5, characterized in that, The arrangement of the pixel-level metasurface minimum units is aperiodic.

7. The infrared microbolometer detector according to any one of claims 1-5, characterized in that, The infrared microbolometer detector includes a wafer-level package cover; The wafer-level package cover is disposed on the side of the microbolometer microelectromechanical system structure away from the first substrate; The pixel-level metasurface layer is disposed on one surface of the wafer-level package cover.

8. The infrared microbolometer detector according to claim 7, characterized in that, The infrared microbolometer detector includes an infrared antireflection layer; The infrared antireflection layer is disposed on the side of the pixel-level metasurface layer away from the first substrate, or the infrared antireflection layer is disposed on the side of the pixel-level metasurface layer close to the first substrate.

9. The infrared microbolometer detector according to any one of claims 1-5, characterized in that, The infrared microbolometer detector includes a wafer-level package cover; The wafer-level package cover is disposed on the side of the microbolometer microelectromechanical system structure away from the first substrate; The pixel-level metasurface layer is disposed on the side of the wafer-level package cover away from the first substrate.

10. The infrared microbolometer detector according to claim 9, characterized in that, The infrared microbolometer detector includes a metasurface optical element and an infrared antireflection layer; The metasurface optical element is disposed on the side of the wafer-level package cover away from the first substrate; The pixel-level metasurface layer is disposed on one surface of the metasurface optical element away from the first substrate; The infrared antireflection layer is disposed on one surface of the metasurface optical element close to the first substrate and / or disposed on one surface of the wafer-level package cover.

11. The infrared microbolometer detector according to any one of claims 7-10, characterized in that, The first substrate has a bonding ring and auxiliary positioning marks. The bonding ring surrounds the microbolometer MEMS structure. The size of the bonding ring is the same as that of the wafer-level package cover. The auxiliary positioning marks are located on both sides of the bonding ring, and the height of the auxiliary positioning marks is greater than that of the bonding ring. The auxiliary positioning marks are used to assist the one-to-one correspondence between the wafer-level package cover and the bonding ring when the wafer-level package cover and the first substrate are bonded.

12. The infrared microbolometer detector according to any one of claims 4-11, characterized in that, Multiple functions of the infrared microbolometer detector are realized by changing the shape of the convex structure or changing the size of the minimum unit of the pixel-level metasurface. The multiple functions at least include dispersion refraction, narrowband filtering, polarization refraction, and local focusing.

13. A design method for an infrared microbolometer detector, characterized in that, Including: Randomly generate pixel-level metasurface units and simulate to obtain the function values of the first heuristic function of the pixel-level metasurface units. The first heuristic function represents the imaging effect of the pixel-level metasurface units. The pixel-level metasurface units include multiple pixel-level metasurface minimum units; Use the simulated annealing algorithm to modify the shape of at least one of the pixel-level metasurface minimum units, and simulate to obtain the function values of the first heuristic function of the modified pixel-level metasurface units; Repeat the step of using the simulated annealing algorithm to modify the shape of at least one of the pixel-level metasurface minimum units until the pixel-level metasurface unit corresponding to the extreme point of the first heuristic function is determined. Determine the pixel-level metasurface unit corresponding to the extreme point of the first heuristic function as the optimal metasurface unit; Arrange the optimal metasurface units in a periodic pattern to form a pixel-level metasurface layer; Simulate the pixel metasurface layer to obtain the function values of the second heuristic function of the pixel metasurface layer. The second heuristic function represents the imaging effect of the pixel metasurface layer; Use the simulated annealing algorithm to modify the shape of at least one of the pixel-level metasurface minimum units, and simulate to obtain the function values of the second heuristic function of the modified pixel-level metasurface units; Repeat the step of using the simulated annealing algorithm to modify the shape of at least one of the pixel-level metasurface minimum units until the pixel-level metasurface layer corresponding to the extreme point of the second heuristic function is determined. Determine the pixel-level metasurface layer corresponding to the extreme point of the second heuristic function as the optimal metasurface layer.

14. The design method of the infrared microbolometer detector according to claim 13, characterized in that, Before simulating to obtain the function values of the first heuristic function of the pixel-level metasurface units or before simulating the pixel metasurface layer to obtain the function values of the second heuristic function of the pixel metasurface layer, the method further includes: Obtain the actual process parameters of the pixel-level metasurface minimum units; Adjust the shape of the pixel-level metasurface minimum units according to the actual process parameters.

15. The design method of the infrared microbolometer detector according to claim 13, characterized in that, The method further includes: If the extreme point of the first heuristic function or the second heuristic function cannot be obtained at the final annealing temperature, reduce the size of the pixel-level metasurface minimum units, and re-enter the step of using the simulated annealing algorithm to modify the shape of at least one of the pixel-level metasurface minimum units.

16. A manufacturing method of an infrared microbolometer detector, characterized in that, Including: Form a detector readout circuit and a microbolometer MEMS structure on the first substrate in sequence; A pixel-level metasurface layer is formed on a side of the microbolometer MEMS structure away from the first substrate. The pixel-level metasurface layer includes a plurality of pixel-level metasurface minimum units, and the size M of the pixel-level metasurface minimum unit satisfies the following conditions: where λ is the wavelength of the incident light, and n meta is the refractive index of the pixel-level metasurface layer.

17. The manufacturing method of the infrared microbolometer detector according to claim 16, wherein The method further includes: Forming a wafer-level package cover; The forming of the pixel-level metasurface layer on the side of the microbolometer MEMS structure away from the first substrate includes: Etching one side surface of the wafer-level package cover to form the pixel-level metasurface layer.

18. The manufacturing method of the infrared microbolometer detector according to claim 17, characterized in that, The method further includes: Forming a bonding ring and auxiliary positioning marks on the first substrate. The bonding ring surrounds the microbolometer MEMS structure. The size of the bonding ring is the same as the size of the wafer-level package cover. The auxiliary positioning marks are located on both sides of the bonding ring, and the height of the auxiliary positioning marks is greater than the height of the bonding ring; Bonding the wafer-level package cover and the first substrate in a direction away from the first substrate with the pixel-level metasurface layer, using the bonding ring and the auxiliary positioning marks.

19. The manufacturing method of the infrared microbolometer detector according to claim 16, characterized in that, The method further includes: Forming a metasurface optical element; The forming of the pixel-level metasurface layer on the side of the microbolometer MEMS structure away from the first substrate includes: Etching one side surface of the metasurface optical element to form the pixel-level metasurface layer.

20. An infrared microbolometer system, characterized in that, Including an infrared lens, a shutter, and the infrared microbolometer detector according to any one of claims 1-12.

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