Uncooled same-frequency heterogeneous infrared detector and preparation method thereof
By integrating high- and low-sensitivity pixels into an uncooled infrared detector, the problem of traditional focal plane arrays being unable to balance sensitivity and anti-saturation, as well as imaging quality and speed, is solved, thus achieving high-quality infrared imaging.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-03-27
AI Technical Summary
Existing uncooled infrared detectors struggle to balance sensitivity and saturation resistance, as well as imaging quality and speed. Traditional homogenized focal plane arrays cannot meet diverse imaging needs.
High-sensitivity and low-sensitivity pixels are integrated on the same focal plane. By designing different thermal capacities of the thermal layer and thermal resistance of the bridge legs, high-sensitivity and low-sensitivity pixels are formed to adapt to different infrared signal intensities and imaging requirements.
It achieves high-quality imaging under different infrared signal environments, taking into account sensitivity, dynamic range and response speed, and adapting to the detection needs of weak and strong signals.
Smart Images
Figure CN121740243A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor device technology, and in particular to an uncooled, same-frequency, heterogeneous infrared detector and its fabrication method. Background Technology
[0002] Infrared imaging technology plays an important role in reconnaissance, industrial inspection, security monitoring, and medical diagnosis due to its advantages such as passive detection, ability to penetrate smoke, and ability to operate at night. Among them, uncooled infrared detectors have become the mainstream choice in the current infrared imaging market due to their small size, low power consumption, low cost, and high reliability, especially in portable and consumer-grade infrared products where they have irreplaceable advantages.
[0003] Existing uncooled infrared detectors typically employ homogeneous focal plane arrays (i.e., all pixels in the array have identical structures, materials, and operating modes). However, with the deepening of application requirements, traditional homogeneous focal plane arrays are gradually revealing their performance bottlenecks. The identical thermal layer and microbridge parameters across all pixels make it impossible to simultaneously achieve both high sensitivity and anti-saturation performance: a high-sensitivity design, while capable of capturing weak infrared signals and achieving high-precision imaging, is highly susceptible to signal saturation (a completely washed-out image) in environments with strong radiation (high temperature, direct sunlight); an anti-saturation design, on the other hand, results in insufficient response to weak infrared signals, failing to identify low-temperature or distant targets. Furthermore, it is difficult to balance imaging quality and imaging speed: while high-sensitivity designs offer high imaging quality, their long thermal response time cannot meet the demands of high-speed imaging; low-sensitivity designs facilitate rapid signal acquisition but suffer from poor imaging quality. Existing heterogeneous designs of focal plane arrays typically focus only on simultaneous detection of two bands (e.g., infrared and visible dual-band imaging) or noise suppression (e.g., special pixel temperature drift compensation), failing to resolve the core contradiction of the difficulty in simultaneously achieving key performance indicators such as sensitivity, dynamic range, and response speed of uncooled infrared detectors. Summary of the Invention
[0004] This invention provides an uncooled, co-frequency heterogeneous infrared detector and its fabrication method, aiming to integrate high- and low-sensitivity pixels on the same focal plane to achieve high-quality infrared imaging.
[0005] The uncooled, same-frequency, heterogeneous infrared detector provided by this invention includes:
[0006] A wafer substrate with readout circuitry on its surface;
[0007] Multiple microbridge structures are disposed on the wafer substrate; each microbridge structure includes a bridge surface suspended on the wafer substrate, bridge piers disposed on the sides of the bridge surface, and bridge legs connecting the bridge surface and the bridge piers. The bridge surface is provided with a thermal layer, and the thermal layer is electrically connected to the readout circuit through the bridge legs and the bridge piers.
[0008] The microbridge structure includes a first microbridge structure and a second microbridge structure integrated on the same wafer substrate according to a preset layout. The bridge height and thermistor layer material of the first microbridge structure are the same as those of the second microbridge structure. The thermal capacity of the thermistor layer of the first microbridge structure is greater than that of the thermistor layer of the second microbridge structure, and the thermal resistance of the bridge legs of the first microbridge structure is higher than that of the bridge legs of the second microbridge structure.
[0009] Optionally, the bridge deck area of the first microbridge structure is greater than that of the second microbridge structure, and the leg length of the first microbridge structure is greater than that of the second microbridge structure.
[0010] Optionally, the ratio of the bridge deck area of the first microbridge structure to that of the second microbridge structure is (1.5:1) to (5:1).
[0011] Optionally, the ratio of the leg length of the first microbridge structure to that of the second microbridge structure is (1.2:1) to (3:1).
[0012] Optionally, the ratio of the leg width of the first microbridge structure to that of the second microbridge structure is (1:1) to (1:2).
[0013] Optionally, the readout circuit is configured with a first sampling channel electrically connected to the first microbridge structure and a second sampling channel electrically connected to the second microbridge structure;
[0014] The first sampling channel and the second sampling channel are configured with different sampling parameters, which include at least one of voltage gain, saturation input power, bias voltage and signal sampling frequency.
[0015] Optionally, the preset layout is:
[0016] The first microbridge structure and the second microbridge structure are located in different partitions of the same wafer substrate.
[0017] Alternatively, the first microbridge structure and the second microbridge structure can be arranged alternately in rows or columns;
[0018] Alternatively, the first microbridge structure and the second microbridge structure are arranged in a checkerboard pattern with intervals.
[0019] Alternatively, the first microbridge structure and the second microbridge structure are randomly arranged according to a preset quantity ratio.
[0020] The uncooled, same-frequency, heterogeneous infrared detector provided by this invention can be prepared by the following method, including the following steps:
[0021] S1, depositing a metal layer on a wafer substrate with readout circuitry on its surface;
[0022] S2, etching the metal layer to form an isolated metal reflective layer and a bridge pier metal connection layer;
[0023] S3, cover the device surface with a filling layer, and etch the filling layer to form the pier area;
[0024] S4, a support layer and a thermal layer are sequentially deposited on the filler layer, and the thermal layer is etched to form a plurality of bridge surfaces; the bridge surfaces include a first bridge surface and a second bridge surface, wherein the thermal capacity of the thermal layer of the first bridge surface is greater than that of the thermal layer of the second bridge surface.
[0025] S5, deposit a first passivation layer on the device surface, etch the first passivation layer, etch a thermistor layer contact hole in the thermistor layer region, and the etching stop layer is the thermistor layer; etch the first passivation layer and the support layer, etch a readout circuit contact hole at the bottom of the pier region, and the etching stop layer is the pier metal connection layer.
[0026] S6, deposit a metal connection layer on the surface of the device, the metal connection layer connecting the thermal layer and the bridge pier metal connection layer, and etch away the metal connection layer in the bridge deck area;
[0027] S7, deposit a second passivation layer on the metal connection layer, and etch each layer of material deposited on the fill layer to form a bridge leg; the bridge leg includes a first bridge leg connecting the first bridge surface and a second bridge leg connecting the second bridge surface, and the thermal resistance of the first bridge leg is higher than that of the second bridge leg.
[0028] S8, Remove the filler layer.
[0029] Optionally, the materials of the first passivation layer and the second passivation layer are silicon nitride.
[0030] Optionally, the thickness of the filling layer is one-quarter of the wavelength of the photosensitive band of the thermal layer.
[0031] Optionally, the material of the thermosensitive layer is vanadium oxide.
[0032] The present invention has the following beneficial effects:
[0033] This invention integrates a first microbridge structure and a second microbridge structure onto the same wafer substrate to form a focal plane pixel array. The first microbridge structure, with a larger thermal capacity in its thermistor layer and higher thermal resistance in its bridge legs, serves as a high-sensitivity pixel, while the second microbridge structure, with a smaller thermal capacity in its thermistor layer and lower thermal resistance in its bridge legs, serves as a low-sensitivity pixel. The thermistor layer material and bridge surface height are identical in both the first and second microbridge structures, ensuring that the high-sensitivity and low-sensitivity pixels share the same photosensitive frequency band. During infrared imaging, the high-sensitivity pixel can capture low-temperature, low-thermal-radiation areas in the scene, extracting rich details, while the low-sensitivity pixel can capture high-temperature, high-radiation areas in the scene, preventing signal saturation. Furthermore, when high-speed imaging is required, the signal rapidly acquired by the low-sensitivity pixel can be primarily read; when high image quality is required, the signal from the high-sensitivity pixel can be primarily read, or multi-frame fusion of the signals acquired by the two types of pixels can be performed to achieve dynamic noise reduction. Therefore, the uncooled, same-frequency, heterogeneous infrared detector proposed in this invention, by integrating high-sensitivity and low-sensitivity pixels, can achieve high-quality infrared imaging. Attached Figure Description
[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0035] Figure 1 This is a schematic diagram of the pixel array layout of some embodiments of the uncooled co-frequency heterogeneous infrared detector of the present invention;
[0036] Figure 2 for Figure 1 A schematic diagram of the planar structure of medium-to-high sensitivity pixels;
[0037] Figure 3 for Figure 1 A schematic diagram of the planar structure of low-to-medium sensitivity pixels;
[0038] Figure 4 The flowcharts are for some embodiments of the method for fabricating the uncooled, same-frequency, heterogeneous infrared detector of the present invention.
[0039] Figure 5 This is one of the process flow diagrams of Embodiment 1 of the present invention;
[0040] Figure 6 This is the second schematic diagram of the process flow of Embodiment 1 of the present invention.
[0041] Explanation of the attached diagram labels: 1. Bridge deck; 2. Bridge leg; 3. Bridge pier. Detailed Implementation
[0042] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0043] The terms "first" and "second" in this invention are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.
[0044] Experimental methods in the embodiments of this invention that do not specify specific conditions are generally performed under conventional conditions and conditions described in the manual, or under conditions recommended by the manufacturer; the general equipment, materials, reagents, etc. used are commercially available unless otherwise specified.
[0045] The uncooled, same-frequency, heterogeneous infrared detector provided in this embodiment of the invention includes a wafer substrate and multiple microbridge structures disposed on the wafer substrate, with a readout circuit provided on the surface of the wafer substrate; see reference. Figure 2 , 3 The microbridge structure is a typical structure of uncooled in-frequency heterogeneous infrared detectors. Each microbridge structure includes a bridge surface 1 suspended on a wafer substrate, a bridge pier 3 located on the side of the bridge surface 1, and a bridge leg 2 connecting the bridge surface 1 and the bridge pier 3. The bridge surface 1 is provided with a thermal layer, which is electrically connected to the readout circuit through the bridge leg 2 and the bridge pier 3. One microbridge structure forms one pixel.
[0046] In this embodiment of the invention, the multiple microbridge structures include a first microbridge structure and a second microbridge structure integrated on the same wafer substrate according to a preset layout. The bridge surface height and the thermal layer material of the first microbridge structure are the same as those of the second microbridge structure, so that the photosensitive frequency bands of different pixels are the same. The thermal capacity of the thermal layer of the first microbridge structure is greater than that of the thermal layer of the second microbridge structure, and the thermal resistance of the bridge legs of the first microbridge structure is higher than that of the bridge legs of the second microbridge structure.
[0047] Specifically, the response process of an uncooled infrared detector pixel is as follows: infrared radiation → heat absorption by the thermistor layer → temperature change of the thermistor layer leading to resistance change → electrical signal output → reset and heat dissipation. The thermal capacity of the thermistor layer represents its ability to store heat. The thermal capacity is positively correlated with the thickness and area of the thermistor layer. The larger the thermal capacity, the stronger the ability of the thermistor layer to store heat, and the more fully it can absorb weak infrared radiation. At the same time, the bridge legs serve as the heat conduction channel between the thermistor layer and the wafer substrate. The longer and thinner the bridge legs, the higher the thermal resistance of the bridge legs, which can reduce the heat loss of the thermistor layer to the substrate and ensure that the thermistor layer converts the absorbed weak heat into a sufficient temperature rise. Therefore, in this embodiment of the invention, the first microbridge structure with a larger thermal capacity of the thermistor layer and higher thermal resistance of the bridge legs forms a high-sensitivity pixel, and the second microbridge structure with a smaller thermal capacity of the thermistor layer and lower thermal resistance of the bridge legs forms a low-sensitivity pixel.
[0048] While high-sensitivity pixels can detect weaker infrared radiation, the high heat capacity of the thermal layer and the high thermal resistance of the bridge legs mean that the thermal layer needs a longer time to cool down (reset), resulting in a slower response speed. Low-sensitivity pixels have a small thermal capacity of the thermal layer and low thermal resistance of the bridge legs, which means that the thermal cycle of the thermal layer heating up and cooling down is short, the response speed is fast, and even if strong radiation is received, it will not heat up to saturation quickly, which is suitable for high temperature and high frequency frame requirements.
[0049] In some specific embodiments, the planar structure of the high-sensitivity pixel is as follows: Figure 2 As shown, the planar structure of low-sensitivity pixels is as follows: Figure 3 As shown, in order to adapt to existing film deposition and etching processes, the bridge surfaces of the first microbridge structure and the second microbridge structure are designed to have the same thickness. By designing the photolithography mask pattern, the bridge surface area of the first microbridge structure is designed to be larger than that of the second microbridge structure, and the leg length of the first microbridge structure is designed to be larger than that of the second microbridge structure, thus realizing the integration of high-sensitivity pixels and low-sensitivity pixels.
[0050] In some preferred embodiments, the ratio of the bridge deck area of the first microbridge structure to that of the second microbridge structure is (1.5:1) to (5:1); the ratio of the leg length of the first microbridge structure to that of the second microbridge structure is (1.2:1) to (3:1); and the ratio of the leg width of the first microbridge structure to that of the second microbridge structure is (1:1) to (1:2).
[0051] In this embodiment of the invention, the core objective of the integrated layout of high- and low-sensitivity pixels is to expand the dynamic range, adapt to weak signal / low temperature and strong signal / high temperature targets, and adapt to high-speed imaging and high-quality imaging. The layout method needs to be designed based on the functional division of pixels, spatial distribution logic, and signal processing adaptability, including but not limited to the following layout methods:
[0052] 1) The first microbridge structure and the second microbridge structure are located in different partitions of the same wafer substrate.
[0053] Specifically, the focal plane is divided into multiple physically isolated regions, each integrating only a single-sensitivity pixel. For example, the upper half of the focal plane is designed as a high-sensitivity region, containing only the first microbridge structure, while the lower half is designed as a low-sensitivity region, containing only the second microbridge structure. Alternatively, the central region of the focal plane is designed as a high-sensitivity region, and the edge regions as low-sensitivity regions. Or, for a specific infrared detection task, the positions of high- and low-sensitivity pixels can be directionally configured according to the infrared signal distribution pattern of the target. For example, for target detection along a line, high-sensitivity pixels are arranged along the line extension direction, and low-sensitivity pixels are arranged vertically. For the boundary between the high- and low-sensitivity regions, a gradual transition with a mixed distribution of the two types of pixels can be designed to avoid imaging stitching marks.
[0054] 2) The first and second microbridge structures are arranged alternately in rows or columns.
[0055] Specifically, the high-sensitivity region and the low-sensitivity region are arranged in an alternating stripe pattern; for example, see [reference needed]. Figure 1 In a pixel array, odd-numbered columns are high-sensitivity pixels, and even-numbered columns are low-sensitivity pixels.
[0056] 3) The first and second microbridge structures are arranged in a checkerboard pattern.
[0057] Specifically, high-sensitivity pixels and low-sensitivity pixels can be arranged one-to-one to form a checkerboard layout, or multiple pixels can be arranged in alternating intervals as repeating units (e.g., 2×2 pixels, 4×4 pixels) to form a checkerboard layout.
[0058] 4) The first microbridge structure and the second microbridge structure are randomly arranged according to a preset quantity ratio.
[0059] Specifically, random arrangement refers to the distribution of high and low sensitivity pixels on the focal plane in a random proportion without fixed repeating units. Random distribution can effectively avoid checkerboard artifacts that may be generated by alternating or spaced arrangement, while suppressing fixed pattern noise and improving image quality. The specific random distribution method can be designed through simulation and other methods.
[0060] In this embodiment of the invention, the sensitivity type of each pixel can be stored by pixel address encoding, and the corresponding signal processing strategy is called according to the type when reading out; the readout circuit is configured with a first sampling channel electrically connected to the first microbridge structure and a second sampling channel electrically connected to the second microbridge structure; the first sampling channel and the second sampling channel are configured with different sampling parameters, including at least one of voltage gain, saturated input power, bias voltage and signal sampling frequency.
[0061] Voltage gain represents the signal amplification factor, indicating the amplification capability of the readout circuit channel for the original electrical signal output by the pixel. The first sampling channel can be configured with high voltage gain to amplify weak signals, ensuring that signals from low-temperature / weak infrared targets can be effectively identified. The second sampling channel can be configured with low gain to limit the amplification amplitude of the signal, preventing signals from high-temperature / strong infrared targets from causing circuit saturation (output signal clipping distortion) and ensuring signal linearity. Saturation input power refers to the minimum incident radiation power density at which the output signal of the readout circuit channel no longer increases linearly with the increase of the input signal. The higher the value, the stronger the channel's anti-saturation capability. The stronger the sensitivity, the better it can adapt to strong radiation signals; the bias voltage refers to the DC operating voltage applied to the thermal layer by the readout circuit. Generally, high-sensitivity pixels can use a lower bias voltage to avoid increased thermal noise caused by high bias, while low-sensitivity pixels use a higher bias voltage to avoid the signal being too weak; the signal sampling frequency refers to the frequency at which the readout circuit collects the analog voltage signal output by the pixel, which determines the signal's time resolution and frame rate limit. High-sensitivity pixels have a slower response speed, so a low sampling frequency can be used to collect the signal without distortion, while reducing circuit power consumption. Low-sensitivity pixels can be configured with a high sampling frequency to ensure that rapidly changing signals are accurately captured.
[0062] In this embodiment of the invention, after the readout circuit reads the signal according to the preset signal processing strategy, it also needs to achieve signal fusion of high and low sensitivity pixels through relevant algorithms. For example, according to the distribution of pixel signal intensity, the signal collected by high sensitivity pixels is mainly used in weak signal areas, the signal collected by low sensitivity pixels is used in strong signal areas, and weighted averaging is used in transition areas to finally obtain an image with rich details from dark to bright areas. Alternatively, if the detector detects a high-speed moving object, it automatically switches from high sensitivity pixels to low sensitivity pixels to collect signals, and performs high and low sensitivity multi-frame fusion noise reduction on the transition frames of the image. Based on the uncooled same-frequency heterogeneous infrared detector provided in this embodiment of the invention, those skilled in the art can design specific signal processing and imaging algorithms according to actual application requirements. It should be understood that this embodiment of the invention lays the hardware foundation for high-quality infrared imaging. Based on this hardware foundation, existing or adapted improved signal processing algorithms can be used to perform signal imaging, stitching, fusion, switching, smoothing, noise reduction, artifact removal, power consumption balancing, and other operations.
[0063] In this invention, a first microbridge structure and a second microbridge structure are integrated on the same wafer substrate to form a focal plane pixel array. The first microbridge structure, with a larger thermal capacity in its thermistor layer and higher thermal resistance in its bridge legs, serves as a high-sensitivity pixel, while the second microbridge structure serves as a low-sensitivity pixel. The thermistor layer material and bridge height are identical for both the first and second microbridge structures, ensuring that the high-sensitivity and low-sensitivity pixels share the same photosensitive frequency band. During infrared imaging, the high-sensitivity pixel can capture low-temperature, weakly radiated areas of the scene, extracting rich details, while the low-sensitivity pixel can capture high-temperature, strongly radiated areas of the scene, preventing signal saturation. The signals from the high-sensitivity and low-sensitivity pixels are fused to generate an image rich in detail from dark to bright areas. Furthermore, when high-speed imaging is required, the signal rapidly acquired by the low-sensitivity pixel can be primarily read; when high image quality is required, the signal from the high-sensitivity pixel can be primarily read. Alternatively, multi-frame fusion of the signals from both types of pixels can be performed to achieve dynamic noise reduction. Therefore, the uncooled, same-frequency, heterogeneous infrared detector proposed in this invention, through the integration of high-sensitivity and low-sensitivity pixels, can achieve high-quality infrared imaging.
[0064] See Figure 4 The uncooled, same-frequency, heterogeneous infrared detector proposed in this embodiment of the invention can be prepared by the following method, including steps S1 to S8:
[0065] S1, depositing a metal layer on a wafer substrate with readout circuitry on its surface.
[0066] The wafer substrate can be a CMOS (Complementary Metal-Oxide-Semiconductor) wafer, and a readout circuit is formed on the surface of the CMOS wafer substrate.
[0067] S2, etching the metal layer to form an isolated metal reflective layer and a pier metal connection layer.
[0068] Among them, the metal connection layer of the bridge pier corresponds to the readout point of the readout circuit; the function of the metal reflective layer is to reflect the infrared light transmitted through the bridge surface to improve the absorption efficiency of the thermosensitive layer. At the same time, the metal reflective layer and the bridge surface located on it form an optical resonant cavity, and the infrared light produces constructive interference at a specific wavelength, which significantly enhances the absorption of infrared radiation of a specific wavelength by the thermosensitive layer.
[0069] S3, cover the device surface with a filling layer, and etch out the pier area from the filling layer; the thickness of the filling layer is 1 / 4 of the target absorption infrared wavelength to meet the requirements of the optical resonant cavity.
[0070] S4, a support layer and a thermistor layer are deposited sequentially on the filler layer, and the thermistor layer is etched to form multiple bridge surfaces; the bridge surfaces formed in this step are located on the metal reflective layer, and the filler layer mainly serves to support the bridge surfaces; the multiple bridge surfaces include a first bridge surface and a second bridge surface, and the thermal capacity of the thermistor layer of the first bridge surface is greater than that of the thermistor layer of the second bridge surface.
[0071] S5, deposit a first passivation layer on the device surface, etch the first passivation layer, etch a thermistor layer contact hole in the thermistor layer region, and the etching stop layer is the thermistor layer; etch the first passivation layer and the support layer, etch a readout circuit contact hole at the bottom of the pier region, and the etching stop layer is the pier metal connection layer; the function of the first passivation layer is to protect the thermistor layer.
[0072] S6. A metal interconnect layer is deposited on the surface of the device. The metal interconnect layer is connected to the thermal layer through the thermal layer contact hole and to the bridge pier metal interconnect layer through the readout circuit contact hole. The metal interconnect layer in the bridge deck area is etched away to avoid short circuit.
[0073] S7, deposit a second passivation layer on the metal connection layer, and etch the material of each layer deposited on the fill layer to form a bridge leg; the bridge leg includes a first bridge leg connecting the first bridge surface and a second bridge leg connecting the second bridge surface, and the thermal resistance of the first bridge leg is higher than that of the second bridge leg.
[0074] S8, remove the fill layer.
[0075] In the embodiments of the present invention for preparing an uncooled, same-frequency, heterogeneous infrared detector, the metal layer is made of, but is not limited to, one or more metal stacks selected from aluminum, titanium, gold, platinum, and chromium; the filling layer is made of, but is not limited to, polyimide or benzocyclobutene, and the filling layer can be removed by a dry adhesive removal process; the support layer can be selected from inorganic ceramic materials such as silicon nitride, silicon carbide, and silicon oxide; the thermistor layer is typically selected from vanadium oxide (V₂O₃). x The materials used can also include infrared-sensitive materials such as hydrogenated amorphous silicon, microcrystalline silicon, and carbon nanotubes; the first passivation layer and the second passivation layer can be inorganic insulating materials such as silicon nitride, silicon oxide, and aluminum oxide; the metal connecting layer can be one or more metal laminates selected from aluminum, titanium, copper, gold, chromium, and platinum; the present invention does not impose special restrictions on the materials, thicknesses, and shapes of the bridge deck, legs, and piers of the microbridge structure. For example, the legs can be selected from various wiring shapes such as straight lines, bends, hollows, and forks, as well as bends such as rounded corners and right angles; the bridge deck can be selected from various planar shapes such as squares, rectangles, circles, ellipses, and polygons; it should be understood that those skilled in the art can select appropriate materials, thicknesses, and shapes of the bridge deck, legs, and piers to prepare specific microbridge structures according to actual conditions, and these selections do not depart from the scope of the technical solution of the present invention.
[0076] Based on the above embodiments, the present invention also proposes the following specific embodiments. It should be noted that the following specific embodiments are merely exemplary and are not intended to limit the scope of protection of the present invention in any way.
[0077] Example 1
[0078] This embodiment fabricates an uncooled, homogeneous infrared detector pixel array, and the process flow is as follows: Figure 5 , 6 As shown, it includes the following steps:
[0079] Step 1: Sequentially deposit a 400nm thick layer of metallic Ti and a 2μm thick layer of metallic Al on a CMOS wafer substrate to obtain a metal layer.
[0080] Step 2: Etch the metal layer. The etching stop layer is the wafer substrate. The metal layer is etched to form the pier metal connection layer in the pier area and the metal reflective layer corresponding to the position on the bridge deck. The pier metal connection layer and the metal reflective layer are isolated from each other.
[0081] Step 3: Coat the surface of the device with a polyimide filling layer. The thickness of the filling layer is 1 / 4 of the wavelength of the target absorption infrared band. Etch the filling layer. The etching stop layer is a metal layer. Etch out the pier area.
[0082] Step 4: Sequentially deposit a 1 μm thick first layer of silicon nitride (SiN) and a 200 nm thick layer of vanadium oxide (VON) on the filler layer. x The first layer of silicon nitride serves as a support layer to support the bridge surface. The vanadium oxide layer is etched to form multiple bridge surfaces, including the first bridge surface and the second bridge surface. The area ratio of the first bridge surface to the second bridge surface is (1.5:1) to (5:1).
[0083] Step 5: Deposit a second silicon nitride layer with a thickness of 100 nm on the surface of the device. The second silicon nitride layer covers the thermistor layer and the first silicon nitride layer. Etch the second silicon nitride layer to etch the thermistor layer contact holes in the thermistor layer area. The etching stop layer is the thermistor layer. Etch the first silicon nitride layer and the second silicon nitride layer to etch the readout circuit contact holes at the bottom of the bridge pier. The etching stop layer is the bridge pier metal connection layer. Deposit a 200 nm thick metal Ti on the surface of the device. Etch away the metal Ti in the bridge surface area.
[0084] Step 6: Deposit a third layer of silicon nitride on the surface of the device.
[0085] Step 7: Etch each layer on the surface of the filling layer to etch out the bridge legs; the bridge legs include a first bridge leg connecting the first bridge surface and a second bridge leg connecting the second bridge surface, the length ratio of the first bridge leg and the second bridge leg is (1.2:1) to (3:1), and the width ratio of the first bridge leg and the second bridge leg is (1:1) to (1:2).
[0086] Step 8: Remove the filler layer using a dry desmearing process.
[0087] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.
Claims
1. A non-cooled heterostructure infrared detector of the same frequency, characterized in that, include: A wafer substrate with readout circuitry on its surface; Multiple microbridge structures disposed on the wafer substrate; The microbridge structure includes a bridge surface suspended on the wafer substrate, bridge piers disposed on the sides of the bridge surface, and bridge legs connecting the bridge surface and the bridge piers. The bridge surface is provided with a thermal layer, and the thermal layer is electrically connected to the readout circuit through the bridge legs and the bridge piers. The microbridge structure includes a first microbridge structure and a second microbridge structure integrated on the same wafer substrate according to a preset layout. The bridge height and thermistor layer material of the first microbridge structure are the same as those of the second microbridge structure. The thermal capacity of the thermistor layer of the first microbridge structure is greater than that of the thermistor layer of the second microbridge structure, and the thermal resistance of the bridge legs of the first microbridge structure is higher than that of the bridge legs of the second microbridge structure.
2. The uncooled homo-frequency heterogeneous infrared detector according to claim 1, characterized in that, The bridge deck area of the first microbridge structure is greater than that of the second microbridge structure, and the leg length of the first microbridge structure is greater than that of the second microbridge structure.
3. The uncooled homomorph infrared detector of claim 1, wherein, The ratio of the bridge surface area of the first microbridge structure to that of the second microbridge structure is (1.5:1) to (5:1).
4. The uncooled homomorph infrared detector of claim 1, wherein, The ratio of the leg length of the first microbridge structure to that of the second microbridge structure is (1.2:1) to (3:1).
5. The uncooled homomorph infrared detector of claim 1, wherein, The ratio of the width of the bridge leg of the first microbridge structure to that of the second microbridge structure is (1:1) to (1:2).
6. The uncooled homomorph infrared detector of claim 1, wherein, The readout circuit is configured with a first sampling channel electrically connected to the first microbridge structure and a second sampling channel electrically connected to the second microbridge structure. The first sampling channel and the second sampling channel are configured with different sampling parameters, which include at least one of voltage gain, saturation input power, bias voltage and signal sampling frequency.
7. The uncooled homomorph infrared detector of claim 1, wherein, The preset layout is as follows: The first microbridge structure and the second microbridge structure are located in different partitions of the same wafer substrate. Alternatively, the first microbridge structure and the second microbridge structure can be arranged alternately in rows or columns; Alternatively, the first microbridge structure and the second microbridge structure are arranged in a checkerboard pattern with intervals. Alternatively, the first microbridge structure and the second microbridge structure are randomly arranged according to a preset quantity ratio.
8. A method for preparing a non-cooled homo-isostatic infrared detector, characterized in that, Includes the following steps: S1, depositing a metal layer on a wafer substrate with readout circuitry on its surface; S2, etching the metal layer to form an isolated metal reflective layer and a bridge pier metal connection layer; S3, cover the device surface with a filling layer, and etch the filling layer to form the pier area; S4, a support layer and a thermal layer are sequentially deposited on the filler layer, and the thermal layer is etched to form a plurality of bridge surfaces; the bridge surfaces include a first bridge surface and a second bridge surface, wherein the thermal capacity of the thermal layer of the first bridge surface is greater than that of the thermal layer of the second bridge surface. S5, deposit a first passivation layer on the device surface, etch the first passivation layer, etch a thermistor contact hole in the thermistor layer region, and the etching stop layer is the thermistor layer; The first passivation layer and the support layer are etched to create readout circuit contact holes at the bottom of the pier area. The etching stop layer is the pier metal connection layer. S6, deposit a metal connection layer on the surface of the device, the metal connection layer connecting the thermal layer and the bridge pier metal connection layer, and etch away the metal connection layer in the bridge deck area; S7, depositing a second passivation layer on the metal connection layer, and etching the layers of material deposited on the filling layer to form bridge legs; the bridge legs include a first bridge leg connecting the first bridge surface and a second bridge leg connecting the second bridge surface, and the thermal resistance of the first bridge leg is higher than that of the second bridge leg; S8, removing the filling layer.
9. The method for fabricating an uncooled, same-frequency, heterogeneous infrared detector according to claim 8, characterized in that, The area of the first bridge surface is larger than that of the second bridge surface, and the length of the first bridge leg is larger than that of the second bridge leg.
10. The method for fabricating an uncooled, same-frequency, heterogeneous infrared detector according to claim 8, characterized in that, The thickness of the filling layer is one fourth of the wavelength of the photosensitive frequency band of the heat-sensitive layer.