Pellicle frame, and pellicle

Abstract

To provide a pellicle frame that prevents the discharge and generation of dust and foreign matter remaining on the frame during the frame manufacturing process, suppresses the generation of additional dust and foreign matter during transport, storage, and use, and even if dust or foreign matter adheres to the frame, allows for easy washing; and to provide a pellicle using such a frame.SOLUTION: The present invention provides a pellicle frame and a pellicle including the pellicle frame. The pellicle frame includes a frame base material made of Ti or a Ti alloy and a metal layer laminated on a surface of the frame base material. The metal layer comprises one or a plurality of layers. The surface of the pellicle frame includes an outermost surface layer of the metal layer, and when the surface of the outermost surface layer is measured at a magnification of 1200x using a laser microscope compliant with JIS B0601, at least the inner surface has a region with an arithmetic mean surface roughness Ra of 0.10 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pellicle frame and pellicle that are attached to lithography photomasks used in the manufacture of semiconductors, liquid crystals, etc. to protect against dust, and more particularly to a pellicle frame and pellicle for EUV. [Background technology]

[0002] In recent years, LSI design rules have been miniaturized from submicron to sub-quarter micron, and at the same time, lithography wavelengths have been shortened. That is, exposure light sources have shifted from mercury lamp g-line (436 nm) and i-line (365 nm) to KrF (248 nm) and ArF (193 nm) excimer lasers, and further to EUV (Extreme Ultra Violet; 13.5 nm), which are now being put into practical use in some cutting-edge devices.

[0003] The manufacture of semiconductors such as LSIs and VLSIs typically involves coating a semiconductor wafer with resist, placing the wafer in an exposure machine along with a lithography photomask bearing the desired circuit pattern, and then irradiating the photomask with light to transfer the circuit pattern onto the semiconductor wafer. While these operations are typically performed in clean rooms designed to minimize dust, dust particles from people, equipment, or the environment often end up on the mask during transportation and installation after mask creation. This dust particles are transferred along with the circuit pattern, resulting in abnormal circuits and defective semiconductors, resulting in reduced manufacturing yields.

[0004] Therefore, as a preventative measure, it is common practice to attach a dust-blocking pellicle to the mask immediately after the mask is made, as described in Non-Patent Document 1. This is because if a pellicle is attached to the mask all at once, even if dust flies in, it is blocked by the pellicle and cannot reach the circuit pattern of the mask, and even if it lands on the pellicle film, it is at a distance from the mask surface, so by focusing the exposure light on the circuit pattern, the dust on the pellicle will not be transferred due to "out of focus."

[0005] A pellicle generally consists of a metal frame, a pellicle film that is highly transparent and light-resistant to the exposure wavelength and is stretched over the upper surface of the frame with an adhesive, and an airtight seal formed on the lower surface of the frame using a relatively light-resistant adhesive such as acrylic or silicone.Furthermore, a vent hole is drilled in the frame and a filter is provided to cover this hole in order to reduce the air pressure difference inside and outside the pellicle after it is attached to the mask.

[0006] Pellicle films are required to have high transmittance and lightfastness at the exposure wavelength. For example, nitrocellulose is used for g-line (436 nm), cellulose propionate for i-line (365 nm), and amorphous fluoropolymers for KrF excimer laser (248 nm) and ArF excimer laser (193 nm). For EUV (extreme ultraviolet; 13.5 nm) exposure, materials with high transmittance and lightfastness to EUV light are selected, and inorganic materials are generally preferred over organic materials. Among these, monocrystalline silicon, polycrystalline silicon, amorphous silicon, or their nitrides, oxynitrides, and carbides, as well as metal silicides such as molybdenum silicide and CNF, are often selected for their low cost, reproducible, and uniform film formation. For further protection, protective films made of SiC, SiO2, Si3N4, SiON, YO3, YN, Mo, Ru, and Rh are also available. In order to obtain high transmittance, thicknesses of the above films of submicron thickness or less have been investigated, and some of these have already been put to practical use.

[0007] Among these, conventional pellicles using transmitted light for exposure, such as g-line (436 nm), i-line (365 nm), KrF excimer laser (248 nm), and ArF excimer laser, which are used under atmospheric pressure, generally use a frame made of relatively low-hardness aluminum or aluminum alloy (duralumin) for light weight, processability, and cost. Black anodizing is typically applied to increase the surface hardness and to prevent stray light from reflecting off the frame. This black anodizing process involves anodizing the aluminum, filling the resulting pores with black pigment or dye, and then sealing them. However, the sealing process is not always perfect, resulting in numerous voids and crater-like irregularities on the surface. These irregularities and pores created by the anodizing process often allow residual dust and foreign matter, or even part of the encapsulated pigment or dye, to escape during processing or the anodizing process, posing a cleanliness challenge. Therefore, in the case of rough devices exposed to long wavelengths, an anodized aluminum frame is often used as is, but in the case of fine devices exposed to short wavelengths, frames designed to prevent the emission of residual dust and foreign matter remaining during processing, or pigments and dyes during black anodizing, from these voids and craters are used (see Non-Patent Document 1 for details).The pellicle is made by stretching the pellicle membrane described above over this frame, and the ventilation filter is made of a nonwoven fabric made of fibers such as PET or PTFE with a diameter of several tens to several hundreds of microns.

[0008] Meanwhile, in recent years, practical applications of pellicles for EUV (extreme ultraviolet; 13.5 nm), which use reflected light for exposure in a vacuum or reduced pressure, have begun. Instead of conventional Al or Al alloy (duralumin) frames, the use of Ti or Ti alloys is being considered (Patent Documents 1 and 2). These Ti or Ti alloys are relatively light, have higher strength and hardness than Al or Al alloys, are less likely to deform, and are corrosion resistant, and do not require the black anodized aluminum treatment that poses a problem in terms of cleanliness. Patent Document 1 describes a Ti or Ti alloy with a linear expansion coefficient of 10 × 10 -6 (1 / K) or less, and the density is 4.6 g / cm 3The following pellicle frame made of Ti or a Ti alloy, Patent Document 2, discloses a pellicle frame made of Ti with a thickness of less than 2.5 mm, having at least one notch formed from the outer surface of the upper end face toward the inner surface. [Prior art documents] [Patent documents]

[0009] [Non-Patent Document 1] "Electronic Materials" July 1997 issue P.103 [Patent Document 1] Japanese Patent Application Publication No. 2019-70745 [Patent Document 2] Japanese Patent Publication No. 2020-126095 Summary of the Invention [Problem to be solved by the invention]

[0010] Unlike conventional exposure methods that use transmitted light, EUV exposure uses reflected light, which means that the mask installation space is extremely narrow due to the impact of securing space for the long reflected light path, and as a result, the space available for EUV pellicles is also extremely limited. Due to these space restrictions and their intended use, pellicle frames are also required to have more precise processing accuracy than before, as well as thorough prevention of dust and foreign matter emissions at sub-micron levels and cleanliness control.

[0011] For this reason, Ti or a Ti alloy is used, which has a higher surface hardness than Al or Al alloys and makes it easier to improve processing precision. When processing the frame, in order to remove scratches, burrs, and irregularities that may become sources of dust or litter during processing, physical polishing is carried out using abrasives, polishing film, sandblasting or abrasive grains, buffing, etc., followed by chemical polishing such as electrolytic polishing, to increase the smoothness of the frame surface and openings.

[0012] However, the inventors have found that no matter how many times the currently performed physical polishing and further chemical polishing such as electrolytic polishing and cleaning are repeated, it is extremely difficult to completely remove from the frame the Ti and Ti alloy powders that are introduced during processing and the various types of dust and foreign matter that are mixed in from the environment.

[0013] The present invention has been made in consideration of the above circumstances, and aims to provide a pellicle frame that prevents the emission and generation of dust and foreign matter remaining on the frame during processing to create the frame, and that can also suppress the generation of new dust and foreign matter during transportation, storage, use, etc., and that can easily wash off dust and foreign matter even if it does adhere to the frame, and a pellicle using the same. [Means for solving the problem]

[0014] Therefore, the present inventors have made extensive efforts to identify the causes of the above problems and to find solutions to them, and as a result have arrived at the present invention. [1] A frame base material made of Ti or a Ti alloy; a metal layer laminated on a surface of the frame base material, the metal layer comprises one or more layers; the surface of the pellicle frame has an outermost surface layer of the metal layer, A pellicle frame having an area on at least the inner surface where the arithmetic mean surface roughness Ra is 0.10 μm or less when the surface of the outermost layer is measured at a magnification of 1200 times using a laser microscope in accordance with JIS B0601. [2] The pellicle frame according to [1], wherein the thickness of the outermost surface layer is 0.10 μm or more. [3] The pellicle frame according to [2], wherein the thickness of the outermost surface layer is 0.10 μm or more and 50 μm or less. [4] The pellicle frame according to any one of [1] to [3], wherein the outermost surface layer has a Vickers hardness of 160 or more. [5] The pellicle frame according to any one of [1] to [4], wherein the main component constituting the outermost surface layer is at least one of Ni and Cr. [6] The pellicle frame according to [5], wherein the main component constituting the outermost surface layer is Ni. [7] The pellicle frame according to [5], wherein the main component constituting the outermost surface layer is Cr. [8] The pellicle frame according to any one of [1] to [7], wherein the reflectance of the surface of the outermost layer is 20.0% or more when measured at a wavelength of 550 nm. [9] A pellicle frame according to any one of [1] to [8], wherein when the surface of the outermost layer is measured at a magnification of 1200 times using a laser microscope in accordance with JIS B0601, at least the inner surface has an area where the arithmetic mean surface roughness Ra is 0.10 μm or less.

[10] A pellicle having the pellicle frame according to any one of [1] to [9] above.

[11] The pellicle according to

[10] , wherein the pellicle is an EUV pellicle.

[12] An exposure master with a pellicle, in which the pellicle described in

[10] or

[11] above is attached to the exposure master.

[13] A method for manufacturing a pellicle, comprising the following steps (1) to (3), performed in the order listed: (1) forming a frame base material made of Ti or a Ti alloy; (2) subjecting the surface of the frame base material to either one or both of physical polishing and chemical polishing, and providing a region on at least the inner surface with an arithmetic mean surface roughness Ra of 0.30 μm or less when the surface is measured at a magnification of 1200 times using a laser microscope in accordance with JIS B0601; (3) A step of laminating an outermost surface layer made of a metal layer including one or more layers on the surface of the frame base material.

[14] The manufacturing method according to

[13] , wherein only physical polishing is performed in the step (2).

[15] The manufacturing method according to

[13] , wherein only chemical polishing is performed in the step (2).

[16] The manufacturing method according to

[13] , wherein in the step (2), both physical polishing and chemical polishing are carried out in the order listed.

[17] The method according to any one of

[13] to

[16] , wherein in the step (3), the outermost layer has a thickness of 0.10 μm or more.

[18] The manufacturing method according to

[17] , wherein in the step (3), the thickness of the outermost surface layer is 0.10 μm or more and 50 μm or less.

[19] The manufacturing method according to any one of

[13] to

[18] , wherein in the step (3), the outermost surface layer has a Vickers hardness of 160 or more.

[20] The method according to any one of

[13] to

[19] above, wherein the main component of the outermost surface layer in the step (3) is at least one of Ni and Cr.

[21] The method according to

[20] , wherein the main component of the outermost surface layer is Ni.

[22] The method according to

[20] , wherein the outermost layer is mainly composed of Cr.

[23] The method according to any one of

[13] to

[22] , wherein in the step (3), the reflectance of the surface of the outermost layer is 20.0% or more when measured at a wavelength of 550 nm.

[24] The manufacturing method according to any one of

[13] to

[23] , wherein, in the step (3), when the surface of the outermost layer is measured at a magnification of 1200 times using a laser microscope in accordance with JIS B0601, at least the inner surface has a region where the arithmetic mean surface roughness Ra is 0.10 μm or less. [Effects of the Invention]

[0015] According to the present invention, it is possible to prevent the emission and generation of dust and foreign matter by fixing dust and foreign matter remaining on the frame during processing to create the pellicle frame and reinforcing irregular parts, and it is also possible to suppress the generation of new dust and foreign matter during transportation, storage, use, etc. Furthermore, it is possible to provide a pellicle frame, pellicle, and pellicle-equipped exposure master plate that can easily be washed off even if dust or foreign matter adheres to the frame. [Brief explanation of the drawings]

[0016] [Figure 1] These are photographs of the outermost surface of a pellicle frame measured with a laser microscope at 1200 to 7200x magnification for "surface roughness Ra" for examples of (1) a physically polished product, (2) a product (physical polishing + chemical polishing), and (3) a product (physical polishing + chemical polishing) + metal lamination. [Figure 2] FIG. 1 is a perspective view showing an example of a pellicle frame of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The inventors have endeavored to identify the root cause of the generation of dust and foreign matter. As a result, they have found that even when a pellicle frame is formed from Ti or a Ti alloy, and then the surface and opening of the frame are physically polished with a grindstone, abrasive grains, or a buff, and / or chemically polished with an electrolytic polishing method, and then cleaned, the surface may appear to the naked eye to be free of dust or foreign matter and extremely smooth and mirror-like. However, when observed with a non-contact laser microscope (e.g., Keyence VK-X3000, 1200x field of view), it is actually found that there are in fact countless irregularities, or rather, large peaks and valleys, as shown in Figure 1. The inventors have discovered that dust and foreign matter remain in the depths of these peaks and valleys during processing, and that new dust and foreign matter are generated from irregularities in the peaks and valleys that are vulnerable to impact. It was realized that this was because the peaks and valleys had become like "garbage dumps" or "garbage generators," causing endless and persistent detection of garbage and foreign objects not only during processing, but also during transportation, storage, and use, and that this was also the reason why it was difficult to completely eliminate them.

[0018] During these investigations, we came to realize the limitations of both methods: when observing the outermost surface of a pellicle frame, we could get a rough overall view of it with the naked eye, but could not see the details; on the other hand, when using various microscopes, especially electron microscopes, the magnification is too high and we could see the details of an extremely limited, tiny field of view, but it was difficult to get a grasp of the overall picture.

[0019] However, through various experiments, the inventors discovered that a method that complements these shortcomings and enables both a general overview and detailed observation is to quantitatively grasp the relative smoothness of the entire frame by observing and calculating the arithmetic mean surface roughness Ra in accordance with JIS B0601 using a non-contact laser microscope at a magnification of 1200x. As can be seen in Figure 1, when comparing observations of surface roughness Ra using a laser microscope at magnifications of 1200x, 3600x, and 7200x, the details at 3600x and 7200x are too fine to grasp the overall picture. In contrast, observation at 1200x is preferable because it provides a good balance of the necessary information about the outermost surface details and the overall picture for the frame of the EUV pellicle of the present invention. Therefore, this magnification was specified in the present invention.

[0020] As mentioned above, the inventors of the present invention found that the peaks and valleys of the frame acted as "garbage pits" or "garbage generators" for dust and foreign matter, and they conducted extensive research into ways to improve this. As a result, they discovered that if the frame base material was subjected to physical and / or chemical treatment in advance to smooth and clean it, and then at least one layer of metal was laminated on this surface layer, it was possible to fix the remaining dust and foreign matter, just as if placing a lid on the above-mentioned "garbage pits" or "garbage generators," and this would also function as a reinforcing layer for irregularities that could cause new dust and foreign matter to be generated, thereby preventing this.

[0021] To make the present invention more effective, it is preferable that the surface layer smoothed by subjecting the frame base material to the above-mentioned physical and / or chemical treatment has, at least on the inner surface, a region in which the arithmetic mean surface roughness Ra according to JIS B0601 is 0.30 μm or less when observed under a laser microscope (1200x magnification). This is because, when the arithmetic mean surface roughness Ra is 0.30 μm or less, by laminating at least one more metal layer on this surface layer, even if the laminated film thickness is somewhat thin, dust and foreign matter remaining in the peaks and valleys or irregularities are sufficiently fixed or reinforced, and it acts as a so-called "dust pit or lid for a dust generator," making it possible to prevent the discharge of remaining dust and foreign matter and the generation of new dust and foreign matter. On the other hand, if the surface is rough with an arithmetic mean surface roughness Ra exceeding 0.30 μm, the peaks and valleys will be too high or too deep, and even with the metal lamination, the "garbage pit" or "garbage generator" will not be completely fixed or reinforced sufficiently, thereby reducing the effect of the invention.

[0022] The arithmetic mean surface roughness Ra of the surface of the frame base material may be calculated by measuring the surface of the frame base material using a laser microscope or the like in accordance with JIS B0601:1994. Specifically, in observing the surface of the frame base material, a Keyence VK-3000 laser microscope was used in accordance with JIS B0601:1994 to measure Ra at 30 random locations within the observation screen at a magnification of 1200x (objective lens magnification of 50x), and the average value of Ra at the 30 locations was taken as the arithmetic mean surface roughness Ra. The arithmetic mean surface roughness Ra is the value expressed in micrometers (μm) calculated by the following formula when a reference length is extracted from a roughness curve in the direction of the mean line, the X axis is taken in the direction of the mean line of this extracted portion, and the Y axis is taken in the direction of the vertical magnification, and the roughness curve is expressed as y = f(x): TIFF2025118905000001.tif14170For the measurements at the 30 locations, 30 lines with a cutoff length of 250 μm are selected at 3 μm intervals in the center of the inner surface of each side of the frame base material, which is the object, and measurements are taken.The arithmetic mean surface roughness Ra of each line is found using the above formula, and the average value of these is calculated as the arithmetic mean surface roughness Ra of the 30 locations. Here, the method for measuring the arithmetic mean surface roughness Ra of the inner surface of the frame base material has been explained as an example, but the arithmetic mean surface roughness Ra of the inner surface of the pellicle frame can also be measured in a similar manner.

[0023] In the present invention, the metal laminated on the frame member, i.e., the metal constituting the metal layer, may be any metal that has affinity with Ti or a Ti alloy. However, if a metal that does not have affinity with Ti or a Ti alloy must be used for the outermost layer, the outermost layer is prone to peeling. Therefore, a metal that has affinity with both Ti or a Ti alloy and the metal constituting the outermost layer can be laminated on the frame member as a base, and then a metal that does not have affinity with Ti or a Ti alloy can be laminated on top of the base metal. This will increase costs, but will prevent peeling of the outermost layer. Therefore, the metal layer may be composed of a single layer or multiple layers. Furthermore, the type of metal to be laminated is not particularly limited, but metals with significantly different thermal expansion coefficients from the Ti or Ti alloy base material of the frame should be avoided.

[0024] On the other hand, among the metals laminated onto the frame component, the metal ultimately constituting the outermost surface layer of the frame is selected from harder metals with a Vickers hardness (HV hardness) of 160 or greater and corrosion resistance, which can protect the Ti or Ti alloy base material from scratches and corrosion during transportation, installation, and use of the frame and the pellicle using it. This is because the Vickers hardness of JIS Class 2 Ti, an example of a frame base material constituting the present invention, is 110 to 155 HV. If the Vickers hardness (HV hardness) of the laminated metal is less than 160, the Ti surface of the frame base material will not be sufficiently protected. Therefore, considering both the above-mentioned hardness and corrosion resistance, metals such as Ni (HV = 500 to 1100 for heat-treated products) and Cr (HV = 800 to 1000 for heat-treated products) are suitable for constituting the outermost surface layer. Therefore, the main component of the outermost surface layer of the metal layer constituting the present invention is preferably at least one of Ni and Cr.

[0025] The thickness of the outermost layer of the metal layer should be determined taking into account its thermal expansion coefficient. A thickness of at least 0.10 μm or more will result in insufficient fixation and reinforcement of the remaining dust and foreign matter in the peaks and valleys and irregularities in the peaks and valleys, resulting in insufficient effectiveness. On the other hand, a thickness greater than 50 μm can easily deform the frame due to thermal stress between the frame base material and the laminated metal caused by the difference in thermal expansion coefficients. This can lead to the laminated metal and other materials dropping off from the irregularities, resulting in dust and foreign matter, or deformation of the exposure pattern. Therefore, a thickness of 0.10 to 50 μm is generally preferred, but ultimately depends on performance and cost. Methods for laminating this metal to the frame base material include physical methods such as sputtering, EB, and MBE, and chemical methods such as MOCVD, LTCVD, electrolytic, and electroless plating. While there are no particular limitations, LTCVD and various electrolytic and electroless plating methods are preferred from the perspective of film thickness uniformity.

[0026] The present invention achieves its effects by fabricating a frame base material from Ti or a Ti alloy, then physically processing it, such as grinding and polishing, optionally chemically processing it, such as electrolytic polishing, thoroughly cleaning it, and then laminating at least one metal layer on it to form the "garbage pit or garbage-generating lid." As can be seen in Figure 1 , until now, simply performing physical processing, such as grinding and polishing, followed by chemical processing, such as electrolytic polishing, and thoroughly cleaning the frame after fabrication has not been enough to prevent the discharge or generation of garbage and other foreign matter. This is because there was no "garbage pit or garbage-generating lid." Therefore, to prevent the accumulation of garbage and other foreign matter from the work environment or humans during frame fabrication, as well as subsequent transport, storage, installation, and use, it is more preferable to ensure that the arithmetic mean surface roughness Ra of the outermost layer of the laminated metal layer is 0.10 μm or less when observed with a laser microscope (1200x magnification). This is because if the unevenness of the outermost surface layer is minimized and flattened as much as possible, even if the above-mentioned dust and foreign matter gets mixed in, there is virtually no place for it to "accumulate," and further accumulation of dust and foreign matter is prevented. The aforementioned metal lamination fixes the remaining dust and foreign matter, and reinforces the irregular parts, preventing the discharge and generation of dust and foreign matter, thereby suppressing further accumulation and discharge of dust and foreign matter. Furthermore, even if dust or foreign matter does adhere to the frame, it can be easily washed off.

[0027] Detection and management of dust and foreign matter on pellicles and pellicle frames, particularly EUV pellicles and their frames, is typically performed using the EUV wavelength. However, because such measuring instruments are extremely expensive, they are currently often performed using instruments with wavelengths of at least 550 nm or less for convenience. Therefore, in the pellicle frame of the present invention, the reflectance of the surface of the outermost layer of the metal layer is preferably 20.0% or greater when measured at a wavelength of at least 550 nm. This is because, for the detection and management of minute dust and foreign matter that EUV poses a problem, a reflectance of less than 20.0% when measured at a wavelength of at least 550 nm makes it difficult to detect the dust and foreign matter, while a reflectance of 20.0% or greater facilitates contrast between the dust and foreign matter, increasing sensitivity and enabling accurate measurement. From the perspective of reflectance, it is also preferable for the arithmetic mean surface roughness Ra of the outermost layer of the laminated metal to be 0.10 μm or less when measured with a laser microscope (observed at 1200x magnification) in order to increase this reflectance. The reflectance can be measured by irradiating the outermost surface layer of the pellicle frame with light having a wavelength of 550 nm, and the average of the measured values can be taken as the reflectance of the surface of the outermost surface layer.

[0028] The method for producing a pellicle of the present invention is characterized by including the following steps (1) to (3), which are carried out in the order listed. (1) forming a frame base material made of Ti or a Ti alloy; (2) subjecting the surface of the frame base material to either one or both of physical polishing and chemical polishing, and providing a region on at least the inner surface with an arithmetic mean surface roughness Ra of 0.30 μm or less when the surface is measured at a magnification of 1200 times using a laser microscope in accordance with JIS B0601; (3) A step of laminating an outermost surface layer made of one or more metal layers on the surface of the frame base material. After the pellicle frame is prepared by the above step (3), the pellicle is manufactured according to a conventional method, such as by stretching a pellicle film on one end surface of the pellicle frame and providing an adhesive layer on the other end surface. An example of a pellicle frame of the present invention is shown in Figure 2, where reference numeral 11 denotes the inner surface of the pellicle frame, reference numeral 12 denotes the outer surface of the pellicle frame, reference numeral 13 denotes the upper end surface of the pellicle frame, reference numeral 14 denotes the lower end surface of the pellicle frame, and reference numeral P denotes the center of the inner surface of the pellicle frame. Note that a jig hole used to peel the pellicle from the photomask is usually provided on the long side of the pellicle frame, but this is not specifically shown in Figure 2.

[0029] In the pellicle of the present invention, a pellicle membrane is attached to the upper end surface of the pellicle frame via an adhesive. There are no limitations on the material of the adhesive, and any known adhesive can be used. For example, a good solvent for the pellicle membrane may be applied and then air-dried for adhesion, or an adhesive such as an acrylic resin, a silicone resin, or an epoxy resin may be used.

[0030] Furthermore, although there are no limitations on the material of the pellicle film, a material with high transmittance and high light resistance at the wavelength of the exposure light source is preferred. For example, amorphous fluoropolymers can be used for excimer lasers. Examples of amorphous fluoropolymers include Cytop (trade name, manufactured by Asahi Glass Co., Ltd.) and Teflon (registered trademark) AF (trade name, manufactured by DuPont Co., Ltd.).

[0031] Furthermore, for EUV exposure, single crystal silicon, polycrystalline silicon, amorphous silicon, or nitrides, oxynitrides, or carbides of these, or metal silicides such as molybdenum silicide, or CNF, etc. may be selected, and in order to further protect these film materials, a protective film such as SiC, SiO2, Si3N4, SiON, YO3, YN, Mo, Ru, or Rh may be provided.

[0032] Furthermore, an adhesive layer for attaching the pellicle frame to a photomask is formed on the lower end surface of the pellicle frame. Known adhesives for the mask can be used, including adhesives made of polybutene resin, polyvinyl acetate resin, SEBS (poly(styrene-ethylene-butadiene-styrene)) resin, acrylic resin, silicone resin, etc. Adhesives made of acrylic resin and silicone resin are particularly preferred.

[0033] The pellicle film adhesive and mask pressure-sensitive adhesive can be applied, for example, by dipping, spraying, brushing, or by using a dispenser coating device, but application using a dispenser coating device is preferred from the standpoints of stability, workability, yield, etc.

[0034] Furthermore, if the viscosity of the pellicle film adhesive and mask adhesive is high and application using an application device is difficult, aromatic solvents such as toluene and xylene, aliphatic solvents such as hexane, octane, isooctane and isoparaffin, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate and butyl acetate, ether solvents such as diisopropyl ether and 1,4-dioxane, or mixed solvents of these can be added as needed.

[0035] A release layer (separator) may be attached to the lower end surface of the mask adhesive to protect the adhesive. The material of the release layer is not particularly limited, but examples include polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), and polypropylene (PP). If necessary, a release agent such as a silicone-based release agent or a fluorine-based release agent may be applied to the surface of the release layer.

[0036] When a hole penetrating from the outer surface to the inner surface is provided in the pellicle frame, a dust filter may be provided for the purpose of removing particles. The filter may be installed inside the hole or on the side surface so as to cover the opening of the hole.

[0037] In the manufacture of a pellicle, the adhesive layer is usually applied and formed first, followed by the application of the pellicle film, but the order can also be reversed. The pellicle film is applied, for example, by applying an adhesive to the upper surface of the pellicle frame, then heating the pellicle frame to harden the adhesive, and finally attaching the upper surface of the pellicle frame, on which the adhesive layer for attaching the pellicle film has been formed, to a pellicle film mounted on an aluminum frame larger than the pellicle frame. Any excess pellicle film that extends beyond the pellicle frame is removed to complete the pellicle.

[0038] The pellicle is attached to an exposure master such as a photomask via an adhesive layer to obtain a pellicle-attached exposure master. The pellicle is placed so as to surround the pattern area formed on the surface of the exposure master.

[0039] In the present invention, it is sufficient that a region where the arithmetic mean surface roughness Ra is equal to or less than the above value is present on a portion of the inner surface of the frame base material or pellicle frame. From the viewpoint of manufacturing efficiency, the frame base material or pellicle frame can be surface-treated so that the arithmetic mean surface roughness Ra is equal to or less than the above value on preferably the entire inner surface, and more preferably the entire frame base material or frame surface (i.e., the entire upper end surface, lower end surface, inner surface, and outer surface of the frame base material or frame). In this case, the frame base material or pellicle frame does not need to be surface-treated in part. [Example]

[0040] The present invention will be specifically explained below by showing examples and comparative examples, but the scope of the present invention is not limited thereto.

[0041] [Example 1] A pellicle frame (external dimensions: 150 mm x 118 mm x 1.5 mm, frame thickness: 4.0 mm) was fabricated using JIS Class 2 Ti. The surface and pores were physically polished using an abrasive sheet and polishing slurry, then cleaned and polished to a mirror finish visible to the naked eye. The pellicle frame was then further polished and cleaned using a chemical electrolytic polishing process until the arithmetic mean surface roughness (Ra) measured using a non-contact laser microscope (1200x magnification) according to JIS B0601 was 0.12 μm. A 0.15 μm thick layer of Ni metal was then laminated onto the pellicle frame using LPCVD and cleaned. The top surface layer after this deposition and cleaning was measured using the same non-contact laser microscope (1200x magnification) and found to have an arithmetic mean surface roughness (Ra) of 0.09 μm according to JIS B0601, a reflectance of 24% at 550 nm, and a Vickers hardness of 550 HV. A 0.1 μm polycrystalline silicon film was stretched over the frame, and a filter consisting of 3 μm-average-diameter polypropylene fiber and 0.15 μm-average-diameter electrospun silica fiber was attached to the frame's air pressure adjustment vent to create an EUV pellicle. This pellicle was then attached via adhesive to a well-cleaned quartz glass plate simulating an exposure mask. This quartz glass plate was then installed in a simulated EUV device, and a pressure-adjusting simulation experiment was conducted in which the quartz glass plate was alternately evacuated and returned to atmospheric pressure, simulating the insertion and removal of the mask, to easily evaluate the effectiveness of the present invention. The simulation experiment involved 100 simulated insertions and removals of a quartz glass plate (a virtual mask) from the EUV device through repeated vacuuming and atmospheric pressure returns. The pellicle was then removed from the virtual mask, and the quartz glass plate was inspected for dust and foreign particles using a laser foreign particle inspection device. As a result, as shown in Table 1, there was no dust or foreign matter of 0.2 μm or larger, and no dust or foreign matter of less than 0.2 μm.

[0042] [Example 2] As in Example 1, a pellicle frame (external dimensions: 150 mm × 118 mm × 1.5 mm, frame thickness: 4.0 mm) was prepared using JIS Class 2 Ti. The surface and holes were then physically polished using an abrasive sheet and abrasive slurry, then cleaned and finished until a mirror finish was achieved as visible to the naked eye. The pellicle frame was then further polished and cleaned using a chemical electrolytic polishing process until the arithmetic mean surface roughness Ra according to JIS B0601 was 0.28 μm as measured under a non-contact laser microscope (observation at 1200x magnification). However, the pellicle preparation and subsequent evaluation were all the same except that instead of laminating Ni metal to a thickness of 0.15 μm using LPCVD, Cr metal was plated to a thickness of 20 μm. After lamination and cleaning, the outermost surface layer was measured with the non-contact laser microscope (observation at 1200x magnification) and found to have an arithmetic mean surface roughness Ra of 0.07μm, a reflectance of 75% at a wavelength of 550nm, and a Vickers hardness of 850HV. As shown in Table 1, the inspection results for dust and foreign matter on the quartz glass plate showed zero dust or foreign matter of 0.2μm or larger, and one dust or foreign matter smaller than 0.2μm.

[0043] [Comparative Example 1] As in Example 1, a pellicle frame (external dimensions: 150 mm x 118 mm x 1.5 mm, frame thickness: 4.0 mm) was prepared using JIS Class 2 Ti. The surface and pores were then physically polished using an abrasive sheet and polishing slurry, cleaned, and polished to a mirror finish visible to the naked eye. The pellicle frame was then further polished and cleaned using a chemical electropolishing process until the arithmetic mean surface roughness Ra (measured under JIS B0601) was 0.23 μm as measured under a non-contact laser microscope (1200x magnification). The pellicle was then polished and cleaned in the same manner as in Example 1, except that the subsequent LPCVD deposition of Ni metal to a thickness of 0.15 μm was omitted. The results of the inspection of the quartz glass plate for dust and foreign matter showed six dust particles and foreign matter 0.2 μm or larger and 15 dust particles and foreign matter smaller than 0.2 μm, as shown in Table 1.

[0044] Comparative Example 2 As in Example 1, a pellicle frame (external dimensions: 150 mm × 118 mm × 1.5 mm, frame thickness: 4.0 mm) was prepared using JIS Class 2 Ti. The surface and holes were then physically polished using an abrasive sheet and abrasive slurry, then cleaned and finished until a mirror finish was achieved as visible to the naked eye. The pellicle frame was then further polished and cleaned using a chemical electrolytic polishing process until the arithmetic mean surface roughness Ra according to JIS B0601 was 0.39 μm as measured with a non-contact laser microscope (observation at 1200x magnification). However, the pellicle preparation and subsequent evaluation were all the same except that instead of subsequently depositing Ni metal to a thickness of 0.15 μm by LPCVD, Ni metal was deposited to a thickness of 0.23 μm by LPCVD. After lamination and cleaning, the outermost surface layer was measured with the non-contact laser microscope (observation at 1200x magnification) and found to have an arithmetic mean surface roughness Ra of 0.19 μm, a reflectance of 26% at a wavelength of 550 nm, and a Vickers hardness of 557 HV. As shown in Table 1, the inspection results for dust and foreign matter on the quartz glass plate showed four pieces of dust and foreign matter larger than 0.2 μm, and 13 pieces of dust and foreign matter smaller than 0.2 μm.

[0045] Comparative Example 3 As in Example 1, a pellicle frame (external dimensions: 150 mm × 118 mm × 1.5 mm, frame thickness: 4.0 mm) was prepared using JIS Class 2 Ti. The surface and holes were then polished using a physical treatment with an abrasive sheet and abrasive slurry, followed by cleaning and finishing until a mirror finish was achieved as visible to the naked eye. The pellicle frame was then further polished and cleaned using a chemical treatment, electrolytic polishing, until the arithmetic mean surface roughness Ra according to JIS B0601 was 0.35 μm as measured under a non-contact laser microscope (observation at 1200x magnification). However, the pellicle preparation and subsequent evaluation were all the same except that instead of depositing Ni metal to a thickness of 0.15 μm by LPCVD, Ni metal was deposited to a thickness of 55 μm by plating. When the outermost surface layer after lamination and cleaning was measured with the non-contact laser microscope (observation at 1200x magnification) mentioned above, the arithmetic mean surface roughness Ra was 0.13μm (some cracks occurred), the reflectance at a wavelength of 550nm could not be measured due to deformation of the frame, and the Vickers hardness was 630HV. As shown in Table 1, the inspection results for dust and foreign matter on the quartz glass plate showed 53 pieces of dust and foreign matter larger than 0.2μm, and 135 pieces of dust and foreign matter smaller than 0.2μm.

[0046] [Table 1]

[0047] According to the results in Table 1, the pellicles using the pellicle frames of Examples 1 and 2 detected very little dust and foreign matter, demonstrating their effectiveness in suppressing the generation of dust and foreign matter. [Explanation of symbols]

[0048] 1 Pellicle frame 11 Inner surface of pellicle frame 12 Outer surface of pellicle frame 13 Upper surface of pellicle frame 14 Lower end surface of pellicle frame P Center of the inner surface

Claims

1. a frame base material made of Ti or a Ti alloy; a metal layer laminated on a surface of the frame base material, the metal layer comprises one or more layers; the surface of the pellicle frame has an outermost surface layer of the metal layer, when the surface of the outermost layer is measured at a magnification of 1200 times using a laser microscope in accordance with JIS B0601, at least the inner surface has a region having an arithmetic mean surface roughness Ra of 0.10 μm or less, A pellicle frame, wherein the reflectance of the surface of the outermost layer is 20.0% or more when measured at a wavelength of 550 nm.

2. 2. The pellicle frame according to claim 1, wherein the outermost surface layer has a thickness of 0.10 μm or more.

3. 3. The pellicle frame according to claim 2, wherein the thickness of the outermost surface layer is 0.10 μm or more and 50 μm or less.

4. 2. The pellicle frame according to claim 1, wherein the outermost surface layer has a Vickers hardness of 160 or more.

5. 2. The pellicle frame according to claim 1, wherein the main component constituting the outermost surface layer is at least one of Ni and Cr.

6. 6. The pellicle frame according to claim 5, wherein the main component constituting the outermost surface layer is Ni.

7. 6. The pellicle frame according to claim 5, wherein the main component constituting the outermost surface layer is Cr.

8. 2. A pellicle frame as described in claim 1, wherein when the surface of the frame base material is measured at a magnification of 1200 times using a laser microscope in accordance with JIS B0601, at least the inner surface has an area having an arithmetic mean surface roughness Ra of 0.30 μm or less.

9. A pellicle having the pellicle frame of claim 1.

10. The pellicle according to claim 9 , wherein the pellicle is an EUV pellicle.

11. An exposure master with a pellicle, comprising the pellicle according to claim 9 or 10 attached to the exposure master.

12. A method for manufacturing a pellicle, comprising the following steps (1) to (3), performed in the order listed: (1) A step of forming a frame base material made of Ti or a Ti alloy; (2) subjecting the surface of the frame base material to either one or both of physical polishing and chemical polishing, and providing a region on at least the inner surface with an arithmetic mean surface roughness Ra of 0.30 μm or less when the surface is measured at a magnification of 1200 times using a laser microscope in accordance with JIS B0601; (3) A step of laminating an outermost surface layer made of a metal layer including one or more layers on the surface of the frame base material. However, in the step (3), the reflectance of the surface of the outermost layer is 20.0% or more when measured at a wavelength of 550 nm.

13. The manufacturing method according to claim 12, wherein in the step (2), only physical polishing is performed.

14. The manufacturing method according to claim 12, wherein in the step (2), only chemical polishing is performed.

15. 13. The manufacturing method according to claim 12, wherein in the step (2), both physical polishing and chemical polishing are carried out in this order.

16. The method according to claim 12, wherein in the step (3), the thickness of the outermost surface layer is 0.10 μm or more.

17. The method according to claim 16, wherein in the step (3), the thickness of the outermost surface layer is 0.10 μm or more and 50 μm or less.

18. 13. The method according to claim 12, wherein in the step (3), the outermost surface layer has a Vickers hardness of 160 or more.

19. The method according to claim 12, wherein the main component of the outermost surface layer in the step (3) is at least one of Ni and Cr.

20. The manufacturing method according to claim 19, wherein the outermost surface layer is mainly composed of Ni.

21. The manufacturing method according to claim 19, wherein the outermost surface layer is mainly composed of Cr.

22. 13. The manufacturing method according to claim 12, wherein, in the step (3), when the surface of the outermost layer is measured at a magnification of 1200 times using a laser microscope in accordance with JIS B0601, at least the inner surface has a region having an arithmetic mean surface roughness Ra of 0.10 μm or less.

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