Film coating process of mask substrate

Abstract

The invention discloses a coating process of a mask substrate, and relates to the technical field of semiconductor manufacturing. The mask assembly with the positioning structure is combined with visual positioning calibration, accurate covering of the first mask and the second mask is achieved, it is ensured that the second film layer is matched with the edge of the first film layer, and the coating thickness uniformity is improved; meanwhile, a transition layer is pretreated, a first film layer is subjected to plasma activation and is compounded with a second film layer in a gradient manner, the interface bonding force of the film layers is enhanced, interface cracking under temperature and humidity circulation is avoided, a flexible composite structure is adopted and is matched with micro-pressure attachment, and the flexible substrate is prevented from wrinkling so as to guarantee uniform film coating; due to the layered design of the gradient composite second film layer, the long-term bending requirement of the flexible screen is met, the display pixel edge precision is improved, deposition parameters can be adjusted in time through full-process real-time monitoring, and batch defects are avoided; the waste of oversize defects is reduced through local replating, the film layer consistency is guaranteed, the process is compatible with rigid and flexible substrates and adapts to multiple devices such as a display screen and a sensor, and the practicability and the popularization value are improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a coating process for a mask substrate. Background Technology

[0002] As a core component in critical processes such as vapor deposition and photolithography, the performance of the surface film layer of a mask substrate directly determines the yield and reliability of the device. Chinese patent application CN117512555A discloses a mask assembly, a coating process, a display screen, and an electronic device for display screen coating. The mask assembly includes a first mask and a second mask. The first mask has multiple first coating areas arranged in an array, and the second mask has multiple groups of second coating areas arranged in an array. The first coating areas and the second coating area groups are correspondingly arranged. Each first coating area includes a central region and an edge region. When the first mask and the second mask are stacked, the central region is blocked by the second mask, and the edge region of the second coating area group is exposed.

[0003] While the aforementioned patents can effectively solve the problem of color misalignment at the edges of the display screen, they still have the following drawbacks:

[0004] 1. In the existing technology, the display screen has no reference positioning during the two mask replacement processes, which makes it impossible for the second film layer to accurately cover the edge area of ​​the first film layer, thus destroying the uniformity of the coating layer thickness. Furthermore, the second film layer is directly deposited on the surface of the first film layer. When the display screen is in a temperature and humidity cycle environment for a long time, the interface is prone to cracking, which increases the risk of encapsulation failure.

[0005] 2. Existing technologies do not take into account the characteristics of the substrate of flexible displays, which affects the edge accuracy of display pixels; and the pressure of rigid masks can easily cause wrinkles on flexible substrates, further reducing the uniformity of coating. The thickness is only achieved by thickening the second film layer. The second film layer made of a single material is brittle and cannot meet the bending resistance requirements of flexible screens. Summary of the Invention

[0006] The purpose of this invention is to provide a coating process for a mask substrate, which performs precise film deposition based on a dual-mask precise positioning mechanism, improves the overall performance of the film based on a gradient composite structure and pretreatment, acquires full-process monitoring data, performs real-time control and defect repair, adapts to flexible and multi-material requirements, and significantly improves coating quality and production efficiency, thereby solving the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A coating process for a mask substrate includes a mask assembly with a positioning structure. The mask assembly consists of a first mask and a second mask. The first mask is configured with an array of first coating areas, and the second mask is configured with second coating areas that correspond one-to-one with the first coating areas.

[0009] The mask substrate is pretreated. Based on the pretreated mask substrate, the first mask is positioned and covered on the mask substrate according to the positioning structure. The first film layer is deposited in the first coating area. After the deposition is completed, the first mask is removed.

[0010] The surface of the first film layer is cleaned and activated. The second mask is positioned and covered on the mask substrate according to the positioning structure, and the edge area of ​​the first film layer is exposed in the second coating area. The edge area is then cleaned in situ.

[0011] Based on the second coating area, a gradient composite second film layer is deposited in the edge area to connect the first film layer and the second film layer into one to form a coating layer;

[0012] The coating process is monitored in real time, and the mask substrate is post-processed after coating is completed.

[0013] Furthermore, the mask substrate undergoes pretreatment, specifically including:

[0014] Based on the material of the mask substrate, select the corresponding cleaning agent, obtain the surface state of the mask substrate, and perform ultrasonic cleaning according to the initial surface contaminant content of the mask substrate;

[0015] Vacuum drying is performed on the surface of the mask substrate after ultrasonic cleaning. During the drying process, a mixed gas is introduced for plasma activation. A transition layer is then prepared based on the plasma-activated mask substrate to obtain the pretreated mask substrate.

[0016] Furthermore, the transition layer fabrication process specifically includes:

[0017] The material of the transition layer is selected based on the material of the mask substrate, including SiO2 transition layer and TiN transition layer;

[0018] The deposition parameters for the SiO2 transition layer are: temperature 150-180℃, SiH4 to N2O volume ratio 1:8-1:12, deposition rate 5-8nm / min, and target thickness 50-80nm; the deposition parameters for the TiN transition layer are: temperature 200-220℃, TiCl4 to NH3 volume ratio 1:5-1:7, deposition rate 3-5nm / min, and target thickness 30-50nm.

[0019] After the transition layer is prepared, the surface flatness is checked to control the surface roughness of the transition layer.

[0020] Furthermore, the positioning structure of the mask assembly includes built-in conical guide sleeves at the four corners and the midpoint of the long side of the first mask, elastic positioning pins on the second mask, and fluorescent reference scale lines on the surfaces of the first and second masks. The elastic positioning pins are adapted to the conical guide sleeves one by one, and the first and second masks are initially positioned by covering the mask substrate according to the positioning structure of the mask assembly.

[0021] Furthermore, based on the positioning structure of the mask assembly, the first mask and the second mask are initially positioned by covering the mask substrate, specifically including:

[0022] The relative position of the first mask and the mask substrate is determined based on the pre-fitting of the tapered guide sleeve and the elastic positioning pin.

[0023] Combined with a visual positioning system, the fluorescent reference scale lines on the surface of the first mask and the preset positioning marks on the mask substrate are simultaneously identified and compared, and the first mask is calibrated based on the comparison results.

[0024] When positioning and covering the second mask, the same positioning method as the first mask is used to position and cover the second mask onto the mask substrate. Based on the pre-fitting of the tapered guide sleeve and the elastic positioning pin, the relative position of the second mask and the mask substrate with the first film layer is determined, and calibration is performed in conjunction with the visual positioning system.

[0025] Based on a preset micro-pressure bonding method, the calibrated second mask is pressed tightly against the mask substrate with the first film layer to ensure that only the edge area of ​​the first film layer is exposed in the second coating area, and then in-situ cleaning and second film layer deposition are performed.

[0026] Furthermore, the process of depositing the first film layer in the first coating region specifically includes:

[0027] Based on the transition layer of the pretreated mask substrate, and combined with the calibrated first mask, a first film layer is deposited in the first coating area.

[0028] Obtain the deposition requirements of the first film layer, and set the deposition parameters of the first film layer according to the deposition requirements. The deposition parameters include the deposition rate and the target film thickness.

[0029] After the first film layer is deposited according to the set deposition parameters, the first mask is removed, and plasma activation treatment is performed again based on the surface state of the first film layer after the first mask is removed.

[0030] Furthermore, the process of gradient composite second film deposition includes:

[0031] Process foundation connection: Based on the edge area of ​​the first film layer after in-situ cleaning, a gradient composite second film layer is deposited in combination with the exposure range of the second coating area. The gradient composite second film layer includes a bottom layer and a top layer.

[0032] Functional deposition of the bottom layer: The bottom layer is a composite layer of SiO2 and polyimide microspheres, wherein the mass fraction of polyimide microspheres is 5%, the diameter of polyimide microspheres is 50-100nm, and the thickness of the bottom layer is 3%-5% of the thickness of the first film layer;

[0033] Top layer enhancement deposition: Based on the completed bottom layer, top layer deposition is performed. The top layer is a composite layer of Si3N4 and Al2O3, where the mass fraction of Al2O3 is 2% and the thickness of the top layer is 2%-5% of the thickness of the first film layer.

[0034] Furthermore, the process of real-time monitoring and adjustment of the coating process includes:

[0035] Real-time monitoring of the film thickness data of the first and second film layers to obtain the deposition status of the first and second film layers;

[0036] X-ray fluorescence spectroscopy data are acquired at preset detection intervals to determine the uniformity of film composition. When the film thickness deviation exceeds the preset film thickness threshold or the composition deviation exceeds the preset composition threshold, the deposition power and the ratio of reactant gas are automatically adjusted.

[0037] Based on the film surface image obtained by laser scanning microscope, defect judgment is performed. If a pinhole or particle larger than the preset defect size is detected, a local re-plating strategy is triggered, and the re-plating area is set to a preset multiple range of the defect area.

[0038] The temperature data of the mask assembly is acquired in real time, and the temperature of the mask assembly is controlled within a preset temperature fluctuation range based on the temperature data.

[0039] Furthermore, after the local plating strategy is implemented, it also includes:

[0040] Based on the intermediate interval ratio of the preset detection interval, the surface image of the film layer in the re-plating area is acquired again, and the defect residual state of the re-plating area is determined based on the acquired surface image of the film layer.

[0041] If residual defects of the preset defect size still exist after replating, adjust the replating power to an appropriate multiple of the original replating power, and repeat the local replating strategy, and the number of replating times shall not exceed the preset maximum number of replating times.

[0042] If the defect is eliminated after replating, the film thickness data of the replated area is monitored, and the film thickness data of the replated area is compared with the film thickness data of the surrounding unplated areas to obtain the film thickness deviation value.

[0043] The film thickness deviation value is compared with the preset film thickness threshold. If the film thickness deviation value is less than or equal to the preset film thickness threshold, the film thickness of the re-plating area is determined to be qualified, and the re-plating process is completed.

[0044] If the film thickness deviation value is greater than the preset film thickness threshold, the deposition parameters are finely adjusted based on the film thickness deviation direction of the re-plating area, and a second micro-re-plating or local etching process is performed on the re-plating area until the film thickness deviation value between the re-plating area and the surrounding un-re-plated area meets the preset film thickness threshold requirement.

[0045] Further post-processing operations are performed, including:

[0046] After obtaining the coated mask substrate, perform a stepped annealing process, heating it to 200℃-250℃ at a heating rate of 5℃ / min and holding it at that temperature for 30-45min, and then cooling it to room temperature at a cooling rate of 3℃ / min.

[0047] SiO2 passivation layer deposition was performed on a mask substrate after stepped annealing. The deposition temperature was set to 180℃-220℃, the volume ratio of SiH4 to N2O was 1:10, and the passivation layer thickness was 50nm-80nm.

[0048] Compared with the prior art, the beneficial effects of the present invention are:

[0049] 1. This invention utilizes a mask assembly with a positioning structure, combined with a visual positioning system to synchronously identify and calibrate the positioning marks on the mask and substrate, to achieve precise positioning and coverage of the first and second masks. This ensures that the second film layer accurately matches the edge area of ​​the first film layer, effectively improving the overall thickness uniformity of the coating layer. Simultaneously, the preparation of the transition layer in the pretreatment stage provides a stable substrate for the deposition of the first film layer, and the plasma activation treatment after the deposition of the first film layer further optimizes the surface activity. Combined with the gradient transition structure of the gradient composite second film layer, this significantly improves the interfacial adhesion of the film layers, preventing interface cracking of the display screen under temperature and humidity cycling conditions and greatly reducing the risk of encapsulation failure.

[0050] 2. The mask assembly of the present invention adopts a flexible composite structure and a preset micro-pressure bonding method to avoid the wrinkling problem caused by the rigid mask to the flexible substrate and ensure the uniformity of the coating. At the same time, the layered design of the gradient composite second film layer meets the long-term bending requirements of the flexible display screen and effectively improves the edge accuracy of the display pixels.

[0051] 3. Through a real-time monitoring and adjustment mechanism throughout the entire process, parameter deviations during deposition are detected and automatically adjusted in a timely manner to avoid batch defects. For detected oversized defects, material waste caused by overall replating is reduced, ensuring the consistency of the replating area with the surrounding film layer and further improving the coating quality. At the same time, the stepped annealing treatment in the post-processing stage can gradually release the internal stress of the film layer, avoiding film cracking caused by stress concentration. The subsequently deposited SiO2 passivation layer can build an effective protective barrier to resist external moisture and impurities, extend the product packaging life, and break through the limitations of existing technologies on substrate materials and shapes. It can meet the high-precision coating requirements of rigid substrates and adapt to the bending application scenarios of flexible substrates. It provides a universal and efficient solution for coating processes of various types of devices such as displays and sensors, improving the practicality and promotion value of the process. Attached Figure Description

[0052] Figure 1 This is a flow chart of the coating process for the mask substrate of the present invention;

[0053] Figure 2 This is a flowchart of the substrate pretreatment process of the present invention;

[0054] Figure 3 This is a flowchart of the dual-mask positioning process of the present invention;

[0055] Figure 4 This is a flowchart of the monitoring and replating steps of the present invention. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] To address the technical issues in existing technologies where two mask changes lack a reference positioning, resulting in the second film layer failing to accurately cover the edge area of ​​the first film layer, disrupting the uniformity of the coating thickness, and causing easy cracking of the film interface and a high risk of encapsulation failure, please refer to [link to relevant documentation]. Figures 1-4 This embodiment provides the following technical solution:

[0058] A coating process for a mask substrate includes a mask assembly with a positioning structure. The mask assembly consists of a first mask and a second mask. Both the first and second masks are flexible composite structures composed of a polyimide-based film and a nickel alloy support mesh. The thickness of the second mask is 50-70 μm. A micro-pressure bonding method of 5-10 kPa is used to achieve gapless bonding between the mask and the flexible mask substrate. The first mask is configured with an array of first coating areas, and the second mask is configured with second coating areas corresponding one-to-one with the first coating areas, exposing only the edge areas of the first coating areas.

[0059] The mask substrate is pretreated. Based on the pretreated mask substrate, the first mask is positioned and covered on the mask substrate according to the positioning structure. The first film layer is deposited in the first coating area. After the deposition is completed, the first mask is removed.

[0060] The surface of the first film layer is cleaned and activated. The second mask is positioned and covered on the mask substrate according to the positioning structure, and the edge area of ​​the first film layer is exposed in the second coating area. The edge area is then cleaned in situ.

[0061] In this embodiment, in-situ cleaning includes: obtaining the exposed edge area of ​​the first membrane layer; removing large particulate contaminants from the edge area using laser dry cleaning, specifically: using a 1064nm infrared laser with a power of 50-100mW and a scanning speed of 10-20mm / s to remove particles ≥0.3μm; and removing residual small particulate contaminants using electrostatic dust removal, specifically: using an ion nozzle with a charge of -50~-100V to remove charged particles ≤0.3μm. The laser dry cleaning and electrostatic dust removal work together to ensure that the amount of residual particles in the edge area after in-situ cleaning meets the cleanliness requirements for subsequent deposition of the second membrane layer.

[0062] Based on the second coating area, a gradient composite second film layer is deposited in the edge area to connect the first film layer and the second film layer to form a coating layer. The interfacial bonding force of the film layer is ≥8MPa, the edge cracking rate of the flexible substrate after 10,000 bending cycles is ≤5%, the pinhole defect density is ≤0.5 / cm², and the encapsulation life is ≥8000h.

[0063] The coating process is monitored in real time, and the mask substrate is post-processed after coating is completed.

[0064] In this embodiment, a flexible composite structure composed of a polyimide-based film and a nickel alloy support mesh is adopted. This structure adapts to the deformation characteristics of the flexible mask substrate, preventing mask deformation during operation and improving the compatibility and structural stability of the mask and flexible substrate. Micro-pressure bonding effectively eliminates gap hazards, improves bonding accuracy, and reduces positional deviation defects. Through dual-mask step-by-step deposition combined with gradient composite deposition, the two film layers are precisely connected by step-by-step deposition in the core and edge areas. The gradient transition further enhances the interfacial bonding effect. Simultaneously, the compatibility between the flexible mask and substrate improves the film bonding performance and flexibility reliability, expanding the application potential of the process in flexible products. This is based on laser dry cleaning and electrostatic dust removal. This integrated graded dust removal solution achieves precise removal of contaminants of different sizes, ensuring that the cleanliness of the film edge area meets the requirements for subsequent deposition. It avoids performance failures such as pinholes and interface peeling caused by particle residue, ensuring the stability of the film structure and extending the product service life. Relying on the positioning structure of the mask assembly, it achieves precise alignment, solving the problems of incomplete existing process steps and batch differences caused by manual positioning. It ensures the consistency of coating precision for different substrates and batches of products, improves process controllability, and ensures the stability of mass production. It can be widely used in fields that require a combination of flexible and high-precision coating, breaking application scenario limitations, broadening the application range of coating technology, and meeting the coating needs of flexible products in multiple fields.

[0065] In this embodiment, the mask substrate undergoes pretreatment, specifically including:

[0066] Based on the material of the mask substrate, such as quartz substrate, silicon substrate, or sapphire substrate, select the corresponding cleaning agent. For quartz substrate, use alkaline silane cleaning agent; for silicon substrate, use hydrofluoric acid mixed cleaning agent; and for sapphire substrate, use neutral alumina cleaning agent. Obtain the surface condition of the mask substrate and perform ultrasonic cleaning according to the initial surface contaminant content. If the contaminant content is ≤5mg / cm², perform one cleaning; if the contaminant content is >5mg / cm², perform two cleanings. The ultrasonic frequency is 20-80kHz, and the cleaning time is 5-30min.

[0067] Vacuum drying was performed on the mask substrate surface based on the humidity after ultrasonic cleaning. The drying temperature was 60-120℃, and the vacuum degree was ≤5×10⁻⁶. -4 The drying time is 10-60 min. During the drying process, a mixed gas is introduced for plasma activation to control the surface roughness of the substrate to 0.1 μm-0.3 μm. A transition layer is then prepared based on the plasma-activated mask substrate to obtain the pretreated mask substrate.

[0068] In this embodiment, the transition layer fabrication process specifically includes:

[0069] The material of the transition layer is selected based on the material of the mask substrate, including SiO2 transition layer and TiN transition layer. Quartz substrate / sapphire substrate is adapted to SiO2 transition layer, and silicon substrate is adapted to TiN transition layer.

[0070] The transition layer was prepared using PECVD. The deposition parameters for the SiO2 transition layer were: temperature 150-180℃, SiH4 to N2O volume ratio 1:8-1:12, deposition rate 5-8 nm / min, and target thickness 50-80 nm. The deposition parameters for the TiN transition layer were: temperature 200-220℃, TiCl4 to NH3 volume ratio 1:5-1:7, deposition rate 3-5 nm / min, and target thickness 30-50 nm.

[0071] After the transition layer was prepared, the surface smoothness was detected by atomic force microscopy (AFM) to control the surface roughness of the transition layer to ≤0.05μm, so as to ensure the improved interfacial bonding force with the subsequent first film layer.

[0072] In this embodiment, an alkaline silane cleaning agent is selected based on the chemical properties of the quartz substrate, a hydrofluoric acid mixed cleaning agent is selected to match the corrosion resistance of the silicon substrate, and a neutral alumina cleaning agent is selected to meet the surface stability requirements of the sapphire substrate.

[0073] In this embodiment, the cleaning levels are divided based on the initial surface contaminant content of the mask substrate. Corresponding cleaning cycles are used for different contamination levels. The cleaning strategy is dynamically adjusted to ensure a balance between cleaning effectiveness and efficiency, optimizing the substrate surface cleanliness. During vacuum drying, a mixed gas is simultaneously introduced for plasma activation, allowing the drying and activation processes to proceed synergistically. This efficiently removes residual moisture from the substrate surface, optimizes surface activity through plasma action, and precisely controls surface roughness to a suitable range. This provides excellent surface adhesion conditions for subsequent transition layer preparation, constructing a transition layer preparation system focused on enhancing the bonding stability between film layers. This provides a high-quality substrate foundation for subsequent double-mask coating, in-situ cleaning, and other processes, ensuring the stability of the entire coating process and the final product performance.

[0074] In this embodiment, the positioning structure of the mask assembly includes built-in conical guide sleeves at the four corners and midpoint of the long side of the first mask, elastic positioning pins on the second mask, and fluorescent reference scale lines on the surfaces of the first and second masks. The elastic positioning pins are individually fitted with the conical guide sleeves. Based on the positioning structure of the mask assembly, the first and second masks are initially positioned by covering the mask substrate. Specifically, this includes:

[0075] The relative position of the first mask and the mask substrate is determined based on the pre-fitting of the tapered guide sleeve and the elastic positioning pin.

[0076] By combining a dual-CCD vision positioning system, the fluorescent reference scale lines on the surface of the first mask and the preset positioning marks on the mask substrate are simultaneously identified and compared. Based on the comparison results, the first mask is calibrated. The preset parameters for the positioning accuracy of the dual-CCD vision positioning system are a wavelength of 550nm, a fluorescent reference scale line width of 50μm, and a resolution of 0.1μm, so that the positioning deviation is ≤1μm.

[0077] When positioning and covering the second mask, the same positioning method as the first mask is used to position and cover the second mask onto the mask substrate. Based on the pre-fitting of the tapered guide sleeve and the elastic positioning pin, the relative position of the second mask and the mask substrate with the first film layer is determined, and calibration is performed in conjunction with the visual positioning system.

[0078] Based on a preset micro-pressure bonding method, the calibrated second mask is pressed tightly against the mask substrate with the first film layer to ensure that only the edge area of ​​the first film layer is exposed in the second coating area, and then in-situ cleaning and second film layer deposition are performed.

[0079] In this embodiment, two CCD cameras are triggered by a synchronous control module to simultaneously acquire images of the fluorescence reference scale line area on the first mask surface and the preset positioning mark area on the mask substrate: one CCD camera focuses on the fluorescence reference scale line on the mask surface, receives the fluorescence reflection signal, and generates a fluorescence image; the other CCD camera focuses on the preset positioning mark on the mask substrate, receives the visible light or dedicated light source reflection signal, and generates a positioning mark image. The acquisition sequence is strictly synchronized to ensure that there is no relative displacement between the mask / substrate positions corresponding to the two images.

[0080] The two acquired images are preprocessed simultaneously to extract clear feature region images. Contour detection and line fitting are performed on the fluorescence image to extract key feature parameters of the fluorescence reference scale line, forming a scale line feature parameter set. Feature point detection and contour analysis are performed on the positioning mark image to extract key feature parameters of the preset positioning mark, forming a positioning mark feature parameter set. The effectiveness of the two sets of feature parameter sets is verified simultaneously.

[0081] Based on the unified coordinate system established in the early stage, the feature coordinates of the fluorescence reference scale line and the feature coordinates of the preset positioning mark are transformed to the same physical coordinate system to eliminate the coordinate deviation caused by the difference in the acquisition angle of the dual CCD. The matching verification of the two sets of features is completed simultaneously to confirm the consistency of their postures. If a deviation is found during the comparison process, the deviation value is calculated in real time and fed back to the system control module. The acquisition angle of the dual CCD camera or the position of the mask substrate is adjusted synchronously until the deviation meets the threshold requirement, thereby realizing dynamic comparison and calibration.

[0082] In this embodiment, the process of depositing the first film layer in the first coating area specifically includes:

[0083] Based on the transition layer of the pretreated mask substrate, a first film layer is deposited in the first coating area using plasma-enhanced chemical vapor deposition (PECVD) in conjunction with a calibrated first mask.

[0084] Obtain the deposition requirements of the first film layer, and set the deposition parameters of the first film layer according to the deposition requirements. The deposition parameters include the deposition rate and the target film thickness.

[0085] After the first film layer is deposited according to the set deposition parameters, the first mask is removed, and plasma activation treatment is performed again based on the surface state of the first film layer after the first mask is removed.

[0086] In this embodiment, the deposition parameters of the first film layer are: deposition rate of 10-15 nm / min, target film thickness of 150-250 nm; the preset mixed gas for plasma activation is a mixture of argon and hydrogen with a volume ratio of 9:1, preset power of 200-300 W, and preset processing time of 3-5 min.

[0087] In this embodiment, the process of gradient composite second film deposition includes:

[0088] Process foundation connection: Based on the edge area of ​​the first film layer after in-situ cleaning, combined with the exposure range of the second coating area, atomic layer deposition (ALD) is used to deposit a gradient composite second film layer. The gradient composite second film layer includes a bottom layer and a top layer, so that the interfacial bonding force between the second film layer and the activated first film layer meets the coating layer performance standards.

[0089] Functional deposition of the bottom layer: The bottom layer is a composite layer of SiO2 and polyimide microspheres, wherein the mass fraction of polyimide microspheres is 5%, and the diameter of polyimide microspheres is 50-100nm. The thickness of the bottom layer is 3%-5% of the thickness of the first film layer, i.e. 4.5-12.5nm, corresponding to the target film thickness of 150-250nm of the first film layer.

[0090] Top-layer enhancement deposition: Based on the completed bottom layer, top-layer deposition is performed. The top layer is a composite layer of Si3N4 and Al2O3, with the mass fraction of Al2O3 being 2%. The thickness of the top layer is 2%-5% of the thickness of the first film layer, i.e., 3-12.5 nm.

[0091] In this embodiment, the bottom layer of the gradient composite second film layer enhances the bending tolerance of subsequent film layers through the elastic buffering effect of polyimide microspheres, while the top layer improves the environmental stability of the film layer through Al2O3 doping modification. Based on the gradient structure design of bottom toughening and adaptation and top layer enhancement and damage resistance, combined with the atomic-level deposition precision of the ALD method, and the complete coating layer formed in conjunction with the first film layer, the performance standards of flexible substrate bending parameters are met, and the film thickness uniformity is monitored in real time to ensure the stability of the gradient composite structure.

[0092] In this embodiment, the process of real-time monitoring and adjustment of the coating process includes:

[0093] The film thickness data of the first and second films are monitored in real time, and the deposition state of the first and second films is obtained by using the quartz crystal oscillation method (sampling frequency 10Hz).

[0094] X-ray fluorescence spectroscopy (XRF) detection data are acquired at preset detection intervals to determine the uniformity of film composition. When the film thickness deviation exceeds the preset film thickness threshold or the composition deviation exceeds the preset composition threshold, the deposition power and the ratio of reaction gas are automatically adjusted.

[0095] Based on the film surface image obtained by laser scanning microscope (resolution 0.1μm), defect judgment is performed. If a pinhole or particle larger than the preset defect size is detected, a local re-plating strategy is triggered, and the re-plating area is set to a preset multiple range of the defect area.

[0096] A miniature thermocouple is embedded in the mask support frame to acquire the temperature data of the mask assembly in real time. Based on the temperature data, the temperature of the mask assembly is controlled within a preset temperature fluctuation range through pulse heating / cooling.

[0097] In this embodiment, the quartz crystal oscillation method is combined with X-ray fluorescence spectroscopy. The former uses high-frequency sampling to capture the film deposition state in real time, ensuring the real-time nature of the film thickness data; the latter detects the uniformity of composition at preset intervals, forming a two-dimensional monitoring linkage of film thickness and composition. When any indicator exceeds the preset threshold, the deposition power and the ratio of reactive gases are automatically adjusted to avoid the lag and error of manual adjustment, correcting deposition deviations in real time, ensuring the uniformity of film thickness and composition, reducing batch defects caused by parameter malfunctions from the source, and maintaining the temperature stability of the mask assembly through real-time monitoring of local temperature and pulsed precise temperature control, avoiding uneven film deposition caused by local temperature deviations, further ensuring the consistency of film quality.

[0098] In this embodiment, after the local plating strategy is executed, the following steps are also included:

[0099] Based on the intermediate interval ratio of the preset detection interval, the surface image of the film layer in the re-plating area is acquired again using a laser scanning microscope, and the defect residual state of the re-plating area is determined based on the acquired film layer surface image.

[0100] If residual defects of the preset defect size still exist after replating, adjust the replating power to an appropriate multiple of the original replating power, and repeat the local replating strategy, and the number of replating times shall not exceed the preset maximum number of replating times.

[0101] If the defect is eliminated after re-plating, the film thickness data of the re-plating area is supplemented by monitoring based on the quartz crystal oscillation method. The film thickness data of the re-plating area is compared with the film thickness data of the surrounding unplated areas to obtain the film thickness deviation value.

[0102] The film thickness deviation value is compared with the preset film thickness threshold. If the film thickness deviation value is less than or equal to the preset film thickness threshold, the film thickness of the re-plating area is determined to be qualified, and the re-plating process is completed.

[0103] If the film thickness deviation value is greater than the preset film thickness threshold, the deposition parameters are finely adjusted based on the film thickness deviation direction of the re-plating area, and a second micro-re-plating or local etching process is performed on the re-plating area until the film thickness deviation value between the re-plating area and the surrounding un-re-plated area meets the preset film thickness threshold requirement, so as to avoid local film thickness unevenness affecting the display effect.

[0104] In this embodiment, a local re-plating strategy is triggered by identifying oversized pinholes or particles using a high-resolution laser scanning microscope. After re-plating, images of the re-plated area are acquired a second time at intermediate intervals to determine the presence of defects. If the defects are not eliminated, the power is adjusted and re-plating is repeated. After the defects are eliminated, the thickness consistency between the re-plated area and the surrounding area is verified by film thickness comparison. If the deviation exceeds the limit, further fine-tuning is performed to avoid the blindness of traditional re-plating. While accurately repairing defects, the impact of uneven local film thickness on the display effect is eliminated, which reduces material waste and ensures the overall performance consistency of the film layer.

[0105] In this embodiment, post-processing operations are performed, including:

[0106] After obtaining the coated mask substrate, a stepped annealing process is performed. The temperature is increased to 200℃-250℃ at a heating rate of 5℃ / min and held for 30-45min. Then, the temperature is decreased to room temperature at a cooling rate of 3℃ / min. The internal stress accumulated during the film deposition process is gradually released through a slow temperature control process, which reduces the risk of film cracking and enhances the bonding stability between the film and the substrate.

[0107] Based on the mask substrate after stepped annealing, a SiO2 passivation layer is deposited using plasma-enhanced chemical vapor deposition (PECVD). SiO2 has both good insulation and resistance to environmental interference, forming a stable bond with the film layer. The deposition temperature is set at 180℃-220℃, the volume ratio of SiH4 to N2O is 1:10, and the passivation layer thickness is 50nm-80nm. An effective protective barrier is built on the film surface to resist external moisture and impurities, extend the product packaging life, and ensure the stability of the film layer's electrical performance.

[0108] In this embodiment, dynamic control ensures the stability of the deposition process, preventing the results of previous basic optimizations from being negated due to process loss of control. Further performance optimization addresses the stress and protection requirements of the post-deposition film. This collaborative approach, from precise process control to subsequent performance enhancement, not only overcomes the limitation of traditional processes where optimization of a single step is insufficient to improve overall quality, but also ensures the stability, consistency, and reliability of the mask substrate deposition throughout the entire chain. This provides key technical support for flexible displays in subsequent product applications, demonstrating significant progress compared to existing deposition processes.

[0109] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A plating process of a mask substrate, characterized by, The mask assembly includes a positioning structure, and is composed of a first mask and a second mask, wherein the first mask is provided with an arrayed first plating area, and the second mask is provided with a second plating area corresponding to the first plating area one by one; The mask substrate is pretreated, the first mask is positioned and covered on the mask substrate based on the pretreated mask substrate according to the positioning structure, a first film layer is deposited in the first plating area, and the first mask is removed after the deposition is completed; The surface of the first film layer is cleaned and activated, the second mask is positioned and covered on the mask substrate according to the positioning structure, the edge area of the first film layer is exposed by the second plating area, and the edge area is cleaned in situ; The second film layer is deposited in the edge area based on the second plating area to connect the first film layer and the second film layer to form a plating film layer; The plating process is monitored in real time, and the mask substrate is post-treated after the plating is completed.

2. The coating process of a mask substrate of claim 1, wherein, The mask substrate is pretreated, specifically including: Based on the material of the mask substrate, a corresponding cleaning agent is selected, the surface state of the mask substrate is obtained, and ultrasonic cleaning is performed according to the initial surface contaminant content of the mask substrate; Based on the surface humidity of the mask substrate after ultrasonic cleaning, vacuum drying is performed, mixed gas is introduced for plasma activation during the drying process, and a transition layer is prepared based on the mask substrate after plasma activation to obtain the pretreated mask substrate.

3. The coating process of a mask substrate of claim 2, wherein, The transition layer preparation process specifically includes: Based on the material of the mask substrate, a corresponding transition layer material is selected, including a SiO2 transition layer and a TiN transition layer; The deposition parameters of the SiO2 transition layer are as follows: temperature 150-180℃, volume ratio of SiH4 to N2O 1:8-1:12, deposition rate 5-8nm / min, and target thickness 50-80nm; The deposition parameters of the TiN transition layer are as follows: temperature 200-220℃, volume ratio of TiCl4 to NH3 1:5-1:7, deposition rate 3-5nm / min, and target thickness 30-50nm; After the preparation of the transition layer is completed, the surface flatness is detected to control the surface roughness of the transition layer.

4. The coating process of a mask substrate of claim 1, wherein, The positioning structure of the mask assembly includes a built-in conical guide sleeve arranged at the four corners and the midpoint of the long side of the first mask, an elastic positioning pin arranged on the second mask, and a fluorescent reference scale line arranged on the surface of the first mask and the second mask, wherein the elastic positioning pin is matched with the conical guide sleeve one by one, and the first mask and the second mask are covered on the mask substrate based on the positioning structure of the mask assembly to be preliminarily positioned.

5. The coating process of a mask substrate of claim 4, wherein, According to the positioning structure of the mask assembly, the first mask and the second mask are covered on the mask substrate to be preliminarily positioned, specifically including: Based on the pre-matching of the conical guide sleeve and the elastic positioning pin, the relative position of the first mask and the mask substrate is determined; Combined with a visual positioning system, the fluorescent reference scale line on the surface of the first mask and the pre-set positioning mark on the mask substrate are synchronously identified and compared, and the first mask is calibrated based on the comparison result; In the positioning and covering of the second mask, the second mask is positioned and covered on the mask substrate in the same manner as the first mask. The relative position of the second mask and the mask substrate with the first film layer is determined based on the pre-fitting of the conical guide sleeve and the elastic positioning pin, and is calibrated in combination with the visual positioning system. After the second mask is calibrated and tightly attached to the mask substrate with the first film layer based on the preset micro-pressure attachment method, it is ensured that only the edge region of the first film layer is exposed in the second film layer deposition region, and then in-situ cleaning and second film layer deposition are performed.

6. The coating process of a mask substrate as claimed in claim 5, wherein, The process of depositing the first film layer in the first film layer deposition region specifically includes: Based on the transition layer of the pretreated mask substrate, the first film layer is deposited in the first film layer deposition region in combination with the calibrated first mask; The deposition requirements of the first film layer are obtained, and the deposition parameters of the first film layer are set according to the deposition requirements. The deposition parameters include deposition rate and target film thickness; After the first film layer is deposited according to the set deposition parameters, the first mask is removed, and the first film layer surface state after the first mask is removed is used for plasma activation treatment again.

7. The masking substrate plating process of claim 6, wherein, The process of gradient composite second film layer deposition includes: Based on the edge region of the first film layer after in-situ cleaning, the gradient composite second film layer is deposited in combination with the exposure range of the second film layer deposition region. The gradient composite second film layer includes a bottom layer and a top layer. The deposited bottom layer is a composite layer of SiO2 and polyimide microspheres, the mass fraction of polyimide microspheres is 5%, the diameter of polyimide microspheres is 50-100 nm, and the thickness of the bottom layer is 3%-5% of the thickness of the first film layer. Based on the deposited bottom layer, the top layer is deposited. The deposited top layer is a composite layer of Si3N4 and Al2O3, the mass fraction of Al2O3 is 2%, and the thickness of the top layer is 2%-5% of the thickness of the first film layer.

8. The coating process of a mask substrate as claimed in claim 1, wherein, The process of real-time monitoring and adjustment of the film deposition process includes: Real-time monitoring of the film thickness data of the first film layer and the second film layer obtains the deposition state of the first film layer and the second film layer; X-ray fluorescence spectrum detection data is obtained at a preset detection interval to judge the uniformity of the film layer composition. When the film thickness deviation exceeds the preset film thickness threshold or the composition deviation exceeds the preset composition threshold, the deposition power and the reaction gas ratio are automatically adjusted; Based on the film layer surface image obtained by the laser scanning microscope, defect judgment is performed. If a pinhole or particle larger than a preset defect size is detected, a local re-plating strategy is triggered, and the re-plating area is set to a preset multiple range of the defect area. Real-time temperature data of the mask assembly is obtained, and the temperature of the mask assembly is controlled within a preset temperature fluctuation range based on the temperature data. 9.The film coating process of a mask substrate of claim 8, wherein, After the local re-plating strategy is executed, it further includes: Based on the intermediate interval ratio of the preset detection interval, the film layer surface image of the re-plated area is collected again, and the defect residual state of the re-plated area is judged based on the collected film layer surface image; If there are residual defects of a preset defect size after re-plating, the re-plating power is adjusted to an adaptive multiple of the original re-plating power, and the local re-plating strategy is repeated, and the re-plating times do not exceed the preset maximum re-plating times. If the defects are eliminated after the supplementary plating, the film thickness data of the supplementary plating area is monitored, the film thickness data of the supplementary plating area is compared with the film thickness data of the surrounding non-supplementary plating area, and a film thickness deviation value is obtained; The film thickness deviation value is compared with a preset film thickness threshold value, if the film thickness deviation value is less than or equal to the preset film thickness threshold value, it is determined that the film thickness of the supplementary plating area is qualified, and the supplementary plating process is completed; If the film thickness deviation value is greater than the preset film thickness threshold value, based on the film thickness deviation direction of the supplementary plating area, the deposition parameters are fine-tuned, the supplementary plating area is subjected to secondary trace supplementary plating or local etching treatment until the film thickness deviation value of the supplementary plating area and the surrounding non-supplementary plating area meets the preset film thickness threshold value requirement.

10. The coating process of a mask substrate as claimed in claim 1, wherein, Post-processing operations are performed, including: After the film plating, the mask substrate is obtained, and a step annealing treatment is performed, the temperature is raised to 200-250°C at a temperature rising rate of 5°C / min, and the temperature is kept for 30-45 min, and the temperature is lowered to room temperature at a temperature lowering rate of 3°C / min; Based on the mask substrate after the step annealing treatment, SiO2 passivation layer deposition is performed, the deposition temperature is set to 180-220°C, the volume ratio of SiH4 to N2O is 1:10, and the passivation layer thickness is 50-80 nm.

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