A processing method to improve the damage resistance of polished substrates for 355nm UV windows.

Abstract

A processing method for improving the damage resistance of a 355nm UV window polishing substrate involves setting up rough grinding, fine grinding, and other processing procedures, analyzing the degree of sub-damage layers that may be caused by auxiliary materials in each process, quantitatively removing dimensions in subsequent processes to eliminate sub-damage generated in previous processes, thereby gradually realizing the processing of optical devices; after fine polishing, the surface is micro-treated with acid to eliminate the hydrolysis layer and most of the sub-damage layers generated in the former process, and finally, a second surface finishing process is performed on the surface of the optical device. The second finishing process fully considers the working wavelength of the optical device, because zirconium oxide or silicon oxide has extremely low absorption at 355nm, and using them as polishing powder and polishing disc raw materials reduces the induced effect of surface residual impurities, improves the damage resistance of the substrate, and thus improves the optical performance of the component.

Description

Technical Field

[0001] This invention relates to the field of optical device processing, and in particular, to a processing method for improving the damage resistance of a 355nm UV window polishing substrate. Background Technology

[0002] Damage is divided into surface damage and volume damage. Volume damage is based on the absorption effect of the material itself. UV-fused silica has relatively small absorption at 355nm, and the damage resistance of the bulk material is much greater than that of the surface. Surface damage is affected by the surface processing method.

[0003] The fabrication of optical components involves processes such as cutting, grinding, polishing, and cleaning. In each of these processes, for example, W28 abrasive has an average particle size of 20 μm, and its sub-damage can reach 60 to 150 micrometers; W7 abrasive has an average particle size of 7 μm, and its sub-damage can reach around 20 micrometers; high-polishing powder has an average particle size of 1.5 μm, and its sub-damage can reach 4 to 5 micrometers; and for low-polishing, various polishing powders have an average particle size of 0.8 to 1.1 μm, and their sub-damage can reach 2 to 3 μm. The particle size of these grinding powders further damages the substrate surface.

[0004] Polishing of the optical surface is the final step. Its purpose is to obtain ideal surface accuracy, reduce surface roughness and surface defects, and remove the damage layer generated by grinding, thereby obtaining a smooth and undamaged processed surface.

[0005] Research from the Lawrence Livermore National Laboratory in the United States shows that polished optical components still suffer from subsurface damage. This damage layer consists of a hydrolysis layer generated by the hydrolysis reaction and a subsurface defect layer. The subsurface defect layer is partially or completely hidden beneath the hydrolysis layer. The absorption of laser energy by polishing particles embedded in the hydrolysis layer, combined with the modulation of the laser electromagnetic field by cracks and scratches in the defects, induces a thermal lensing effect. This results in the laser damage threshold of the optical surface being much lower than that of the substrate itself, with polishing particles having the most significant impact on the laser damage threshold. Furthermore, polishing impurities can induce damage at the interface between the antireflection coating and the substrate, thereby reducing the antireflection coating's damage resistance.

[0006] Therefore, how to overcome the defects of existing technologies, reduce sub-damage, improve the surface smoothness of optical devices, and design optical devices for specific operating wavelengths have become technical problems that need to be solved in the existing technologies. Summary of the Invention

[0007] The purpose of this invention is to propose a processing method to improve the damage resistance of a 355nm UV window polishing substrate, which can reduce the surface sub-damage of optical devices, improve the damage resistance of optical devices at the working wavelength, and thus improve the optical performance of optical components.

[0008] A processing method for improving the damage resistance of a 355nm UV window polishing substrate includes:

[0009] The formed UV window film substrate is first rough-polished using a double-sided polishing method. After cleaning the polished substrate, it is mounted on a photoresist plate using a photoresist method. After coating and drying, it is coarsely and finely ground with silicon carbide sand. After meeting the dimensional requirements, the residual sand particles on the substrate surface are cleaned, and then it is placed on a high-speed polishing machine for rough polishing. After rough polishing, it is polished for the first time using a traditional asphalt disc polishing method. The finely polished substrate is then cleaned using multi-tank ultrasonic cleaning, and then placed in a specific acid solution for surface treatment. After treatment, the substrate is cleaned again using ultrasonic cleaning, and then a second fine polishing is performed. In this process, a quantitative processing method is used to remove a certain amount of size by grinding and polishing to eliminate the sub-damage caused by the previous processing.

[0010] Optionally, the secondary polishing involves applying a light adhesive to the substrate onto a light adhesive plate. The entire light adhesive plate is placed inside a ring and positioned opposite an asphalt polishing disc. The ring rests against a roller bracket and rotates with the main shaft of the polishing machine. The rotation of the asphalt polishing disc causes the substrate to rotate as well. The substrate and the light adhesive plate are integrated, causing the ring to rotate slowly with the light adhesive plate. A motor is installed on the roller bracket, which accelerates the rotation of the ring, causing the light adhesive plate to rotate within the ring and then move around the inner side of the ring as the main shaft rotates, resulting in more uniform polishing of the substrate surface.

[0011] Optionally, no pressure is required during the secondary polishing process. The polishing sheet and substrate only rely on their own weight to contact the asphalt polishing disc. The spindle speed is 12-15 RPM. The polishing fluid is contained in the agitator. The polishing fluid is prevented from crystallizing by continuous stirring. The polishing fluid is drawn into the hose by the peristaltic pump and finally transferred to the asphalt polishing disc to achieve the secondary polishing process.

[0012] Optionally, the polishing powder in the polishing liquid used for secondary polishing includes zirconium oxide or silicon oxide, and the asphalt polishing disc used for secondary fine polishing is made of zirconium oxide or silicon oxide.

[0013] Optionally, the subsequent process employs quantitative processing, involving grinding and polishing to remove a certain amount of dimensional defects, thereby eliminating sub-damage caused by the preceding process. This is manifested in the following ways:

[0014] The coarse grinding is performed using W28 abrasive, removing 0.3–0.4 mm of material, and the grinding time is 25–30 minutes.

[0015] The fine grinding is performed using W7 abrasive, removing 0.12–0.15 mm of material, and the grinding time is 30–35 minutes.

[0016] The coarse polishing is performed using cerium oxide with an average particle size of 1-2 μm, removing 0.025-0.03 mm of material, and the polishing time is 40-50 minutes.

[0017] The initial fine polishing uses cerium oxide with an average particle size of 0.5 μm for polishing, removing 0.008 to 0.01 mm of material, and the polishing time is 2.5 to 3 hours.

[0018] The polishing solution used for secondary fine polishing has a polishing powder to pure water ratio of 1:2, an average particle size of 80nm, a fine polishing removal size greater than 0.005mm, and a polishing time of 7-8 hours.

[0019] Optionally, the surface treatment in the specific acid solution is as follows: etching is performed using HF (hydrofluoric acid) at a concentration of 5%, at room temperature, and the substrate is immersed in the etching solution for 10 minutes.

[0020] Optionally, in the secondary polishing process, a peristaltic pump is used to automatically add polishing fluid. The peristaltic pump rotates at 8-10 RPM, and the polishing fluid is not recycled, thereby reducing the sub-loss in the final process.

[0021] Optionally, during the secondary polishing process, the polishing slurry is continuously agitated by a stirrer.

[0022] Optionally, the zirconium oxide or silicon oxide in the polishing slurry is ball-milled to make its particle size more uniform.

[0023] In summary, the present invention has the following advantages:

[0024] 1. The sub-damage caused by grinding auxiliary materials is removed by quantitative processing. The subsequent process adopts quantitative processing, grinding and polishing to remove a certain amount of size, eliminating the sub-damage generated by the previous process, leaving only the slight sub-damage from the polishing process.

[0025] 2. Hydrofluoric acid treatment removes the deep sub-damage layer and hydrolysis layer remaining from polishing, followed by secondary fine polishing with ultra-fine particles to reduce surface defects and improve the substrate's resistance to damage, thereby enhancing the optical performance of the components.

[0026] 3. The auxiliary materials selected for the secondary polishing have relatively low absorption at 355nm, reducing the impact of residual impurities from polishing on the film layer. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the UV substrate to be processed onto the photoresist plate according to a specific embodiment of the present invention.

[0028] Figure 2 This is a partial schematic diagram of the secondary polishing process according to a specific embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram of the entire process of secondary fine polishing according to a specific embodiment of the present invention.

[0030] The technical features referred to by the reference numerals in the figure are as follows:

[0031] 01. Substrate; 02. Glossy sheet; 03. Roller bracket; 04. Ring; 05. Asphalt polishing disc; 06. Aluminum plate; 07. Hoses; 08. Peristaltic pump; 09. Auxiliary material mixer. Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0033] The main features of this invention are: setting up processing procedures such as rough grinding and fine grinding, analyzing the degree of sub-damage layer that may be caused by auxiliary materials in each process, quantitatively removing dimensions in the subsequent process, eliminating the sub-damage generated in the previous process, and thus gradually realizing the processing of optical devices; after fine polishing, the surface is micro-treated with acid to eliminate the hydrolysis layer and most of the sub-damage layer generated in the previous process, and finally the surface of the optical device is subjected to secondary surface finishing. The secondary finishing fully considers the working wavelength of the optical device. Because zirconium oxide has extremely low absorption at 355nm, zirconium oxide is used as polishing powder and polishing disc material to reduce the induced effect of surface residual impurities, improve the damage resistance of the substrate, and thus improve the optical performance of the component.

[0034] Therefore, this invention differs from existing technologies. Conventional processing methods in existing technologies aim to meet optical specifications without considering the subsurface condition of the substrate. They consider surface finish to meet the required standards, assuming that damage is solely determined by the coating process. In contrast, this invention further analyzes the subsurface of optical components. Combining the characteristics of processing materials, quantitative grinding and polishing are performed, followed by a subsequent process to eliminate the sub-damage layer generated in the previous process. Acid treatment further eliminates sub-damage, and finally, ultra-low absorption zirconia is used for fine polishing to minimize the degree of sub-damage.

[0035] For details, see Figures 1-3 The diagram illustrates the corresponding apparatus and a secondary fine polishing schematic diagram in the processing method for polishing substrate damage of a 355nm UV window according to a specific embodiment of the present invention.

[0036] A processing method for improving the damage resistance of a 355nm UV window polishing substrate includes:

[0037] The formed UV window substrate 01 is first rough-polished using a double-sided polishing method. After cleaning the polished substrate, it is mounted on a photoresist plate 02 using a photoresist method. After coating and drying, it is coarsely and finely ground with silicon carbide sand. After meeting the dimensional requirements, the residual sand particles on the substrate surface are cleaned, and then it is placed on a high-speed polishing machine for rough polishing. After rough polishing, it is first finely polished using a traditional asphalt disc polishing method. The finely polished substrate 01 is then cleaned using multi-slot ultrasonic cleaning, and then placed in a specific acid solution for surface treatment. After treatment, the substrate 01 is cleaned again using ultrasonic cleaning, and then a second fine polishing is performed. In this process, a quantitative processing method is used, where grinding and polishing remove a certain amount of size and eliminate the sub-damage caused by the previous processing.

[0038] Specifically, the secondary polishing involves applying a light adhesive to the substrate 01 onto a light adhesive plate 02. The entire light adhesive plate 02 is placed inside a circular ring 04, opposite an asphalt polishing disc 05. The asphalt polishing disc can be placed on an aluminum plate 07. The circular ring 04 rests against a roller bracket 03 and rotates with the polishing machine's main shaft. The rotation of the asphalt polishing disc 05 drives the substrate 01 to rotate. The substrate 01 and the light adhesive plate 02 are integrated, and the circular ring 04 will also rotate slowly with the light adhesive plate 02. A motor is installed on the roller bracket 03, which accelerates the rotation of the circular ring 04, causing the light adhesive plate 02 to rotate within the circular ring 04 and then move around the inner side of the circular ring 04 with the rotation of the main shaft, resulting in more uniform polishing of the substrate 01 surface.

[0039] No pressure is required during the secondary polishing process. The polishing plate and substrate only rely on their own weight to contact the asphalt polishing disc. The spindle speed is 12-15 RPM. The polishing liquid is contained in the agitator 09. The polishing liquid is prevented from crystallizing by continuous stirring. The polishing liquid is drawn into the hose 07 by the peristaltic pump 08 and finally transferred to the asphalt polishing disc 05 to realize the secondary polishing process of the surface.

[0040] Furthermore, the polishing fluid used for secondary polishing is zirconium oxide, and the asphalt polishing disc 05 used for secondary fine polishing is made of zirconium oxide. This auxiliary material has low absorption at 355nm, which further reduces the impact of residual impurities from polishing on the film layer.

[0041] The subsequent process employs quantitative processing, involving grinding and polishing to remove a certain amount of dimensional defects and eliminate sub-damage caused by the preceding process. This is manifested in the following ways:

[0042] The coarse grinding is performed using W28 abrasive, removing 0.3–0.4 mm of material, and the grinding time is 25–30 minutes.

[0043] The fine grinding is performed using W7 abrasive, removing 0.12–0.15 mm of material, and the grinding time is 30–35 minutes.

[0044] The coarse polishing is performed using cerium oxide with an average particle size of 1-2 μm, removing 0.025-0.03 mm of material, and the polishing time is 40-50 minutes.

[0045] The initial fine polishing uses cerium oxide with an average particle size of 0.5 μm for polishing, removing 0.008 to 0.01 mm of material, and the polishing time is 2.5 to 3 hours.

[0046] The polishing powder used in the secondary polishing liquid includes zirconium oxide or silicon oxide. The ratio of polishing powder to pure water is 1:2, the average particle size is 80nm, the fine polishing removes a size greater than 0.005mm, and the polishing time is 7-8 hours.

[0047] Furthermore, in the secondary polishing process, a peristaltic pump 08 is used to automatically add polishing fluid. The peristaltic pump 08 rotates at a speed of 8-10 RPM, and the polishing fluid is not recycled, thereby reducing the sub-loss in the final process.

[0048] During the secondary polishing process, the polishing slurry is continuously agitated by the agitator 09 to ensure that the polishing slurry does not agglomerate and form oversized particles, which would cause deep sub-damage again.

[0049] In this invention, the zirconium oxide in the polishing slurry is ball-milled to make its particle size more uniform.

[0050] Alternatively, the polishing slurry used for finishing can also be a silicon dioxide polishing slurry with a particle size of 80 nm, since silicon dioxide has very low absorption at 355 nm.

[0051] Further optionally, the surface treatment in the specific acid solution specifically involves etching with HF (hydrofluoric acid) at a concentration of 5% at room temperature for 10 minutes while immersing the substrate in the etching solution.

[0052] Hydrofluoric acid treatment removes the deep sub-damage layer and hydrolysis layer remaining from polishing, assisting in subsequent secondary fine polishing with ultra-fine particles, reducing surface defects and improving the substrate's resistance to damage.

[0053] In summary, the present invention has the following advantages:

[0054] 1. The sub-damage caused by grinding auxiliary materials is removed by quantitative processing. The subsequent process adopts quantitative processing, grinding and polishing to remove a certain amount of size, eliminating the sub-damage generated by the previous process, leaving only the slight sub-damage from the polishing process.

[0055] 2. By treating with hydrofluoric acid, the deep sub-damage layer and hydrolysis layer remaining from polishing are removed. Then, a second fine polishing with ultra-fine particles is used to reduce surface sub-layer defects, improve the substrate's damage resistance, and thus improve the optical performance of the components.

[0056] 3. The auxiliary materials selected for the secondary polishing have relatively low absorption at 355nm, reducing the impact of residual impurities from polishing on the film layer.

[0057] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection of the present invention as defined by the submitted claims.

Claims

1. A processing method for improving the damage resistance of a 355nm UV window polishing substrate, characterized in that, include: The formed UV window film substrate is first rough polished using a double-sided polishing method. After the polished substrate is cleaned, it is mounted on a photoresist plate using a photoresist method. After being painted and dried, it is rough and fine ground with silicon carbide sand. After meeting the dimensional requirements, the residual sand particles on the substrate surface are cleaned, and then it is placed on a high-speed polishing machine for rough polishing. After rough polishing, it is polished for the first time using a traditional asphalt disc polishing method. The finely polished substrate is then cleaned using multi-tank ultrasonic cleaning, and then placed in a specific acid solution for surface treatment. After treatment, the substrate is cleaned again using ultrasonic cleaning, and then a second fine polishing is performed. In this process, a quantitative processing method is used to remove a certain amount of size by grinding and polishing to eliminate the sub-damage caused by the previous processing. in, The polishing powder in the polishing fluid used for secondary polishing includes zirconium oxide or silicon oxide, and the asphalt polishing disc used for secondary fine polishing is made of zirconium oxide or silicon oxide. The subsequent process employs quantitative processing, involving grinding and polishing to remove a certain amount of dimensional defects and eliminate sub-damage caused by the preceding process. This is manifested in the following ways: The coarse grinding is performed using W28 abrasive, removing 0.3–0.4 mm of material, and the grinding time is 25–30 minutes. The fine grinding is performed using W7 abrasive, removing 0.12–0.15 mm of material, and the grinding time is 30–35 minutes. The coarse polishing is performed using cerium oxide with an average particle size of 1-2 μm, removing 0.025-0.03 mm of material, and the polishing time is 40-50 minutes. The initial fine polishing uses cerium oxide with an average particle size of 0.5 μm, removing 0.008–0.01 mm of material, and the polishing time is 2.5–3 hours. The polishing solution used for secondary fine polishing has a polishing powder to pure water ratio of 1:2, an average particle size of 80nm, a fine polishing removal size greater than 0.005mm, and a polishing time of 7-8 hours.

2. The processing method according to claim 1, characterized in that: The secondary polishing involves applying a light adhesive to the substrate onto a light adhesive plate. The entire light adhesive plate is placed inside a ring, opposite the asphalt polishing disc. The ring rests against a roller bracket and rotates with the main shaft of the polishing machine. The rotation of the asphalt polishing disc causes the substrate to rotate as well. The substrate and the light adhesive plate are integrated, causing the ring to rotate slowly with the light adhesive plate. A motor is installed on the roller bracket, which accelerates the rotation of the ring, causing the light adhesive plate to rotate within the ring and then move around the inner side of the ring with the rotation of the main shaft, resulting in more uniform polishing of the substrate surface.

3. The processing method according to claim 2, characterized in that: No pressure is required during the secondary polishing process. The polishing plate and substrate only rely on their own weight to contact the asphalt polishing disc. The spindle speed is 12-15 RPM. The polishing fluid is contained in the agitator and is transferred to the asphalt polishing disc by a peristaltic pump.

4. The processing method according to any one of claims 2-3, characterized in that: The specific surface treatment in the acid solution is as follows: etching is performed using HF (hydrofluoric acid) at a concentration of 5%, at room temperature, with the substrate immersed in the etching solution for 10 minutes.

5. The processing method according to claim 4, characterized in that: In the secondary polishing process, a peristaltic pump is used to automatically add polishing fluid. The peristaltic pump speed is 8-10 RPM. The polishing fluid is not recycled, thereby reducing the sub-loss in the final process.

6. The processing method according to claim 4, characterized in that: During the secondary polishing process, the polishing fluid is continuously agitated by a stirrer.

7. The processing method according to claim 1, characterized in that: Zirconia or silicon dioxide in the polishing slurry is ball-milled to make its particle size more uniform.

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