Pellicle frame, pellicle and exposure master plate with pellicle, method for manufacturing a pellicle frame, exposure method, method for manufacturing a semiconductor device and method for manufacturing a liquid crystal display panel

Abstract

The present invention relates to a pellicle frame constituting a pellicle for photolithography, wherein the pellicle frame is made of pure titanium or a titanium alloy and the surface thereof is subjected to a mechanical polishing process, an electrolytic degreasing process, and a chemical polishing process. Thus, provided are: a pellicle frame in which the amount of dust particles remaining on the surface is reduced; and a method for producing a pellicle frame.

Description

[Technical Field]

[0001] This invention relates to a pellicle attached to a lithography photomask as a dust filter, a pellicle frame, and an exposure master plate with a pellicle. Furthermore, it relates to a method for manufacturing a pellicle frame, an exposure method, a method for manufacturing a semiconductor device, and a method for manufacturing a liquid crystal display panel. [Background technology]

[0002] In recent years, LSI design rules have been miniaturized to the sub-quarter micron level, and consequently, exposure light sources have been shortened in wavelength. Specifically, exposure light sources have shifted from mercury lamps with g-line (436nm) and i-line (365nm) to KrF excimer lasers (248nm) and ArF excimer lasers (193nm), and furthermore, EUV (Extreme Ultra Violet) lithography using EUV light with a dominant wavelength of 13.5nm is being considered.

[0003] In the manufacturing of semiconductor devices such as LSIs and ultra-large-scale integrated circuits (ULSIs) or liquid crystal display panels, patterns are created by irradiating semiconductor wafers or liquid crystal master plates with light. However, if dust adheres to the lithography photomasks and reticles (hereinafter collectively referred to as "exposure master plates") used in this process, this dust can absorb or bend light, causing deformation of the transferred pattern, rough edges, and blackening of the background, resulting in problems with dimensions, quality, and appearance.

[0004] These operations are usually performed in a cleanroom, but even then, it is difficult to keep the exposure plate clean at all times. Therefore, a method is commonly adopted in which a pellicle is attached to the surface of the exposure plate as a dust filter before exposure. In this case, foreign matter does not adhere directly to the surface of the exposure plate but adheres to the pellicle, so if the focus is set on the pattern of the exposure plate during lithography, the foreign matter on the pellicle will not be affected by the transfer.

[0005] The basic structure of this pellicle consists of a pellicle frame made of metal such as aluminum, with a pellicle film that has high transmittance to the light used for exposure stretched across its upper surface, and an airtight gasket formed on its lower surface. The airtight gasket generally uses an adhesive layer, and a protective sheet is attached to protect this adhesive layer. The pellicle film is made of nitrocellulose, cellulose acetate, fluorine-based polymers, etc., which transmit light used for exposure (g-line (436nm), i-line (365nm) from a mercury lamp, KrF excimer laser (248nm), ArF excimer laser (193nm), etc.) well, but for EUV exposure, ultrathin silicon films and carbon films are being considered as pellicle films.

[0006] Conventionally, aluminum frames have been used for pellicle frames. An anodic oxide coating is applied to the aluminum frame for corrosion resistance and other purposes. If there are protrusions on the surface of the aluminum frame before the anodic oxide coating is applied, these protrusions will remain even after the coating is formed. To prevent this, it is known that the aluminum frame is chemically polished before applying the anodic oxide coating (Patent Document 1).

[0007] On the other hand, titanium frames are being considered for EUV (Extreme UV) lithography. Because titanium frames have high strength and corrosion resistance, there is no need to apply an anodized coating to improve strength, as is the case with aluminum frames. Therefore, in titanium frames, scratches and burrs caused during processing are generally removed by mechanical polishing, which is more cost-effective and productive than chemical polishing. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 6008784 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, the inventors found that even after removing scratches and burrs by mechanical polishing and repeating several cleaning processes, particles such as titanium powder generated by mechanical polishing remain on the surface of the pellicle frame. These particles are recognized as foreign matter during inspection processes during pellicle manufacturing, pellicle installation, and pellicle use. Furthermore, even if no foreign matter is detected during the inspection process described above, there is a risk that particles may fall off the pellicle frame due to vibration or EUV irradiation during pellicle use.

[0010] The present invention was made to solve the above-mentioned problems, and aims to provide a pellicle frame with reduced dust particles remaining on the surface and a method for manufacturing a pellicle frame. [Means for solving the problem]

[0011] To achieve the above objective, the present invention provides a pellicle frame that constitutes a pellicle for photolithography, The pellicle frame is made of pure titanium or titanium alloy, and on the surface Mechanical polishing treatment, Electrolytic degreasing treatment, The present invention provides a pellicle frame characterized by having undergone a chemical polishing treatment.

[0012] Because the pellicle frame of the present invention is made of titanium or titanium alloy, it is superior in terms of ease of processing, light weight, and heat resistance. Furthermore, the amount of dust particles and organic matter (oil, scale, and adsorbed debris that adheres to the surface) remaining on the surface is reduced. Hereafter, dust particles and organic matter will be collectively referred to as particles. Therefore, it is possible to prevent the presence of these particles from causing problems during inspection processes such as pellicle manufacturing. Additionally, it is possible to prevent adverse effects during photolithography, such as particles falling from the pellicle frame in an exposure environment.

[0013] At this time, the said pellicle frame In the particle evaluation where it is immersed in pure water and irradiated with ultrasonic waves for more than one minute, the number of particles with an equivalent spherical diameter of 1 to 15 μm released into the pure water is such that the surface area of the said pellicle frame is 1 cm 2 per square centimeter can be 1500 or less.

[0014] In this way, the pellicle frame with extremely reduced number of surface particles is obtained.

[0015] Also, the unevenness existing on the inner surface of the said pellicle frame can be 5 μm or less.

[0016] If there is unevenness on the surface, it may affect the foreign matter inspection. However, if it is suppressed to a size (height or depth) of 5 μm or less in this way, the influence on the inspection can be reduced.

[0017] Also, the said pellicle frame In the ion elution test where it is immersed in pure water at 90 °C for 3 hours and the eluted ion concentration is measured, based on the elution concentration into 100 ml of the said pure water per 50 cm of the surface area of the said pellicle frame 2 the elution concentration of acetate ions is 10 ppb or less, the elution concentration of formate ions is 100 ppb or less, the elution concentration of Cl ions is 10 ppb or less, the elution concentration of NO2 ions is 10 ppb or less, the elution concentration of NO3 ions is 10 ppb or less, the elution concentration of SO4 ions is 10 ppb or less, the elution concentration of oxalate ions is 10 ppb or less, the elution concentration of phosphate ions is 10 ppb or less, the elution concentration of NH4 ions is 100 ppb or less, it can be such that of these.

[0018] In this way, for a pellicle frame with reduced various generated ions, the influence on the exposure environment by these ions can be particularly reduced.

[0019] Furthermore, the present invention relates to a method for manufacturing a pellicle frame that constitutes a pellicle for photolithography, On the surface of the pellicle frame made of pure titanium or titanium alloy, Mechanical polishing treatment, Electrolytic degreasing treatment, The present invention provides a method for manufacturing a pellicle frame, characterized by being manufactured by chemical polishing.

[0020] The pellicle frame manufacturing method of the present invention offers advantages in terms of ease of processing, light weight, and heat resistance, and allows for the production of a pellicle frame with a reduced number of particles remaining on the surface, such as dust particles and organic matter. Consequently, it is possible to prevent the pellicle frame from getting stuck in the inspection process or adversely affecting photolithography due to the above-mentioned particles.

[0021] At this time, the mechanical polishing process is performed It can consist solely of magnetic polishing, barrel polishing, or a combination thereof.

[0022] This method further reduces the amount of dust particles remaining on the surface of the pellicle frame.

[0023] Furthermore, the magnetic polishing process is performed as follows: This can be performed using a rod-shaped SUS magnetic media in the washing water in which the pellicle frame is immersed.

[0024] By performing the polishing process in cleaning water (solvent) using the magnetic media described above, even if titanium or other particles are generated during polishing, they quickly diffuse into the solvent, and the amount of dust remaining on the surface is significantly reduced.

[0025] Furthermore, the chemical polishing treatment is performed as described above. It can consist of chemical polishing or electrolytic polishing.

[0026] This method effectively removes particles adhering to the surface.

[0027] Furthermore, the present invention relates to a pellicle for photolithography comprising a pellicle frame and a pellicle film stretched over the pellicle frame, The present invention provides a pellicle characterized in that the pellicle frame is the pellicle frame described above. Furthermore, the present invention relates to an exposure master and an exposure master with a pellicle attached, The present invention provides an exposure master plate with a pellicle, characterized in that the pellicle is the pellicle described above.

[0028] With such pellicles and pellicle-attached exposure plates according to the present invention, the number of particles adhering to the surface of the pellicle frame is extremely small, which prevents adverse effects during inspection processes and photolithography.

[0029] The present invention also provides an exposure method characterized by using the above-described exposure master plate with a pellicle for exposure. The present invention also provides a method for manufacturing a semiconductor device, characterized by comprising a step of exposure using the above-described exposure master plate with a pellicle. The present invention also provides a method for manufacturing a liquid crystal display panel, characterized by comprising a step of exposure using the above-described exposure master plate with a pellicle.

[0030] With the exposure method of the present invention, the number of particles adhering to the surface of the pellicle frame is extremely small, and it is possible to prevent adverse effects during photolithography caused by particles falling from the pellicle frame in the exposure environment. [Effects of the Invention]

[0031] According to the present invention, the amount of dust particles remaining on the surface of the pellicle frame can be reduced. Furthermore, by applying a chemical polishing treatment after mechanical polishing, even if particles generated by mechanical polishing adhere to the surface of the pellicle frame, they can be removed, thereby reducing the amount of particles that pose a risk of later detachment. In particular, the height or depth of the irregularities can be kept to 5 μm or less, providing a method for manufacturing a pellicle frame with good foreign matter inspection properties. [Brief explanation of the drawing]

[0032] [Figure 1] This is a schematic diagram showing an example of the pellicle frame, pellicle, and exposure master plate with pellicle according to the present invention. [Best Mode for Carrying Out the Invention]

[0033] Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto. As mentioned above, titanium is an example of a pellicle frame, and it was common practice to remove surface scratches and burrs by mechanical polishing. However, it was found that particles remained on the surface, which posed a risk of causing problems during inspection or adversely affecting photolithography. Therefore, the inventors conducted diligent research and discovered that if a pellicle frame is made of pure titanium or a titanium alloy and subjected to mechanical polishing, electrolytic degreasing, and chemical polishing treatments on its surface, the number of particles on the surface can be significantly reduced, preventing the above-mentioned problems from occurring. This led to the completion of the present invention.

[0034] Figure 1 shows an example of the pellicle frame of the present invention, along with the pellicle and exposure master plate with pellicle of the present invention. Figure 1 as a whole shows the exposure master plate with pellicle. First, let's explain the overall structure. The pellicle frame (hereinafter sometimes simply referred to as the frame) 1 of the present invention has a film-side adhesive 2 on its upper end surface, and a mask-side adhesive 3 on its lower end surface. The pellicle film 4 is stretched over the pellicle frame 1 via the film-side adhesive 2, thereby forming the pellicle 5 of the present invention. Furthermore, the pellicle 5 is attached to the exposure master plate (photomask or reticle) 6 via the mask-side adhesive 3 of the pellicle frame 1, thus constituting the exposure master plate 7 with pellicle of the present invention.

[0035] The following provides a detailed description of each part. The pellicle frame 1 can be any frame shape, and its shape corresponds to the shape of the photomask on which the pellicle 5 is attached. Generally, it is a rectangular (or square) frame shape. Furthermore, the pellicle frame 1 has a surface for attaching the pellicle film 4 (in this case, the upper end surface) and a surface that faces the photomask when the photomask is attached (in this case, the lower end surface).

[0036] The material used for the pellicle frame 1 is pure titanium or a titanium alloy, which is superior in terms of ease of processing, light weight, heat resistance, and improved inspectability. The dimensions of the pellicle frame 1 are not particularly limited, but since the height of the EUV pellicle is limited to 2.5 mm or less, the thickness of the EUV pellicle frame 1 is smaller than that, less than 2.5 mm. Furthermore, the thickness of the pellicle frame 1 for EUV is preferably 1.5 mm or less, taking into account the thickness of the pellicle film 4, mask adhesive 3, etc.

[0037] Additionally, the sides of the pellicle frame 1 are typically provided with jig holes (not shown) used for handling and separating the pellicle 5 from the photomask. The size of the jig holes is 0.5 to 1.0 mm in width (or diameter in the case of a circular frame) in the thickness direction of the frame 1. There are no restrictions on the shape of the holes; they can be circular or rectangular.

[0038] Furthermore, the frame 1 is provided with ventilation sections 8 to mitigate pressure changes inside and outside the pellicle 5. There are no restrictions on the shape or number of ventilation sections 8. Notches may also be provided on the upper and lower ends of the frame 1 to serve as ventilation sections. A filter 9 can be installed in the ventilation section 8 to prevent foreign matter from entering the pellicle 2. There are no restrictions on where the filter 9 can be installed; it can be on the inside of the pellicle frame 1, inside the ventilation section 8, or on the outside of the pellicle frame 1. In Figure 1, it is installed on the outside of the pellicle frame 1.

[0039] Furthermore, while conventional titanium pellicle frames only undergo mechanical polishing as surface treatment, the surface of the pellicle frame 1 of the present invention is subjected not only to mechanical polishing but also to electrolytic degreasing and chemical polishing (specific examples of these treatments will be described later). As a result, the surface has significantly reduced particles, resulting in a high-quality product.

[0040] The dust particles adhering to the pellicle frame 1 can be evaluated, for example, by measuring the number of particles when the pellicle frame 1 is immersed in pure water. By irradiating the pellicle frame 1 with ultrasound for one minute in pure water, the number of particles with an equivalent spherical diameter of 1 to 15 μm released into the pure water is measured over a surface area of ​​1 cm² of the pellicle frame 1. 2 A particle count of 1500 or less is particularly preferable. Such a low number significantly reduces the risk of dust particles adhering to the pellicle frame 1 adversely affecting the inspection process. A particle count of 1200 or less is more preferable, and 1000 or less is even more preferable. Naturally, the fewer particles there are, the better. A count of 0 is extremely preferable. Examples of ultrasonic irradiation conditions include an oscillation frequency of 38 kHz and an irradiation time of 1 minute. Furthermore, the number of particles can be measured, for example, using a particle counter in a liquid.

[0041] Furthermore, the various ions generated from the pellicle frame 1 can be evaluated, for example, by an ion elution test in which the pellicle frame 1 is immersed in pure water at 90°C for 3 hours and the concentration of eluted ions is measured. In this evaluation, the surface area of ​​the pellicle frame 1 is 50 cm². 2 Preferably, the elution concentrations in 100 ml of pure water are 10 ppb or less for acetate ions, 100 ppb or less for formate ions, 10 ppb or less for Cl ions, 10 ppb or less for NO2 ions, 10 ppb or less for NO3 ions, 10 ppb or less for SO4 ions, 10 ppb or less for oxalate ions, 10 ppb or less for PO4 ions, and 100 ppb or less for NH4 ions. Such low values ​​particularly reduce the influence of various ions generated from the pellicle flame on the exposure environment. The lower the elution concentration of these various ions, the better. 0 ppb is extremely preferable. For measuring the elution concentrations of various ions, methods such as ion chromatography can be used.

[0042] Furthermore, even if there are irregularities, or steps, on the inner surface 10 of the pellicle frame 1 that are larger than 0 μm in size (depth or height), it is preferable that their size is 5 μm or less. Such small irregularities can minimize their impact on foreign object inspection, etc. Naturally, it is extremely preferable if there are no steps (i.e., the irregularities are 0 μm).

[0043] A film-side adhesive 2 is provided on the upper end surface of the pellicle frame 1 as described above. There are no restrictions on the material of the film-side adhesive 2; known materials such as silicone adhesives and acrylic adhesives can be used. To firmly hold the pellicle film 4, an adhesive with strong adhesion is preferred. There are no restrictions on the shape of the film-side adhesive 2; it may be flattened. There are no particular restrictions on the thickness of the film-side adhesive layer 2, but since the height of the pellicle 5 is basically limited to 2.5 mm, it is preferable that it be 0.5 mm or less.

[0044] A mask-side adhesive 3 for attaching to a photomask is formed on the lower end surface of the pellicle frame 1. There are no restrictions on the material of the mask-side adhesive 3; known materials such as silicone adhesives and acrylic adhesives can be used. There are no particular restrictions on the shape of the mask adhesive 3; it may be flattened. There are no particular restrictions on the thickness of the mask-side adhesive layer 3, but since the height of the pellicle 5 is limited to 2.5 mm, it is preferable that it be 0.5 mm or less.

[0045] In addition, a protective cover (not shown) can be provided to protect the adhesives, such as the membrane-side adhesive 2 and the mask-side adhesive 3, so as to cover them. The material of the protective cover is not particularly limited, but for example, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), polypropylene (PP), etc. can be used. Furthermore, if necessary, a release agent such as a silicone-based release agent or a fluorine-based release agent may be applied to the surface as a release layer. Applying a release agent makes it easier to peel the protective cover off the adhesives 2 and 3. There are no restrictions on the shape of the protective cover; it just needs to be large enough to completely cover the adhesives 2 and 3. The shape of the protective cover may be different on the side of the membrane-side adhesive 2 and the side of the mask-side adhesive 3. A gripping part may be provided on a part of the protective cover to make it easier to grip when peeling it off.

[0046] Furthermore, there are no restrictions on the material of the pellicle film 4, but it is preferable to use a material with high transmittance at the wavelength of the exposure light source and high light resistance. For example, for EUV exposure, an ultrathin silicon film or carbon film can be used. Examples of carbon films include graphene, diamond-like carbon, and carbon nanotube films. If the pellicle film is difficult to handle on its own, a pellicle film supported by a frame made of silicon or the like can be used. In that case, the pellicle 5 can be easily manufactured by bonding the frame region to the pellicle frame 1.

[0047] The pellicle 5 of the present invention not only serves as a protective member to prevent foreign matter from adhering to the exposure plate 6 within the exposure apparatus, but also functions as a protective member to protect the exposure plate 6 during storage and transportation. Methods for manufacturing an exposure master plate 7 with a pellicle attached by attaching the pellicle 5 to an exposure master plate 6 such as a photomask include the aforementioned method of attaching with mask adhesive, as well as electrostatic adsorption and mechanical fixing methods.

[0048] As described above, the pellicle frame 1, pellicle 5, and pellicle-attached exposure plate 7 of the present invention have significantly reduced particles such as dust particles on the surface of the pellicle frame compared to conventional products, and can reduce particles that may later detach. Therefore, it can pass inspection processes for foreign matter at each stage, and it is possible to prevent problems from occurring during photolithography due to particles adhering to the surface.

[0049] Next, the flow of the manufacturing method for the pellicle frame of the present invention, which can produce the pellicle frame 1 as described above, will be explained. First, prepare a material made of pure titanium or titanium alloy and machine it into the shape of a pellicle frame. Afterward, surface scratches and burrs caused by machining are removed by mechanical polishing (physical polishing). Examples of mechanical polishing methods include barrel polishing and magnetic polishing. Magnetic polishing is preferable because there is less possibility of abrasive particles or media remaining on the frame surface. Alternatively, a method consisting only of a combination of these methods may also be used.

[0050] Furthermore, there are no particular restrictions on the methods used for magnetic polishing or barrel polishing; known methods can be used. In one example of magnetic polishing, a pellicle frame is placed in a PP container containing cleaning water (e.g., a mixture of surfactant and water) and magnetic media (e.g., a rod-shaped object made of stainless steel). A permanent magnet placed at the bottom of the PP container is then rotated by a motor. This causes the magnetic media inside the PP container to move and collide with the pellicle frame, thereby polishing it. Another example of barrel polishing involves placing a pellicle frame into a container filled with cleaning water and media, and then rotating or revolving the container, vibrating it, or rotating a turntable located at the center of the bottom of the container, similar to a washing machine. This causes the media to collide with the pellicle frame, thereby enabling polishing.

[0051] After mechanical polishing, the pellicle frame is subjected to electrolytic degreasing. There are no particular restrictions on the method of electrolytic degreasing, and known methods can be used. For example, by applying an electric current with the workpiece as the cathode or anode in an alkaline degreasing solution and utilizing the stirring action of the gas generated from the workpiece surface, oil, scale, and adsorbed debris attached to the surface can be effectively removed. If organic matter adheres to the frame surface after mechanical polishing, it can cause unevenness in the dissolution of the base material during chemical polishing, as described later, potentially leading to surface irregularities. Therefore, performing the electrolytic degreasing treatment described above before chemical polishing effectively removes organic matter and improves the surface smoothness after chemical polishing.

[0052] Next, the pellicle frame is subjected to chemical polishing. There are no particular restrictions on the method of chemical polishing, and known methods can be used. For example, chemical polishing treatments using acidic or alkaline solutions with dissolving power, or electropolishing treatments using electrolytes can be used.

[0053] When the above chemical polishing treatment is applied to the frame, especially in the case of titanium frames, a crystalline structure precipitates on the surface, creating grain boundaries. Depending on the properties of the frame's base material, generally, the stronger the chemical polishing treatment, the larger the irregularities and steps between crystals tend to be near the grain boundaries. The height or depth of these irregularities and steps between crystals on the surface can be appropriately adjusted in the machining, mechanical polishing, and chemical polishing treatment conditions of the frame shape, particularly to keep them below 5 μm, as mentioned above. Keeping them within the above numerical range is preferable because it can further reduce the impact on foreign object inspection.

[0054] The pellicle frame 1 of the present invention can be manufactured as described above, but other treatments, such as coloring, can also be applied to the pellicle frame. In that case, by performing a chemical polishing treatment as the final step, any particles that have adhered to the surface of the pellicle frame in the previous step can be easily removed. Furthermore, a frame cleaning step may be added as appropriate during or before / after machining, mechanical polishing, electrolytic degreasing, or chemical polishing, for the purpose of removing polishing residue, machine oil, etc. There are no particular restrictions on the cleaning method, and known methods can be used. Examples include degreasing cleaning using an alkaline aqueous solution or a neutral detergent, or ultrasonic cleaning using pure water.

[0055] Furthermore, the exposure method of the present invention uses the above-described exposure master plate with a pellicle for exposure. The manufacturing method of a semiconductor device or liquid crystal display panel of the present invention includes a step of exposing a substrate (semiconductor wafer or liquid crystal master plate) using the above-described exposure master plate with a pellicle. For example, in the lithography process, which is one of the manufacturing processes of a semiconductor device or liquid crystal display panel, the above-described exposure master plate with a pellicle is placed in a stepper and exposed in order to form a photoresist pattern corresponding to an integrated circuit on the substrate. Generally, in EUV exposure, a projection optical system is used in which EUV light is reflected by the exposure master plate and guided to the substrate, and these are performed under reduced pressure or vacuum. As a result, even if foreign matter adheres to the pellicle during the lithography process, these foreign matter will not form an image on the wafer coated with photoresist, thus preventing short circuits or disconnections of integrated circuits, etc., caused by the image of foreign matter. Therefore, the yield in the lithography process can be improved by using an exposure master plate with a pellicle. [Examples]

[0056] The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited thereto. (Examples) Titanium pellicle frame (external dimensions 150mm x 118mm x 1.5mm, frame width 4.0mm, surface area 68cm²) 2 I prepared ). The manufactured titanium pellicle frame was placed inside a PP container containing cleaning water (specifically, Priority Co., Ltd.'s magnetic polishing cleaning solution G100) and magnetic media (made of stainless steel), and subjected to magnetic polishing. A motor-driven permanent magnet was placed at the bottom of the PP container, and by rotating the permanent magnet with the motor, the magnetic media was moved and collided with the pellicle frame to perform the magnetic polishing process. After magnetic polishing, the frame was washed with pure water, and then electrolytic degreasing was performed using a 10 g / L NaOH solution at a voltage of 6 V for 5 minutes. Subsequently, the frame was immersed in a chemical polishing solution (specifically, TCP-08 manufactured by Mitsubishi Gas Chemical Co., Ltd.) and subjected to chemical polishing treatment.

[0057] After chemical polishing, the frame was washed with pure water, then immersed in pure water again and subjected to ultrasonic cleaning for 5 minutes. Afterward, the parts were immersed in pure water again and ultrasonically cleaned for 30 minutes under reduced pressure. After ultrasonic cleaning, the frame was rinsed with pure water, then air-blown, and finally dried.

[0058] After completing the above steps, the following liquid particle evaluation was performed on the frame. First, 3 liters of pure water were placed in a glass beaker that had been ultrasonically cleaned with pure water. Then, 50 ml of the pure water in the glass beaker was measured using a liquid particle counter (NP500T, manufactured by Nippon Denshoku Industries Co., Ltd.) and recorded as a blank value. Subsequently, the flame was immersed in pure water in a glass beaker and subjected to ultrasonic irradiation at an oscillation frequency of 38 kHz for one minute. After removing the flame, 50 ml of pure water in the glass beaker was again subjected to a liquid particle counter (the same measuring instrument as above). The difference between this value and the blank value was recorded as the number of particles attributable to the flame. Assuming that the particles diffuse uniformly in the water, the number of particles released from the frame into the water was estimated. The measurement results are shown in Table 1.

[0059] (Comparative Example 1) Titanium frame with the same shape as the example (external dimensions 150mm x 118mm x 1.5mm, frame width 4.0mm, surface area 68cm²) 2 I prepared ). After washing the frame with pure water, electrolytic degreasing was performed using a 10 g / L NaOH solution at a voltage of 6 V for 5 minutes.

[0060] After electrolytic degreasing, the frame was washed with pure water, then immersed in pure water and subjected to ultrasonic cleaning for 5 minutes. After ultrasonic cleaning, the frame was rinsed with pure water, then air-blown, and finally dried.

[0061] For the frame that has completed the above process (different from the example, no magnetic polishing treatment, chemical polishing treatment, and ultrasonic cleaning for 30 minutes in a reduced-pressure environment), the same in-liquid particle evaluation as in the example was performed, and the measurement results in Table 1 were obtained.

[0062] (Comparative Example 2) A titanium frame having the same shape as in the example (outer dimensions: 150 mm × 118 mm × 1.5 mm, frame width: 4.0 mm, surface area: 68 cm 2 ) was prepared. After washing the frame with pure water, degreasing treatment was performed using a NaOH solution with a concentration of 10 g / L at a voltage of 6 V for 5 minutes.

[0063] After washing the frame after degreasing treatment with pure water, it was immersed in pure water and ultrasonic cleaning was performed for 5 minutes. Then, it was immersed in pure water again, and ultrasonic cleaning was performed for 30 minutes in a reduced-pressure environment. After ultrasonic cleaning, the frame was washed with pure water, air-blowing was performed, and then it was dried.

[0064] For the frame that has completed the above process (different from the example, no magnetic polishing treatment and chemical polishing treatment), the same in-liquid particle evaluation as in the example was performed, and the measurement results in Table 1 were obtained.

[0065]

Table 1

[0066] <Regarding the particle number evaluation> Table 1 shows the number of particles with each equivalent spherical diameter and their total value. Also, the value obtained by dividing the total value by the surface area of the pellicle frame "the number of particles released per 1 cm 2 of the pellicle frame (50 ml of pure water)" and the converted value obtained by multiplying that value by 60 (3 L / 50 ml) "the total number of particles released by 1 cm 2 of the pellicle frame (in terms of 3 L of pure water conversion)" are shown. The surface area of the pellicle frame per 1 cm in each example 2The number of particles per unit area, i.e., "pellicle frame 1cm" in Table 1. 2 The total number of particles emitted (calculated per 3L of pure water) was 641 in Example, compared to 8629 in Comparative Example 1 and 1928 in Comparative Example 2. As can be seen from this particle evaluation, the number of particles such as dust particles adhering to the surface of the flame in Example was significantly reduced.

[0067] (Comparative Example 3) A pellicle frame was manufactured in the same manner as in the examples, except that electrolytic degreasing and chemical polishing were not performed, and the same liquid particle evaluation was carried out as in the examples. Pellicle frame surface area 1 cm 2 The number of particles per unit area was 10,252. This was a significantly worse result compared to the 641 in the example. This is likely because, since electrolytic degreasing and chemical polishing were not performed, a large amount of organic matter adhering to the surface, as well as dust particles generated during magnetic polishing, remained, and these could not be effectively removed by pure water washing.

[0068] <About the ion elution test> The amount of ion elution was evaluated for the pellicle frames of the Examples and Comparative Examples 1 and 2. Specifically, each pellicle frame was placed in a polyethylene bag, 100 ml of pure water was added, and the bag was sealed. The bag was then immersed at 90°C for 3 hours. The extracted water, from which the eluted components from the pellicle frames were extracted, was analyzed using an ion chromatograph (Thermo Fisher Scientific ICS-2100) at a cell temperature of 35°C, a column (IonPacAS11-HC) temperature of 40°C, and an ion flow rate of 1.5 ml / min.

[0069] Acetate ions, formate ions, chloride ions, nitrite ions, nitrate ions, sulfate ions, oxalate ions, phosphate ions, and ammonium ions were detected from the above-mentioned extracted water, and the pellicle frame surface area was 50 cm². 2 The elution concentration per 100 ml of pure water was determined.

[0070] The results are shown in Table 2. The quantitative limit (lower limit) of the ion chromatograph used for evaluation varied depending on the ion species, ranging from 0.01 to 0.001 ppm. The units for each value in Table 2 are ppb, and "0" indicates that the ion species was not quantified.

[0071] [Table 2]

[0072] As shown in Table 2, both the Example and Comparative Examples 1 and 2 showed low ion elution concentrations and excellent results. Considering this together with the particle number evaluation results, it can be seen that the Example is a high-quality pellicle frame that significantly reduces the number of particles on the surface while also reducing the amount of ions generated.

[0073] <About Pellicle Manufacturing> The frame of the example was washed with a neutral detergent and pure water. A mixture of 100 parts by mass of silicone adhesive (X-40-3264, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1 part by mass of hardener (PT-56, manufactured by Shin-Etsu Chemical Co., Ltd.) was added and mixed, and this mixture was applied to the entire circumference of the upper end surface of the frame to a thickness of 0.1 mm. Furthermore, a mixture of 100 parts by mass of acrylic adhesive (SK Dyne 1499M, manufactured by Soken Chemical Co., Ltd.) and 0.1 parts by mass of hardener (L-45, manufactured by Soken Chemical Co., Ltd.) was added and mixed, and this mixture was applied to the entire circumference of the lower end surface of the frame to a thickness of 0.1 mm. Next, the pellicle frame was heated at 100°C for 12 hours to cure the adhesive on the upper and lower end surfaces. Subsequently, an ultra-thin silicone film was pressed onto the adhesive on the upper end surface of the frame to complete the pellicle.

[0074] <Regarding the unevenness of the inner surface> Each corner of the pellicle frame in the example was cut, and the steps and irregularities on the inner surface (inner wall surface) of each side were observed using a laser microscope (Olympus 3D measuring laser microscope LEXT OLS4000). Further details about the 3D measuring laser microscope OLS400 are as follows: ·LSM Department Light source: 405nm semiconductor laser • Color Observation Department Light source: white LED

[0075] The observation method is described below. First, four frame pieces were created by cutting the four corners of the frame with a cutter. The frame pieces were placed on the microscope stage so that the inner surface of each piece faced the objective lens. Hereafter, the direction from one corner to the next will be referred to as the "length direction," and the direction from the top surface to the bottom surface will be referred to as the "thickness direction." For the four frame pieces mentioned above, the presence or absence of irregularities and steps at the grain boundaries was checked in a 1cm area along the length direction using a 20x objective lens (MPLAPONLEXT20, measurement area 640μm × 640μm) at 1x zoom. If a length of 1cm could not be secured, observation was performed in several locations to total 1cm. Observation with a 20x objective lens allows for easy observation of the crystal grains on the surface and enables observation of a wide area. However, the outer edge region of the frame is often sloped toward the edge, and burrs and scratches may be present, making it unsuitable for observation. Therefore, it is desirable to observe the area excluding the outer edge region, which accounts for 10% of the thickness.

[0076] The height or depth of steps or indentations can be measured by taking images with a laser microscope. However, laser microscopes have a poor ability to detect height at low magnifications, so measurements at high magnifications using 50x or 100x objective lenses are recommended. Here, depending on the size of the steps or irregularities being observed, images were captured using either a 50x objective lens (MPLAPONLEXT50, measurement area 256μm × 256μm) or a 100x objective lens (MPLAPONLEXT100, measurement area 128μm × 128μm). The height or depth of the steps or irregularities was measured by performing step measurements on the captured images. In step measurements, a one-shot filter (height noise reduction, surface correction) was applied to remove the effects of noise and undulation. The difference between the highest and lowest points of the steps or irregularities was measured and confirmed to be 5μm or less. Thus, even if irregularities exist on the inner surface of the pellicle frame in this example, their height or depth is extremely small, which can be said to indicate good quality in this respect as well.

[0077] For the observation, the noise reduction conditions for the height of the surface irregularities and the surface correction conditions were as follows. [Conditions for reducing height-related noise] serrated surface High brightness: 4095 interpolation Low brightness: 0 interpolation [Surface correction conditions] Tilt correction (automatic)

[0078] This specification includes the following embodiments: [1]: A pellicle frame that constitutes a pellicle for photolithography, The pellicle frame is made of pure titanium or titanium alloy, and on the surface Mechanical polishing treatment, Electrolytic degreasing treatment, Pellicle frames are those that have undergone a chemical polishing treatment. [2]: The pellicle frame is, In particle evaluation by immersing in pure water and irradiating with ultrasound for one minute, the number of particles with an equivalent spherical diameter of 1 to 15 μm released into the pure water corresponds to the surface area of ​​the pellicle frame (1 cm²). 2 The pellicle frame described above [1] has 1500 or fewer pieces per frame. [3]: The pellicle frame according to [1] or [2] above, wherein the irregularities on the inner surface of the pellicle frame are 5 μm or less. [4]: The pellicle frame is, In an ion elution test, where the ion concentration is measured after immersion in pure water at 90°C for 3 hours, the pellicle frame has a surface area of ​​50 cm². 2 The elution concentration per 100 ml of pure water is as follows: Acetate ions are 10 ppb or less. Formate ions are less than 100 ppb. Cl ions are less than 10 ppb. NO2 ions are below 10 ppb. NO3 ions are less than 10 ppb. SO4 ions are less than 10 ppb. Oxalate ions are 10 ppb or less. PO4 ions are 10 ppb or less. NH4 ions are less than 100 ppb. A pellicle frame of any of the above [1] to [3]. [5]: A method for manufacturing a pellicle frame that constitutes a pellicle for photolithography, On the surface of the pellicle frame made of pure titanium or titanium alloy, Mechanical polishing treatment, Electrolytic degreasing treatment, A method for manufacturing pellicle frames by applying a chemical polishing treatment. [6]: The mechanical polishing treatment is performed as follows: A method for manufacturing the pellicle frame described above [5], comprising only magnetic polishing, barrel polishing, or a combination thereof. [7]: The magnetic polishing process is performed as follows: A method for manufacturing the pellicle frame described above [6], using a rod-shaped SUS magnetic media in washing water in which the pellicle frame is immersed. [8]: The chemical polishing treatment is performed as follows: A method for manufacturing a pellicle frame according to any of the above [5] to [7], comprising a chemical polishing treatment or an electropolishing treatment. [9]: A pellicle for photolithography comprising a pellicle frame and a pellicle film stretched over the pellicle frame, A pellicle in which the pellicle frame is any of the pellicle frames described in [1] to [4] above.

[10] : An exposure master and an exposure master with a pellicle attached, The pellicle is the pellicle described in [9] above, and the exposure plate is a pellicle-attached plate.

[11] : An exposure method using the pellicle-attached exposure master plate described in

[10] above.

[12] : A method for manufacturing a semiconductor device, comprising the step of exposure using the exposure master plate with pellicle described in

[10] above.

[13] : A method for manufacturing a liquid crystal display panel, comprising the step of exposure using the exposure master plate with pellicle described in

[10] above.

[0079] Furthermore, the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. A method for manufacturing a pellicle frame that constitutes a pellicle for photolithography, On the surface of the pellicle frame made of pure titanium or titanium alloy, When manufacturing by applying mechanical polishing, electrolytic degreasing, and chemical polishing in that order, A method for manufacturing a pellicle frame, characterized in that, as the mechanical polishing treatment, the pellicle frame is immersed in washing water containing a surfactant and subjected to magnetic polishing.

2. The aforementioned mechanical polishing treatment The method for manufacturing a pellicle frame according to claim 1, characterized in that it consists solely of the combination of the magnetic polishing treatment and the barrel polishing treatment.

3. The aforementioned magnetic polishing process, A method for manufacturing a pellicle frame according to claim 1, characterized in that it is carried out using a rod-shaped magnetic medium made of stainless steel.

4. The aforementioned chemical polishing treatment A method for manufacturing a pellicle frame according to any one of claims 1 to 3, characterized by comprising a chemical polishing treatment or an electrolytic polishing treatment.

Images