A method for surface treatment of a quartz glass article

Abstract

This invention discloses a surface treatment method for quartz glass products, belonging to the field of quartz glass product surface treatment technology. The method includes sequential conventional surface treatment, mechanical polishing, and chemical mechanical polishing. Conventional surface treatment reduces the surface roughness Ra of the quartz glass product to below 300 nm, mechanical polishing reduces the roughness Ra to below 15 nm, and chemical mechanical polishing reduces the roughness Ra to below 5 nm. This invention eliminates surface and subsurface defects in quartz glass products through gradient surface treatment, enhancing surface integrity and ensuring uniform etching in a fluorine-containing plasma etching environment, significantly improving service life. This method eliminates coating processing steps, resulting in low production costs, and eliminates the generation of non-volatile particles during use, thus improving chip manufacturing yield.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology for quartz glass products, and more specifically, to a treatment method for controlling the surface roughness of quartz glass products in a plasma etching process. Background Technology

[0002] Quartz glass products are widely used in high-end optical components, semiconductor photomasks, and precision instrument windows due to their excellent optical transmittance, high thermal stability, and chemical inertness. In the semiconductor chip manufacturing process, diffusion furnace tubes, quartz boats, quartz rings, focusing rings, and other process devices are all made of high-purity quartz glass products, making them an indispensable consumable in the semiconductor industry.

[0003] In the semiconductor dry etching process, the high-purity quartz glass focusing ring, as a support component for the silicon wafer, is directly subjected to intense etching by fluorine-containing plasma. Since the etching rate of silicon dioxide under plasma is significantly higher than that of silicon, the surface of the quartz glass focusing ring is easily damaged. After being damaged, it is prone to particulate contamination, resulting in a short service life and requiring continuous and regular replacement, which greatly increases the usage cost of semiconductor chip manufacturing.

[0004] Currently, the mainstream method to improve the service life of quartz glass products under plasma is to prepare a protective coating of materials such as alumina and yttrium oxide on their surface, utilizing the high plasma resistance of the coating material to protect the quartz glass products. For example, patent publication number CN120736898A discloses a nanostructured plasma protective composite coating and its preparation method. This coating is prepared by combining yttrium oxide with a second ceramic component and using a vacuum cold spraying and heating process, thus improving the coating's etching resistance. However, such coating preparation methods often employ atmospheric plasma spraying and other processes, significantly increasing the production cost of quartz glass products. Furthermore, protective coatings such as yttrium oxide generate a significant amount of non-volatile particulate pollution during use, severely affecting chip production yield and failing to meet the high precision requirements of semiconductor processes. Summary of the Invention

[0005] The main objective of this invention is to propose a surface treatment method for quartz glass products. By performing a gradient surface treatment on quartz glass products, surface and subsurface defects are eliminated, surface integrity is enhanced, and the service life of quartz glass products in a fluorine-containing plasma etching environment is improved, while reducing production costs and minimizing particulate contamination.

[0006] To address the aforementioned technical problems, this invention proposes a surface treatment method for quartz glass products. The method steps are as follows: S1. Pre-treat the surface of quartz glass products to reduce the surface roughness Ra of quartz glass products to below 300nm; S2. The quartz glass product after step S1 is treated by mechanical polishing to remove surface roughness defects and broken layers, so that the surface roughness Ra of the quartz glass product is reduced to below 15nm. S3. The quartz glass products processed in step S2 are treated with chemical mechanical polishing to remove surface damage and defects, thereby reducing the surface roughness Ra of the quartz glass products to below 5 nm.

[0007] In the above technical solution, further, in step S1, the pretreatment is to treat the surface of the quartz glass product by one or more of the following methods: grinding, flat grinding, and precision sandblasting.

[0008] In any of the above technical solutions, further, in step S2, the polishing abrasive used in the mechanical polishing method is one or more of alumina, silicon carbide, diamond, cerium oxide, and zirconium oxide.

[0009] In any of the above technical solutions, further, in step S3, the chemical mechanical polishing method is carried out using a polishing pad and a polishing liquid in combination; The polishing pad is made of polyurethane or porous polyurethane.

[0010] In any of the above technical solutions, the abrasive in the polishing liquid is nano-silica; the particle size of the nano-silica is 40nm.

[0011] In any of the above technical solutions, the pH value of the polishing liquid is further 9-10.

[0012] Beneficial effects: Compared with existing technologies, This invention does not involve the processing of any protective coatings or film materials, which significantly reduces the production cost of quartz glass products compared to existing coating preparation methods. At the same time, due to the absence of coating materials, quartz glass products will not generate non-volatile particulate pollution caused by coating peeling during plasma etching processes, greatly reducing the amount of particles generated. This is beneficial to improving the yield of chip manufacturing processes and meeting the high-precision production requirements of the semiconductor industry. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a comparison image of quartz plasma etching before (left) and after (right) in Example 1; Figure 2 These are electron microscope comparison images of quartz plasma etching before (left) and after (right) in Example 1; Figure 3 This is a comparison image of quartz plasma etching before (left) and after (right) in Example 2; Figure 4 These are electron microscope (EM) comparison images of quartz plasma etching before (left) and after (right) in Example 2; Figure 5 This is a comparison image of quartz plasma etching before (left) and after (right) in Example 3.

[0015] Figure 6 These are electron microscope comparison images of quartz plasma etching before (left) and after (right) in Example 3; Figure 7 This is a comparison image of quartz plasma etching before (left) and after (right) in Comparative Example 1; Figure 8 This is a comparison of electron microscope images of quartz plasma etching before (left) and after (right) in Comparative Example 1; Figure 9 This is a comparison image of quartz plasma etching before (left) and after (right) in Comparative Example 2; Figure 10 This is a comparison of electron microscope images of quartz plasma etching before (left) and after (right) in Comparative Example 2. Detailed Implementation

[0016] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of this application, and not all of the embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0017] It should be noted that, as shown in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, and these steps and elements do not constitute an exclusive list; the method or apparatus may also include other steps or elements.

[0018] This invention proposes a surface treatment method for quartz glass products, the specific steps of which are as follows: S1. Conventional Surface Treatment: The surface of the quartz glass product is pretreated using conventional surface treatment methods to reduce the surface roughness Ra of the quartz glass product to below 300nm. The conventional surface treatment methods are one or more combinations of grinding, flat grinding, and precision sandblasting, which can quickly remove macroscopic surface defects generated after the machining of quartz glass products, laying the foundation for subsequent fine polishing.

[0019] S2. Mechanical polishing treatment: The quartz glass products after conventional surface treatment are treated with mechanical polishing to remove surface roughness defects and broken layers, so that the surface roughness Ra of the quartz glass products is reduced to below 15nm; the polishing abrasive used in the mechanical polishing method is one or more combinations of alumina, silicon carbide, diamond, cerium oxide, and zirconium oxide, which further refines the surface of the quartz glass products through mechanical grinding and eliminates most of the micro-rough structure.

[0020] S3. Chemical Mechanical Polishing (CMP): CMP is used to treat mechanically polished quartz glass products, removing surface damage and defects and reducing the surface roughness Ra to below 5 nm. This step utilizes commercially available polishing pads and polishing slurries. The polishing pads are made of polyurethane or porous polyurethane, and the abrasive in the polishing slurry is nano-silica. The pH value of the polishing slurry is 9-10, and the preferred nano-silica particle size is 40 nm. CMP combines chemical corrosion and mechanical abrasion, effectively eliminating surface damage, microcracks, and residual stress layers in quartz glass products, eliminating subsurface damage, and obtaining a uniformly composed passivated surface.

[0021] The quartz glass products processed by the method of the present invention are suitable for dry plasma etching processes in semiconductor chip manufacturing. Specifically, the etching gas is a mixture of fluorine-containing gas and oxygen. Under conventional plasma etching power, gas flow rate and etching time conditions, the quartz glass products are placed directly in the fluorine-containing plasma etching environment as silicon wafer support components and are subjected to the etching effect of the plasma.

[0022] Because plasma etching is highly anisotropic, the etching rate at defects on the surface of quartz glass is much higher than at defect-free areas. Therefore, quartz glass products with surface defects will rapidly develop an uneven structure under plasma treatment, losing their performance. This invention, through the aforementioned gradient surface treatment, fundamentally enhances the surface integrity of quartz glass products. This ensures that all parts of the surface are etched at the same rate when facing a plasma etching environment, effectively controlling changes in surface roughness and exhibiting stronger fatigue and damage resistance, thus significantly extending the service life for stable operation. Simultaneously, no volatile particles are generated throughout the entire process, preventing particle contamination of silicon wafers and effectively improving the yield of chip manufacturing processes.

[0023] The surface treatment method for quartz glass products of this application will be described in detail below through the following embodiments.

[0024] Example 1: This embodiment proposes a surface treatment method for quartz glass products, including the following steps: S1. Surface pretreatment: The quartz glass products are surface treated with a 200-1000 mesh abrasive pad. The surface roughness Ra of the treated quartz glass products is 230 nm. S2. Mechanical polishing treatment: The surface of the quartz glass product is polished sequentially with diamond polishing liquid with particle sizes of 6μm, 3μm and 1μm to remove surface roughness defects and broken layers. After treatment, the surface roughness of the quartz glass product is 11nm. S3. Chemical mechanical polishing treatment: A chemical mechanical polishing slurry with a solid content of 37% and a particle size of 40nm nano silica was selected. The overall pH was 9.7. The surface of the quartz glass product was chemically mechanically polished, and the surface roughness of the quartz glass product after treatment was 3.98nm. S4. Verification of Plasma Etching Conditions: CF4 plasma was used to etch the surface of the chemically mechanically polished quartz glass product. The etching parameters were: power 500W, CF4 flow rate 80sccm, O2 flow rate 20sccm, and time 1h. Using a white light interferometer, the surface roughness of the quartz glass product after plasma etching was measured to be 9.58nm.

[0025] like Figures 1-2 As shown in the metallographic microscope and scanning electron microscope images, the overall state of the sample did not change significantly before and after plasma etching. The surface of the quartz glass product was uniform, without obvious defects, and the change in surface roughness was small. It had excellent resistance to damage in the fluorine-containing plasma etching environment and could maintain a stable working state for a long time.

[0026] Example 2: This embodiment proposes a surface treatment method for quartz glass products, including the following steps: S1. Surface pretreatment: The quartz glass products are surface treated with a 200-1000 mesh abrasive pad. After treatment, the surface roughness of the quartz glass products is 270 nm. S2. Mechanical polishing treatment: The surface of the quartz glass product is polished sequentially with diamond polishing slurries with particle sizes of 6μm, 3μm and 1μm to remove surface roughness defects and broken layers. The surface roughness of the quartz glass product after treatment is 13nm. S3. Chemical mechanical polishing treatment: A chemical mechanical polishing slurry with a solid content of 37% and a particle size of 40nm nano-silica was selected. The overall pH was 9.7. The surface of the quartz glass product was chemically mechanically polished. After the treatment, the surface roughness of the quartz glass product was 2.94nm. S4. Verification of Plasma Etching Conditions: CF4 plasma was used to etch the surface of the chemically mechanically polished quartz glass product. The etching parameters were: power 500W, CF4 flow rate 80sccm, O2 flow rate 20sccm, and time 1h. Using a white light interferometer, the surface roughness of the quartz glass product after plasma etching was measured to be 10.29nm.

[0027] like Figures 3-4 As shown in the metallographic microscope and scanning electron microscope images, the overall state of the sample did not change significantly before and after plasma etching. The surface of the quartz glass product was uniform, without obvious defects, and the change in surface roughness was small. It had excellent resistance to damage in the fluorine-containing plasma etching environment and could maintain a stable working state for a long time.

[0028] Example 3: This embodiment proposes a surface treatment method for quartz glass products, including the following steps: S1. Surface pretreatment: The quartz glass products are surface treated with a 200-1000 mesh abrasive pad. After treatment, the surface roughness of the quartz glass products is 260nm. S2. Mechanical polishing treatment: The surface of the quartz glass product is polished sequentially with diamond polishing slurries with particle sizes of 6μm, 3μm and 1μm to remove surface roughness defects and broken layers. After treatment, the surface roughness of the quartz glass product is 12nm. S3. Chemical mechanical polishing treatment: A chemical mechanical polishing slurry with a solid content of 37% and a particle size of 40nm nano silica was selected. The overall pH was 9.7. The surface of the quartz glass product was chemically mechanically polished, and the surface roughness of the quartz glass product after treatment was 3.58nm. S4. Verification of Plasma Etching Conditions: CF4 plasma was used to etch the surface of the chemically mechanically polished quartz glass product. The etching parameters were: power 500W, CF4 flow rate 80sccm, O2 flow rate 20sccm, and time 1h. Using a white light interferometer, the surface roughness of the quartz glass product after plasma etching was measured to be 11.58nm.

[0029] like Figures 5-6 As shown in the metallographic microscope and scanning electron microscope images, the overall state of the sample did not change significantly before and after plasma etching. The surface of the quartz glass product was uniform, without obvious defects, and the change in surface roughness was small. It had excellent resistance to damage in the fluorine-containing plasma etching environment and could maintain a stable working state for a long time.

[0030] Comparative Example 1: This comparative example describes the process and effect of processing quartz glass components using only mechanical polishing.

[0031] The steps are as follows: S1. Surface pretreatment: The quartz glass products are surface treated with a 200-1000 mesh abrasive pad. After treatment, the surface roughness of the quartz glass products is 253nm. S2. Mechanical polishing treatment: The surface of the quartz glass product is polished sequentially with diamond polishing liquid with particle sizes of 6μm, 3μm and 1μm. After the treatment, the surface roughness of the quartz glass product is 15nm. S3. Mechanical polishing treatment: The surface of the quartz glass product is polished using a fine alumina polishing slurry with a particle size of 600-300nm. After the treatment, the surface roughness of the quartz glass product is 1.79nm. S4. Verification of Plasma Etching Conditions: CF4 plasma was used to etch the surface of mechanically polished quartz glass products. The etching parameters were: power 500W, CF4 flow rate 80sccm, O2 flow rate 20sccm, and time 1h. Using a white light interferometer, the surface roughness of the quartz glass products after plasma etching was measured to be 82nm.

[0032] like Figures 7-8 As shown in the metallographic and scanning electron microscope images, numerous point-like defects appeared on the overall surface of the sample after plasma etching, resulting in an uneven surface and a significant increase in surface roughness. This prevented the sample from maintaining normal operation under fluorine-containing plasma etching conditions. The reason is that mechanical polishing alone cannot eliminate subsurface damage and residual stress layers in quartz glass products. The anisotropy of plasma etching rapidly erodes defective areas, leading to rapid surface deterioration.

[0033] Comparative Example 2 It is generally believed that flame firing of quartz glass products can eliminate surface defects caused by processing, thereby obtaining a higher surface quality.

[0034] This comparative example describes the process and effect of processing quartz glass components using mechanical polishing combined with full-scale fine firing.

[0035] The steps are as follows: S1. Surface pretreatment: The quartz glass products are surface treated with a 200-1000 mesh abrasive pad. After treatment, the surface roughness of the quartz glass products is 253nm. S2. Mechanical polishing treatment: The surface of the quartz glass product is polished sequentially with diamond polishing liquid with particle sizes of 6μm, 3μm and 1μm. After the treatment, the surface roughness of the quartz glass product is 15nm. S3. Fine sintering treatment: The quartz glass products are subjected to full flame fine sintering treatment, and the surface roughness of the quartz glass products after treatment is 35.02nm; S4. Verification of Plasma Etching Conditions: The surface of the sintered quartz glass product was etched using CF4 plasma. The etching parameters were: power 500W, CF4 flow rate 80sccm, O2 flow rate 20sccm, and time 1h. The surface roughness of the quartz glass product after plasma etching was measured to be 983nm using a white light interferometer.

[0036] like Figures 9-10 As shown in the metallographic and scanning electron microscope images, numerous scratches appeared on the overall surface of the sample after plasma etching. This was accompanied by an uneven surface on the solid particles, resulting in a sharp increase in surface roughness and a complete loss of usability. The reason is that flame sintering causes new thermal stress defects on the surface of quartz glass products. Simultaneously, the surface roughness increases significantly after sintering, and plasma etching rapidly damages the surface structure, generating a large amount of particulate contamination.

[0037] The roughness changes of the samples before and after plasma etching in the examples and comparative examples are shown in the table below. Show As can be seen from the results of Examples 1-3 and Comparative Examples 1-2, the method provided by the present invention can effectively suppress crack propagation, eliminate subsurface damage, and obtain a passivated surface with uniform composition by treating the surface of quartz glass products, thereby fundamentally strengthening the surface integrity of quartz glass products and significantly extending their service life under fluorine-containing plasma.

[0038] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for surface treatment of quartz glass products, characterized in that, The method steps are as follows: S1. Pre-treat the surface of quartz glass products to reduce the surface roughness Ra of quartz glass products to below 300nm; S2. The quartz glass product after step S1 is treated by mechanical polishing to remove surface roughness defects and broken layers, so that the surface roughness Ra of the quartz glass product is reduced to below 15nm. S3. The quartz glass products processed in step S2 are treated with chemical mechanical polishing to remove surface damage and defects, thereby reducing the surface roughness Ra of the quartz glass products to below 5 nm.

2. A method for surface treatment of quartz glass products according to claim 1, characterized in that, In step S1, the pretreatment involves treating the surface of the quartz glass product using one or more of the following methods: grinding, flat grinding, and precision sandblasting.

3. A method for surface treatment of quartz glass articles as described in claim 1, characterized in that, In step S2, the polishing abrasive used in the mechanical polishing method is one or more of alumina, silicon carbide, diamond, cerium oxide, and zirconium oxide.

4. A surface treatment method for quartz glass articles according to claim 1, characterized in that, In step S3, the chemical mechanical polishing method is performed using a polishing pad and a polishing liquid. The polishing pad is made of polyurethane or porous polyurethane.

5. A surface treatment method for quartz glass articles according to claim 4, characterized in that, The abrasive in the polishing slurry is nano-silica.

6. A method for surface treatment of quartz glass articles as described in claim 5, characterized in that, The particle size of the nano-silica in the polishing solution is 40 nm.

7. A method for surface treatment of quartz glass articles as described in claim 4, characterized in that, The pH value of the polishing solution is 9-10.

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