Integration method of quantum dot film and readout circuit with through holes in surface

Abstract

The invention relates to an integration method of a quantum dot film and a readout circuit with through holes in the surface, which comprises the following five key steps: firstly, carrying out surface pretreatment on a CMOS (Complementary Metal Oxide Semiconductor) readout circuit with through holes, secondly, dispersing CdSe / ZnS core-shell structure quantum dots subjected to ligand exchange treatment in a high-boiling-point organic solvent to prepare ink, and controlling the concentration within the range of 100-300 mg / mL; thirdly, forming a wet film with the thickness of 300-1000 nm through wet processes such as blade coating and the like, and operating in an environment with strictly controlled temperature and humidity; fourthly, after the solvent is partially volatilized, a vacuum environment within the range of 50 mTorr to 2 Torr is introduced, air in the through holes is promoted to be exhausted through the pressure gradient, and pore self-healing is achieved by means of the fluidity of the wet film; and finally, drying and curing at the temperature of 40-80 DEG C under normal pressure to finish film shaping. By accurately regulating and controlling the solvent volatilization behavior and the film layer structure continuity, the problems that the thin film in the through hole area is prone to blistering and breaking and the like are effectively solved, and the yield and the performance consistency of the device are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photoelectric detection device manufacturing technology, in particular to a quantum dot film and surface via readout circuit integration method. BACKGROUND

[0002] In recent years, quantum dot infrared detectors have shown great application potential in infrared imaging, night vision monitoring, biomedical detection and other fields due to their excellent photoelectric performance and tunable spectral response characteristics. Compared with traditional silicon-based or compound semiconductor detectors, quantum dot detectors have the advantages of simple preparation process, low cost and large-area preparation, and are considered as an important development direction of the next generation of infrared detection technology.

[0003] The core of quantum dot infrared detectors is to effectively integrate quantum dot films with CMOS readout circuits to form a complete detector array. In this device structure, the quantum dot film acts as a photosensitive layer responsible for converting infrared light signals into electrical signals, while the readout circuit is responsible for amplifying, processing and outputting weak photoelectric signals. The effective integration between the two directly determines the overall performance of the device.

[0004] Currently, readout circuits are usually prepared using standard CMOS technology, and their surfaces have a dense via hole structure. The main function of these via holes is to achieve electrical connection between different layers of the circuit, which is an indispensable key structure in modern integrated circuit design. The diameter of the typical readout circuit via hole is in the range of 1-10 μm, and the depth can reach 1-2 μm. In a large-scale detector array, the via hole density can reach millions per square centimeter.

[0005] However, it is these via hole structures that pose a serious technical challenge to the integration of quantum dot films. Traditional film deposition methods such as spin coating, blade coating, drop coating and other wet processes can form uniform films on flat surfaces, but they face serious process problems when encountering via hole structures.

[0006] Specifically, the existing technology has the following key problems: 1. Difficult air removal in via holes is the most critical technical obstacle: During the wet film forming process, when quantum dot ink is applied to the surface of the readout circuit, the air originally present in the via hole will be sealed inside the hole. As the solvent evaporates, the air in the via hole expands when heated, which will squeeze the wet film outward and form bubbles at the edge of the via hole. These bubbles will leave holes or cracks after the solvent is completely dried, seriously damaging the continuity of the film.

[0007] 2. Cracking of thin film at via hole is very common: due to the surface unevenness caused by via hole structure, non-uniform stress distribution will occur during the drying process of the thin film, and the edge of the via hole often becomes a stress concentration point, which is prone to crack and expand to the surrounding. These cracks not only destroy the integrity of the thin film, but also seriously affect the electrical connectivity between the quantum dots and the readout circuit.

[0008] 3. Low device yield becomes the main bottleneck of industrialization: due to the randomness and universality of thin film defects at via hole, a large number of pixels will become blind due to electrical connectivity problems. Even in the preparation of laboratory prototype, the yield of the device is often less than 50%, which is far lower than the requirement of industrial application, which not only increases the production cost, but also seriously restricts the large-scale application of quantum dot detectors.

[0009] In order to solve these problems, researchers have tried various technical routes. For example, by optimizing the rheological properties of quantum dot ink to improve its spreading on the via hole structure; using a multi-step coating process to gradually fill the via hole; or pre-treating the surface of the readout circuit to improve the interface properties. However, these methods either have limited effect or high process complexity, and have not fundamentally solved the core problem of thin film cracking at via hole.

[0010] Therefore, it is urgent to develop a quantum dot thin film integration method specifically for via hole readout circuit. This method should effectively solve the problem of air discharge in the via hole, significantly improve the continuity of the thin film at the via hole, and improve the electrical performance and preparation yield of the device, laying a solid technical foundation for the industrial application of quantum dot infrared detectors. This not only has important scientific value, but also has great engineering application significance and business prospects SUMMARY

[0011] In order to improve the above-mentioned technical problems, the present application provides a quantum dot thin film and surface readout circuit with via hole integration method.

[0012] The quantum dot thin film and surface readout circuit with via hole integration method provided by the present application adopts the following technical scheme: A quantum dot thin film and surface readout circuit with via hole integration method, comprising the following steps: Step one Readout circuit surface pretreatment: systematic surface treatment is performed on the CMOS readout circuit with via hole, standard cleaning process is used to remove organic contaminants and particle impurities on the surface, and surface cleanliness is ensured to meet process requirements, Oxygen plasma treatment or chemical cleaning method is used to improve the surface wettability, and create favorable conditions for uniform spreading of subsequent quantum dot ink; Step two Preparation of quantum dot ink: quantum dot material after ligand exchange treatment is dispersed in selected organic solvent system; solvent selection needs to take into account the volatility rate, viscosity characteristics and compatibility with quantum dots, preferably high boiling point solvents such as DFP, DMF, Quantum dot concentration is precisely controlled in the range of 100-300 mg / mL, ensuring a good coating process window; Step three Wet film formation: using wet process such as blade coating, drop coating or spin coating to deposit quantum dot ink on the surface of pretreated readout circuit, Process parameters need to be optimized according to the specific device structure and requirements, typical blade coating speed is controlled in 20-50 mm / s, forming a wet film of 300-1000 nm thickness, Environmental conditions are strictly controlled, humidity is maintained below 50% RH, temperature is controlled at 20-40℃; Step four Vacuum assisted treatment: when the solvent is volatilized to 50-80% residual amount, the sample preparation environment is vacuumed, The final vacuum degree is precisely controlled in the range of 50 mTorr - 2 Torr, preferably 200-500 mTorr, the time to vacuum the sample environment to the lowest point is generally controlled in 10 seconds-300 seconds, preferably 30-60 seconds, The processing time of target vacuum degree is adjusted according to the film thickness and solvent type, usually 5 seconds-300 seconds, the optimal processing time is 15-30 seconds; Step five: atmospheric pressure drying and curing: after vacuum treatment, the sample is returned to normal pressure environment, and drying and curing continue. The temperature can be appropriately increased to 40-80℃ in this stage to accelerate the volatilization of the remaining solvent, and the drying time is usually 10-30 minutes. At this time, the air in the via hole has been effectively discharged, and the film can complete the final curing process under less stress.

[0013] By adopting the technical scheme, efficient cleaning treatment and lyophilicity regulation of the surface of the CMOS readout circuit are realized. By introducing a standard cleaning process and oxygen plasma or chemical cleaning means, the surface residual organic pollutants and particulate impurities are effectively removed, and the surface wettability is significantly improved. Not only the spreading uniformity of the quantum dot ink is improved, but also the foundation for subsequent film formation quality and film layer continuity is laid. The problems such as film defects, empty spots or local delamination caused by poor local wettability are prevented. By stably dispersing the quantum dot material such as CdSe / ZnS treated by ligand exchange in high-boiling-point organic solvents such as DFP and DMF, the dispersion and fluorescence performance of the quantum dots are ensured, the volatility and viscosity control required in the film formation process are considered, and the precise control of the quantum dot concentration (100-300 mg / mL) further widens the process window suitable for various coating methods. By adopting wet film deposition processes such as blade coating, drop coating or spin coating, and by precisely controlling the blade coating speed (20-50 mm / s) and environmental parameters (temperature control at 20-40 DEG C, humidity control below 50% RH), a wet film with uniform thickness and good coverage is realized. This step ensures good coverage and self-adaptive wrapping of the quantum dot film layer on the through-hole area, effectively avoids the film breaking and film breaking phenomenon caused by surface tension disturbance at the edge of the through-hole, introduces a vacuum assisted processing mechanism to solve the problem of air retention in the through-hole and film breaking, introduces a medium-low vacuum environment (preferably 200-500 mTorr) when the solvent is volatilized to the middle stage (residual amount 50-80%), uses the pressure difference between the through-hole structure and the film layer to drive the air in the hole to the outside, and the wet film still has a certain flowability, which can spontaneously backfill the hole space, so as to obtain a continuous film structure without causing surface bubbling or cavitation. By adjusting the vacuum duration (10-300 seconds to the lowest vacuum, and maintaining the target vacuum for 5-300 seconds), different solvent systems and film thicknesses can be adapted, and good universality and compatibility are achieved. After vacuum treatment, the atmospheric pressure is restored and the film is dried and solidified at a suitable temperature (40-80 DEG C, drying time 10-30 minutes), so as to realize the full volatilization of the residual solvent in the film, promote the directional arrangement of the quantum dots and the densification of the film, and reduce the film cracking, uneven shrinkage or poor adhesion caused by changes in the through-hole structure.

[0014] Optionally, the process mechanism of the vacuum assisted processing step is as follows: a moderate vacuum environment can generate sufficient pressure gradient to drive the air in the through-hole to diffuse outward through the wet film; At the same time, since the solvent has not been completely volatilized at this time, the wet film still maintains a certain flowability and can spontaneously fill the gap after the air is discharged, so as to ensure the continuity of the film; Precise control of the vacuum degree avoids the sudden boiling of the solvent, preventing new defects on the surface of the film.

[0015] By adopting the technical scheme, effective discharge of residual air in the through hole and spontaneous filling of the wet film gap are realized, the continuity and density of the film in the through hole area are significantly improved, and meanwhile, precise control of the vacuum degree can avoid defects such as film rupture and bubbles caused by violent boiling of the solvent, thereby ensuring the complete formation and high-quality integration of the quantum dot film on the complex microstructure surface and improving the consistency and yield of the device.

[0016] Optionally, the treatment time of the oxygen plasma treatment in step one is 30 to 120 seconds, and the power is controlled in the range of 100 to 300 W, so as to optimize the surface wettability.

[0017] By adopting the technical scheme, the oxygen plasma treatment is adopted, the treatment time is controlled in the range of 30 to 120 seconds, and the power is controlled in the range of 100 to 300 W, so as to effectively remove the organic contaminants and residues on the surface of the CMOS readout circuit, introduce surface polar groups, significantly improve the surface energy and wettability of the material, thereby enhancing the spreading uniformity and adhesion of the quantum dot ink on the surface, providing guarantee for uniform deposition and film formation quality of the subsequent film, and improving the consistency and stability of the overall device.

[0018] Optionally, the quantum dot material in step two is a quantum dot with a CdSe / ZnS core-shell structure, and the ligand is a short-chain carboxylic acid or an amine small molecule.

[0019] By adopting the technical scheme, the quantum dot with a CdSe / ZnS core-shell structure is adopted, and a short-chain carboxylic acid or an amine small molecule is introduced as a ligand, so as to significantly improve the dispersion stability and concentration control ability of the quantum dot in the high-boiling-point organic solvent, reduce the steric hindrance between ligands, enhance the close packing and electronic coupling effect between quantum dots, help to form a dense and uniform film structure, and at the same time, have excellent optical stability and surface passivation effect, thereby effectively improving the photoelectric performance and environmental resistance of the device.

[0020] Optionally, the high-boiling-point solvent for dispersing the quantum dot in step two contains a volatile control additive such as 1,2-dichlorobenzene or hexanediol, so as to improve the uniformity of the film.

[0021] By adopting the technical scheme, the volatile control additive such as 1,2-dichlorobenzene or hexanediol is introduced into the high-boiling-point solvent, so as to effectively adjust the volatilization rate and fluidity of the quantum dot ink, prolong the film formation window time of the wet film, inhibit the "coffee ring effect" and local accumulation phenomenon in the drying process, and realize uniform deposition of the film and improvement of the surface flatness.

[0022] Optionally, in step three, the doctoring adopts a wire bar coating method, and the wire bar has a diameter of 5-20 μm to regulate the film thickness.

[0023] By adopting the above technical solution, the wire bar coating method is adopted, and the wire bar has a diameter of 5-20 μm, so that the coating thickness and uniformity of the quantum dot ink can be accurately controlled, the wet film thickness in the range of 300-1000 nm can be adjusted, defects such as cracks, wrinkles or incomplete coverage caused by too thick or too thin film layer can be effectively avoided, the thin film is ensured to uniformly cover the surface with a through hole, the continuity and mechanical stability of the thin film are improved, and the performance and reliability of the overall device are improved.

[0024] Optionally, in the wet film forming process in step three, the environmental humidity is controlled between 30% and 45% RH to avoid film aggregation or defects caused by too high humidity.

[0025] By adopting the above technical solution, the environmental humidity in the wet film forming process is strictly controlled within the range of 30% to 45% RH, which effectively prevents the aggregation, crystallization and surface defects of the quantum dot film caused by too high humidity. The appropriate humidity environment promotes the uniform spreading of the quantum dot ink and the stable evaporation of the solvent, ensures that the thin film forms a dense, continuous and bubble-free structure, and thus improves the optical performance and mechanical stability of the thin film, and guarantees the high-quality integration and reliable operation of the device on the complex through-hole structure.

[0026] Optionally, the vacuum device for vacuumizing in step four is a rotary vane pump combined with a molecular pump system to realize a rapid and stable low vacuum environment.

[0027] By adopting the above technical solution, the vacuum device combining the rotary vane pump and the molecular pump can realize a rapid and stable low vacuum environment (50 mTorr to 2 Torr), effectively control the vacuum degree and vacuumizing speed of the sample environment, ensure accurate regulation of the pressure gradient during the solvent partial evaporation stage, promote rapid air exhaust in the through hole, avoid defects caused by sudden boiling of the solvent, and at the same time, the stable vacuum environment guarantees the flowability of the wet film, which is conducive to the spontaneous filling of the film pores and the continuous film forming, and improves the denseness of the film and the overall performance of the device.

[0028] Optionally, the time for vacuumizing the sample environment to the lowest point in step four is preferably controlled between 40 and 50 seconds to balance the time window of air exhaust and solvent retention.

[0029] By adopting the above technical solution, the time for vacuumizing the sample environment to the minimum vacuum point is preferably controlled between 40 to 50 seconds, which can effectively balance the sufficient exhaust of air in the through hole and the moderate retention of solvent in the wet film. This time window ensures the smooth diffusion of air driven by pressure gradient, while maintaining the fluidity of the wet film, preventing film cracking or bubbling caused by too fast solvent evaporation, significantly improving the continuity and uniformity of the film, and ensuring the high-quality film formation of quantum dot film on the surface of complex through hole structure and the reliability of the device.

[0030] Optionally, the drying and curing process in step five is completed by using a hot plate or a hot air circulation device, and slowly cooled to room temperature at the end of drying to reduce the risk of cracking caused by thermal stress of the film.

[0031] By adopting the above technical solution, the drying and curing process is completed by using a hot plate or a hot air circulation device, and slowly cooled to room temperature at the end of drying, which effectively controls the temperature change rate of the film, significantly reduces the risk of film layer cracking, warping or peeling caused by thermal stress, promotes the densification and stable curing of the quantum dot film, ensures the integrity and mechanical strength of the film layer structure, improves the combination reliability of the film and the readout circuit with through holes, and further improves the long-term stability and service life of the device.

[0032] In summary, the present application includes at least one of the following beneficial technical effects: Fundamental improvement of film quality: Through vacuum-assisted air exhaust technology, the film cracking problem at the through hole has been solved, which has plagued the industry for many years. The film continuity is greatly improved from 60% in traditional process to more than 95%, and the breakage rate at the edge of the through hole is reduced by more than 80%. This improvement is structural and does not depend on specific quantum dot materials or readout circuit design, and has wide applicability; Leap-forward improvement of manufacturing yield: The device yield is improved from 50% in traditional process to more than 90%, which is of great significance to industrialization. According to a typical 320x256 pixel array, the yield improvement is equivalent to reducing about 20,000 blind pixels, and the product quality meets the standard of commercial application; Effective control of production cost: Although a vacuum treatment step is added, the actual unit product cost is actually reduced by 25% due to the significant improvement in yield. At the same time, this method does not require expensive special equipment, only a regular vacuum pump and control system, and the equipment investment cost is reasonable; Significant improvement of process stability and reproducibility: A process control system based on physical mechanism is established, eliminating the randomness of air exhaust in traditional methods, laying a solid foundation for large-scale production.

[0033] 5. Technology universality and scalability: The method is suitable for various types of quantum dot materials (HgTe, PbS, PbSe, etc.) and different specifications of readout circuits, has good technology universality, and at the same time, the process parameters can be flexibly adjusted according to the specific application requirements, and has strong scalability. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a flowchart of the integration method of the quantum dot film and the readout circuit with a surface having a through hole according to an embodiment of the present application.

[0035] Figure 2 is a comparison diagram of the quantum dot film on the surface of the circuit according to the present application and the quantum dot film deposited by traditional blade coating without using the method of the present application in embodiment 1. DETAILED DESCRIPTION

[0036] The following will be described in detail with reference to the accompanying drawings. Figure 1 The present application will be further described in detail.

[0037] The embodiment of the present application discloses an integration method of a quantum dot film and a readout circuit with a surface having a through hole. Referring to Figure 1 An integration method of a quantum dot film and a readout circuit with a surface having a through hole, comprising the following steps: Step one Surface pretreatment of readout circuit: systematic surface treatment is performed on the CMOS readout circuit with a through hole, standard cleaning process is adopted to remove organic contaminants and particle impurities on the surface, and the surface cleanliness is ensured to meet the process requirements, Oxygen plasma treatment or chemical cleaning method is adopted to improve the surface wettability, and favorable conditions are created for uniform spreading of the subsequent quantum dot ink; Step two Preparation of quantum dot ink: the quantum dot material treated by ligand exchange is dispersed in a selected organic solvent system; the solvent selection needs to consider the volatilization rate, viscosity characteristics and compatibility with quantum dots, and high-boiling point solvents such as DFP and DMF are preferably selected, The quantum dot concentration is accurately controlled in the range of 100-300 mg / mL, and a good coating process window is ensured; Step three Wet film forming: quantum dot ink is deposited on the surface of the pretreated readout circuit by using wet processes such as blade coating, drop coating or spin coating, The process parameters need to be optimized according to the specific device structure and requirements, and the typical blade coating speed is controlled in the range of 20-50 mm / s, and a wet film with a thickness of 300-1000 nm is formed, The environmental conditions are strictly controlled, the humidity is maintained below 50% RH, and the temperature is controlled at 20-40℃; Step four Vacuum assisted process: when the solvent is evaporated to a residual amount of 50-80%, the sample preparation environment is vacuumed, The final vacuum degree is precisely controlled in the range of 50 mTorr - 2 Torr, preferably 200-500 mTorr, and the time for vacuuming the sample environment to the lowest point is generally controlled in the range of 10 seconds - 300 seconds, preferably 30-60 seconds, The processing time of the target vacuum degree is adjusted according to the film thickness and the type of solvent, and is generally 5 seconds - 300 seconds, and the optimal processing time is 15-30 seconds; Step five: atmospheric pressure drying and curing: after the vacuum treatment is completed, the sample is returned to the atmospheric pressure environment, and the drying and curing continue. The temperature can be appropriately increased to 40-80℃ in this stage to accelerate the evaporation of the remaining solvent, and the drying time is generally 10-30 minutes. At this time, the air in the through hole has been effectively discharged, and the film can complete the final curing process under less stress.

[0038] The above-mentioned step-by-step quantum dot film and surface through-hole readout circuit integration method realizes multiple significant technical effects through precise design and parameter control of each process step: First, in step one, standard cleaning process and oxygen plasma or chemical treatment means are used to thoroughly clean and optimize the wettability of the CMOS readout circuit surface, which not only effectively removes organic contamination and particle impurities, but also improves the spreading uniformity of the quantum dot ink through surface polarity adjustment, laying a foundation for subsequent film quality and avoiding film discontinuity and insufficient adhesion problems.

[0039] Secondly, in step two, the ligand-exchanged quantum dots are dispersed in a high-boiling-point organic solvent to form an ink system with precisely controllable concentration, ensuring the dispersion stability and processability of the quantum dots. The selected solvent (such as DFP, DMF) has good volatility behavior and quantum dot compatibility, and the concentration range is controlled in the range of 100-300 mg / mL, effectively expanding the wet film forming process window, making the film easier to control, reducing particle accumulation and sedimentation, and ensuring the uniformity and density of the film.

[0040] In step three, wet processes such as blade coating, drop coating or spin coating are used to deposit quantum dot ink on the readout circuit surface to form a wet film with controllable thickness (300-1000 nm), and the environmental humidity (≤50%RH) and temperature (20-40℃) are strictly controlled to effectively avoid water vapor condensation, liquid film shrinkage or surface wrinkles under high humidity conditions, ensuring stable and repeatable film forming process, and achieving uniform coverage in the through-hole area.

[0041] The introduction of vacuum-assisted processing in Step Four is one of the key innovations of this method. By introducing a precisely controlled low vacuum environment (50 mTorr - 2 Torr, preferably 200-500 mTorr) at a stage when the solvent has not yet completely evaporated, the pressure gradient is used to drive the air inside the via to escape outward through the wet film. At the same time, the wet film maintains a certain fluidity to spontaneously fill the via and its edge area after the gas is discharged, effectively preventing the formation of bubbles, voids, or edge cracking phenomena. The vacuum processing time and vacuum degree are matched and controlled to avoid the disturbance of the film layer caused by the violent boiling of the solvent, achieving complete and defect-free film formation in the via area.

[0042] Finally, in the atmospheric pressure drying and curing process of Step Five, the temperature is reasonably increased (40-80°C) and the curing time is maintained for 10-30 minutes, further accelerating the evaporation of residual solvents and improving the film density and mechanical strength. The pre-removal of air in the via allows the film to be uniformly cured under less stress, effectively avoiding cracking or peeling problems caused by internal stress accumulation.

[0043] The test results of the wet film formation are shown in Table 1 Table 1: Example 1 Readout circuit surface pretreatment: A standard 320x256 pixel CMOS readout circuit was used, with a via diameter of 5 μm, a via pitch of 15 μm, and a depth of 1 μm. First, the surface was cleaned with acetone, isopropyl alcohol, and deionized water for 5 minutes each to remove organic matter and particle contamination. Then, it was dried with nitrogen and treated in an oxygen plasma cleaning machine (power 300 W, time 2 minutes) to improve the surface wettability. (2) HgTe quantum dot ink preparation: HgTe quantum dots (average particle size 8 nm) exchanged with mercaptoethanol ligands were redispersed in DFP solvent, and the concentration was adjusted to 120 mg / mL; (3) Wet film formation: The quantum dot ink was deposited on the pretreated readout circuit surface using a doctor blade method at a speed of 10 mm / s, forming a wet film about 500 nm thick. Environmental conditions: temperature 25°C, relative humidity 40%; (4) Vacuum-assisted processing: After standing at room temperature for 3 minutes, when the solvent was evaporated to about 70%, the sample was placed in a vacuum environment, and the vacuum degree reached 500 mTorr in about 45 seconds and was maintained for 30 seconds. During this process, it was observed that the air bubbles inside the via gradually disappeared, and the film surface became smooth again.

[0044] (5) Atmospheric pressure drying and curing: After restoring the atmospheric pressure, the sample was placed on a 40°C hot stage for 30 minutes to complete the solvent evaporation and film curing.

[0045] Example 2 The difference compared with Example 1 is that: Quantum dot material and ink: PbS quantum dots (average particle size 6 nm) were used, which were dispersed in DMF after ligand exchange with 1,2-ethanedithiol, with a concentration of 150 mg / mL; Film forming process: drop coating method was used to form film, 50 μL of quantum dot ink was uniformly dropped on the surface of the readout circuit, and the wet film was formed by natural spreading.

[0046] Example 3 The difference compared with Example 1 is that: Readout circuit specifications: a large-scale array of 640x512 pixels was used, with a through-hole diameter of 3 μm, a through-hole pitch of 10 μm, a depth of 1.5 μm, and a higher through-hole density.

[0047] Key points of the technology of the present application: 1. Vacuum treatment is introduced at a specific stage of solvent evaporation of the quantum dot film (solvent residual amount 50-80%), through precise control of the pressure difference (vacuum degree 50 mTorr-2 Torr) to force the air in the through-hole to be discharged, while avoiding the defects of the film caused by too fast evaporation of the solvent. The key to this technical breakthrough is to find the best balance point between the flowability of the film and the air discharge efficiency; 2. Precise control of process timing: the choice of vacuum treatment timing is the key to success or failure. Too early treatment will result in too strong flowability of the film, causing unevenness; too late treatment will not effectively discharge the air. Through in-depth study of film drying, the present patent determines that the optimal time for the sample environment to be vacuumed to the lowest point is 30-60 seconds. At the same time, the optimal treatment time for the target vacuum degree is 15-30 seconds.

[0048] The implementation principle of the embodiment of the quantum dot film and surface readout circuit with through holes integrated method is: the depth regulation and control of quantum dot ink wet deposition and solvent control volatilization behavior, and the introduction of key vacuum assisted processing for through hole structure, to realize high uniformity, high density and no hollow quantum dot film covering effect, to ensure the reliable integration of CMOS readout circuit, the surface of the through hole type CMOS circuit often causes organic pollution and insufficient wettability due to the existence of microstructure and metal contact layer, and then affects the spreading behavior of quantum dot ink, the method effectively improves the surface polarity through standard cleaning process and oxygen plasma treatment, improves the wetting ability of the ink on the surface of the circuit, so that the ink is uniformly distributed in the subsequent coating process, avoiding the problems of uneven film thickness or desorption caused by the difference in interfacial energy; The stable dispersion of quantum dot material in high boiling point organic solvent (such as DFP, DMF) is the basis for forming a continuous and uniform film layer, and by selecting appropriate ligands (such as mercaptoethanol and ethylenediamine) for surface passivation, the dispersion of quantum dots in the solvent is enhanced, and the concentration of the ink is controlled between 100-300 mg / mL, so that it has good spreading, thickness control ability and surface tension characteristics in the wet process (such as blade coating, drop coating, spin coating), so as to realize the controllable film thickness (300-1000 nm) and complete coverage; After the ink is deposited, the residual amount of solvent is still 50-80%, and the low vacuum environment (50 mTorr-2 Torr) is introduced in time, at this stage, the wet film still has certain flowability, which can flow again after the air in the through hole is driven out by pressure difference, and fill the pores, realize the "self-healing" of the film layer, and accurately control the rate and target holding time (preferably 30-60 seconds of vacuum, 15-30 seconds of holding) of vacuumizing to avoid the phenomena of film blistering and cracking caused by sudden change of evaporation rate; After vacuum treatment, the atmospheric pressure is restored, and moderate heating (40-80 DEG C) is used to completely evaporate the solvent and shape the film, which can realize uniform solidification under low internal stress, avoid the problems of interface desorption and film cracking caused by pore residual gas expansion or film shrinkage, and improve the mechanical stability and electrical consistency of the film layer; The method is verified on CMOS readout circuits with different pixel sizes (such as 320x256 and 640x512 pixel arrays) with different specifications of through hole density (such as 5 μm / 15 μm / 1 μm depth or 3 μm / 10 μm / 1.5 μm depth), the results show that the method can realize defect-free film forming in the dense through hole area, and the process adaptability in high density readout structure is verified.

[0049] The above are preferred embodiments of the present application, and do not limit the protection scope of the present application, therefore: any equivalent changes made on the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for integrating quantum dot films with readout circuits having vias, comprising: The method comprises the following steps: ​ Step one Surface pretreatment of readout circuit: systematic surface treatment is performed on the CMOS readout circuit with through holes. Standard cleaning process is used to remove organic contaminants and particulate impurities on the surface, so as to ensure that the surface cleanliness meets the process requirements. Oxygen plasma treatment or chemical cleaning method is used to improve the surface wettability, so as to create favorable conditions for the uniform spreading of the subsequent quantum dot ink. Step two Preparation of quantum dot ink: the quantum dot material treated by ligand exchange is dispersed in a selected organic solvent system; the solvent selection needs to consider the volatility rate, viscosity characteristics and compatibility with quantum dots, and high-boiling solvents such as DFP and DMF are preferably selected. The concentration of quantum dots is accurately controlled in the range of 100-300 mg / mL, so as to ensure a good coating process window. Step three Wet film forming: quantum dot ink is deposited on the surface of the pretreated readout circuit by using wet processes such as blade coating, drop coating or spin coating, etc. The process parameters need to be optimized according to the specific device structure and requirements. The typical blade coating speed is controlled in the range of 20-50 mm / s, and a wet film with a thickness of 300-1000 nm is formed. The environmental conditions are strictly controlled, the humidity is kept below 50% RH, and the temperature is controlled in the range of 20-40℃. Step four Vacuum assisted treatment: when the solvent is volatilized to a residual amount of 50-80%, the sample preparation environment is vacuumized. The final vacuum degree is accurately controlled in the range of 50 mTorr-2 Torr, preferably 200-500 mTorr. The time for vacuumizing the sample environment to the lowest point is generally controlled in the range of 10 seconds-300 seconds, preferably 30-60 seconds. The treatment time of the target vacuum degree is adjusted according to the film thickness and the type of solvent, and is generally 5 seconds-300 seconds, and the optimal treatment time is 15-30 seconds. Step five: atmospheric pressure drying and curing: after the vacuum treatment is completed, the sample is returned to the atmospheric pressure environment for drying and curing. The temperature can be appropriately increased to 40-80℃ in this stage to accelerate the volatilization of the remaining solvent, and the drying time is usually 10-30 minutes. At this time, the air in the through hole has been effectively discharged, and the film can complete the final curing process under the condition of smaller stress.

2. The method of claim 1, wherein the method further comprises: forming a plurality of quantum dots on the substrate; and forming a plurality of readout circuits on the substrate. The process mechanism of the vacuum assisted treatment step is as follows: a moderate vacuum environment can generate sufficient pressure gradient to drive the air in the through hole to diffuse outward through the wet film. At the same time, since the solvent has not been completely volatilized at this time, the wet film still maintains a certain fluidity, which can spontaneously fill the gap after the air is discharged, so as to ensure the continuity of the film. The accurately controlled vacuum degree avoids the sudden boiling of the solvent, preventing new defects from being generated on the surface of the film.

3. The integration method of claim 1, wherein: The treatment time of the oxygen plasma treatment in step one is 30-120 seconds, and the power is controlled in the range of 100-300 W, so as to optimize the surface wettability.

4. The integration method of claim 1, wherein: The quantum dot material in step two is a quantum dot with CdSe / ZnS core-shell structure, and the ligand thereof is a short-chain carboxylic acid or an amine small molecule.

5. The integration method of claim 1, wherein: The high-boiling point solvent for dispersing quantum dots in step two contains 1,2-dichlorobenzene or hexanediol as a volatility control additive, so as to improve the uniformity of the film layer.

6. The integration method of claim 1, wherein: The line bar diameter is selected as 5-20 μm in the line bar coating method in step three to control the film thickness.

7. The integration method of claim 1, wherein: The environmental humidity is controlled between 30% and 45% RH in the wet film forming process in step three to avoid the film aggregation or defects caused by high humidity.

8. The integration method of claim 1, wherein: The vacuum device for vacuumizing in step four is a rotary vane pump combined with a molecular pump system to achieve a fast and stable low vacuum environment.

9. The integration method of claim 1, wherein: The time for vacuumizing the sample environment to the lowest point is preferably controlled between 40 and 50 seconds in step four to balance the time window of air discharge and solvent retention.

10. The integration method of claim 1, wherein: The drying and curing process in step five is completed by using a hot plate or a hot air circulation device, and slowly cooled to room temperature at the end of drying to reduce the risk of cracking caused by thermal stress of the film.

Images