Cleaning system of glass substrate for photomask plate and cleaning method thereof

Abstract

The invention relates to a cleaning system of a glass substrate for a photomask plate and a cleaning method thereof, and the cleaning system comprises a first cleaning module and a pickling module; the first cleaning module comprises a first cleaning tank and a first rinsing tank which are sequentially arranged in the conveying direction of a glass substrate to be cleaned. The first cleaning tank is provided with a first cleaning solution, the first cleaning solution comprises a surfactant and an oxidizing agent, and the first cleaning tank is provided with an ultrasonic device; the first rinsing tank is provided with first rinsing liquid and an ultrasonic device; the pickling module is arranged at the downstream of the first cleaning module in the conveying direction of the glass substrate, and the pickling module comprises a first pickling tank, a second pickling tank and an acid liquor flushing tank which are sequentially arranged in the conveying direction of the glass substrate to be cleaned; the first pickling tank is provided with a second pickling solution; the second pickling tank is provided with a second pickling solution; and acid flushing liquid is arranged in the acid liquid flushing tank. The cleaning effect can be effectively improved, and meanwhile white spot corrosion on the surface of the substrate is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photomask substrate processing, in particular to a photomask plate cleaning system and a cleaning method thereof. BACKGROUND

[0002] The photomask substrate, also known as the uniform glue chromium plate, is the mainstream photosensitive material for current and future microfabrication photomask manufacturing. Its core mission is to serve as the "genetic blueprint" of integrated circuits. In the photolithography process, the designed micro-nano circuit pattern is repeatedly transferred to the surface of a silicon wafer with extremely high precision and consistency. This process determines the performance and quality of the chip. Therefore, the cleanliness and integrity of the photomask plate itself are crucial. Any small particles, organic matter or metal ion cross-contamination will cause transfer distortion.

[0003] The photomask substrate is mainly composed of a substrate and a chromium layer. The substrate material is mainly glass. In order to obtain a high-precision photomask plate, the glass substrate is required to have high flatness and high smoothness. In order to obtain a glass substrate with high flatness and high smoothness, a chemical mechanical polishing process is usually used to polish the substrate material. During the polishing process, a polishing liquid including components such as cerium oxide, aluminum oxide and silicon oxide is usually used as a polishing auxiliary material. After polishing, the particles such as cerium oxide, aluminum oxide and silicon oxide in the polishing liquid and organic matter will adhere to the surface of the glass substrate. Therefore, the surface of the glass substrate needs to be cleaned in the subsequent process to meet the needs of the subsequent process. The existing cleaning system usually uses an ultrasonic cleaning tank, a strong acid tank and a rinsing tank / washing tank to clean the surface of the polished glass substrate.

[0004] However, the existing cleaning system has poor cleaning effect on the polished glass substrate, and there are still a large number of particles on the surface of the substrate after cleaning (the particle removal rate is only about 60%), and white spot corrosion easily occurs on the surface of the substrate. SUMMARY

[0005] Therefore, the purpose of the present application is to overcome the defects or deficiencies of the prior art. On the one hand, a cleaning system for a glass substrate of a photomask plate is provided, which can effectively reduce the number of particles on the surface of the substrate after cleaning, improve the cleaning effect, and avoid corrosion of the glass substrate during the cleaning process.

[0006] A cleaning system for a glass substrate of a photomask plate, comprising a first cleaning module and an acid cleaning module; The first cleaning module comprises a first cleaning tank and a first rinsing tank arranged in sequence along the conveying direction of the glass substrate to be cleaned. The first cleaning tank is provided with a first cleaning liquid, and the first cleaning tank is provided with an ultrasonic device, and the glass substrate immersed in the first cleaning liquid can be ultrasonically cleaned. The first rinsing tank is provided with a first rinsing liquid, and the first rinsing tank is provided with an ultrasonic device, and the glass substrate immersed in the first rinsing liquid can be ultrasonically rinsed. The acid washing module is arranged downstream of the first cleaning module along the glass substrate conveying direction, and the acid washing module comprises a first acid washing tank, a second acid washing tank and an acid liquid flushing tank arranged in sequence along the conveying direction of the glass substrate to be cleaned. The first acid washing tank is provided with a first acid washing liquid, and the first acid washing tank can perform acid washing on the glass substrate immersed in the first acid washing liquid, wherein the first acid washing liquid has a dehydrating property. The second acid washing tank is provided with a second acid washing liquid, and the second acid washing tank can perform acid washing on the glass substrate immersed in the second acid washing liquid, wherein the solute concentration in the second acid washing liquid is lower than the solute concentration in the first acid washing liquid. The acid liquid flushing tank is provided with an acid flushing liquid, and the glass substrate immersed in the acid liquid flushing tank can be flushed.

[0007] Compared with the prior art, the cleaning system for the glass substrate of the photomask plate disclosed by the application is based on the analysis of the residual particulate matter on the surface of the glass substrate after the conventional cleaning process, and the glass substrate is sequentially subjected to acid washing by concentrated acid and dilute acid. The dehydrating property of the concentrated acid carbonizes the organic matter, fingerprint stains and biofilm on the glass substrate. Then, the carbonized matter is removed by the acidity of the dilute acid, and the solubility of metal ions is increased to reduce the metal residues on the surface of the substrate, thereby improving the cleaning effect. At the same time, the dilute acid is used as a transitional cleaning before the glass substrate is rinsed, which can avoid the formation of a film layer on the surface of the glass substrate due to the generation of acid vapor when the high-temperature concentrated acid directly enters the normal-temperature water environment, thereby preventing the corrosion of the glass substrate.

[0008] In some embodiments, the first acid washing liquid is concentrated sulfuric acid, and the second acid washing liquid is dilute sulfuric acid.

[0009] In some embodiments, the cleaning system for the glass substrate of the photomask plate further comprises a second cleaning module arranged downstream of the acid washing module along the conveying direction of the glass substrate; the second cleaning module comprises a second cleaning tank and a second rinsing tank arranged in sequence along the conveying direction of the glass substrate; the second cleaning tank is provided with a second cleaning liquid, and the second cleaning tank is provided with an ultrasonic device, and the glass substrate immersed in the second cleaning liquid can be ultrasonically cleaned; the second rinsing tank is provided with a second rinsing liquid, and the second rinsing tank is provided with an ultrasonic device, and the glass substrate immersed in the second rinsing liquid can be ultrasonically rinsed.

[0010] In some embodiments, the cleaning system for the glass substrate for photomask plate further comprises a third cleaning module arranged downstream of the second cleaning module along the glass substrate conveying direction; the third cleaning module comprises a third cleaning tank and at least one third rinsing tank arranged in sequence along the glass substrate conveying direction; the third cleaning tank is provided with a third cleaning liquid, and the third cleaning tank is provided with an ultrasonic device to perform ultrasonic cleaning on the glass substrate immersed in the third cleaning liquid; the third rinsing tank is provided with a third rinsing liquid, and the third rinsing tank is provided with an ultrasonic device to perform ultrasonic rinsing on the glass substrate immersed in the third rinsing liquid.

[0011] In some embodiments, the third rinsing tank has a tank body for accommodating the glass substrate, and the material of the tank body is plastic.

[0012] In some embodiments, the cleaning system for the glass substrate for photomask plate further comprises a drying module arranged downstream of the third cleaning module along the glass substrate conveying direction; the drying module comprises a drying tank to perform dehydration drying treatment on the glass substrate.

[0013] In another aspect, the present application also provides a cleaning method for a glass substrate for photomask plate, comprising the following steps: First cleaning: immersing the glass substrate to be cleaned into a first cleaning liquid to perform ultrasonic cleaning on the glass substrate, and then immersing the glass substrate into a first rinsing liquid to perform ultrasonic rinsing on the glass substrate, wherein the first cleaning liquid comprises a surfactant and an oxidizing agent. Pickling: immersing the glass substrate into a first pickling liquid to perform first pickling on the glass substrate, and then immersing the glass substrate into a second pickling liquid to perform pickling on the glass substrate, wherein the first pickling liquid has a dehydration property, and the solute concentration in the second pickling liquid is lower than that in the first pickling liquid.

[0014] In some embodiments, the cleaning method for the glass substrate for photomask plate further comprises the following steps after pickling: Second cleaning: immersing the glass substrate into a second cleaning liquid to perform ultrasonic cleaning on the glass substrate, and then immersing the glass substrate into a second rinsing liquid to perform ultrasonic rinsing on the glass substrate.

[0015] In some embodiments, the cleaning method for the glass substrate for photomask plate further comprises the following steps after the second cleaning: Third cleaning: immersing the glass substrate into a third cleaning liquid to perform ultrasonic cleaning on the glass substrate, and then immersing the glass substrate into a third rinsing liquid to perform ultrasonic rinsing on the glass substrate.

[0016] In some embodiments, the cleaning method for the glass substrate for photomask plate further comprises the following step at the end: Drying: drying treatment is performed on the glass substrate.

[0017] For better understanding and implementation, the present application is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Structure diagram of the cleaning system for the glass substrate for photomask plate according to Embodiment 1 of the present application; Figure 2 Structure diagram of the cleaning system for the glass substrate for photomask plate according to Embodiment 2 of the present application; Figure 3 Structure diagram of the cleaning system for the glass substrate for photomask plate according to Embodiment 3 of the present application; Figure 4 Structure diagram of the third rinsing tank in the cleaning system for the glass substrate for photomask plate according to Embodiment 4 of the present application; Figure 5 View shown on the detection instrument before cleaning the glass substrate (substrate 1) in the cleaning system for the glass substrate for photomask plate according to Embodiment 4 of the present application; Figure 6 View shown on the detection instrument after cleaning the glass substrate (substrate 1) in the cleaning system for the glass substrate for photomask plate according to Embodiment 4 of the present application; Figure 7 View shown on the detection instrument before cleaning the glass substrate (substrate 1) in the cleaning system for the glass substrate for photomask plate according to Comparative Embodiment 1 of the present application; Figure 8 View shown on the detection instrument after cleaning the glass substrate (substrate 1) in the cleaning system for the glass substrate for photomask plate according to Comparative Embodiment 1 of the present application; Figure 9 View shown under light after cleaning the glass substrate (substrate 1) in the cleaning system for the glass substrate for photomask plate according to Comparative Embodiment 1 of the present application; Figure 10 View shown on the detection instrument after cleaning the glass substrate (substrate 1) in the cleaning system for the glass substrate for photomask plate according to Comparative Embodiment 2 of the present application; Figure 11 View shown under light after cleaning the glass substrate (substrate 1) in the cleaning system for the glass substrate for photomask plate according to Comparative Embodiment 2 of the present application; Figure 12 View shown on the detection instrument after cleaning the glass substrate (substrate 1) in the cleaning system for the glass substrate for photomask plate according to Comparative Embodiment 3 of the present application; Figure 13The view shown under light after the cleaning system for the glass substrate of the photomask plate of the present application cleaned the glass substrate (substrate 1) of comparative example 3.

[0019] Reference signs: 10, first cleaning module; 11, first cleaning tank; 12, first rinsing tank; 20, pickling module; 21, first pickling tank; 22, second pickling tank; 23, acid liquid rinsing tank; 31, drying tank; 40, second cleaning module; 41, second cleaning tank; 42, second rinsing tank; 50, third cleaning module; 51, third cleaning tank; 52, third rinsing tank; 520, water bath tank; 521, rinsing tank body; 522, ultrasonic vibration plate. DETAILED DESCRIPTION

[0020] After the glass substrate for making a photomask plate is treated by a polishing process, particles such as cerium oxide, aluminum oxide and silicon oxide contained in the polishing liquid adhere to the surface of the substrate, so the surface of the glass substrate needs to be cleaned by a cleaning process to make the smoothness of the substrate surface meet the needs of subsequent process treatment. At present, when cleaning the substrate, strong acid pickling is mostly used in combination with ultrasonic cleaning, rinsing and rinsing to clean the substrate.

[0021] The existing cleaning system usually adopts ultrasonic cleaning tank, strong acid tank and rinsing tank / rinsing tank in combination. The glass substrate is first treated by ultrasonic cleaning to remove the particles on the surface of the substrate; the dehydration of concentrated sulfuric acid is used to carbonize the organic matter, fingerprint oil stain and biological membrane on the surface of the substrate under high temperature conditions, and then a large amount of pure water is used to rinse the glass substrate to remove the carbide, particles and residual pickling liquid on the surface of the glass substrate. However, in the actual production process, the cleaning effect of the above cleaning method is often not ideal. When the equipment detects the cleaned glass substrate, it is found that there are still a large number of particles on the surface of the glass substrate, and the particle removal rate before and after cleaning only reaches 60%, and white spot corrosion appears on the glass substrate.

[0022] After the inventors analyzed the particles on the substrate cleaned by the above-mentioned existing cleaning process, it was found that most of the particles remaining on the surface of the glass substrate were carbides, that is, the particles carbonized and adhered to the surface of the substrate by the large amount of water in the rinsing tank were not effectively removed, and directly rinsing the glass substrate carrying concentrated acid, the concentrated acid was easily evaporated into acid vapor and adhered to the glass substrate, forming a film layer that could not be removed by subsequent processes, and then forming white spot corrosion on the surface of the glass substrate.

[0023] Based on the above, the application provides a cleaning system and method for a glass substrate for a photomask plate, wherein a tank containing dilute acid is arranged downstream of the strong acid tank along the substrate conveying direction, the carbon compound formed after the concentrated acid treatment is further dissolved by the acidity of the dilute acid, the cleaning effect is improved, a "transition cleaning" is formed between the concentrated acid pickling and the pure water flushing, the acid vapor formed by the evaporation of the concentrated acid in the flushing process is prevented from adhering to the surface of the substrate, a film layer that cannot be removed by the subsequent process is formed, and the glass substrate is further corroded.

[0024] Based on the above preparation design idea, the cleaning system and method for a glass substrate for a photomask plate of the application are described in detail below.

[0025] Example 1 Figure 1 The specific structure of one embodiment of the cleaning system for a glass substrate for a photomask plate of the application is shown, wherein the direction indicated by the arrow is the conveying direction of the glass substrate. Figure 1 As shown in the figure, one embodiment of the cleaning system for a glass substrate for a photomask plate of the application includes a first cleaning module 10 and an acid pickling module 20.

[0026] Specifically, the first cleaning module 10 includes a first cleaning tank 11 and a first rinsing tank 12 arranged in sequence along the conveying direction of the glass substrate to be cleaned. The acid pickling module 20 is arranged downstream of the first cleaning module 10 along the conveying direction of the glass substrate, and the acid pickling module 20 includes a first acid pickling tank 21, a second acid pickling tank 22, and an acid liquid flushing tank 23 arranged in sequence along the conveying direction of the glass substrate.

[0027] The first cleaning tank 11 has a body for accommodating the glass substrate, and the body is made of stainless steel. The tank contains a first cleaning solution, which consists of an alkaline cleaning agent, hydrogen peroxide, and water. The alkaline cleaning agent is primarily a surfactant, and the hydrogen peroxide is electronic-grade hydrogen peroxide. The volume ratio of the alkaline cleaning agent to hydrogen peroxide is 1:(1.5-2), and the volume ratio of the mixture of alkaline cleaning agent and hydrogen peroxide to water is 1:(20-50). The alkaline cleaning agent is an alkaline surfactant comprising 1.0-10% surfactant (fatty alcohol polyoxyethylene ether), 1.0-15% potassium hydroxide, 1.0-15% sodium hydroxide, 5.0-20% aminocarboxylic acid chelating agent, 1.0-20% diol solvent, and the remainder is water. The alkaline solution system provides a more stable environment for hydrogen peroxide. After reducing the surface tension of the glass substrate by using an alkaline surfactant, hydrogen peroxide can completely adhere to the particles on the substrate, causing them to oxidize and decompose. The bottom of the first cleaning tank 11 has an oscillating shaft that can vibrate up, down, left, and right, with an oscillation frequency of once every 5-20 seconds. The first cleaning solution in the tank is in an internal circulation state, circulating through a filter element at a flow rate of 20-50 L / min. The first cleaning tank 11 is equipped with an ultrasonic device with a single-frequency ultrasonic frequency of 20-40 kHz and a power of 1.5-2.5 kW.

[0028] During cleaning, the glass substrate to be cleaned is placed in the first cleaning tank 11, which contains the first cleaning solution. The oscillating shaft and ultrasonic device are then activated to perform ultrasonic cleaning on the glass substrate. The cleaning temperature is 30-50℃, and the cleaning time is 300-500 seconds. By ultrasonically cleaning the glass substrate immersed in the first cleaning solution, polishing powder, metal particles, and other particulate matter remaining on the glass substrate after polishing are removed.

[0029] The first rinsing tank 12 has a stainless steel body capable of accommodating a glass substrate. The tank contains a first rinsing solution, specifically pure water. The bottom of the first rinsing tank 12 has a vibrating shaft that can vibrate up, down, left, and right at a frequency of once every 5-20 seconds. The first rinsing solution within the tank is in an internal circulation state, circulating through a filter element at a flow rate of 20-50 L / min. The first rinsing tank 12 is equipped with an ultrasonic device with multiple frequencies, ranging from 20-50 kHz, and a power of 1.5-2.5 kW.

[0030] During cleaning, the glass substrate, after being cleaned in the first cleaning tank 11, is placed in the first rinsing tank 12 containing the first rinsing solution. The oscillating shaft and ultrasonic device are activated, and the ultrasonic device switches back and forth between 2-3 frequencies to perform ultrasonic rinsing on the glass substrate. The cleaning temperature is 30-50℃, and the cleaning time is 300-500 seconds. By circulating and rinsing the glass substrate cleaned in the first cleaning tank 11, particulate matter washed off in the first cleaning tank 11 and contaminants introduced during the cleaning process are removed. At the same time, the first cleaning solution remaining on the surface of the glass substrate is removed to prevent the alkaline first cleaning solution from being introduced into the subsequent pickling tank, which would cause acid-base neutralization and weaken the pickling effect.

[0031] The first pickling tank 21 has a tank body for accommodating the glass substrate, and the tank body is made of PP (polypropylene). The tank body contains a first pickling solution, which is composed of concentrated sulfuric acid with a concentration of 98%.

[0032] During cleaning, the glass substrate, after being cleaned in the first rinsing tank 12, is placed in the first pickling tank 21 containing the first pickling solution. The glass substrate undergoes its first pickling process using the first pickling solution at a temperature of 90-110℃ for 300-500 seconds. The dehydrating properties of the high-concentration sulfuric acid rapidly dehydrate and carbonize organic matter, fingerprints, oil stains, and biofilms adhering to the surface of the glass substrate. Furthermore, the strong oxidizing properties of the concentrated sulfuric acid oxidize the carbonized substances into carbon dioxide and water vapor, thereby removing the carbonized substances.

[0033] The second pickling tank 22 has a tank body for accommodating the glass substrate, and the tank body is made of PP. The tank body contains a second pickling solution, which is composed of 50% dilute sulfuric acid and water, wherein the ratio (volume ratio) of 50% dilute sulfuric acid to water is 1:(20-30).

[0034] During cleaning, the glass substrate, after being cleaned in the first pickling tank 21, is placed inside. A second pickling solution is then applied to the glass substrate for a second pickling process. The pickling temperature is 50-70℃, and the pickling time is 100-300 seconds. Because the sulfuric acid concentration in the second pickling solution is low, it has almost no oxidizing properties. During pickling, the acidity of the dilute sulfuric acid dissolves the carbides still adhering to the substrate surface, further removing residues. Simultaneously, compared to concentrated sulfuric acid, dilute sulfuric acid increases the solubility of metal oxides, thereby reducing metal ion residues on the glass substrate surface.

[0035] The acid rinsing tank 23 has a tank body that can accommodate the glass substrate, and the tank body is made of PP. The tank body contains an acid rinsing solution, specifically ultrapure water. In this embodiment, the rinsing tank 50 is a QDR tank (Quick Drain Spray Rinsing Tank), which is commercially available. The QDR tank can realize overflow, water injection, spraying, drainage, and bubbling functions. By rapidly injecting ultrapure water from the bottom of the tank body, and overflowing and bubbling from the bottom of the tank body, residual sulfuric acid on the glass substrate is continuously carried away. After completing the rapid water injection, overflow, and bubbling, the water in the tank body is rapidly drained to prevent residual acid from the previous acid pickling process from forming a film layer that is difficult to remove by subsequent cleaning processes due to evaporation or reaction. The water drainage is accompanied by spraying, keeping the glass substrate moist and preventing water stains from remaining on the substrate surface due to a period of air drying.

[0036] During cleaning, the glass substrate that has been pickled in the second pickling tank 22 is placed in the acid rinsing tank 23. The glass substrate is rinsed by bubbling with continuously flowing ultrapure water. The rinsing temperature is room temperature and the rinsing time is 100-300 seconds.

[0037] In the aforementioned cleaning system, the alkaline first cleaning solution in the first cleaning tank 11, combined with ultrasonic vibration, can wash away most of the particulate matter adhering to the surface of the glass substrate. However, the first rinsing tank 12 removes the washed-off particulate matter and the alkaline first cleaning solution remaining on the glass substrate surface, preventing the introduction of alkaline solution into the subsequent acid washing process, which would cause acid-base neutralization and weaken the acid washing effect. Next, a first acid wash is performed on the glass substrate using high-concentration sulfuric acid at high temperature. The dehydrating properties of the concentrated sulfuric acid rapidly dehydrate and carbonize organic matter, fingerprints, oil stains, and biofilms adhering to the surface of the glass substrate. The strong oxidizing properties of concentrated sulfuric acid are used to convert carbides into water and carbon dioxide. Following this, a second acid wash is performed on the glass substrate using dilute sulfuric acid. The acidity of the dilute sulfuric acid dissolves or loosens the carbides and metal oxides remaining on the surface of the glass substrate, further removing carbide particles and reducing metal residue. Finally, the glass substrate is bubble-washed with continuously flowing ultrapure water to thoroughly remove any undissolved but loosened particles, ensuring the glass substrate surface remains highly clean.

[0038] To improve the carbonization capacity and efficiency of concentrated sulfuric acid in the first pickling tank 21, the operating temperature of the first pickling tank 21 is 90-110℃. However, if the glass substrate treated with concentrated acid at this temperature is directly placed into the acid rinsing tank 23 and rinsed at room temperature, the glass substrate will break due to the rapid temperature change. Therefore, a second pickling tank 22 is set between the first pickling tank 21 and the acid rinsing tank 23. In addition to dissolving the carbides remaining on the substrate surface with the second pickling solution, the second pickling tank 22 also serves as a "transition tank" between the first pickling tank 21 and the acid rinsing tank 23. This prevents the glass substrate from being directly transferred from a high-concentration acid environment to a pure water environment, which would generate acid vapor and adhere to the glass substrate. It also prevents the glass substrate from cracking due to a sudden change from a high-temperature environment to a room-temperature environment.

[0039] Furthermore, in order to dry the cleaned glass substrate, the cleaning system also includes a drying module located downstream of the pickling module 20 in the glass substrate conveying direction.

[0040] Specifically, the drying module includes a drying tank 31, which is a slow-lift drying tank with a body for accommodating the glass substrate. The body of the tank is made of stainless steel. The glass substrate is dried and dehydrated by lifting it at extremely low speeds. The drying tank 31 is also equipped with a carbon dioxide generator. By introducing carbon dioxide, static electricity on the surface of the glass substrate is removed, preventing particles from re-adhering to the surface of the glass substrate.

[0041] During cleaning, the glass substrate that has undergone the previous cleaning / acid washing / rinsing process is placed in the drying tank 31 for drying. The slow lifting speed is 200-300 mm / min, the drying temperature is 50-60℃, and the drying time is 300-400 seconds.

[0042] To automate the cleaning process, a transfer module can be added to the aforementioned cleaning system to transport the glass substrate along a specific direction. This transfer module is specifically a robotic arm, which picks up and places the glass substrate between different tanks. Since transferring materials along a specific direction using a robotic arm is existing technology, it will not be described in detail here.

[0043] Example 2 Figure 2 The specific structure of Embodiment 2 of the cleaning system for the glass substrate of the photomask of the present invention is shown. The only difference between the cleaning system for the glass substrate of the photomask in this embodiment and Embodiment 1 is that the cleaning system in this embodiment further includes a second cleaning module 40. Figure 2As shown, in this embodiment, the second cleaning module 40 is located downstream of the pickling module 20 along the glass substrate conveying direction to be cleaned. The second cleaning module 40 includes a second cleaning tank 41 and a second rinsing tank 42 arranged sequentially along the glass substrate conveying direction.

[0044] Specifically, the second cleaning tank 41 has a tank body capable of accommodating the glass substrate, and the tank body is made of stainless steel. A second cleaning solution is contained within the tank, and the composition of the second cleaning solution is the same as that of the first cleaning solution. The bottom of the second cleaning tank 41 has an oscillating shaft that can vibrate up, down, left, and right, with an oscillation frequency of once every 5-20 seconds. The second cleaning solution within the tank is in an internal circulation state, circulating through a filter element at a flow rate of 20-50 L / min. The second cleaning tank 41 is equipped with an ultrasonic device, which has multiple frequencies, ranging from 40-100 kHz, and a power of 1.8-2.5 kW.

[0045] During cleaning, the glass substrate is placed in the second cleaning tank 41, which contains the second cleaning solution. The oscillating shaft and ultrasonic device are activated, and the ultrasonic device switches between 2-3 frequencies to perform ultrasonic cleaning on the glass substrate. The cleaning temperature is 30-50℃, and the cleaning time is 300-500 seconds. By ultrasonically cleaning the glass substrate immersed in the second cleaning solution at a higher ultrasonic frequency than that in the first cleaning tank 11, in addition to further removing larger particles such as polishing powder and particulate metal remaining on the glass substrate, it is also possible to remove fine particles.

[0046] The second rinsing tank 42 has a body capable of accommodating a glass substrate, and the body is made of stainless steel. The tank contains a second rinsing solution, specifically pure water. Similar to the first rinsing tank 12, the bottom of the second rinsing tank 42 has a vibrating shaft that can vibrate up, down, left, and right, with a vibration frequency of once every 5-20 seconds. The second rinsing solution within the tank is in an internal circulation state, circulating through a filter element at a flow rate of 20-50 L / min. The second rinsing tank 42 is equipped with an ultrasonic device with multiple frequencies, ranging from 80-180 kHz, and a power of 1.5-2.5 kW.

[0047] During cleaning, the glass substrate, after being cleaned in the first cleaning tank 41, is placed in the second rinsing tank 42 containing the second rinsing solution. The oscillating shaft and ultrasonic device are activated, and the ultrasonic device switches back and forth between 2-3 frequencies to perform ultrasonic cleaning on the glass substrate. The rinsing temperature is 30-50℃, and the rinsing time is 300-500s. By circulating and rinsing the glass substrate cleaned in the second cleaning tank 41, the cleaning solution eluted in the second cleaning tank 41, residual pickling solution and particulate matter from the previous process, as well as contaminants introduced during the cleaning process, are removed.

[0048] Thus, by performing a second cleaning and rinsing process on the glass substrate through the second cleaning module 40, the cleaning solution, pickling solution and particulate matter that may remain on the surface of the glass substrate after the cleaning by the first cleaning module 10 and the pickling module 20 can be further removed, thereby further improving the surface cleanliness of the glass substrate after cleaning.

[0049] Example 3 After the first cleaning module 10 and the second cleaning module 40, most of the particulate matter, organic matter, fingerprints, oil stains, and biofilms adhering to the glass substrate surface from the polishing process have been removed. However, fine particles still remain on the glass substrate surface and were not completely removed in the previous cleaning process. Furthermore, as the number of functional modules in the cleaning system increases, the robotic arm's travel distance also increases, leading to wear during operation. The resulting fine debris may adhere to the glass substrate during this process. To address this issue... Figure 3 The specific structure of Embodiment 3 of the cleaning system for the glass substrate of the photomask of the present invention is shown. The only difference between the cleaning system for the glass substrate of the photomask in this embodiment and Embodiment 2 is that Embodiment 3 further includes a third cleaning module 50. Figure 3 As shown, the third cleaning module 50 is located downstream of the second cleaning module 40 along the glass substrate conveying direction. The third conveying module 50 includes a third cleaning tank 51 and three third rinsing tanks 52 arranged sequentially along the glass substrate conveying direction.

[0050] Specifically, the third cleaning tank 51 has a tank body capable of accommodating the glass substrate, and the tank body is made of stainless steel. The tank body contains a third cleaning solution, which is composed of electronic-grade NH4OH, electronic-grade hydrogen peroxide, and ultrapure water in a ratio of 1:(1-3):50. In this embodiment, the third cleaning tank 51 is specifically an SC-1 (Standard Clean 1) ultrasonic cleaning tank, which is commercially available. The SC-1 ultrasonic cleaning tank is equipped with an ultrasonic device with multiple frequencies, ranging from 80-180 kHz, and a power of 2.5-3.0 kW.

[0051] During cleaning, the glass substrate that has been circulated in the second rinsing tank 42 is placed in the third cleaning tank 51 containing the third cleaning solution. The ultrasonic device is started, and the glass substrate is ultrasonically cleaned by switching back and forth between 2-3 frequencies. The cleaning temperature is 30-50℃, and the rinsing time is 300-500s to remove fine particles from the surface of the glass substrate.

[0052] The third rinsing tank 52 has a tank body capable of accommodating the glass substrate, and the tank body is made of stainless steel. The tank contains a first rinsing solution and a third rinsing solution, the third rinsing solution being ultrapure water. The third rinsing tank 52 is equipped with an ultrasonic device, specifically including an ultrasonic transducer plate disposed at the bottom of the tank body, which can perform ultrasonic cleaning on the glass substrate immersed in the third rinsing solution. Figure 3 As shown, the cleaning system of this embodiment includes three third rinsing tanks 52. The ultrasonic devices of the three third rinsing tanks 52 are all 2.5-3.0KW in power, and the ultrasonic frequencies are 400-500KHZ, 500-600KHZ and 600-700KHZ respectively (along the glass substrate conveying direction).

[0053] During cleaning, the glass substrate is sequentially immersed in each of the third rinsing tanks 52, and the ultrasonic device is activated. By switching between 3-5 frequencies, the glass substrate is ultrasonically rinsed sequentially. By using multiple third rinsing tanks 52 for ultrasonic rinsing of the glass substrate, and by gradually increasing the ultrasonic frequency, the rinsing force is gradually enhanced, which can more effectively remove fine particles and particles that have re-adhered to the surface of the glass substrate after previous processes. Compared to rinsing with large amounts of ultrapure water, this embodiment, by setting up multiple water bath ultrasonic tanks and cleaning in stages, achieves high cleaning efficiency and powerful force, saving water while achieving the same level of cleanliness as rinsing with large amounts of ultrapure water.

[0054] Of course, if the cleanliness of the substrate surface is required to be very high, four, five or even more third rinsing tanks 52 can be set as needed; while if the cleanliness of the substrate surface is not required to be so high, one or two third rinsing tanks 52 can be set as needed.

[0055] Since the first cleaning module 10, the acid washing module 20 and the second cleaning module 40 have already removed the larger particles, the third cleaning module 50 is set up to target the smaller particles and the metal impurities introduced during the transfer process. This can more effectively improve the cleaning efficiency and the cleaning effect, thereby improving the cleanliness of the glass substrate.

[0056] Example 4 Although the cleaning system of Example 3 has greatly improved the surface cleanliness of the glass substrate, the inventors found in actual production practice that some metal particles still adhered to the surface of the glass substrate after cleaning by the system of Example 3. After analyzing each process of the cleaning system of Example 3, the inventors found that the metal particles mainly came from the metal tank body of the third rinsing tank 52. Since the metal tank body is conducive to the ultrasonic vibration generated by the metal ultrasonic plate to improve the ultrasonic cleaning effect, the tank body and ultrasonic plate of the third rinsing tank 52 are usually made of stainless steel. However, the metal tank body is prone to generating fine metal particles under the vibration generated by the ultrasonic plate, and these fine metal particles adhere to the glass substrate with the third rinsing solution. To solve this problem, the third rinsing tank 52 was improved based on Example 3. Figure 4 The specific structure of the third rinsing tank 52 in the cleaning system of Embodiment 4 of the present invention is shown. For example... Figure 4 As shown, the third rinsing tank 52 in this embodiment includes a water bath 520, a rinsing tank body disposed within the water bath, and an ultrasonic transducer plate 522 disposed at the bottom of the water bath. The rinsing tank body is used to accommodate the glass substrate. The rinsing tank body is made of plastic, specifically PP in this embodiment. PP has ultra-high cleanliness. The water bath method allows the glass substrate to contact the metal water bath and ultrasonic transducer plate, which can prevent the introduction of metal particles into the glass substrate during ultrasonic rinsing and improve the cleanliness of the glass substrate after cleaning.

[0057] More preferably, except for the third rinsing tank 52, the tank bodies of the second cleaning tank 41, the second rinsing tank 42, the third cleaning tank 51 and the drying tank 31 are all made of PP or PE material to further reduce the introduction of metal contamination.

[0058] The following comparison of the results of Example 4 with those of Comparative Examples 1-3 further illustrates the technical effect of the cleaning system for glass substrates used in photomasks of the present invention.

[0059] Comparative Examples 1-3 The only difference between Comparative Example 1 and Example 4 is that the acid pickling module 20 of the cleaning system in Comparative Example 1 does not have a second acid pickling tank 22. The other modules, the order of module setup, and the technical parameters (including ultrasonic frequency, cleaning / rinsing time, and cleaning / rinsing temperature) set in each functional tank during the cleaning process are the same as in Example 4.

[0060] The only difference between Comparative Example 2 and Example 4 is that in the pickling module 20 of the cleaning system in Comparative Example 2, the order of the first pickling tank 21 and the second pickling tank 22 is swapped. The other modules, the order of module settings, and the technical parameters (including ultrasonic frequency, cleaning / rinsing time, and cleaning / rinsing temperature, etc.) set in each functional tank during the cleaning process are the same as in Example 4.

[0061] The only difference between Comparative Example 3 and Example 4 is that the material of the third rinsing tank 52 in the third cleaning module of the cleaning system in Comparative Example 3 is stainless steel. The other modules, the order of module setup, and the technical parameters (including ultrasonic frequency, cleaning / rinsing time, and cleaning / rinsing temperature) set in each functional tank during the cleaning process are the same as in Example 4.

[0062] Test (or validation) method Sixteen glass substrates from the same batch, treated with the same polishing process, were cleaned using the cleaning systems of Example 4 and Comparative Examples 1-3 (four glass substrates were cleaned in each example / comparative example). The number of particles on the substrate surface before and after cleaning in Examples 4 and 1-3 was then measured using a testing instrument. The particle removal rate was calculated, and the appearance of the substrates was observed visually. The results are shown in Table 1 below. Table 1

[0063] As can be seen from the test results in Table 1, after cleaning with the cleaning system of Example 4, the number of particles on the substrate surface decreased from tens of thousands to tens of particles, and the particle removal rate was as high as 99%. Figures 5-6 The images show the surface of substrate 1 before and after cleaning using the cleaning system of Example 4, as inspected by an instrument. (Comparison) Figure 5 and Figure 6 As can be seen directly, before cleaning, a large number of particles were densely distributed on the surface of substrate 1. After cleaning by the cleaning system of Example 4, almost no particle residue was visible on the surface of substrate 1, and the cleaning effect was significant.

[0064] In contrast, in Example 1, no dilute sulfuric acid was used after concentrated sulfuric acid pickling. A large number of particles were still attached to the cleaned glass substrate, and the particle removal rate was only 60%. Figures 7-8 The surfaces of substrate 1 before and after cleaning using the cleaning system of Comparative Example 1 are shown, as detected by instruments. Figure 7 and Figure 8 It can be visually observed that the distribution of particles on substrate 1 is more uniform after cleaning, but the density has not changed significantly. A large number of particles still remain on the surface of substrate 1 after cleaning, and white corrosion spots (such as...) can be observed on the surface of substrate 1 after cleaning. Figure 9(As indicated by the dashed line). The reason for this is that when the glass substrate is acid-washed with high-temperature concentrated sulfuric acid, the dehydrating property of the concentrated sulfuric acid will rapidly carbonize the organic matter, fingerprints, oil stains, and biofilm on the substrate surface. Its strong oxidizing property will further oxidize the carbides to generate carbon dioxide and water to remove the carbides. However, as the cleaning process continues, the concentrated sulfuric acid is consumed, and the carbides removal effect weakens. Therefore, a lot of carbides remain on the substrate surface and cannot be completely removed. When the glass substrate is directly immersed in room temperature pure water from the high-temperature, high-concentration concentrated sulfuric acid environment, the acid vapor carried by the substrate is evaporated into acid vapor and adheres to the surface of the glass substrate, forming a film layer that is difficult to remove in subsequent processing steps. This results in white spot corrosion on the surface of the glass substrate. Furthermore, due to the drastic temperature change in the cleaning environment, the glass substrate is prone to cracking.

[0065] By comparing the cleaning system in Example 2, the number of particles on the surface of substrate 1 was significantly reduced after cleaning, with a particle removal rate reaching 90%. However, due to... Figure 10 As shown in the instrumental analysis of the surface of substrate 1 after cleaning with the cleaning system of Comparative Example 2, it can be clearly seen that a relatively large amount of particulate matter remains on the surface of substrate 1 after cleaning with Comparative Example 2, and its surface cleanliness is far inferior to that of the substrate surface cleaned with the cleaning system of Example 4. The reason for this is that Comparative Example 2 uses a two-stage acid wash with dilute and concentrated sulfuric acid, which is more effective at removing organic matter, oil, and biofilm compared to Comparative Example 1. However, after the concentrated sulfuric acid wash, the glass substrate was not subjected to a subsequent transition acid wash; instead, it was directly placed in a room-temperature pure water environment. Therefore, the glass substrate exhibits the same white spot corrosion as in Comparative Example 1 (e.g., ...). Figure 11 (As indicated by the dashed line), and there is a risk of substrate breakage.

[0066] By comparing the cleaning system of Example 3, the number of particles on the surface of substrate 1 was significantly reduced after cleaning, with a particle removal rate of 90%. However, due to... Figure 12 As shown in the instrumental analysis of the surface of substrate 1 after cleaning with the cleaning system of Comparative Example 2, it can be clearly seen that a small amount of particulate matter remains on the surface of the glass substrate after cleaning with the cleaning system of Comparative Example 3, and its surface cleanliness is far inferior to that of the glass substrate after cleaning with the cleaning system of Example 4. Visual observation reveals that the surface of the glass substrate cleaned with the cleaning system of Comparative Example 3 contains fine metal particulate contaminants (such as…). Figure 13 (As indicated by the dashed line). The reason for this is that although Comparative Example 3 includes an SC-1 ultrasonic bath to remove metal particles adhering to or introduced by the aforementioned cleaning process from the glass substrate surface, the material of the third rinsing tank 52 in the third cleaning module of the water bath ultrasonic bath for accommodating the glass substrate is stainless steel. While the stainless steel tank is advantageous for coordinating with the ultrasonic vibrations generated by the metal ultrasonic transducer plate, enhancing the ultrasonic cleaning effect, it may also introduce tiny metal particles that adhere to the glass substrate, leading to metal contamination.

[0067] Based on the above analysis of the cleaning effects of Example 4 and Comparative Examples 1-3, the present invention achieves an extremely high particle removal rate by setting a second pickling tank 22 containing dilute sulfuric acid downstream of the first pickling tank 21 containing concentrated sulfuric acid, so as to sequentially perform strong acid pickling and dilute acid pickling treatment on the glass substrate. Combined with the plastic rinsing tank of the third rinsing tank 52 in the third cleaning module, the surface of the cleaned substrate is smooth and free from corrosion.

[0068] Compared to existing technologies, the cleaning system for glass substrates used in photomasks described in this invention is based on the analysis of particulate matter remaining on the surface of the glass substrate after traditional cleaning processes. It sequentially acid-washes the glass substrate with concentrated and dilute acids. The concentrated acid's dehydrating properties carbonize organic matter, fingerprints, oil stains, and biofilms on the glass substrate, while the dilute acid removes the carbonized material and increases the solubility of metal ions, reducing metal residue on the substrate surface and thus improving the cleaning effect. Simultaneously, using dilute acid as a transitional cleaning before rinsing the glass substrate avoids the formation of acid vapors from high-temperature concentrated acid directly entering a room-temperature water environment, which could form a difficult-to-remove film on the glass substrate surface, causing corrosion. Furthermore, by using a plastic material for the third rinsing tank in the third cleaning module, the introduction of metal contamination is reduced, further improving the cleanliness of the glass substrate surface.

[0069] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments and claims of this application are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that, unless otherwise stated, “a plurality” means two or more; the terms “first,” “second,” “third,” etc., are used only to distinguish and not to describe a particular order or sequence, nor should they be construed as indicating or implying relative importance. The term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items. When the above description relates to drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of this application, those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0070] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A cleaning system for a glass substrate used in photomasks, characterized in that: Includes a first cleaning module and an acid pickling module; The first cleaning module includes a first cleaning tank and a first rinsing tank arranged sequentially along the conveying direction of the glass substrate to be cleaned. The first cleaning tank is equipped with a first cleaning solution and an ultrasonic device, which can perform ultrasonic cleaning on glass substrates immersed in the first cleaning solution. The first cleaning solution includes a surfactant and an oxidant. The first rinsing tank is equipped with a first rinsing solution and an ultrasonic device, which can perform ultrasonic rinsing on the glass substrate immersed in the first rinsing solution. The pickling module is located downstream of the first cleaning module along the glass substrate conveying direction. The pickling module includes a first pickling tank, a second pickling tank and an acid rinsing tank arranged sequentially along the glass substrate conveying direction to be cleaned. The first pickling tank is provided with a first pickling solution, and the first pickling tank can pickle a glass substrate immersed in the first pickling solution, wherein the first pickling solution has dehydrating properties. The second pickling tank is provided with a second pickling solution. The second pickling tank can pickle glass substrates immersed in the second pickling solution, wherein the solute concentration in the second pickling solution is lower than the solute concentration in the first pickling solution. The acid rinsing tank is equipped with acid rinsing solution, which can be used to rinse the glass substrate immersed in the acid rinsing tank.

2. The cleaning system for glass substrates used in photomasks according to claim 1, characterized in that: The first pickling solution is concentrated sulfuric acid, and the second pickling solution is dilute sulfuric acid.

3. The cleaning system for glass substrates used in photomasks according to claim 1, characterized in that: It also includes a second cleaning module disposed downstream of the pickling module along the glass substrate conveying direction; The second cleaning module includes a second cleaning tank and a second rinsing tank arranged sequentially along the glass substrate conveying direction. The second cleaning tank is equipped with a second cleaning solution and an ultrasonic device, which can perform ultrasonic cleaning on the glass substrate immersed in the second cleaning solution. The second rinsing tank is equipped with a second rinsing solution and an ultrasonic device, which can perform ultrasonic rinsing on the glass substrate immersed in the second rinsing solution.

4. The cleaning system for glass substrates used in photomasks according to claim 3, characterized in that: It also includes a third cleaning module disposed downstream of the second cleaning module along the glass substrate conveying direction. The third conveying module includes a third cleaning tank and at least one third rinsing tank arranged sequentially along the glass substrate conveying direction. The third cleaning tank is equipped with a third cleaning solution and an ultrasonic device, which can perform ultrasonic cleaning on the glass substrate immersed in the third cleaning solution. The third rinsing tank is equipped with a third rinsing solution and an ultrasonic device, which can perform ultrasonic rinsing on the glass substrate immersed in the third rinsing solution.

5. The cleaning system for glass substrates used in photomasks according to claim 4, characterized in that: The third rinsing tank has a tank body for accommodating a glass substrate, and the tank body is made of plastic.

6. The cleaning system for glass substrates for photomasks according to any one of claims 1-5, characterized in that: It also includes a drying module disposed downstream of the glass substrate conveying direction in the third cleaning module. The drying module includes a drying tank, which can dehydrate and dry the glass substrate.

7. A method for cleaning a glass substrate for a photomask, characterized in that, Includes the following steps: First cleaning: Immerse the glass substrate to be cleaned in the first cleaning solution and perform ultrasonic cleaning on the glass substrate. After completion, immerse the glass substrate in the first rinsing solution and perform ultrasonic rinsing on the glass substrate. The first cleaning solution includes surfactants and oxidants. Pickling: The glass substrate is immersed in a first pickling solution to perform a first pickling. After completion, the glass substrate is immersed in a second pickling solution to perform a second pickling. The first pickling solution has dehydrating properties, and the solute concentration in the second pickling solution is lower than that in the first pickling solution.

8. The cleaning method for the glass substrate of the photomask according to claim 7, characterized in that: After pickling, the following steps are performed: Second cleaning: Immerse the glass substrate in the second cleaning solution and perform ultrasonic cleaning on the glass substrate. After completion, immerse the glass substrate in the second rinsing solution and perform ultrasonic rinsing on the glass substrate.

9. The cleaning method for the glass substrate of the photomask according to claim 8, characterized in that: After the second cleaning, the following steps are performed: Third cleaning: Immerse the glass substrate in the third cleaning solution and perform ultrasonic cleaning on the glass substrate. After completion, immerse the glass substrate in the third rinsing solution and perform ultrasonic rinsing on the glass substrate.

10. The cleaning method for a glass substrate for a photomask according to any one of claims 7-9, characterized in that: Finally, the following steps are performed: Drying: The glass substrate is dried.

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