Method for cleaning quartz glass substrate for photomask after magnetorheological polishing

Abstract

The invention provides a cleaning method for a quartz glass substrate for a photomask after magnetorheological polishing, and belongs to the technical field of optical element production. The method comprises the following steps: carrying out jet cleaning on a quartz glass substrate subjected to magnetorheological polishing; placing the quartz glass substrate in a mixed solution of diluted hydrochloric acid and citric acid, and carrying out ultrasonic cleaning; placing the quartz glass substrate in an alkaline solution, and carrying out megasonic cleaning; placing the quartz glass substrate in a dilute hydrofluoric acid solution, and carrying out megasonic cleaning; and carrying out Malangori slow pulling drying on the quartz glass substrate. According to the cleaning method for the quartz glass substrate for the photomask after magneto-rheological polishing, all components of the magneto-rheological polishing liquid can be removed and cleaned in a targeted and efficient mode, and it is avoided that particles and organic matter are left on the quartz glass substrate, and follow-up manufacturing and application of the photomask are affected; and convenient and efficient post-cleaning technical support is provided for ultra-precision polishing of the quartz glass substrate for the photomask.

Description

Technical Field

[0001] The present application belongs to the technical field of optical element production, and specifically relates to a method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing. Background Art

[0002] With the rapid development of the era of electronic information intelligence, the development demand of ultra-large-scale integrated circuits and the continuous reduction of process nodes, the manufacturing process has become more and more complex and sophisticated, and the requirements for the accuracy of photomasks used for projection exposure in the photolithography process are getting higher and higher. In addition to being affected by factors such as alignment accuracy, film quality and pattern resolution, the surface flatness of the quartz glass substrate used to carry the coating pattern determines the quality of the photomask. The quartz glass substrate with excellent surface flatness is conducive to the uniformity of the coating in the manufacture of the photomask, thereby ensuring that the critical size and overlay accuracy of the pattern meet the specifications. Compared with traditional single-sided polishing, double-sided polishing can effectively avoid material deformation problems caused by stress differences and bonding errors, and can efficiently achieve uniform removal of the material surface, which has obvious processing advantages for low-thickness flat optical components. At present, double-sided polishing technology can realize the production of quartz glass substrates with relatively high surface flatness (<0.5 microns) on a large scale, thereby meeting the photomask manufacturing specification requirements of mature processes (>55 nanometers). However, in the advanced process stage, especially the photomask quartz glass substrates required for extreme ultraviolet lithography require a surface flatness of no more than 100 nanometers. The double-sided polishing technology is easily affected by the surface shape of the polishing disk and the polishing pad, and it is difficult to achieve local surface control of the quartz glass substrate processing, and cannot meet the production of photomask quartz glass substrates with ultra-high flatness.

[0003] Magnetorheological polishing technology mainly controls magnetorheological fluid polishing liquid through gradient magnetic field and magnetorheological effect. During magnetorheological processing, magnetorheological fluid is injected into the tiny gap formed between the quartz glass substrate and the polishing disk. The relative movement between the quartz glass substrate and the polishing disk causes the magnetorheological fluid to generate shear force on the surface of the quartz glass substrate, and the magnitude of the yield stress of the rheological fluid and the magnetic field distribution can be adjusted to control the micro-removal efficiency and surface quality. Then, through the calculation and correction of the polishing motion path and removal function by computer and software, the polishing process can be effectively controlled to achieve precise polishing and meet the quality requirements of ultra-precision devices.

[0004] In magnetorheological polishing technology, iron powder is commonly used as magnetic sensitive material, cerium oxide is used as polishing abrasive, and some chemical additives are added to improve the rheological properties and abrasive dispersion of the polishing liquid. In the actual polishing process, the polishing liquid inevitably contacts the surface of the quartz glass substrate, and a certain amount of iron particles, iron ions, cerium oxide particles and chemical additives will remain. In order to avoid dilution and deterioration of the polishing liquid, water cannot be used to clean the surface of the quartz glass substrate during processing. Long magnetorheological processing time will cause the polishing liquid to dry and adhere, affecting the surface cleanliness of the quartz glass substrate. Since transition metal ions have unpaired electrons and can absorb ultraviolet light to undergo energy level transitions, residual iron ions will cause the ultraviolet light transmittance of the quartz glass substrate to decrease. If these residual polishing liquid components are not removed, the performance of the photomask quartz glass substrate will be seriously reduced. Therefore, surface cleaning technology is an important link in magnetorheological ultra-precision processing of quartz glass substrates.

[0005] Currently, the advanced cleaning process for precision optical quartz glass substrates uses the RCA cleaning method, but due to the composition of the magnetorheological polishing fluid, the cleaning efficiency is poor, and the residue of particles and organic matter on the quartz glass substrate will affect the subsequent manufacturing application of the photomask. Summary of the invention

[0006] In order to solve at least one of the technical problems existing in the background technology, the present application provides a method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing, which can efficiently remove and clean the various components of the magnetorheological polishing liquid in a targeted manner, avoid the residue of particles and organic matter on the quartz glass substrate and affect the subsequent manufacturing application of the photomask, and provide convenient and efficient post-cleaning technical support for ultra-precision polishing of quartz glass substrates for photomasks.

[0007] The technical solution adopted in this application is:

[0008] The present application embodiment provides a method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing, comprising:

[0009] Performing jet cleaning on the quartz glass substrate after magnetorheological polishing;

[0010] The quartz glass substrate after jet cleaning is placed in a mixture of dilute hydrochloric acid and citric acid for ultrasonic cleaning, and after the cleaning is completed, the residual mixture attached to the quartz glass substrate is removed;

[0011] Placing the quartz glass substrate in an alkaline solution and performing megasonic cleaning, and removing the residual alkaline solution attached to the quartz glass substrate after the cleaning is completed;

[0012] Placing the quartz glass substrate in a dilute hydrofluoric acid solution and performing megasonic cleaning, and removing the residual dilute hydrofluoric acid solution attached to the quartz glass substrate after the cleaning is completed;

[0013] The quartz glass substrate was dried by Marangoni slow pull.

[0014] According to the cleaning method of the quartz glass substrate for photomask after magnetorheological polishing provided in the embodiment of the present application, first, the quartz glass substrate after magnetorheological polishing is jet cleaned, and this process can remove loose particles and some water-soluble polishing liquid components on the surface of the quartz glass substrate and wet the quartz glass substrate, so as to prepare for subsequent more in-depth cleaning; then, the quartz glass substrate after jet cleaning is placed in a mixture of dilute hydrochloric acid and citric acid for ultrasonic cleaning, which can remove metal residues such as iron powder and iron ions, and effectively remove metal impurities left in the magnetorheological polishing process. After the cleaning is completed, the residual mixed liquid attached to the quartz glass substrate is removed to ensure the cleanliness of the surface of the quartz glass substrate, prepare for the next step of cleaning, and avoid the chemical reaction caused by liquid mixing to cause damage to the quartz glass substrate; the third step is to place the quartz glass substrate in an alkaline solution for megasonic cleaning. Sonic wave cleaning, this step is mainly aimed at removing cerium oxide particles and organic residues, effectively removing non-metallic particles and organic substances remaining during the polishing process, removing residual alkaline solution attached to the quartz glass substrate after cleaning, ensuring the cleanliness of the surface of the quartz glass substrate, preparing for the next cleaning step, and avoiding liquid mixing to produce chemical reactions that cause damage to the quartz glass substrate; the fourth step is to place the quartz glass substrate in a dilute hydrofluoric acid solution for megasonic cleaning, this step is specifically aimed at removing embedded particles, while improving the hydrophilicity of the surface of the quartz glass substrate, removing residual dilute hydrofluoric acid solution attached to the quartz glass substrate after cleaning, ensuring the cleanliness of the surface of the quartz glass substrate, preparing for the next cleaning step, and avoiding liquid mixing to produce chemical reactions that cause damage to the quartz glass substrate; finally, the quartz glass substrate is subjected to Marangoni slow pull drying for easy storage. The entire cleaning process effectively removes various residues left during the magnetorheological polishing process through precise chemical formulas and cleaning step settings, improves the cleanliness of the quartz glass substrate, and thus improves the manufacturing quality and performance of the photomask.

[0015] According to one embodiment of the present application, the step of jet cleaning the quartz glass substrate after magnetorheological polishing includes:

[0016] Ultrapure water is used to evenly rinse the surface of the quartz glass substrate through a nozzle at a pressure of 0.05MPa-1MPa to remove loose particles and water-soluble polishing liquid components on the surface of the quartz glass substrate and wet the quartz glass substrate.

[0017] According to one embodiment of the present application, the step of uniformly washing the surface of the quartz glass substrate with ultrapure water through a nozzle at a pressure of 0.05 MPa-1 MPa to remove loose particles and water-soluble polishing liquid components on the surface of the quartz glass substrate and wet the quartz glass substrate includes:

[0018] The injection pressure of the control fluid is 0.5 MPa, and the injection state of the control fluid is fan-shaped or cone-shaped.

[0019] According to one embodiment of the present application, the step of placing the jet-cleaned quartz glass substrate in a mixture of dilute hydrochloric acid and citric acid for ultrasonic cleaning, and removing the residual mixture attached to the quartz glass substrate after cleaning, comprises:

[0020] The concentration of the dilute hydrochloric acid is 0.5%-5%, the concentration of the citric acid is 0.01%-2%, and the single ultrasonic cleaning time is 200 seconds-1000 seconds;

[0021] The use temperature of the mixed solution of dilute hydrochloric acid and citric acid is 25°C-60°C.

[0022] According to one embodiment of the present application, the step of single ultrasonic cleaning time of 200 seconds to 1000 seconds includes:

[0023] The frequency of the ultrasonic wave is controlled to be 80kHz-160kHz, and the waveform is a spherical wave.

[0024] According to one embodiment of the present application, the step of placing the quartz glass substrate in an alkaline solution, performing megasonic cleaning, and removing the residual alkaline solution attached to the quartz glass substrate after the cleaning is completed includes:

[0025] The alkaline solution comprises an inorganic base, a chelating agent, an anionic surfactant, a nonionic surfactant and pure water. The pH value of the alkaline solution is 12.5-9.5, the use temperature is 30° C.-70° C., and the single megasonic cleaning time is 60 seconds-600 seconds.

[0026] According to one embodiment of the present application, the step of placing the quartz glass substrate in a dilute hydrofluoric acid solution, performing megasonic cleaning, and removing the residual dilute hydrofluoric acid solution attached to the quartz glass substrate after cleaning comprises:

[0027] The concentration of the dilute hydrofluoric acid solution is 0.3wt.%-1wt.%, the operating temperature is 10°C-20°C, and the single megasonic cleaning time is 30 seconds-300 seconds.

[0028] According to one embodiment of the present application, the frequency of the megasonic wave is 750kHz-2000kHz, and the waveform is a sine wave.

[0029] According to one embodiment of the present application, the step of performing Marangoni slow pull drying on the quartz glass substrate comprises:

[0030] The solvent used for drying includes isopropyl ketone, and the carrier gas includes nitrogen.

[0031] According to one embodiment of the present application, the step of removing the residual mixed liquid attached to the quartz glass substrate after the cleaning is completed includes:

[0032] The quartz glass substrate was jet cleaned and overflow rinsed using ultrapure water;

[0033] The step of removing the residual alkaline solution attached to the quartz glass substrate after the cleaning is completed comprises:

[0034] The quartz glass substrate was jet cleaned and overflow rinsed using ultrapure water;

[0035] The step of removing the residual dilute hydrofluoric acid solution attached to the quartz glass substrate after the cleaning is completed comprises:

[0036] The quartz glass substrate was overflow rinsed with ultrapure water. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0038] Figure 1 A schematic flow chart of a method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] In order to more clearly illustrate the overall concept of the present application, a detailed description is given below in an illustrative manner in conjunction with the accompanying drawings.

[0040] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below. It should be noted that the embodiments of the present application and the features in each embodiment may be combined with each other without conflict.

[0041] In addition, in the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0042] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0043] In the present application, unless otherwise clearly specified and limited, a first feature "above" or "below" a second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples.

[0044] like Figure 1 As shown, the embodiment of the present application provides a method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing, comprising:

[0045] Step 100: jet cleaning the quartz glass substrate after magnetorheological polishing.

[0046] Step 200: placing the jet-cleaned quartz glass substrate in a mixture of dilute hydrochloric acid and citric acid for ultrasonic cleaning, and removing the residual mixture attached to the quartz glass substrate after the cleaning is completed.

[0047] Step 300: placing the quartz glass substrate in an alkaline solution and performing megasonic cleaning, and removing the residual alkaline solution attached to the quartz glass substrate after the cleaning is completed.

[0048] Step 400: placing the quartz glass substrate in a dilute hydrofluoric acid solution and performing megasonic cleaning. After the cleaning is completed, the residual dilute hydrofluoric acid solution attached to the quartz glass substrate is removed.

[0049] Step 500: Perform Marangoni slow pull drying on the quartz glass substrate.

[0050] In step 100, jet cleaning is the first step of cleaning the quartz glass substrate after magnetorheological polishing, the purpose of which is to remove loose particles and water-soluble polishing liquid components on the surface of the substrate and prepare for the next cleaning step.

[0051] Specifically, a jet cleaning device can be applied, and the jet cleaning device includes:

[0052] High-pressure pump: provides the necessary water pressure to ensure that the water flow can effectively impact the surface of the quartz glass substrate, thereby effectively removing surface dirt.

[0053] Nozzle: The design of the nozzle is crucial. It determines the shape of the water flow - it can be fan-shaped or cone-shaped. Both forms help increase the contact area between water and the substrate surface and improve cleaning efficiency.

[0054] Control system: used to adjust the water pressure to ensure that the jet can effectively remove pollutants without damaging the quartz glass substrate itself.

[0055] In step 200, ultrasonic cleaning is a method of using ultrasonic vibration energy to remove contaminants from the surface or internal pores of an object. When ultrasonic waves propagate in a liquid, a series of compression and rarefaction areas are generated, forming tiny vacuum bubbles, which produce strong local hydraulic shock waves when they burst, a phenomenon known as cavitation. The cavitation effect can effectively remove dirt and other attachments on the surface of an object.

[0056] During the ultrasonic cleaning process, the quartz glass substrate after jet cleaning is placed in a mixture of dilute hydrochloric acid and citric acid. Then use ultrasonic cleaning equipment to clean micron-level particles. The role of ultrasound is to enhance the effect of chemical cleaning through cavitation effect, so as to better remove metal residues such as iron powder and iron ions on the surface of the quartz glass substrate. In simple terms, the quartz glass substrate is immersed in the mixed liquid, heated, ultrasonically assisted, and the quartz glass substrate is shaken up and down, and then taken out after cleaning.

[0057] After ultrasonic cleaning, the residual mixture attached to the quartz glass substrate needs to be removed. The purpose of this is to prevent any residual chemicals from affecting the performance of the substrate during subsequent processing.

[0058] The equipment needed for ultrasonic cleaning mainly includes:

[0059] Ultrasonic Cleaner: A container with an ultrasonic transducer that produces ultrasonic waves of a specific frequency.

[0060] Heating system: used to keep the temperature of the mixed liquid within a suitable range, which helps to improve the cleaning effect.

[0061] Oscillation system: In some designs, the oscillation system can make the quartz glass substrate being cleaned move slightly, helping the ultrasonic wave to better cover every corner of the quartz glass substrate.

[0062] In step 300, megasonic cleaning is a technology that uses high-frequency sound waves (megahertz level) for cleaning. Compared with conventional ultrasonic cleaning, megasonic waves have a higher frequency and a sine wave waveform, and are usually used to clean submicron and nanometer particles. Megasonic cleaning uses the energy of sound waves to generate tiny bubbles in the liquid. The rapid formation and rupture of these bubbles (cavitation effect) can generate strong microjets on the surface of the object, thereby peeling off and removing pollutants.

[0063] Similar to the ultrasonic cleaning method, the quartz glass substrate is immersed in an alkaline solution, heated, and then assisted by megasonic waves, the quartz glass substrate is shaken up and down, and then taken out after cleaning.

[0064] After cleaning, the alkaline solution remaining on the surface of the quartz glass substrate needs to be removed. This is to avoid any residual chemicals from contaminating or damaging the substrate during subsequent processing.

[0065] The equipment needed for megasonic cleaning mainly includes:

[0066] Megasonic cleaning tank: A container with a megasonic transducer that can generate megasonic waves of a specific frequency.

[0067] Heating device: used to maintain the temperature of the alkaline cleaning solution to ensure cleaning under optimal conditions.

[0068] Stirring device: Make the quartz glass substrate shake slightly in the alkaline cleaning solution to improve the cleaning effect.

[0069] Control system: used to adjust the frequency and power of the megasonic waves to suit different types of contaminants and substrates.

[0070] In step 400, similarly, when the quartz glass substrate is immersed in dilute hydrofluoric acid, the substrate is shaken up and down with the assistance of megasonic waves, and then taken out after cleaning.

[0071] This step can effectively remove embedded particles on the surface of the quartz glass substrate, and through the use of dilute hydrofluoric acid, the hydrophilicity of the surface of the quartz glass substrate is improved, providing a clean surface for subsequent processing steps and ensuring the quality of the photomask.

[0072] In step 500, which is the last step of the cleaning process, the goal is to safely and efficiently dry the quartz glass substrate without leaving any moisture or solvent residue.

[0073] The Marangoni effect refers to the phenomenon that liquid flows due to the difference in surface tension at the interface of two different liquids. In the slow pull drying process, this effect is used to control the evaporation rate of the liquid, ensure that the surface of the substrate is dried evenly, and avoid the formation of spots or stripes caused by water droplets or droplets.

[0074] Drying process:

[0075] Solvent selection: The solvents used for drying include isopropyl ketone, isopropyl alcohol, etc.

[0076] Carrier gas usage: Carrier gas is usually nitrogen, which is used to provide an inert environment to prevent pollutants in the air from adhering to the quartz glass substrate.

[0077] Pulling rate: By controlling the pulling rate, ensure that the liquid on the surface of the quartz glass substrate can evaporate smoothly without leaving any traces.

[0078] Specific operations:

[0079] Immersing the cleaned quartz glass substrate in a drying solvent (such as isopropyl ketone);

[0080] Slowly lift the quartz glass substrate from the solvent, and control the pulling speed so that the solvent forms a uniform film on the surface of the quartz glass substrate;

[0081] During the pulling process, nitrogen carrier gas continuously blows across the surface of the quartz glass substrate to help accelerate the evaporation of the solvent while protecting the substrate from external contamination.

[0082] Furthermore, after the pulling is completed, the quartz glass substrate can be stored in an antistatic clean box to prevent secondary contamination.

[0083] Marangoni slow pull drying can effectively reduce the contamination caused by uneven evaporation of liquid during the drying process, ensuring the high cleanliness of the quartz glass substrate. By controlling the evaporation process, water stains or streaks that may occur during rapid drying are avoided. This method is also suitable for simultaneous processing of multiple quartz glass substrates, which improves efficiency. Using inert gas (such as nitrogen) as a carrier gas reduces the adhesion of impurities in the air and ensures the purity of the quartz glass substrate.

[0084] According to the cleaning method of the quartz glass substrate for photomask after magnetorheological polishing provided in the embodiment of the present application, first, the quartz glass substrate after magnetorheological polishing is jet cleaned, and this process can remove loose particles and some water-soluble polishing liquid components on the surface of the quartz glass substrate and wet the quartz glass substrate, so as to prepare for subsequent more in-depth cleaning; then, the quartz glass substrate after jet cleaning is placed in a mixture of dilute hydrochloric acid and citric acid for ultrasonic cleaning, which can remove metal residues such as iron powder and iron ions, and effectively remove metal impurities left in the magnetorheological polishing process. After the cleaning is completed, the residual mixed liquid attached to the quartz glass substrate is removed to ensure the cleanliness of the surface of the quartz glass substrate, prepare for the next step of cleaning, and avoid the chemical reaction caused by liquid mixing to cause damage to the quartz glass substrate; the third step is to place the quartz glass substrate in an alkaline solution for megasonic cleaning. Sonic wave cleaning, this step is mainly aimed at removing cerium oxide particles and organic residues, effectively removing non-metallic particles and organic substances remaining during the polishing process, removing residual alkaline solution attached to the quartz glass substrate after cleaning, ensuring the cleanliness of the surface of the quartz glass substrate, preparing for the next cleaning step, and avoiding liquid mixing to produce chemical reactions that cause damage to the quartz glass substrate; the fourth step is to place the quartz glass substrate in a dilute hydrofluoric acid solution for megasonic cleaning, this step is specifically aimed at removing embedded particles, while improving the hydrophilicity of the surface of the quartz glass substrate, removing residual dilute hydrofluoric acid solution attached to the quartz glass substrate after cleaning, ensuring the cleanliness of the surface of the quartz glass substrate, preparing for the next cleaning step, and avoiding liquid mixing to produce chemical reactions that cause damage to the quartz glass substrate; finally, the quartz glass substrate is subjected to Marangoni slow pull drying for easy storage. The entire cleaning process effectively removes various residues left during the magnetorheological polishing process through precise chemical formulas and cleaning step settings, improves the cleanliness of the quartz glass substrate, and thus improves the manufacturing quality and performance of the photomask.

[0085] In some embodiments of the present application, the step of jet cleaning the quartz glass substrate after magnetorheological polishing includes:

[0086] Ultrapure water is used to evenly rinse the surface of the quartz glass substrate through a nozzle at a pressure of 0.05MPa-1MPa to remove loose particles and water-soluble polishing liquid components on the surface of the quartz glass substrate and wet the quartz glass substrate.

[0087] Specifically, ultrapure water refers to water that has undergone multiple purification treatments to remove almost all impurities in the water, including dissolved ions, organic matter, microorganisms, particulate matter, etc., so that the water quality reaches a very high purity standard.

[0088] Ultrapure water is sprayed evenly onto the surface of the quartz glass substrate through the nozzle to ensure that the water flow covers the entire surface and is even. Jet cleaning can effectively remove loose particles on the surface of the quartz glass substrate, such as iron powder, iron ions, cerium oxide particles, etc., which remain during the magnetorheological polishing process. It can also remove some water-soluble polishing liquid components. Wetting the surface of the quartz glass substrate helps the subsequent chemical cleaning agent to adhere and function better, laying the foundation for the next cleaning step.

[0089] In some embodiments of the present application, the step of uniformly washing the surface of the quartz glass substrate with ultrapure water through a nozzle at a pressure of 0.05 MPa-1 MPa to remove loose particles and water-soluble polishing liquid components on the surface of the quartz glass substrate and wet the quartz glass substrate includes:

[0090] The injection pressure of the control fluid is 0.5 MPa, and the injection state of the control fluid is fan-shaped or cone-shaped.

[0091] Specifically, the fluid injection pressure is set to 0.5 MPa. This pressure is strong enough to effectively wash away loose particles and water-soluble polishing liquid components on the substrate surface, but it will not damage the quartz glass substrate due to excessive pressure. Ultrapure water is sprayed onto the surface of the quartz glass substrate in a fan-shaped or cone-shaped form through the nozzle. The fan-shaped spray can provide a larger coverage area, while the cone-shaped spray can provide deeper penetration. Both can ensure that the water flow can evenly cover the substrate surface and achieve a uniform flushing effect.

[0092] In addition, in actual operation, it is necessary to ensure that the distance between the nozzle and the substrate is appropriate to ensure that the water flow can evenly cover the surface of the substrate, while avoiding uneven flushing or excessive pressure that may damage the substrate due to a distance that is too close or too far.

[0093] In some embodiments of the present application, the quartz glass substrate after jet cleaning is placed in a mixture of dilute hydrochloric acid and citric acid for ultrasonic cleaning, and the step of removing the residual mixed solution attached to the quartz glass substrate after cleaning includes:

[0094] The concentration of dilute hydrochloric acid is 0.5%-5%, the concentration of citric acid is 0.01%-2%, and the single ultrasonic cleaning time is 200 seconds-1000 seconds;

[0095] The use temperature of the mixed solution of dilute hydrochloric acid and citric acid is 25°C-60°C.

[0096] Specifically, in the mixed solution, hydrochloric acid: citric acid = 5:1, and the use temperature is controlled between 25°C and 60°C to promote chemical reactions and improve cleaning effects. The time for a single ultrasonic cleaning is set between 200 seconds and 1000 seconds to ensure that the residues on the surface of the quartz glass substrate are fully cleaned.

[0097] Cleaning principle: Dilute hydrochloric acid can react with metal ions (such as iron ions) on the surface of the substrate and convert them into soluble salts; citric acid, as a chelating agent, can further stabilize these metal ions and prevent them from redepositing on the substrate surface. Ultrasonic waves enhance the effect of chemical cleaning by generating cavitation effect, making it easier for pollutants on the surface of the substrate to be removed by the cleaning liquid.

[0098] Concentration control can ensure that the concentration of dilute hydrochloric acid and citric acid is within the specified range. Too high or too low concentration may affect the cleaning effect.

[0099] Temperature control can keep the temperature of the mixture within a set range. Too high or too low a temperature will affect the speed and effect of the chemical reaction.

[0100] Time control can adjust the cleaning time according to the degree of contamination of the substrate. Too short a cleaning time may not completely remove the contaminants, while too long a time may cause unnecessary corrosion or chemical reactions.

[0101] In some embodiments of the present application, the step of single ultrasonic cleaning time of 200 seconds to 1000 seconds includes:

[0102] The frequency of the ultrasonic wave is controlled to be 80kHz-160kHz, and the waveform is a spherical wave.

[0103] Specifically, the frequency of the ultrasonic wave is set to 80kHz to 160kHz. Within this frequency range, the ultrasonic wave can effectively produce a cavitation effect, thereby enhancing the effect of chemical cleaning.

[0104] Waveform control: Use spherical waves as the waveform of the ultrasonic wave. Spherical waves can produce a uniform cavitation effect in the cleaning liquid, ensuring that every part of the surface of the quartz glass substrate can be effectively cleaned.

[0105] In some embodiments of the present application, the quartz glass substrate is placed in an alkaline solution and subjected to megasonic cleaning. After the cleaning is completed, the step of removing the residual alkaline solution attached to the quartz glass substrate includes:

[0106] The alkaline solution includes an inorganic base, a chelating agent, an anionic surfactant, a nonionic surfactant and pure water. The pH value of the alkaline solution is 12.5-9.5, the use temperature is 30° C.-70° C., and the single megasonic cleaning time is 60 seconds-600 seconds.

[0107] Specifically, the inorganic base may include sodium hydroxide and potassium hydroxide, the chelating agent may include potassium citrate, sodium citrate, and sodium ethylenediaminetetraacetate, the anionic surfactant may include at least one of carboxylates, sulfonates, sulfates, and phosphates and their derivatives, and the nonionic surfactant may include at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, polyether, fatty acid polyoxyethylene ester, alkylamine, and alkyl alcohol amide.

[0108] Chelating agents are used to stabilize and remove metal ions. Anionic surfactants help emulsify and remove organic pollutants such as oils and fats. Nonionic surfactants can improve the wetting ability of the solution and help remove insoluble pollutants. Pure water is used as a solvent to ensure the purity of the solution.

[0109] The pH value of the alkaline solution is set between 12.5 and 9.5 to ensure that it is sufficiently alkaline to effectively decompose and remove organic pollutants. The use temperature of the alkaline solution is set between 30℃ and 70℃. Higher temperatures can speed up the chemical reaction rate and improve cleaning efficiency.

[0110] The alkaline solution can react with the organic contaminants on the surface of the quartz glass substrate, decomposing or converting them into a state that is easy to clean. Megasonic waves enhance the effect of chemical cleaning by generating microjets produced by the collapse of tiny bubbles, helping to remove contaminants on the surface of the quartz glass substrate.

[0111] In some embodiments of the present application, the quartz glass substrate is placed in a dilute hydrofluoric acid solution and subjected to megasonic cleaning. After the cleaning is completed, the step of removing the residual dilute hydrofluoric acid solution attached to the quartz glass substrate includes:

[0112] The concentration of the dilute hydrofluoric acid solution is 0.3wt.%-1wt.%, the operating temperature is 10°C-20°C, and the single megasonic cleaning time is 30 seconds-300 seconds.

[0113] Specifically, wt.% represents weight percentage, that is, the concentration of the dilute hydrofluoric acid solution is set between 0.3 weight percent (wt.%) and 1 weight percent (wt.%) to ensure the cleaning effect. The dilute hydrofluoric acid can react with certain contaminants (such as silica gel, silicate, etc.) on the surface of the quartz glass substrate to dissolve or transform them, thereby removing these contaminants. Megasonic waves enhance the effect of chemical cleaning by generating microjets produced by the collapse of tiny bubbles, helping to remove contaminants on the surface of the substrate.

[0114] Furthermore, when cleaning in alkaline solutions and dilute hydrofluoric acid solutions, there are also requirements for the parameter settings of the megasonic wave. Specifically, in some embodiments of the present application, the frequency of the megasonic wave is 750kHz-2000kHz, and the waveform is a sine wave. The frequency of the megasonic wave is set to 750kHz to 2000kHz. Within this frequency range, the megasonic wave can produce finer bubbles, which will produce a stronger microjet effect when they burst, thereby enhancing the cleaning effect. A sine wave is used as the waveform of the megasonic wave. The sine wave can provide a relatively stable energy output to ensure uniform distribution of energy during the cleaning process.

[0115] In some embodiments of the present application, the step of performing Marangoni slow pull drying on the quartz glass substrate comprises:

[0116] The solvent used for drying includes isopropyl ketone, and the carrier gas includes nitrogen.

[0117] Specifically, isopropyl ketone is used as a drying solvent. Isopropyl ketone is a commonly used solvent. Because of its good volatility, it can evaporate quickly and dissolve some residual pollutants. Nitrogen (N2) is used as a carrier gas. Nitrogen is an inert gas that can provide an oxygen-free environment to prevent pollutants in the air from attaching to the substrate surface again.

[0118] The nitrogen flow rate needs to be appropriate. Too large a flow rate may cause the solvent to evaporate too quickly, resulting in an uneven drying effect; too small a flow rate may not be sufficient to prevent the adhesion of air pollutants.

[0119] Ensure the cleanliness of the drying environment to prevent dust and particles from adhering to the substrate surface during the drying process.

[0120] In some embodiments of the present application, the step of removing the residual mixed liquid attached to the quartz glass substrate after cleaning is completed includes:

[0121] The quartz glass substrate was jet cleaned and overflow rinsed using ultrapure water;

[0122] The step of removing the residual alkaline solution attached to the quartz glass substrate after cleaning comprises:

[0123] The quartz glass substrate was jet cleaned and overflow rinsed using ultrapure water;

[0124] The step of removing the residual dilute hydrofluoric acid solution attached to the quartz glass substrate after cleaning comprises:

[0125] The quartz glass substrate was overflow rinsed with ultrapure water.

[0126] After completing the different chemical cleaning steps, removing the residual solution adhering to the quartz glass substrate is a critical step to ensure the final cleanliness of the substrate surface.

[0127] The steps of removing the residual mixed liquid mainly include:

[0128] Jet cleaning: Use ultrapure water to evenly rinse the surface of the quartz glass substrate through a nozzle at a pressure of 0.05MPa to 1MPa.

[0129] Control the injection pressure of the fluid: set the pressure to 0.5MPa to ensure that the water flow has sufficient impact force.

[0130] Control the spray state of the fluid: the spray state is fan-shaped or cone-shaped to ensure that the water flow can evenly cover the surface of the substrate.

[0131] Overflow rinsing: After jet cleaning, the quartz glass substrate is continuously rinsed with ultrapure water to completely remove the residual mixed liquid.

[0132] Overflow rinsing process: The substrate surface is continuously rinsed with a continuous flow of ultrapure water to ensure that all residual mixed liquid is completely removed.

[0133] The steps of removing the residual alkaline solution mainly include:

[0134] Jet cleaning: Ultrapure water is also used to evenly rinse the surface of the quartz glass substrate through a nozzle at a pressure of 0.05 MPa to 1 MPa to remove the residual alkaline solution on the surface of the substrate.

[0135] Control the injection pressure of the fluid: set the pressure to 0.5MPa.

[0136] Control the spray state of the fluid: the spray state is fan-shaped or cone-shaped.

[0137] Overflow rinsing: After jet cleaning, the quartz glass substrate is continuously rinsed with ultrapure water to completely remove the residual alkaline solution.

[0138] Overflow rinsing process: The substrate surface is continuously rinsed with a continuous flow of ultrapure water to ensure that all residual alkaline solution is completely removed.

[0139] The steps for removing the residual dilute hydrofluoric acid solution mainly include:

[0140] Overflow rinsing: Use ultrapure water to directly perform overflow rinsing on the quartz glass substrate to completely remove the residual dilute hydrofluoric acid solution.

[0141] Overflow rinsing process: The substrate surface is continuously rinsed with a continuous flow of ultrapure water to ensure that all residual dilute hydrofluoric acid solution is completely removed.

[0142] In some embodiments of the present application, an optical defect detection device substrate can also be used for scanning detection. No large-area particle agglomeration and organic residue are observed on the surface of the quartz glass substrate, and most of the same-orientation defects are glass surface defects caused by magnetorheological processing, indicating that the cleaning effect is good.

[0143] In addition, the above cleaning process can be repeated multiple times according to the polishing liquid contamination and residue of the quartz glass substrate.

[0144] Anything not described in this application can be achieved by adopting or drawing on existing technologies.

[0145] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0146] The above is only the embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing, characterized in that: include: Performing jet cleaning on the quartz glass substrate after magnetorheological polishing; The quartz glass substrate after jet cleaning is placed in a mixture of dilute hydrochloric acid and citric acid for ultrasonic cleaning, and after the cleaning is completed, the residual mixture attached to the quartz glass substrate is removed; Placing the quartz glass substrate in an alkaline solution and performing megasonic cleaning, and removing the residual alkaline solution attached to the quartz glass substrate after the cleaning is completed; Placing the quartz glass substrate in a dilute hydrofluoric acid solution and performing megasonic cleaning, and removing the residual dilute hydrofluoric acid solution attached to the quartz glass substrate after the cleaning is completed; The quartz glass substrate was dried by Marangoni slow pull.

2. The method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing according to claim 1, characterized in that: The step of jet cleaning the quartz glass substrate after magnetorheological polishing comprises: Ultrapure water is used to evenly rinse the surface of the quartz glass substrate through a nozzle at a pressure of 0.05MPa-1MPa to remove loose particles and water-soluble polishing liquid components on the surface of the quartz glass substrate and wet the quartz glass substrate.

3. The method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing according to claim 2, characterized in that: The step of using ultrapure water through a nozzle at a pressure of 0.05 MPa-1 MPa to uniformly rinse the surface of the quartz glass substrate to remove loose particles and water-soluble polishing liquid components on the surface of the quartz glass substrate and wet the quartz glass substrate comprises: The injection pressure of the control fluid is 0.5 MPa, and the injection state of the control fluid is fan-shaped or cone-shaped.

4. The method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing according to claim 1, characterized in that: The step of placing the jet-cleaned quartz glass substrate in a mixture of dilute hydrochloric acid and citric acid for ultrasonic cleaning, and removing the residual mixture attached to the quartz glass substrate after the cleaning is completed, comprises: The concentration of the dilute hydrochloric acid is 0.5%-5%, the concentration of the citric acid is 0.01%-2%, and the single ultrasonic cleaning time is 200 seconds-1000 seconds; The use temperature of the mixed solution of dilute hydrochloric acid and citric acid is 25°C-60°C.

5. The method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing according to claim 4, characterized in that: The step of single ultrasonic cleaning time of 200 seconds to 1000 seconds comprises: The frequency of the ultrasonic wave is controlled to be 80kHz-160kHz, and the waveform is a spherical wave.

6. The method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing according to claim 1, characterized in that: The step of placing the quartz glass substrate in an alkaline solution and performing megasonic cleaning, and removing the residual alkaline solution attached to the quartz glass substrate after the cleaning is completed, comprises: The alkaline solution comprises an inorganic base, a chelating agent, an anionic surfactant, a nonionic surfactant and pure water. The pH value of the alkaline solution is 12.5-9.5, the use temperature is 30° C.-70° C., and the single megasonic cleaning time is 60 seconds-600 seconds.

7. The method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing according to claim 1, characterized in that: The step of placing the quartz glass substrate in a dilute hydrofluoric acid solution, performing megasonic cleaning, and removing the residual dilute hydrofluoric acid solution attached to the quartz glass substrate after the cleaning is completed comprises: The concentration of the dilute hydrofluoric acid solution is 0.3wt.%-1wt.%, the operating temperature is 10°C-20°C, and the single megasonic cleaning time is 30 seconds-300 seconds.

8. The method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing according to claim 6 or 7, characterized in that: The frequency of megasonic waves is 750kHz-2000kHz, and the waveform is a sine wave.

9. The method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing according to claim 1, characterized in that: The step of performing Marangoni slow pull drying on the quartz glass substrate comprises: The solvent used for drying includes isopropyl ketone, and the carrier gas includes nitrogen.

10. The method for cleaning a quartz glass substrate for a photomask after magnetorheological polishing according to claim 1, characterized in that: The step of removing the residual mixed liquid attached to the quartz glass substrate after the cleaning is completed comprises: The quartz glass substrate was jet cleaned and overflow rinsed using ultrapure water; The step of removing the residual alkaline solution attached to the quartz glass substrate after the cleaning is completed comprises: The quartz glass substrate was jet cleaned and overflow rinsed using ultrapure water; The step of removing the residual dilute hydrofluoric acid solution attached to the quartz glass substrate after the cleaning is completed comprises: The quartz glass substrate was overflow rinsed with ultrapure water.

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