Infrared focal plane detector and preparation method of light receiving structure thereof

Abstract

The application provides an infrared focal plane detector and a preparation method of a light-receiving structure thereof. The infrared focal plane detector comprises a plurality of photosensitive units, an indium column array and a silicon readout circuit; the plurality of photosensitive units are interconnected with the silicon readout circuit through the indium column array; a light-receiving structure is arranged at a position corresponding to each photosensitive unit on a light-receiving side of the photosensitive unit; the light-receiving structure is an inner recess structure on the light-receiving side and faces the photosensitive unit; and the inner recess structure has a maximum internal width greater than the size of the corresponding opening. The preparation method of the light-receiving structure comprises the following steps: smearing a layer of photoresist on the surface of the light-receiving side of the photosensitive unit and determining the position of the light-receiving structure on the surface; performing mask processing on the light-receiving structure; etching the light-receiving structure by using an etching solution; and performing antireflection coating on the light-receiving structure. The application absorbs incident light through the light-receiving structure and reflects the incident light inside the light-receiving structure to improve the absorption rate of the infrared focal plane detector for the incident light.

Description

Technical Field

[0001] This application relates to the field of infrared focal plane detector technology, specifically to an infrared focal plane detector and a method for fabricating its light-receiving structure. Background Technology

[0002] An infrared focal plane array (IFA) is an imaging sensor that simultaneously acquires and processes infrared information, and it has wide applications in both military and civilian fields. Currently, IFAs are divided into cooled and uncooled types. The structure of cooled IFAs dictates that they require back-side illumination.

[0003] Existing cooled infrared focal plane detectors employ planarization processes on their back light-receiving surfaces and deposit anti-reflection coatings to reduce incident light reflection, thereby improving transmittance. However, the amount of incident light on the planar surface produced by this planarization process is still not ideal, as some incident light is still reflected and cannot pass through the light-receiving surface of the cooled infrared focal plane detector, resulting in the infrared focal plane detector's performance failing to reach higher standards.

[0004] Therefore, it is necessary to design a light-receiving structure for an infrared focal plane detector to improve its performance. Summary of the Invention

[0005] This application provides an infrared focal plane detector to address the problem of low incident light absorption in existing infrared focal plane detectors. This application also provides a method for fabricating the light-receiving structure of an infrared focal plane detector.

[0006] An infrared focal plane detector provided in this application includes multiple photosensitive units, an indium pillar array, and a silicon readout circuit.

[0007] The plurality of photosensitive units are interconnected with the silicon readout circuit via the indium pillar array;

[0008] A light-receiving structure is provided on one side of the light-receiving surface of the photosensitive unit corresponding to the position of each photosensitive unit. The light-receiving structure is an inwardly recessed structure on one side of the light-receiving surface facing the photosensitive unit, and the maximum width of the inwardly recessed structure is greater than the size of the corresponding opening.

[0009] Optionally, the light-receiving structure is a perforated light-receiving aperture, and the light-receiving apertures are arranged in an array; or

[0010] The light-receiving structure is a groove-shaped light-receiving groove, with multiple light-receiving grooves distributed at intervals.

[0011] Optionally, the transverse dimension of the longitudinal cross-section of the light-receiving structure gradually increases along the depth direction.

[0012] Optionally, the longitudinal cross-sectional shape of the light-receiving structure is trapezoidal, and the short side of the trapezoid corresponds to the opening.

[0013] Optionally, the light-receiving structure includes an inner groove with a trapezoidal longitudinal cross-section and an opening with a rectangular cross-section, wherein the size of the rectangular opening is smaller than the short side of the trapezoid.

[0014] Optionally, an anti-reflective film or an anti-reflective film may be provided on the light-receiving surface.

[0015] Optionally, the light-receiving surface includes the bottom surface of the recessed structure of the light-receiving structure and the surface between the opening portions of adjacent recessed structures.

[0016] Optionally, an anti-reflective film or an anti-reflective film may also be provided on the sidewall portion near the bottom of the recessed structure.

[0017] Another embodiment of this application provides a method for fabricating a light-receiving structure of an infrared focal plane detector, the method comprising the following steps:

[0018] A layer of photoresist is applied to the light-receiving surface of the photosensitive unit, and the position of the light-receiving structure is determined on its surface.

[0019] The light-receiving structure is masked.

[0020] After the masking process, the light-receiving structure is then etched using an etchant.

[0021] Remove the photoresist from the light-receiving surface of the photosensitive unit and deposit an antireflection film on it.

[0022] Optionally, a light-receiving structure is provided on one side of the light-receiving surface of the photosensitive unit corresponding to the position of each photosensitive unit.

[0023] Compared with the prior art, this application has the following advantages:

[0024] This application provides an infrared focal plane detector, comprising multiple photosensitive units, an indium pillar array, and a silicon readout circuit. The multiple photosensitive units are interconnected with the silicon readout circuit via the indium pillar array. A light-receiving structure is disposed on one side of the light-receiving surface of each photosensitive unit, corresponding to the position of each photosensitive unit. The light-receiving structure is an inwardly recessed structure with one side of the light-receiving surface facing the photosensitive unit, and the maximum internal width of the inwardly recessed structure is greater than the size of the corresponding opening. This application embodiment improves the absorption rate of the infrared focal plane detector for incident light by using the light-receiving structure on the photosensitive unit to reflect the incident light multiple times and absorb the reflected light. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a conventional infrared focal plane detector according to an embodiment of this application;

[0026] Figure 2 This is a schematic diagram of the structure of the improved infrared focal plane detector according to an embodiment of this application;

[0027] Figure 3 This is a top view of the light-receiving structure of the aperture structure in an embodiment of this application;

[0028] Figure 4 This is a top view of the light-receiving structure of the groove-shaped structure in an embodiment of this application;

[0029] Figure 5 This is a schematic diagram of the structure of the first mask of the light-receiving structure in an embodiment of this application;

[0030] Figure 6 This is a schematic diagram of the structure of the photosensitive structure undergoing the first corrosion according to an embodiment of this application;

[0031] Figure 7 This is a schematic diagram of the structure of the second mask of the light-receiving structure in an embodiment of this application;

[0032] Figure 8 This is a schematic diagram of the structure of the light-receiving structure for pore enlargement and corrosion in an embodiment of this application;

[0033] Figure 9 This is a partial view of the light-receiving structure of the infrared focal plane detector in an embodiment of this application.

[0034] Figure label:

[0035] 10: Photosensitive unit; 10-a: Light-receiving surface;

[0036] 101: First structural layer; 102: Second structural layer;

[0037] 1011: Light-receiving structure; 1011-a: Light-receiving aperture; 1011-b: Light-receiving groove;

[0038] 1011-1: Opening;

[0039] 20: Indium pillar array;

[0040] 30: Silicon readout circuit;

[0041] 40: Photoresist;

[0042] 50: Anti-reflective coating (or anti-reflective coating). Detailed Implementation

[0043] To enable those skilled in the art to better understand the purpose, technical solutions, and advantages of the embodiments of this application, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, and not all embodiments.

[0044] It should be further clarified that the terminology used in the specification, claims, and accompanying drawings of this application, such as referring to an element as being "on" or "connected" to another element, means that the element may be directly on or connected to another element, or that there may be intermediate elements. In contrast, when an element is referred to as being "directly" on or "directly connected" to another element, there will be no intermediate elements.

[0045] In the embodiments of this application, the terms "first," "second," "third," etc., are used to distinguish similar objects and are not used to describe a specific order or sequence. Such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in an order other than that shown in the figures or descriptions herein. Furthermore, terms such as "comprising," "including," and "containing" indicate the presence of the claimed feature but do not exclude one or more other features. Spatial relationship terms such as "above," "below," "left," "right," "front," and "back" indicate the spatial positional relationship between one feature and another in the figures. It should be understood that spatial relationship terms include not only the orientation shown in the figures but also different orientations of the device during use or operation. For example, when the device in the figures is reversed, a feature previously described as "below" its feature can now be described as "above" its feature.

[0046] In recent years, with the rapid development of optoelectronic technology, infrared detection systems have been widely used and researched in both military and civilian fields. Infrared detectors, as the core components of infrared detection systems, have received increasing attention from researchers. Among them, InSb (indium antimonide) infrared focal plane array detectors are one of the most widely used mid-band infrared detectors in the world, with a response in the 3–5 μm band. Furthermore, InSb infrared focal plane array detectors possess advantages such as high sensitivity, strong light absorption, high detectivity, and simple material growth. To further improve the light absorption capability of InSb infrared focal plane array detectors, an antireflection coating is typically deposited on the back surface after planarization to reduce incident light reflection, thereby increasing the transmittance of the incident light.

[0047] Currently, the method of improving the transmittance of incident light by applying a planarization process to the back of the InSb (indium antimonide) infrared focal plane detector and then depositing an antireflection film is not ideal, given that the light-receiving area on the back is fixed. This method also results in some incident light not being absorbed, leading to a lower incident light absorption rate of the InSb (indium antimonide) infrared focal plane detector and further degrading its performance.

[0048] To address the aforementioned issues, this application provides an infrared focal plane detector, comprising multiple photosensitive units 10, an indium pillar array 20, and a silicon readout circuit 30. The multiple photosensitive units 10 are interconnected with the silicon readout circuit 30 via the indium pillar array 20. A light-receiving structure 101 is provided on one side of the light-receiving surface 10-a of each photosensitive unit, corresponding to the position of each photosensitive unit. The light-receiving structure is an inwardly recessed structure with one side of the light-receiving surface facing the photosensitive unit, and the maximum internal width of the inwardly recessed structure is greater than the size of the corresponding opening. In this application embodiment, the light-receiving structure 1011 can absorb reflected light generated by incident light, further improving the absorption rate of incident light on the back side of the InSb (indium antimonide) infrared detector, thereby enhancing the performance of the InSb (indium antimonide) infrared detector.

[0049] The following is an explanation of some of the terms or nouns that appear in the description of the embodiments of this application.

[0050] Light-receiving aperture (or light-receiving slot): refers to an aperture (or slot) made on the light-receiving surface of a flip-chip interconnect detector to collect incident light.

[0051] InSb etching solution: a mixed solution of hydrofluoric acid (HF) and hydrogen peroxide (H2O2). The ratio of the InSb etching solution can be set according to the actual situation during the preparation process. In the embodiment of this application, the InSb etching solution is prepared with a ratio of hydrofluoric acid: hydrogen peroxide: water of 1:1:50.

[0052] Anti-reflective coating (AR) is a surface optical coating that increases the light transmittance of a surface by reducing reflected light. Specifically, anti-reflective coatings utilize the principle of light interference, causing the light reflected from the front and back surfaces of the film to interfere with each other.

[0053] InSb: Indium antimonide (CAS No. 1312-41-0, molecular formula InSb), with a molecular weight of 236.578, is a compound semiconductor with a metallic luster. It is an important material for making infrared detectors with wavelengths of 3-5 μm, and is used to make photovoltaic or photoconductive units, multi-element and focal plane infrared detectors, and magnetic sensitive devices.

[0054] Flip-chip bonding: The chip with bumps is flipped onto the corresponding pads on the substrate. The solder joints serve as the connection between the chip and the peripheral circuits, while also providing a heat dissipation channel and mechanical support for the chip.

[0055] Photoresist: Also known as photoresist, photoresist is a photosensitive material whose properties change upon exposure to light. It is one of the key materials for micro-patterning in microelectronics technology, mainly used in the electronics and printing industries. Photoresist is divided into positive and negative photoresist: positive photoresist, after exposure to light, becomes more easily dissolved in the exposed areas; after development, it dissolves completely, leaving only the unexposed areas to form the pattern. Negative photoresist, on the other hand, becomes less easily dissolved in the exposed areas after exposure to light; after development, the exposed areas remain to form the pattern.

[0056] Mask: The full name is microcontroller mask. It refers to a photomask containing program data that is incorporated into the microcontroller during manufacturing. In semiconductor manufacturing, many chip processing steps utilize photolithography. The patterned "subject" used in these steps is called a mask (also called a "mask"). Its function is to cover a selected area on the silicon wafer with an opaque pattern template, so that subsequent etching or diffusion will only affect areas outside the selected area. Image mask: A selected image, graphic, or object is used to obscure (fully or partially) the image being processed, controlling the area or process of image processing. The specific image or object used for covering is called a mask or template. In optical image processing, masks can be films, filters, etc. In digital image processing, masks are two-dimensional matrix arrays, and sometimes multi-valued images are used.

[0057] Planarization process: Simply put, it is a process of keeping the surface of a crystal flat and smooth. Currently, planarization processes include traditional planarization technology and chemical mechanical planarization technology.

[0058] Traditional planarization techniques include reverse etching, glass reflow, and spin coating; moreover, traditional planarization techniques can only achieve localized planarization.

[0059] Chemical mechanical planarization (CMP) is a global planarization technique, the only method capable of providing global planarization of silicon wafers. It planarizes the silicon wafer surface through the relative movement between the wafer and a polishing head. Abrasive particles are placed between the wafer and the polishing head, and pressure is applied simultaneously. CMP equipment, also known as a polishing machine, consists of a wafer holder or carrier head facing a polishing pad on a rotating disk. CMP achieves a uniform silicon wafer surface by removing raised patterns at a rate higher than the rate of removing lower pattern blocks. Because it can polish silicon wafers to the desired thickness and flatness uniformly, it has become one of the most widely used techniques.

[0060] The embodiments of this application will be further described in detail below with reference to specific examples.

[0061] like Figure 1 As shown, this is an existing infrared focal plane detector. Generally, an infrared focal plane detector chip is formed on the surface of an InSb (indium antimonide) wafer. Multiple chips are formed on each wafer at the same time. Each infrared focal plane detector chip contains a plurality of infrared detection units. In subsequent processes, the chip is cut into a detection surface of an infrared detector. In the embodiment of this application, the infrared detection units form a PN junction.

[0062] Please refer to Figure 1 Existing infrared focal plane detectors include multiple photosensitive units 10, an indium pillar array 20, and a silicon readout circuit 30; the multiple photosensitive units 10 are interconnected with the silicon readout circuit 30 through the indium pillar array 20.

[0063] The photosensitive unit 10 includes a first structural layer 101 and a second structural layer 102. The first structural layer 101 is N-type InSb (indium antimonide), and the second structural layer 102 is P-type InSb (indium antimonide), with the second structural layer 102 located below the first structural layer 101. In the prior art, to improve the transmittance of incident light from an infrared focal plane detector, a planarization process is first performed on the back light-receiving portion. Subsequently, an antireflection film is deposited on the surface of the first structural layer 101, i.e., the N-type InSb (indium antimonide), to improve the performance of the incident light from the infrared focal plane detector.

[0064] The thickness of the antireflection coating deposited on the surface of the N-type InSb (indium antimonide) is related to the incident light incident on the N-type InSb (indium antimonide). Generally, the thickness of the antireflection coating can be determined by the ratio of one-quarter of the wavelength of the incident light to its refractive index. However, this method still results in some incident light not being absorbed.

[0065] In order to overcome the inability to utilize the reflected light generated after the incident light is reflected in the prior art, the embodiments of this application improve upon the existing infrared focal plane detector.

[0066] like Figure 2 The diagram shown is a structural schematic of an improved infrared focal plane detector according to an embodiment of this application. The infrared focal plane detector provided in this embodiment includes multiple photosensitive units 10, an indium pillar array 20, and a silicon readout circuit 30. The multiple photosensitive units 10 are interconnected with the silicon readout circuit 30 through the indium pillar array 20. A light-receiving structure 1011 is provided on one side of the light-receiving surface 10-a of each photosensitive unit, corresponding to the position of each photosensitive unit. The light-receiving structure 1011 is a recessed structure with one side of the light-receiving surface facing the photosensitive unit, and the maximum internal width of the recessed structure is greater than the size of the corresponding opening 1011-2.

[0067] When incident light shines on the light-receiving surface 10-a of the plurality of photosensitive units 10 on the infrared focal plane detector, a light-receiving structure 1011 is provided on one side of the light-receiving surface 10-a of each photosensitive unit. The incident light shines into the light-receiving structure 1011, which is a concave structure with a maximum internal width greater than the size of the corresponding opening 1011-1, causing the incident light to undergo multiple reflections within the light-receiving structure 1011. At this time, the light-receiving structure 1011 absorbs a portion of the reflected light generated by the multiple reflections of the incident light within itself. In other words, the light-receiving structure 1011 improves the absorption rate of the infrared focal plane detector for incident light by absorbing the reflected light generated by the incident light.

[0068] Specifically, such as Figure 3 This is a top view of the aperture-shaped light-receiving structure. The light-receiving structure 1011 is a light-receiving aperture 1011-a with an array distribution. That is, a light-receiving aperture 1011-a is provided on one side of the light-receiving surface of the photosensitive unit 10, corresponding to the position of each photosensitive unit. The light-receiving aperture 1011-a can better absorb the incident light that shines on it.

[0069] The light-receiving structure 1011 can also be configured as a groove-shaped structure, such as... Figure 4The image shows a top view of a groove-shaped light-receiving structure 1011. Specifically, the light-receiving structure 1011 is a groove-shaped light-receiving groove 1011-b, with multiple light-receiving grooves 1011-b spaced apart. In this embodiment, the specific configuration of the light-receiving structure 1011 can be selected according to the specific working conditions. Whether the light-receiving structure 1011 is configured as a hole-like structure or a groove-shaped structure, as long as the requirements of the light-receiving structure 1011 are met, it is acceptable.

[0070] Next, the structure of the light-receiving aperture will be described. The transverse dimension of the longitudinal cross-section of the light-receiving structure 1011 gradually increases along the depth direction, as follows: Figure 2 As shown, the transverse dimension of the longitudinal section of the light-receiving structure 1011 is gradually increased along its depth direction, so that the longitudinal section shape of the light-receiving structure 1011 is trapezoidal, and the short side of the trapezoid corresponds to the opening.

[0071] The light-receiving structure 1011 includes an inner groove with a trapezoidal longitudinal cross-section and an opening 1011-1 with a rectangular cross-section. The size of the rectangular opening 1011-1 is smaller than the short side of the trapezoid.

[0072] Specifically, the light-receiving structure 1011 can have different configurations at the opening 1011-1, such as... Figure 2 As shown, steps are provided on the left and right sides of the light-receiving structure 1011. These steps are located at the opening 1011-1 of the light-receiving structure and extend towards the opening 1011-1, forming a rectangular cross-section opening 1011-1. The incident light enters the interior of the light-receiving structure 1011 from this rectangular cross-section opening 1011-1. It can be understood that the steps on the left and right sides of the opening 1011-1 of the light-receiving structure, with each step extending towards the opening, make the size of the opening 1011-1 smaller than the short side of the trapezoidal inner groove in the longitudinal cross-section of the light-receiving structure 1011. In other words, the rectangular cross-section opening 1011-1 is smaller than the short side of the trapezoid, and the rectangular cross-section opening 1011-1 is located above the short side of the trapezoid.

[0073] When the area of ​​the photosensitive unit 10 is the same, the light-receiving structure 1011 on the photosensitive element 10 has a trapezoidal longitudinal cross-sectional shape in its recessed structure. When incident light irradiates the recessed structure, it is emitted multiple times in the trapezoidal longitudinal cross-sectional shape of the recessed structure, so that the light-receiving structure 1011 can absorb the reflected light generated by the reflection of the incident light, thereby improving the performance of the infrared focal plane detector.

[0074] The light-receiving structure may not have a step at the opening 1011-1. The light-receiving structure 1011 bends directly from its interior to the left and right sides of the opening 1011-1. That is, the interior of the inner groove structure of the light-receiving structure 1011 gradually narrows from the bottom to the opening 1011-1, so that the size of the opening 1011-1 is smaller than the maximum width of the interior of the inner groove structure.

[0075] In order to improve the absorption rate of incident light of the infrared focal plane detector, an anti-reflection film or an anti-reflection film is provided on the surface of the light-receiving surface 10-a of the photosensitive unit 10 and on the side wall near the bottom of the recessed structure. The thickness of the anti-reflection film or the coated anti-reflection film is related to the incident light, and the coating thickness can generally be determined by the ratio of one-quarter of the incident light wavelength to its refractive index.

[0076] Wherein, the light-receiving surface 10-a is the bottom surface of the recessed structure of the light-receiving structure 1011 and the surface between the opening portions of adjacent recessed structures.

[0077] The infrared focal plane detector in this application is an improvement on the original infrared focal plane detector. Specifically, a light-receiving structure 1011 is provided on one side of the light-receiving surface 10-a of the photosensitive unit 10, corresponding to the position of each photosensitive unit. The light-receiving structure 1011 is an inwardly recessed structure with one side of the light-receiving surface facing the photosensitive unit, and the maximum width of the inwardly recessed structure is greater than the size of the corresponding opening 1011-1. This allows the light-receiving structure 1011 to absorb the reflected light generated by the reflection of incident light in the light-receiving structure 1011, thereby improving the absorption rate of the infrared focal plane detector for incident light.

[0078] This application also provides another embodiment, which is a method for fabricating a light-receiving structure of an infrared focal plane detector, based on the above-mentioned structure of the infrared focal plane detector, and the steps are as follows:

[0079] A layer of photoresist is applied to the surface of the light-receiving surface 10-a of the photosensitive unit 10, and the position of the light-receiving structure 1011 is determined on its surface; the light-receiving structure 1011 is then masked; after the masking process, the light-receiving structure 1011 is etched using an etching solution; the photoresist on the light-receiving surface 10-a of the photosensitive unit 10 is removed, and an anti-reflection coating is deposited on it.

[0080] Specifically, a light-receiving structure 1011 is provided on one side of the light-receiving surface 10-a of the photosensitive unit 10 corresponding to the position of each photosensitive unit. That is, the light-receiving structure 1011 is provided on one side of the light-receiving surface 10-a of the photosensitive unit 10 to ensure that each photosensitive unit can absorb more incident light through its light-receiving structure 1011.

[0081] The position of the light-receiving structure 1011 is determined by alignment marks. The alignment marks are visible patterns placed on the mask and silicon wafer to determine their position and orientation. The alignment mark technology is relatively mature and will not be explained in detail here.

[0082] The photosensitive unit 10 includes a first structural layer 101 and a second structural layer 102. The first structural layer 101 is N-type InSb, and the second structural layer 102 is P-type InSb. The second structural layer 102 is located below the first structural layer 101, that is, the N-type InSb is located above the P-type InSb. Figure 1 As shown, the N-type InSb is a whole, while the P-type InSb is a separate individual, and there is a gap between each P-type InSb.

[0083] The position of the light-receiving structure 1011 is determined by the alignment marks and is set directly above the platform of the second structural layer 102. That is, a light-receiving structure 1011 is set directly above each of the P-type InSb.

[0084] The masking process for the light-receiving structure 1011 includes a first masking process and a second masking process. After the first masking process, exposure and development are performed.

[0085] like Figure 5 As shown, the first masking of the light-receiving structure 1011 requires cleaning the surface of the N-type InSb on the back of the existing infrared focal plane detector and removing any residual moisture. Then, a layer of photoresist is spin-coated onto its surface to ensure uniform adhesion. In this embodiment, a positive photoresist is used for the first masking of the light-receiving structure 1011, exposing the positive photoresist at the light-receiving structure. Therefore, the positive photoresist at the light-receiving structure 1011 dissolves, while the positive photoresist at other locations remains unexposed and does not dissolve.

[0086] The photoresist also includes a negative photoresist, which is the opposite of the positive photoresist. The negative photoresist is not easily dissolved when exposed, but it dissolves in the unexposed parts. Therefore, the choice between the positive or negative photoresist can be made by spin-coating the N-type InSb surface according to the actual situation.

[0087] Next, a photomask is placed on the N-type InSb surface after the positive photoresist has been applied, and the first photolithography exposure is performed. Then, development and fixing are performed to complete the first photomask process.

[0088] like Figure 6 As shown, the light-receiving structure 1011 undergoes a first etching treatment of X micrometers, and the etching solution used is an InSb etching solution; where X is the width of the light-receiving structure 1011, and the value of X is not less than 4 micrometers.

[0089] After the first masking process is performed on the light-receiving structure 1011, a first etching process is required, such as... Figure 7 The image shows the shape of the light-receiving structure 1011 after the first masking and first etching processes, with the size of the opening being substantially consistent with the internal size. In this embodiment, the etching solution used is an InSb etching solution, but other etching solutions (such as nitric acid or lactic acid) can also be used to etch the light-receiving structure.

[0090] The InSb etching solution is a corrosive solution prepared by mixing hydrofluoric acid (HF) and hydrogen peroxide (H2O2). The proportion of the InSb etching solution can be set according to the actual situation during the preparation process. In this embodiment, the InSb etching solution is prepared with a ratio of hydrofluoric acid: hydrogen peroxide: water of 1:1:50.

[0091] The prepared InSb etching solution is dripped onto the light-receiving structure 1011 to perform the first etching treatment. During this first etching of the light-receiving structure 1011, the width x preset value of the light-receiving structure 1011 must be no less than 4 micrometers. In other words, during the first etching treatment of the light-receiving structure 1011, it must be ensured that the width of the light-receiving structure 1011 is greater than or equal to 4 micrometers.

[0092] The width X of the light-receiving structure 1011 is predetermined by the photomask.

[0093] like Figure 7 As shown, after the first etching process, the light-receiving structure 1011 undergoes the second masking process. Before the second masking process, the previously applied photoresist needs to be removed.

[0094] Before performing a second masking process on the light-receiving structure 1011, it is necessary to remove the photoresist applied to the N-type InSb surface during the previous masking process. The technology for removing the photoresist from the N-type InSb surface is relatively mature, and there are many methods available. Therefore, we will not elaborate further here; a suitable method can be selected based on the actual situation. After removing the photoresist from the N-type InSb surface and ensuring the surface is clean, a layer of photoresist is then spin-coated onto the N-type InSb surface. In this embodiment, the second spin-coated photoresist is the same as the first spin-coated photoresist, both using positive photoresist. However, it is possible that the types of photoresist used in the two applications are different; the choice can be made based on the actual situation.

[0095] Please refer to Figure 7 After applying a second positive photoresist to the N-type InSb surface, a mask is placed on the N-type InSb surface after applying the positive photoresist for a second photolithography exposure, followed by development and fixing, thus completing the second masking process.

[0096] like Figure 8 As shown, after the second masking treatment of the light-receiving structure 1011, the InSb etching solution is used to perform hole enlargement etching on the light-receiving structure 1011, so that the maximum width inside the light-receiving structure 1011 is greater than the size of the corresponding opening 1011-1.

[0097] After the second masking process is performed on the light-receiving structure 1011, a second etching process is required. After the first etching process, as... Figure 8 As shown, the light-receiving structure 1011 is formed into a cylindrical shape. The size of the opening 1011-1 of the light-receiving structure and the width of the interior of the light-receiving structure 1011 are basically consistent. In this embodiment, X is limited to a certain value, not less than 4 micrometers. Therefore, a second etching is required, which involves holistic etching around the light-receiving structure 1011. It is necessary to ensure that after the second etching, the maximum width of the interior of the light-receiving structure 1011 is greater than the size of the corresponding opening. When the shape of the light-receiving structure 1011 is as shown... Figure 8 When the corrosion stops, the corrosion ceases.

[0098] In the specific etching process, the prepared InSb etching solution is dripped onto the light-receiving structure 1011 formed after the first etching, and a second etching treatment is performed on it. During the second etching of the light-receiving structure 1011, the width of the etched portion is determined using a photoresist plate; that is, the width X inside the light-receiving structure is increased by approximately 2 micrometers compared to the first etching, and then etching is stopped.

[0099] The light-receiving structure is an inwardly recessed structure on one side of the light-receiving surface 10-a, facing the photosensitive unit.

[0100] like Figure 8 As shown, after two masking processes and two etching processes, the light-receiving structure 1011 is an inwardly recessed structure with one side of the light-receiving surface facing the photosensitive unit 10. At the same time, the maximum width inside the light-receiving structure 1011 is made larger than the size of the corresponding opening 1011-1. When incident light shines on the inwardly recessed structure in the light-receiving structure 1011, the incident light will be reflected multiple times in the light-receiving structure 1011. At this time, the light-receiving structure 1011 will absorb the reflected light generated by the incident light being reflected in the light-receiving structure 1011, so as to improve the absorption rate of the infrared focal plane detector for the incident light.

[0101] like Figure 9 As shown, after the second etching of the light-receiving structure 1011 is completed, the second photoresist applied to the N-type InSb surface is removed, and an antireflection film is deposited on the entire InSb surface. The thickness of the antireflection film is related to the incident light. Generally, the thickness of the film can be determined by the ratio of one-quarter of the incident light wavelength to its refractive index, thus completing the fabrication of the entire infrared focal plane detector light-receiving structure.

[0102] The specific working process will be described below.

[0103] like Figure 2The image shows the infrared focal plane detector light-receiving structure 1011 of this application embodiment formed after the above steps. The photosensitive unit 10 includes a first structural layer 101 and a second structural layer 102. The first structural layer 101 is N-type InSb, and the second structural layer 102 is P-type InSb. The second structural layer 102 is located below the first structural layer 101. A layer of photoresist is coated on the surface of the light-receiving surface 10-a of the photosensitive unit 10, and the position of the light-receiving structure 1011 is determined on its surface. That is, the light-receiving structure 1011 is disposed on the surface of the N-type InSb layer of the first structural layer 101. The position of the light-receiving structure 1011 is relative to the second structural layer 10-a. 2. The mesa of P-type InSb are in the same radial direction; the light-receiving structure 1011 is masked, and then etched with an etchant to form the final light-receiving structure 1011; subsequently, an anti-reflection film is deposited on the N-type InSb surface and inside the light-receiving structure of the entire infrared focal plane detector. On the one hand, the light-receiving structure 1011 can confine the incident light in the light-receiving aperture and reflect and absorb it multiple times, thereby improving the absorption rate of the incident light; on the other hand, the light-receiving structure 1011 increases the actual light-receiving area under the premise of the same photosensitive element center distance, thereby improving the sensitivity of the detector without increasing noise.

[0104] The above description is merely a preferred embodiment disclosed in this application, but the scope of protection of this application is not limited thereto. Any possible changes and modifications can be made by those skilled in the art without departing from the spirit and scope of this application, and all such changes and modifications are within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection defined in the claims of this application.

Claims

1. An infrared focal plane detector, applied to a cooled photon detector, characterized in that, include: Multiple photosensitive units, indium pillar array and silicon readout circuit; The plurality of photosensitive units are interconnected with the silicon readout circuit via the indium pillar array; A light-receiving structure is provided on one side of the light-receiving surface of the photosensitive unit corresponding to the position of each photosensitive unit. The light-receiving structure is an inwardly recessed structure on one side of the light-receiving surface facing the photosensitive unit, and the maximum width inside the inwardly recessed structure is greater than the size of the corresponding opening. The photosensitive unit includes a first structural layer and a second structural layer. The first structural layer is N-type indium antimonide, and the second structural layer is P-type indium antimonide. The second structural layer is located below the first structural layer. The light-receiving structure includes an inner groove with a trapezoidal longitudinal cross-section and an opening with a rectangular cross-section. The size of the rectangular opening is smaller than the short side of the trapezoid. An anti-reflective film or an anti-reflective film is provided on the side wall near the bottom of the inner groove structure.

2. The infrared focal plane detector according to claim 1, characterized in that, The light-receiving structure is a perforated light-receiving aperture, and the light-receiving apertures are arranged in an array; or The light-receiving structure is a groove-shaped light-receiving groove, with multiple light-receiving grooves distributed at intervals.

3. The infrared focal plane detector according to claim 1 or 2, characterized in that, The transverse dimension of the longitudinal cross-section of the light-receiving structure gradually increases along the depth direction.

4. The infrared focal plane detector according to claim 1 or 2, characterized in that, The longitudinal cross-sectional shape of the light-receiving structure is trapezoidal, and the short side of the trapezoid corresponds to the opening.

5. The infrared focal plane detector according to any one of claims 1 to 4, characterized in that, An anti-reflective film or an anti-reflective film is provided on the light-receiving surface.

6. The infrared focal plane detector according to claim 5, characterized in that, The light-receiving surface includes the bottom surface of the recessed structure of the light-receiving structure and the surface between the opening portions of adjacent recessed structures.

7. A method for fabricating a light-receiving structure for an infrared focal plane detector, applied to a cooled photon detector, characterized in that, The method includes the following steps: A layer of photoresist is applied to the light-receiving surface of the photosensitive unit, and the position of the light-receiving structure is determined on its surface. The light-receiving structure is masked. After the masking process, the light-receiving structure is then etched using an etchant. Remove the photoresist from the light-receiving surface of the photosensitive unit and deposit an anti-reflection film on it; The photosensitive unit includes a first structural layer and a second structural layer. The first structural layer is N-type indium antimonide, and the second structural layer is P-type indium antimonide. The second structural layer is located below the first structural layer. The light-receiving structure includes an inner groove with a trapezoidal longitudinal cross-section and an opening with a rectangular cross-section. The size of the rectangular opening is smaller than the short side of the trapezoid. An anti-reflective film or an anti-reflective film is provided on the side wall near the bottom of the inner groove structure.

8. The method for fabricating a light-receiving structure for an infrared focal plane detector according to claim 7, wherein a light-receiving structure is provided on one side of the light-receiving surface of the photosensitive unit corresponding to the position of each photosensitive unit.

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