Subsurface defect calibration plate manufacturing method based on ultra-thin glass sealing cover and calibration plate

Abstract

The invention provides a subsurface defect calibration plate manufacturing method based on an ultra-thin glass sealing cover and a calibration plate, and belongs to the technical field of optical detection calibration. The method comprises the steps that a main glass substrate and a glass cover plate are prepared, the main glass substrate and the glass cover plate are both made of glass materials, and the glass cover plate is an ultra-thin cover plate; processing a simulated defect structure on the surface of the main glass substrate based on a micro-nano processing technology, and taking the surface with the simulated defect structure as a defect surface; coating the defect surface with an optical adhesive, and determining the coating thickness of the optical adhesive according to the refractive index between the optical adhesive and the main glass substrate; and fitting a glass cover plate with the defect surface to form the subsurface defect calibration plate. The subsurface defect calibration plate manufacturing method based on the ultra-thin glass sealing cover and the calibration plate provided by the invention are used for realizing stable packaging and accurate calibration of subsurface defects.

Description

Technical Field

[0001] This application relates to the field of optical inspection and calibration technology, and in particular to a method for fabricating a subsurface defect calibration plate based on an ultrathin glass cap and the calibration plate itself. Background Technology

[0002] In high-end optical equipment manufacturing, semiconductor lithography, and precision optical instruments, the imaging accuracy, laser damage threshold, and lifespan of optical components directly determine the core performance of the equipment. Subsurface defects, as key hidden dangers beneath the surface of optical components, include various forms such as scratches and pits. They can interfere with the normal operation of optical systems through scattering and absorbing light, seriously affecting the accuracy of test data and the stability of equipment operation. With continuous technological advancements, various industries are constantly raising their quality requirements for optical components, placing more stringent standards on the detection accuracy, sensitivity, and reliability of subsurface defects. Accurate defect calibration is a core prerequisite for ensuring the accuracy of testing equipment calibration and guaranteeing the reliability of test results. Therefore, the development of high-performance subsurface defect calibration boards has become a key technological requirement in the field of optical inspection.

[0003] To meet the basic requirements of subsurface defect detection and calibration, some technologies employ thin-film deposition encapsulation processes. This involves depositing a thin film on the surface of a substrate with simulated defects to encapsulate the defects and simulate the subsurface defect state of actual optical components. However, the interfacial adhesion between the film and the substrate is weak, and failures such as film peeling and cracking are prone to occur during long-term use or when the ambient temperature and humidity change. Furthermore, the film thickness is usually difficult to exceed the hundreds of micrometers, making uniformity control challenging and leading to distortion of the optical response characteristics of subsurface defects, thus affecting calibration accuracy. In addition, existing encapsulation processes lack precision in the selection of adhesives and the control of coating thickness, often resulting in residual bubbles or incomplete defect coverage. This further reduces the accuracy and long-term stability of the calibration board, failing to meet the high-precision calibration requirements of high-end optical systems for complex types of subsurface defects. Summary of the Invention

[0004] In view of this, this application provides a method for manufacturing a subsurface defect calibration plate based on an ultra-thin glass cap and a calibration plate, so as to achieve stable encapsulation and accurate calibration of subsurface defects.

[0005] Specifically, this application is implemented through the following technical solution: The first aspect of this application provides a method for fabricating a subsurface defect calibration plate based on an ultrathin glass cap, the method comprising: A main glass substrate and a glass cover are prepared, both of which are made of glass, and the glass cover is an ultra-thin cover. Based on micro-nano fabrication technology, simulated defect structures are fabricated on the surface of the main glass substrate, and the surface where the simulated defect structures exist is used as the defect surface. An optical adhesive is applied to the defective surface, and the coating thickness of the optical adhesive is determined based on the refractive index between the optical adhesive and the main glass substrate. The glass cover plate is attached to the defect surface to form the subsurface defect calibration plate.

[0006] A second aspect of this application provides a calibration plate, which is prepared based on the above method, and the calibration plate comprises: Main glass substrate; A simulated defect structure is located on the surface of the main glass substrate; An optical adhesive layer is coated on the surface of the main glass substrate where the simulated defect structure exists; A glass cover plate, which is located above the optical adhesive layer.

[0007] The method and calibration plate for fabricating subsurface defect calibration plates based on ultrathin glass caps provided in this application use ultrathin glass with the same material as the main glass substrate and a thickness of 0.05mm~0.2mm as the cap. It is paired with a low-viscosity UV-curable optical adhesive with a refractive index matching the glass. The bonding process is assisted by a vision alignment system, combined with laser direct-write lithography-inductively coupled plasma etching or femtosecond laser micro-nano processing technology. It fundamentally solves the problems of easy peeling and cracking of thin films, interference of detection signals caused by additional optical path difference introduced by thick glass, residual adhesive bubbles or incomplete defect coverage, and calibration failure caused by alignment deviation in traditional packaging. It not only achieves long-term stable packaging of subsurface defects, but also ensures calibration accuracy through precise control of defect size, meeting the high-performance requirements of high-end optical systems for subsurface defect detection and calibration. Attached Figure Description

[0008] Figure 1 A flowchart of an embodiment of the method for fabricating a subsurface defect calibration plate based on an ultrathin glass cap provided in this application; Figure 2 This is a schematic diagram of the structure of the calibration plate provided in Embodiment 2 of this application; Explanation of reference numerals in the attached figures: 1: Main glass substrate; 2: Simulate defective structures; 3: Optical adhesive layer; 4: Glass cover plate. Detailed Implementation

[0009] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0010] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0011] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0012] The following specific embodiments are given to illustrate the technical solution of this application in detail.

[0013] Figure 1 This is a flowchart of an embodiment of the method for fabricating a subsurface defect calibration plate based on an ultrathin glass cap provided in this application. Please refer to... Figure 1 The method provided in this embodiment may include: S101. Prepare a main glass substrate and a glass cover plate, wherein the main glass substrate and the glass cover plate are both made of glass, and the glass cover plate is an ultra-thin cover plate.

[0014] It is understandable that both the main glass substrate and the glass cover are cuboid in shape, the thickness of the glass cover is much smaller than that of the main glass substrate, the main glass substrate is located at the bottom of the overall structure, and the simulated defect structure is processed on the upward-facing surface when the main glass substrate is placed on a plane.

[0015] Optionally, the glass material is fused silica glass or K9 optical glass, the thickness of the glass cover is 0.05mm to 0.2mm, and the refractive index difference between the main glass substrate and the glass cover is less than or equal to 0.015.

[0016] Specifically, suitable glass materials are selected based on the chemical stability of the glass. The main glass substrate and glass cover plate that meet the optical performance and structural requirements are then processed based on the selected glass materials. Fused silica glass or K9 optical glass are preferred as the glass materials. The thickness of the glass cover plate is controlled within the range of 0.05mm to 0.2mm. The refractive index difference between the main glass substrate and the glass cover plate must be less than or equal to 0.015.

[0017] Furthermore, considering the chemical stability of glass materials, fused silica glass possesses excellent resistance to high and low temperatures, chemical inertness, and a low coefficient of expansion, while K9 optical glass exhibits good optical transmittance and processing adaptability. Both can meet the requirements of the calibration plate for long-term use, including resistance to environmental corrosion and resistance to aging. Therefore, they are chosen as the glass materials. Simultaneously, they assist in verifying key indicators such as the optical uniformity and refractive index stability of the materials, ensuring the absence of obvious impurities, bubbles, and optical defects. Based on the application requirements of the calibration plate, such as the optical path size and installation specifications of the compatible testing equipment, the size and specifications of the main glass substrate are determined, such as a standard 50mm×50mm×5mm or a customized size. The glass cover is processed to an ultra-thin specification of 0.05mm~0.2mm. The refractive index difference between the two is controlled to ≤0.015 to avoid introducing additional optical interference due to refractive index mismatch.

[0018] Furthermore, the main glass substrate and glass cover are pretreated by first ultrasonically cleaning with deionized water for 12-18 minutes at a power of 250-300W to remove surface dust and oil; then plasma cleaning for 6-10 minutes at a power of 90-130W to optimize the surface activity of the substrate and improve the adhesion of subsequent adhesives; finally, nitrogen is used to dry the substrate to avoid water stains affecting processing accuracy.

[0019] Furthermore, before preparing the main glass substrate and the glass cover, the glass material is determined based on the chemical stability of the glass.

[0020] S102. Based on micro-nano fabrication technology, simulated defect structures are fabricated on the surface of the main glass substrate, and the surface where the simulated defect structures exist is taken as the defect surface.

[0021] Optionally, the simulated defect structure includes at least scratch-type defects and pit-type defects, and the defect surface includes at least four different sizes of scratch-type defects and three different sizes of pit-type defects.

[0022] Based on the above description, it can be understood that the simulated defect structure is processed on the surface of the main glass substrate, and the surface of the main glass substrate with the simulated defect structure is used as the defect surface, which always faces upward.

[0023] Furthermore, when processing different types of defects on the same surface, the defects of each type are concentrated in the center of the main glass substrate. This avoids the effective use of defects due to limitations in the processing equipment and the obstruction of the edge area by the fixture when fixing the main glass substrate. In addition, the spacing between defects of different types and sizes can be determined according to the resolution of the camera imaging. Based on the minimum distance characteristic that the camera imaging resolution can clearly distinguish adjacent targets, the spacing between each type of defect is planned to ensure that the images of different defects can be clearly separated in actual imaging, without overlap or blurring interference. This ensures accurate identification, individual observation and effective calibration of various defects in the subsequent calibration process, and avoids imaging confusion caused by improper spacing settings, which would affect the calibration accuracy. Optionally, the micro / nano fabrication process is a combination of laser direct-write lithography and inductively coupled plasma etching (ICP-CEL) or a femtosecond laser micromachining process. In the laser direct-write lithography and ICP-CEL composite process, the linewidth of scratch-type defects is 1 μm to 450 μm, the length is 4 mm to 12 mm, and the depth is 80 nm to 2.5 μm; the diameter of pit-type defects is 1 μm to 0.8 mm, and the depth is 120 nm to 3.2 μm. In the femtosecond laser micromachining process, the linewidth of scratch-type defects is 2 μm to 500 μm, the length is 4 mm to 12 mm, and the depth is 1 μm to 3 μm; the diameter of pit-type defects is 2 μm to 1 mm, and the depth is 1.5 μm to 3.5 μm.

[0024] Specifically, the micro-nano fabrication process uses a combination of laser direct writing lithography and inductively coupled plasma etching, or femtosecond laser micromachining. Among them, the combination of laser direct writing lithography and inductively coupled plasma etching is suitable for high-precision, small-size defect processing, while femtosecond laser micromachining has the advantages of high processing efficiency and adaptability to complex defect morphologies. It can be flexibly selected according to the defect precision requirements.

[0025] Furthermore, the different technical principles and precision characteristics of the processes lead to different defect sizes for different processing methods. The combined laser-direct-write lithography and inductively coupled plasma etching (ICP-CPE) process achieves precise transfer of micron-level fine patterns through laser-direct-write lithography, and then replicates the lithographic pattern size using ICP-CPE. Laser-direct-write lithography offers higher pattern resolution, capable of stably processing fine structures with a linewidth of 1μm, and can also be extended to larger linewidths of 450μm. In contrast, femtosecond laser micromachining etches the glass substrate directly by focusing a laser beam. Its processing precision is limited by the diffraction limit of the focused laser spot; in practice, the minimum diameter of the focused spot is typically around 2μm. Therefore, its corresponding lower limit for defect size is slightly higher than that of the laser-direct-write lithography-etching process. Subsurface defects range in linewidth from 1μm to hundreds of micrometers, requiring a combination of both processes to process the entire linewidth range.

[0026] Furthermore, the combined process of laser-direct-write lithography and inductively coupled plasma etching (ICP-CPE) is suitable for processing small-sized, high-precision defects. Laser-direct-write lithography enables precise transfer of defect patterns, while ICP-CPE uses a mixture of CHF3 and SF6 etching gases at a volume ratio of 2:1 to 3:1, with an etching power of 350 to 550 W and a gas pressure of 2.8 to 4.2 mTorr, achieving precise control over defect depth and linewidth. Femtosecond laser micromachining is suitable for processing large-sized defects. Utilizing the ultrashort pulse characteristics of femtosecond lasers, it reduces the heat-affected zone, preventing substrate cracking. By adjusting the laser power and scanning speed, the defect morphology can be flexibly controlled. Integrating multiple defect sizes on the same main glass substrate can cover different detection range requirements.

[0027] By setting two core simulated defects—scratches and pits—and configuring scratch and pit defects of different sizes, and adapting to two high-precision processing methods—laser direct-write lithography and inductively coupled plasma etching (ICP-C) composite process and femtosecond laser micromachining—the calibration board precisely matches the range of key parameters such as linewidth, length, diameter, and depth of defects under different processes. This comprehensively covers the common types and size gradients of subsurface defects in actual optical components, and ensures the consistency and stability of defect morphology through precise control of micro-nano fabrication technology. The calibration board can provide standardized calibration benchmarks for optical inspection equipment in multiple scenarios and dimensions, effectively improving the identification accuracy and sensitivity of inspection equipment for subsurface defects of different types and scales, and meeting the stringent calibration requirements of high-end optical systems for defect detection.

[0028] Furthermore, after fabricating simulated defect structures on the surface of the main glass substrate based on micro / nano fabrication, the method provided in this embodiment includes: (1) Use acetone to ultrasonically clean the defective surface to dissolve organic residual impurities; (2) The defective surface is subjected to secondary ultrasonic cleaning with anhydrous ethanol to remove acetone residue and dehydrate the defective surface; (3) Use nitrogen gas to dry the defective surface after the secondary ultrasonic cleaning to complete the cleaning.

[0029] Specifically, after simulating defect structures on the surface of the main glass substrate, the defect surface is treated with a three-stage cleaning process: ultrasonic cleaning with acetone, secondary ultrasonic cleaning with anhydrous ethanol, and drying with nitrogen. Acetone ultrasonic cleaning is used to dissolve organic residues, secondary ultrasonic cleaning with anhydrous ethanol is used to remove acetone residues and achieve dehydration, and nitrogen drying is used to remove residual droplets on the defect surface, ensuring that the defect surface is free of visible impurities, organic residues, and moisture after cleaning.

[0030] Furthermore, analytical grade acetone was selected as the cleaning solution. The main glass substrate with simulated defect structures was placed in the ultrasonic cleaning tank with the defect surface facing upwards, ensuring that the acetone surface completely covered the defect surface. The ultrasonic cleaning equipment was set to a power of 80~120W and a frequency of 40kHz, with the cleaning time controlled at 10~15 minutes. The cavitation effect of ultrasound was used to generate microbubbles. The impact force generated when the bubbles burst assisted the acetone in dissolving residual photoresist, processing debris, oil, and other organic impurities on the defect surface, ensuring that impurities in the gaps of the defect structure were also fully dissolved. After cleaning with acetone, the main glass substrate was transferred to an ultrasonic cleaning tank containing anhydrous ethanol to prevent the defect surface from being exposed to the air and absorbing dust. Similarly, ensure that the anhydrous ethanol completely covers the defect surface. Set the ultrasonic cleaning equipment to 60-100W power and 40kHz frequency, and clean for 8-10 minutes. Utilize the polar solubility of anhydrous ethanol to remove residual acetone from the defect surface. At the same time, take advantage of the volatile nature of ethanol to dehydrate the defect surface, preventing residual moisture from oxidizing the defect structure or affecting subsequent bonding. Remove the main glass substrate after the second ultrasonic cleaning and place it in a nitrogen drying device. Ensure that the nitrogen flow evenly covers the entire defect surface to thoroughly blow away any residual ethanol droplets and any tiny dust particles that may be attached. After drying, observe the defect surface under a microscope to confirm that there are no droplet traces, visible impurities, or organic residues, thus completing the defect surface cleaning.

[0031] A three-stage cleaning process, consisting of acetone ultrasonic cleaning to dissolve organic residues on the defect surface, anhydrous ethanol ultrasonic cleaning to remove acetone residues and dehydrate the surface, and nitrogen drying to remove residual droplets and fine dust, achieves comprehensive and deep removal of impurities from the defect surface. This process avoids the adverse effects of organic residues and moisture adhesion on the subsequent optical adhesive coating effect and bonding strength, while ensuring the cleanliness and dryness of the defect surface. This lays the foundation for the accurate encapsulation of the simulated defect structure and the stability of the optical performance of the calibration board, effectively reducing calibration deviations caused by surface impurities and improving the overall calibration accuracy and long-term reliability of the subsurface defect calibration board.

[0032] S103. Apply an optical adhesive to the defect surface, and determine the coating thickness of the optical adhesive based on the refractive index between the optical adhesive and the main glass substrate.

[0033] Optionally, the optical adhesive is a UV-curable optical adhesive with a viscosity range of 5~20 mPa·s and a refractive index of 1.46~1.54. The refractive index difference between the optical adhesive and the main glass substrate is less than or equal to 0.025, and the coating thickness is 3~15 μm.

[0034] Specifically, a UV-curable optical adhesive with a viscosity range of 5-20 mPa·s is selected to ensure moderate fluidity during coating, facilitating uniform spreading without covering defective structures or wasting adhesive due to excessive fluidity. The refractive index of 1.46-1.54 is highly compatible with the refractive index range of fused silica glass (approximately 1.46) and K9 optical glass (approximately 1.51), and the refractive index difference between the adhesive and the main glass substrate is strictly controlled to be ≤0.025, reducing light reflection and scattering losses at the adhesive-substrate interface. The refractive index matching coefficient between the adhesive and the main glass substrate is calculated through optical simulation. The smaller the refractive index difference, the more the coating thickness can be adjusted within the range of 3-15 μm. For example, if the main glass substrate is K9 optical glass with a refractive index of 1.51, using an optical adhesive with a refractive index of 1.50 allows for a coating thickness of 8-10 μm, ensuring bonding strength while avoiding the introduction of additional optical path differences due to excessive thickness.

[0035] Furthermore, after the defective surface is coated with an optical adhesive, the defective surface is cured in stages using ultraviolet light with a wavelength of 365~405nm and a light intensity of 200~400mW / cm². The first stage of curing time is 30~60 seconds, the second stage of curing time is 60~120 seconds, and the time interval between the first stage of curing time and the second stage of curing time is 5~10 minutes.

[0036] Furthermore, a low-viscosity UV-curable optical adhesive is selected. Its low viscosity ensures that the adhesive fully fills the defect gaps while preventing air bubbles from forming during coating. The refractive index of the adhesive is strictly matched to that of the glass substrate, with the difference controlled within 0.025, reducing interference from interface light reflection on the scattering signal of subsurface defects. A high-precision dispensing machine is used to apply the adhesive in a ring along the substrate edge, followed by spin coating at a low speed of 500-800 rpm for 5-10 seconds using a spin coater, ensuring uniform coverage of the defect area. The coating thickness is controlled at 3-15 μm, ensuring complete coverage of the defects without exceeding the substrate edge.

[0037] A high-precision dispensing machine is used to uniformly apply the adhesive along the path from the edge of the defect surface to the center. During the application process, the dispensing pressure is controlled at 0.02~0.05MPa to ensure that the coating thickness is uniform, without accumulation or missed areas. After the coating is completed, staged ultraviolet curing is immediately performed. In the first stage, ultraviolet light with a wavelength of 365~405nm and a light intensity of 200~400mW / cm² is used for 30~60 seconds to achieve initial setting of the adhesive. After an interval of 5~10 minutes, the second stage of curing is performed, with irradiation at the same wavelength and light intensity for 60~120 seconds to ensure that the adhesive is completely cured. After curing, the adhesive layer is free of bubbles and cracks.

[0038] S104. The glass cover plate is attached to the defect surface to form the subsurface defect calibration plate.

[0039] Specifically, a vision alignment system is used in conjunction with a precision displacement platform with a positioning accuracy of ≤10μm to precisely align the glass cover plate with the defect surface coated with cured optical adhesive, with an alignment accuracy of ≤20μm. During the bonding process, a uniform pressure of 0.03~0.08MPa is applied and maintained for 10~20 seconds to form a subsurface defect calibration plate. After molding, the subsurface defect calibration plate is micro-chamfered and cleaned to ensure that the surface roughness is ≤3nm.

[0040] Furthermore, the main glass substrate is fixed on a precision displacement platform with the defect surface facing upwards, and the glass cover is adsorbed onto the adsorption device of the vision alignment system. The vision alignment system acquires image information of the edge markers on the defect surface and the edge markers on the glass cover, transmitting this information to the control system for real-time comparison. The control system then adjusts the position of the main glass substrate using the precision displacement platform, ensuring that the alignment deviation between the glass cover and the defect surface is ≤20μm. This ensures that the glass cover completely covers the defect area without any offset that would expose any part of the defect. After alignment, the glass cover is slowly lowered until it contacts the adhesive layer on the defect surface, and a uniform pressure of 0.03~0.08MPa is applied. The pressure is applied using a surface contact method to avoid... Excessive local pressure can cause deformation of the defective structure or overflow of the adhesive. Maintain the pressure for 10-20 seconds to ensure that the glass cover and the defective surface are tightly bonded by the adhesive, ensuring that there are no air bubbles or gaps at the interface. After the structure is formed, use a diamond tool to perform micro-beveling on the edges of the calibration plate, with a beveling size of 0.3-0.8mm, to avoid sharp edges that could scratch operators or damage the testing equipment during use. Then, use a lint-free cloth soaked in optical-grade isopropyl alcohol to gently wipe the upper and lower surfaces of the calibration plate in one direction to remove residual adhesive and surface impurities that overflowed during the bonding process. Finally, ensure that the surface roughness of the calibration plate is ≤3nm, with no visible scratches or stains, and complete the overall forming of the subsurface defect calibration plate.

[0041] Furthermore, when bonding the glass cover plate to the defective surface, a visual alignment system is used in conjunction with a precision displacement platform with a positioning accuracy of less than or equal to 10 μm to achieve alignment, with an alignment accuracy of less than or equal to 20 μm. During the bonding process, a pressure of 0.03~0.08 MPa is applied uniformly and the pressure is maintained for 10~20 seconds.

[0042] Furthermore, after forming the subsurface defect calibration plate, the method provided in this embodiment includes: (1) The subsurface defect calibration plate is micro-chamfered using a diamond tool, with a chamfer size of 0.3~0.8mm; (2) Use a lint-free cloth dipped in optical grade isopropanol to wipe the subsurface defect calibration plate in one direction to remove residual adhesive and impurities on the surface. The surface roughness of the subsurface defect calibration plate is less than or equal to 3 nm.

[0043] The calibration plate is micro-beveled to a size of 0.3~0.8mm using diamond tools, eliminating sharp edges and preventing damage to operators or testing equipment caused by edge impacts. This also improves the structural safety and installation compatibility of the calibration plate. Next, a lint-free cloth soaked in optical-grade isopropyl alcohol is used to wipe the surface in one direction, precisely removing residual adhesive and impurities. This ensures the surface roughness is controlled within 3nm, guaranteeing a smooth and clean surface and reducing light scattering and reflection interference. This further strengthens the optical performance stability of the calibration plate and enhances its long-term reliability, ensuring that the calibration plate can continuously provide accurate and stable calibration benchmarks for optical testing equipment.

[0044] Furthermore, taking fused silica glass as an example, the preparation process of the subsurface defect calibration plate is illustrated below: JGS1 fused silica glass was selected as the main glass substrate, with dimensions of 40mm×40mm×2.5mm, surface finish grade V, and refractive index of 1.458. The ultra-thin capping glass had dimensions of 40mm×40mm×0.1mm and was also made of JGS1 glass. Both glass substrates were sequentially ultrasonically cleaned with deionized water for 15 minutes, oxygen plasma cleaned for 8 minutes (power 110W), and dried with nitrogen. AZ7010 photoresist was coated, and the coating process involved spin-coating at low speed (900 rpm) for 7 seconds and high speed (3800 rpm) for 28 seconds, resulting in a film thickness of 2.2μm. Pre-baking was performed at 105℃ for 4.5 minutes. Laser direct writing exposure was performed with an exposure dose of 22mJ / cm², resulting in a defect pattern of 1μm. Scratches with linewidths of 2μm, 3μm, 4μm, and 5μm and a length of 6mm, and pits with a diameter equal to the linewidth; Development: Immersion in AZ300MIF developer for 55 seconds, fixing with isopropanol for 38 seconds; Post-baking: 125℃, 2.8 minutes; Etching: CHF3:SF6=2.5:1, etching power 450W, gas pressure 3.5mTorr, scratch etching for 90 seconds to a depth of 1.2μm, pit etching for 130 seconds to a depth of 1.8μm; Acetone ultrasonic cleaning for 10 minutes at 250W, followed by ultrasonic cleaning with anhydrous ethanol for 7 minutes, nitrogen drying, and vacuum drying in a drying oven for 2 hours at a temperature of 75℃ and a vacuum degree of 3×10. - 3Pa; UV-curable optical adhesive (model NOA73, viscosity 12 mPa·s, refractive index 1.462) was applied to the prepared defect surface. After circular application using a dispensing machine, it was spin-coated at 600 rpm for 8 seconds to achieve a coating thickness of 8 μm. Then, the position of the glass cover plate was adjusted using a precision displacement platform to align the glass edges of the main glass substrate and the glass cover plate with a deviation of 18 μm. A pressure of 0.06 MPa was applied for 15 seconds to remove air bubbles. Further, staged curing was performed. The first stage involved curing under 365 nm UV light for 45 seconds, followed by an 8-minute interval. The second stage involved curing under 350 mW / cm² UV light for 90 seconds. A 0.5 mm chamfer was applied using a diamond tool, and the surface was cleaned with optical-grade isopropanol to obtain a subsurface defect calibration plate.

[0045] Furthermore, as another optional embodiment, taking K9 glass as an example, the preparation process of the subsurface defect calibration plate is illustrated as follows: K9 optical glass was selected as the main glass substrate, with dimensions of 50mm×50mm×3mm, surface finish grade V, and refractive index of 1.516. The ultra-thin cover glass had dimensions of 50mm×50mm×0.15mm and was also made of K9. The pretreatment process was the same as that for the fused silica glass. Femtosecond laser micromachining was used to process defects. The femtosecond laser parameters were: wavelength 1064nm, pulse width 200fs, power 15W, and scanning speed 300μm / s. The processed defect patterns were scratches with line widths of 2μm, 10μm, 50μm, and 100μm and a length of 8mm, and pits with diameters of 3μm, 8μm, and 15μm. After ultrasonic cleaning with acetone for 12 minutes, the glass was transferred to anhydrous ethanol for ultrasonic cleaning for 8 minutes, then dried with nitrogen and dried in a vacuum drying oven for 2.5 hours at a temperature of 80℃ and a vacuum degree of 4×10⁻⁶. -3 Pa; Apply UV-curable optical adhesive, model EPO-TEK353ND, viscosity 18 mPa·s, refractive index 1.512, after dispensing, spin-coating at 700 rpm for 10 seconds, coating thickness 12 μm; assisted by a vision alignment system, the alignment deviation of the two glass edges is 22 μm, apply 0.07 MPa pressure for 18 seconds to remove air bubbles; staged curing, the first stage light intensity is 280 mW / cm². 2 UV curing for 55 seconds, followed by a 10-minute interval, and then a second stage with a light intensity of 380 mW / cm². 2 Curing time was 110 seconds; the micro-beveling parameter was 0.6 mm; the surface was cleaned with optical-grade isopropanol to obtain a subsurface defect calibration plate.

[0046] The subsurface defect calibration plate fabrication method based on ultrathin glass cap provided in this embodiment achieves stable encapsulation and accurate calibration of subsurface defects, meeting the stringent testing requirements of high-end optical systems. In material selection, fused silica glass or K9 optical glass is chosen based on chemical stability, paired with an ultrathin glass cap of 0.05mm~0.2mm. The refractive index difference between the main substrate and the cap is controlled to be ≤0.015, ensuring both the structural stability and resistance to environmental interference of the calibration plate, while reducing optical adaptation deviations. The defect processing stage employs a combination of laser direct-write lithography and inductively coupled plasma etching, or femtosecond laser micromachining, to precisely prepare simulated defects including four different sizes of scratches and three different sizes of pits, covering common defect types and size gradients in actual optical components, ensuring the comprehensiveness and authenticity of the calibration benchmark. A three-stage cleaning process achieves deep impurity removal and dehydration of defect surfaces, laying a clean foundation for subsequent bonding and encapsulation. The optical adhesive is a UV-curable product, with a coating thickness controlled between 3 and 15 μm based on its refractive index matching with the main substrate. Combined with a staged UV curing process, this avoids issues such as residual bubbles and incomplete defect coverage while reducing optical scattering interference. The bonding process utilizes a vision alignment system and a precision displacement platform to achieve precise alignment of less than 20 μm. A uniform pressure holding process ensures the tightness and stability of the encapsulation. After molding, micro-beveling and cleaning with optical-grade isopropanol result in a surface roughness of less than 3 nm. This approach avoids the defects of traditional thin-film encapsulation, such as easy peeling and cracking, and optical path difference interference in conventional glass bonding. It also considers the long-term reliability and calibration accuracy of the calibration board, providing a standardized, high-performance calibration solution for subsurface defect detection in high-end optical equipment manufacturing, semiconductor lithography, and other fields.

[0047] Corresponding to the aforementioned embodiment of a method for fabricating a subsurface defect calibration plate based on an ultrathin glass cap, this application also provides an embodiment of a calibration plate.

[0048] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the calibration plate provided in this application. Please refer to... Figure 2 The calibration board provided in this embodiment includes: Main glass substrate 1; Simulated defect structure 2, wherein the simulated defect structure 2 is located on the surface of the main glass substrate 1; An optical adhesive layer 3 is coated on the surface of the main glass substrate 1 where the simulated defect structure 2 exists; Glass cover plate 4, which is located above the optical adhesive layer 3.

[0049] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for fabricating a subsurface defect calibration plate based on an ultrathin glass cap, characterized in that, The method includes: A main glass substrate and a glass cover are prepared, both of which are made of glass, and the glass cover is an ultra-thin cover. Based on micro-nano fabrication technology, simulated defect structures are fabricated on the surface of the main glass substrate, and the surface where the simulated defect structures exist is used as the defect surface. An optical adhesive is applied to the defective surface, and the coating thickness of the optical adhesive is determined based on the refractive index between the optical adhesive and the main glass substrate. The glass cover plate is attached to the defect surface to form the subsurface defect calibration plate.

2. The method according to claim 1, characterized in that, The glass material is fused silica glass or K9 optical glass, the thickness of the glass cover is 0.05mm~0.2mm, and the refractive index difference between the main glass substrate and the glass cover is less than or equal to 0.

015.

3. The method according to claim 1, characterized in that, The simulated defect structure includes at least scratch-type defects and pit-type defects, and the defect surface includes at least four different sizes of scratch-type defects and three different sizes of pit-type defects.

4. The method according to claim 1, characterized in that, After fabricating simulated defect structures on the surface of the main glass substrate based on micro / nano fabrication, the process includes: The defective surface was ultrasonically cleaned with acetone to dissolve residual organic impurities. The defective surface is subjected to secondary ultrasonic cleaning using anhydrous ethanol to remove acetone residue and dehydrate it. The defective surface after the secondary ultrasonic cleaning is dried using nitrogen gas, thus completing the cleaning process.

5. The method according to claim 1, characterized in that, The optical adhesive is a UV-curable optical adhesive with a viscosity range of 5~20 mPa·s and a refractive index of 1.46~1.

54. The refractive index difference between the optical adhesive and the main glass substrate is less than or equal to 0.025, and the coating thickness is 3~15 μm.

6. The method according to claim 1, characterized in that, After applying an optical adhesive to the defective surface, the process includes: The defect surface is cured in stages using ultraviolet light with a wavelength of 365~405nm and a light intensity of 200~400mW / cm². The first stage of curing time is 30~60 seconds, the second stage of curing time is 60~120 seconds, and the time interval between the first stage of curing time and the second stage of curing time is 5~10 minutes.

7. The method according to claim 1, characterized in that, After forming the subsurface defect calibration plate, the process includes: The subsurface defect calibration plate was micro-beveled using a diamond tool, with a beveling size of 0.3~0.8mm; The subsurface defect calibration plate is wiped in one direction with a lint-free cloth soaked in optical grade isopropyl alcohol to remove residual adhesive and impurities on the surface. The surface roughness of the subsurface defect calibration plate is less than or equal to 3 nm.

8. The method according to claim 1, characterized in that, The micro / nano fabrication process is a combination of laser direct-write lithography and inductively coupled plasma etching (ICP-CEL) or femtosecond laser micromachining. In the laser direct-write lithography and ICP-CEL combination process, the linewidth of scratch-type defects is 1 μm to 450 μm, the length is 4 mm to 12 mm, and the depth is 80 nm to 2.5 μm; the diameter of pit-type defects is 1 μm to 0.8 mm, and the depth is 120 nm to 3.2 μm. In the femtosecond laser micromachining process, the linewidth of scratch-type defects is 2 μm to 500 μm, the length is 4 mm to 12 mm, and the depth is 1 μm to 3 μm; the diameter of pit-type defects is 2 μm to 1 mm, and the depth is 1.5 μm to 3.5 μm.

9. The method according to claim 1, characterized in that, When bonding the glass cover plate to the defective surface, a visual alignment system is used in conjunction with a precision displacement platform with a positioning accuracy of less than or equal to 10 μm to achieve alignment. The alignment accuracy is less than or equal to 20 μm. During the bonding process, a pressure of 0.03~0.08 MPa is applied and the pressure is maintained for 10~20 seconds.

10. A calibration plate, characterized in that, The calibration plate is prepared based on the method of any one of claims 1-9, and the calibration plate comprises: Main glass substrate; A simulated defect structure is located on the surface of the main glass substrate; An optical adhesive layer is coated on the surface of the main glass substrate where the simulated defect structure exists; A glass cover plate, which is located above the optical adhesive layer.

Images