Mask frame, mask and method for preparing mask frame

Abstract

The present invention relates to a mask frame and a preparation method thereof, and a mask. The mask frame comprises: a frame substrate, a black anodized film with a thickness of 2.0 to 7.5 μm formed on the surface of the frame substrate, and a transparent polymer electrodeposition coating formed on the anodized film. The mask comprises: the mask frame and a mask film arranged on one end face of the mask frame.

Description

Technical Field

[0001] The present invention relates to a pellicle for planographic printing used for dust removal of a photomask in the preparation of a semiconductor device or a liquid crystal display, a pellicle frame constituting the pellicle, and a method for preparing the pellicle frame. Background Art

[0002] In the production of semiconductor devices such as LSI and super LSI or liquid crystal displays, photolithography technology is used to form a pattern by irradiating light onto a semiconductor wafer or a liquid crystal plate (original plate).

[0003] In the photolithography process, if dust adheres to the photomask (exposure plate), the dust will absorb light or distort light. As a result, there are problems such as deformation of the transferred pattern, rough edges, and black base, which may affect the size, quality, and appearance. Therefore, these operations are usually performed in a clean room, but it is difficult to keep the photomask completely clean even in a clean room. Therefore, in order to remove dust, a mask that can well transmit the exposure light is usually installed on the surface of the photomask. As a result, dust does not adhere directly to the surface of the photomask but adheres to the mask film. Therefore, if the focus is overlapped with the pattern on the photomask in advance during exposure, the dust on the mask film has nothing to do with the transfer.

[0004] The structure of a common mask is shown in Figure 2 In the mask, a mask film 101 that can well transmit the exposure light is laid on the upper end surface of the mask frame 102 through an adhesive 103, and an adhesive layer 104 for sticking the mask on the photomask 105 is formed on the lower end surface of the mask frame 102. In addition, a diaphragm (not shown) that can be peeled off and used to protect the adhesive layer 104 can also be set on the lower end surface of the adhesive layer 104. Such a mask is set according to the pattern area 106 formed on the surface of the photomask. Therefore, the pattern area 106 is isolated from the outside by the mask to prevent dust from adhering to the photomask.

[0005] In recent years, LSI design rules have been refined to sub-quarter micron. As a result, the size of particles that are the target of contamination suppression has also become smaller. In addition, the wavelength of the exposure light source has also become shorter, making it easier to generate tiny particles that cause haze due to exposure.

[0006] The reason is that since the energy of light increases due to the shortened wavelength of exposure, the gaseous substances present in the exposure atmosphere react to generate reaction products on the mask substrate. For example, acids such as sulfuric acid, nitric acid, and organic acids are mixed into the anodized film on the surface of the aluminum alloy used for the mask frame. These acids are separated from the anodized film on the surface of the frame under the exposure environment and are retained in the space between the mask and the mask. By irradiating the short-wavelength ultraviolet rays during exposure in this state, sulfuric acid compounds such as ammonium sulfate are generated.

[0007] Therefore, the existing frameworks subjected to anodizing treatment (anodizing treatment) have been gradually avoided because they contain sulfate ions. Therefore, for example, in Patent Document 1, a mask subjected to polymer coating is proposed as a framework without sulfate ion elution. In this document, as polymer coating, a black matte photodeposited coating film using a matte coating colored with a black pigment is disclosed.

[0008] In addition, Patent Document 2 discloses a mask frame having a pure aluminum film formed on the surface of a frame substrate made of an aluminum alloy, and then an anodized and black-dyed frame is subjected to an electrodeposition coating to form a transparent acrylic resin film. The pure aluminum film is used to cover the crystals on the surface of the aluminum alloy that cause bright spots (defects) and are mistaken for foreign matter on the surface of the mask frame, thereby improving the appearance quality or reliability of the mask.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Publication No. 2007-333910;

[0012] Patent document 2: Japanese Patent Application Publication No. 2014-206661. Summary of the invention

[0013] Problems to be solved by the invention

[0014] In the exposure process of photolithography, it is usually set so that the mask frame is not irradiated with exposure light, but part of the reflected or refracted light at the edge of the pattern may be irradiated onto the inner side of the mask frame as stray light. When such stray light is irradiated onto the inner side of the mask frame that is polymer-coated as described in Patent Document 1, there is a risk that the polymer coating layer (polymer coating layer) is etched and pigment particles dispersed therein may fall off.

[0015] It should be noted that the maximum amount of stray light irradiated to the inner side of the mask frame is about 1.5% of the intensity of the ArF laser irradiated to the photomask pattern area. At present, since the light resistance of the ArF mask film is required to be about 100,000 J, the light resistance required for the inner side of the mask frame is equivalent to 1500 J.

[0016] On the other hand, when a coating film is formed by electrodeposition coating on a frame substrate having an anodic oxide film formed thereon, it is sometimes difficult to form a uniform coating film, and the yield rate is significantly reduced. This is believed to be because the anodic oxide film is non-conductive.

[0017] In addition, when the thickness non-uniformity of the electrodeposition coating is relatively slight, it is difficult to detect the non-uniform part, and it is difficult to detect defective products by appearance inspection. In this case, the thinner film may be damaged by the exposure light, and the anodic oxide film may be exposed, resulting in blurring.

[0018] Therefore, an object of the present invention is to provide a mask frame which can prevent the photomask from being contaminated by acid detachment or the like even when stray light is irradiated to the inner side of the mask frame during the exposure process of photolithography, thereby suppressing the occurrence of surface defects mistaken for foreign matter and making it easy to perform appearance inspection, and a mask including the mask frame. In addition, an object of the present invention is to provide a method for preparing the mask frame with a good yield.

[0019] Means for solving problems

[0020] The inventors have conducted intensive research to solve the above-mentioned problem and found that the problem can be solved by setting the anodized film to a specific range with a relatively small thickness and then providing a transparent polymer electrodeposition coating on the anodized film, thereby coming up with the present invention. That is, the present invention is as follows.

[0021] [1] A mask frame comprising: a frame substrate, a black anodized film having a thickness of 2.0 to 7.5 μm formed on a surface of the frame substrate, and a transparent polymer electrodeposition coating film formed on the anodized film.

[0022] [2] The mask frame described in [1], wherein the transparent polymer electrodeposition coating film does not contain an uneven component that is unevenly present in the transparent polymer electrodeposition coating film.

[0023] [3] The mask frame described in [1] or [2], wherein the transparent polymer electrodeposition coating film does not contain a dye.

[0024] [4] The mask frame described in any one of [1] to [3], wherein the visible light transmittance of the transparent polymer electrodeposition coating exceeds 50%.

[0025] [5] A mask comprising: the mask frame described in any one of [1] to [4], and a mask film provided on one end surface of the mask frame.

[0026] [6] A method for preparing a mask frame, which comprises, in sequence: a step of forming an anodized film with a thickness of 2.0 to 7.5 μm on the surface of a frame substrate, a step of coloring the anodized film in black, and a step of forming a transparent polymer electrodeposition coating on the anodized film.

[0027] Effects of the Invention

[0028] According to the present invention, a mask frame and a mask including the mask frame can be provided, wherein the mask frame does not contaminate the photomask due to acid detachment or the like even when stray light is irradiated to the inner side of the mask frame during the exposure process of photolithography, thereby suppressing the occurrence of surface defects mistaken for foreign matter and facilitating appearance inspection. In addition, a method for preparing the mask frame with a good yield can be provided.

[0029] In addition, compared with the conventional structure of the polymer-coated mask frame, the irradiation amount of the exposure light can be increased, or the energy of the exposure light used can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] [ Figure 1 ] is a cross-sectional schematic diagram of a mask involved in one embodiment of the present invention.

[0031] [ Figure 2 ] is a cross-sectional schematic diagram showing the general structure of a conventional mask. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

[0033] [1] Mask framework

[0034] The mask frame according to the present embodiment includes a frame base, a black anodized film having a thickness of 2.0 to 7.5 μm formed on the surface of the frame base, and a transparent polymer electrodeposition coating film formed on the anodized film.

[0035] (Frame base material)

[0036] As the frame substrate of the mask frame, a material capable of forming an anodic oxide film can be used. Among them, aluminum and aluminum alloys are preferably used from the aspects of strength, rigidity, lightness, processability, cost, etc. As aluminum alloys, JIS A7075, JIS A6061, JIS A5052, etc. can be listed.

[0037] (anodized film)

[0038] The anodic oxide film is a film obtained by electrolytically treating the surface of the frame substrate, and in the case of the present invention, specifically refers to an alumite film.

[0039] The thickness of the anodic oxide film is 2.0 to 7.5 μm, preferably 2.0 to 7.0 μm, and more preferably 3.0 to 5.0 μm. The thickness of the anodic oxide film of the conventional mask frame is about 10 μm, but the film thickness is reduced in the present embodiment. In this way, the film resistance will not be excessively increased, so a polymer electrodeposition coating with uniform film thickness can be implemented in the subsequent process. In particular, by setting it to less than 7.5 μm, the color spots of the mask frame, that is, the difference in black tones caused by the uneven film thickness of the transparent polymer electrodeposition coating film, can be suppressed. In addition, the surface anomalies of the mask frame, that is, the generation of defects caused by the parts where the transparent polymer electrodeposition coating film is not formed, can be suppressed. As a result, the generation of surface defects that are mistaken for foreign matter is suppressed, and it becomes easy to perform appearance inspection. In addition, by setting the film thickness to more than 2 μm, a black mask frame that is conducive to the appearance inspection of the presence or absence of foreign matter is obtained.

[0040] The anodic oxide film involved in this embodiment is black. By being black, a mask that can easily detect foreign matter even in foreign matter inspection can be obtained. Here, "black" means that the L value of the mask frame is black to the extent of being 35 or less. In order to make it black, for example, it is sufficient to color the anodic oxide film in black in the coloring process described later.

[0041] (Transparent polymer electrodeposition coating)

[0042] The transparent polymer electrodeposition coating film is a transparent polymer coating film formed by electrodeposition coating. The electrodeposition coating film may be any of a cationic electrodeposition coating film and an anionic electrodeposition coating film.

[0043] The resin used for the transparent polymer electrodeposition coating includes epoxy resin, acrylic resin, amino acrylic resin, polyester resin and the like. It can be selected from known resins as long as heat resistance, light resistance, strength and the like are taken into consideration. However, as described later, it is preferred to select the transparent polymer electrodeposition coating so that the visible light transmittance exceeds 50%.

[0044] The transparent polymer electrodeposition coating may be a single layer, but may also be laminated with two or more layers. In the case of lamination, any of the laminated transparent polymer electrodeposition coatings preferably contains the same resin composition. In this way, it is difficult to produce failures such as peeling from the interface of the transparent polymer electrodeposition coating.

[0045] The transparent polymer electrodeposition coating film preferably does not contain uneven components and dyes that are unevenly present in the transparent polymer electrodeposition coating film. As uneven components, there are components (particularly granular uneven components) that are unevenly present in the transparent polymer electrodeposition coating film, such as pigments and fillers, and components that produce flickering (キラつき) in the appearance inspection of the mask frame. Regarding dyes, since flickering is sometimes produced, it is preferably not contained. In other words, the transparent polymer electrodeposition coating film is preferably composed of only resin components.

[0046] The visible light transmittance of the transparent polymer electrodeposition coating film is preferably more than 50%, more preferably 80% or more. The visible light transmittance can be measured using a commercially available spectrophotometer.

[0047] If the transparent polymer electrodeposition coating film transmits visible light well, the color tone of the base of the transparent polymer electrodeposition coating film can be reflected as the color tone of the mask frame. At this time, if the anodic oxide film as the base of the transparent polymer electrodeposition coating film is black, the mask frame is also black. If the color tone of the mask frame is black, a mask that is easy and conducive to detecting foreign matter can be obtained even in the appearance inspection for checking the presence or absence of foreign matter.

[0048] With such a structure, the L value of the mask frame is preferably set to 35 or less, and more preferably set to 30 or less. Here, the L value is an index showing the brightness of a color when a black body (an ideal object that absorbs all wavelengths incident on its surface and neither reflects nor transmits) is 0 and the opposite white is 100. If the L value exceeds 35, it becomes difficult to detect foreign matter in the appearance inspection, and the operability is reduced.

[0049] The thickness of the transparent polymer electrodeposition coating film is not limited, but is preferably 2 μm or more, more preferably 2.0 to 10.0 μm, in consideration of the energy of ArF laser light generally used as exposure light.

[0050] The mask frame as described above corresponds to the shape of the photomask to which the mask is attached, and is generally in a quadrilateral frame shape such as a rectangular frame shape or a square frame shape.

[0051] The mask frame may be provided with an air pressure adjustment hole, so that there is no air pressure difference inside and outside the closed space formed by the mask and the photomask, and the expansion or depression of the mask film can be prevented.

[0052] It is preferred to install a dust removal filter on the air pressure adjustment hole. The dust removal filter can prevent foreign matter from invading the closed space between the mask and the photomask from the air pressure adjustment hole.

[0053] As the material of the dust removal filter, resin, metal, ceramic, etc. are listed. In addition, it is also preferable to equip the outer part of the dust removal filter with a chemical filter that adsorbs or decomposes chemical substances in the environment.

[0054] An adhesive may be applied to the inner peripheral surface of the mask frame or the inner wall surface of the air pressure adjustment hole in order to capture foreign matter present in the closed space between the mask and the photomask.

[0055] In addition, a hole or a groove for inserting an operating jig may be provided on the mask frame, and a concave portion or a convex portion may be provided as required.

[0056] [2] Method for preparing mask frame

[0057] The preparation method of the mask frame involved in this embodiment includes, in sequence: a process of forming an anodized film with a thickness of 2.0~7.5μm on the surface of the frame substrate (anodized film forming process), a process of coloring the anodized film into black (coloring process), and a process of forming a transparent polymer electrodeposition coating on the anodized film (transparent polymer electrodeposition coating forming process).

[0058] (Anodic Oxide Film Forming Step)

[0059] In the anodic oxide film forming step, an anodic oxide film is formed on the frame substrate, but it is preferably roughened by sandblasting or chemical grinding before that. Regarding the surface roughening method of the frame substrate, a conventionally known method can be used. For example, for a frame substrate of an aluminum alloy, a method of spraying the surface with stainless steel, corundum (silicon carbide), glass beads, etc., or chemically grinding with an alkaline solution such as NaOH can be used.

[0060] After any of the above roughening, an anodic oxide film is formed on the surface of the frame substrate. The anodic oxide film can be formed by a known method. Usually, the anodic oxide film (aluminum oxide) of aluminum and aluminum alloy is formed by sulfuric acid method, oxalic acid method, chromic acid method, etc. In the common mask frame, sulfuric acid aluminum oxide using sulfuric acid method is mostly used.

[0061] In particular, when sulfuric acid-resistant aluminum is formed by the sulfuric acid method, the film thickness can be well adjusted to a range of 2.0 to 7.5 μm by adjusting the processing time and other conditions. In addition, by making the film thickness within the range of 2.0 to 7.5 μm, the generation of surface defects that are mistaken for foreign matter is suppressed, and it becomes easier to perform appearance inspection, and products that are not originally defective products will no longer be judged as defective products, which can improve the yield rate of the mask.

[0062] (Coloring process)

[0063] In the coloring step, a blackening treatment is performed to color the anodic oxide film black. If the mask frame is black, stray light is suppressed in the appearance inspection of the mask frame for checking the presence or absence of dust by reflection of light by irradiating the mask frame with light, making it easier to check dust.

[0064] The blackening treatment can be carried out by a known method, and a treatment using a black dye or an electrolytic deposition treatment (secondary electrolysis) can be listed, preferably a dyeing treatment using a black dye, and more preferably a dyeing treatment using an organic black dye. It is generally believed that the content of the acid component of the organic dye is small, and it is preferred to use an organic dye with a small content of sulfuric acid, acetic acid and formic acid. As such an organic dye, commercially available "TAC411", "TAC413", "TAC415", "TAC420" (all of which are made by Okuno Pharmaceutical) and the like can be listed, which can be implemented as follows: the frame material after anodizing treatment is immersed in a dye solution modulated to a specified concentration, and the dyeing treatment is carried out for about 10 minutes under the treatment conditions of a treatment temperature of 40 to 60 ° C and a pH of 5 to 6.

[0065] After the blackening treatment, the anodic oxide film is preferably sealed. There are no particular restrictions on the sealing treatment, and a known method such as using water vapor or a sealing bath can be used. However, from the perspective of sealing the acid component, the sealing treatment using water vapor is preferred. As the conditions for the sealing treatment using water vapor, for example, as long as the temperature is 105-130°C, the relative humidity is 90-100% (RH), and the pressure is 0.4-2.0 kg / cm 2 G treatment may be performed for about 12 to 60 minutes. In addition, after the sealing treatment, it is preferred to use pure water for washing, for example.

[0066] (Transparent polymer electrodeposition coating film forming process)

[0067] In the transparent polymer electrodeposition coating forming step, a transparent polymer electrodeposition coating is formed on the anodized film subjected to the above treatment. By forming the transparent polymer electrodeposition coating, the color tone of the black mask frame can be reflected, and the inspection for the presence of foreign matter becomes easy even in the appearance inspection.

[0068] Resins used for transparent polymer electrodeposition coatings include epoxy resins, acrylic resins, amino acrylic resins, polyester resins, and the like. Resins may be selected from known resins in consideration of heat resistance, light resistance, strength, and the like.

[0069] It should be noted that since the transparent polymer electrodeposition coating preferably does not contain uneven components such as dyes, pigments or fillers, it is preferred to design the material so as not to contain these components. This can prevent glitter caused by particles, that is, prevent the dyes or uneven components from becoming foreign matter and forming bright spots.

[0070] Transparent polymer electrodeposition coating films are formed by electrodeposition coating due to advantages such as uniformity of film thickness and smoothness.

[0071] Regarding electrodeposition coating, both thermosetting resins and ultraviolet curing resins can be used. In addition, for various resins, both anion electrodeposition coating and cationic electrodeposition coating can be used, but since the amount of gas generated is small, the possibility of defects such as pinholes on the coating film is low, so the anion electrodeposition coating method with the coated object as the anode is preferred.

[0072] Coating equipment used for electrodeposition coating or coating materials for electrodeposition coating can be purchased as commercial products from some companies. For example, there can be mentioned electrodeposition coating materials sold under the trade name of Elecoat from Shimizu Co., Ltd.

[0073] [3] Mask

[0074] The mask according to the present embodiment includes a mask frame and a mask film provided on one end surface of the mask frame.

[0075] As the material of the mask film, there is no particular restriction, and the material with high transmittance and high light resistance under the wavelength of the light of exposure is preferred. For example, an existing amorphous fluoropolymer used for excimer laser is used. As examples of amorphous fluoropolymers, Cytop (サイトップ) (trade name made by Asahi Glass Co., Ltd.), Teflon (Teflon) (registered trademark), AF (trade name made by DuPont Co., Ltd.), etc. can be listed. These polymers can be dissolved in a solvent as needed when making the mask film, for example, suitable dissolutions such as fluorine-based solvents can be used. In addition, when EUV light is used as an exposure light source, an extremely thin silicon film or graphene film with a film thickness of less than 1 μm can be used.

[0076] When bonding the mask film to the mask frame, a good solvent for the mask film may be applied to the mask frame and then air-dried for bonding, or an acrylic resin adhesive, epoxy resin adhesive, silicone resin adhesive, fluorine-containing silicone adhesive, etc. may be used for bonding.

[0077] The mask further has a device (means) for mounting on the photomask, and an adhesive layer is usually provided on the other end face of the mask frame. The adhesive layer is spread over the entire circumference of the lower end face of the mask frame and is formed in a width that is the same as or less than the width of the mask frame. The preferred thickness is 0.2 to 0.5 mm.

[0078] As the material of the adhesive layer, known adhesives such as rubber adhesives, polyurethane adhesives, acrylic adhesives, SEBS adhesives, SEPS adhesives, and silicone adhesives can be used. When EUV light is used as an exposure light source, a silicone adhesive having excellent light resistance is preferably used. In addition, an adhesive having less outgassing that can cause blurring is preferred.

[0079] Usually, the diaphragm provided on the lower end surface of the adhesive layer can also be omitted by designing a mask storage container, etc. In the case of providing a diaphragm, for example, a film composed of polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), polypropylene (PP), etc. can be used as a diaphragm. In addition, a release agent such as a silicone release agent or a fluorine release agent can be applied to the surface of the diaphragm as needed.

[0080] A schematic cross-sectional view of a specific example of the mask according to this embodiment is shown in Figure 1 First, the mask frame 2 includes: a frame substrate 7, a black anodized film 8 formed on the frame substrate 7, and a transparent polymer electrodeposition coating film 9 formed on the anodized film 8. On the upper end surface of the mask frame 2, a mask film 1 that transmits the exposure light well is laid by an adhesive 3, and an adhesive layer 4 for sticking the mask on the photomask 5 is formed on the lower end surface of the mask frame 2. In addition, a removable diaphragm (not shown) for protecting the adhesive layer 4 can be provided on the lower end surface of the adhesive layer 4. Such a mask is provided in accordance with the pattern area 6 formed on the surface of the photomask. Therefore, the pattern area 6 is isolated from the outside by the mask to prevent dust from adhering to the photomask. Example

[0081] Hereinafter, the present invention will be described based on Examples, but the present invention is not limited to these Examples.

[0082] <Example 1>

[0083] First, as a frame substrate for the mask, an aluminum frame with a frame size of 149 mm × 115 mm × 4.5 mm and a frame thickness of 2 mm was prepared. The surface of the frame substrate was subjected to sandblasting. The sandblasting was performed using a sandblasting device, spraying glass beads (30 to 100 μm) at a discharge pressure of 1.5 kg for 10 minutes.

[0084] Next, an anodic oxide film (aluminum oxide) with a thickness of 7.0 μm was formed on the frame substrate by a sulfuric acid method. The electrolytic bath used to form the anodic oxide film was 15 mass % sulfuric acid, the electrolytic voltage was set to 20 V, and the charge was set to 15 c / cm 2 , set the processing time to 20 minutes.

[0085] The anodized film was immersed in a dye solution obtained by adjusting "TAC420" (produced by Okuno Pharmaceutical) to a specified concentration, and the anodized film was colored black for 10 minutes under the treatment conditions of a treatment temperature of 40 to 60°C and a pH of 5 to 6. The anodized film was then dried at a temperature of 110°C, a relative humidity of 90 to 100% (RH), and a pressure of 1.0 kg / cm 2 G treatment for 15 minutes to seal the pores.

[0086] Next, after washing the frame substrate with pure water, an anionic electrodeposition coating (temperature 25°C, voltage 140V, 5 minutes) was applied to the frame substrate using an electrodeposition coating that does not contain particles such as pigments or fillers (Elecoat AM manufactured by Shimizu Corporation). As a result, a transparent polymer electrodeposition coating with a thickness of 9 μm was formed on the anodized film. The frame subjected to the electrodeposition coating was heated at 200°C for 60 minutes to cure the transparent polymer electrodeposition coating to produce a mask frame. In addition, for the transparent polymer electrodeposition coating (thickness: 10 μm) prepared separately, when the transmittance in the visible light region was measured using UV-1850 manufactured by Shimadzu Corporation, it was 82%.

[0087] The L value of the mask frame thus obtained was measured using a spectrocolorimeter (NF-555 manufactured by Nippon Denshoku Industries, Ltd.) and found to be 23.

[0088] When 10 mask frames were similarly prepared and subjected to appearance inspection, all the frames showed no color spots observed when the transparent polymer electrodeposition coating film was uneven or surface abnormalities observed when the transparent polymer electrodeposition coating film was not formed.

[0089] A mask film (a mask film with a thickness of 0.28 μm made of Cytop (Stop) S type manufactured by Asahi Glass Co., Ltd.) is laid on one end face of the mask frame where no color spots or surface abnormalities are observed using an adhesive (Cytop (Stop) A type manufactured by Asahi Glass Co., Ltd.), and an adhesive layer is formed on the other end face using a silicone adhesive (X-40-3264 manufactured by Shin-Etsu Chemical Co., Ltd.) to complete the mask.

[0090] The irradiation of the inner side of the frame of the produced mask was set to 5mJ / cm 2 / pulse, 500 Hz ArF laser. When the state of the inner side surface of the frame was inspected in a dark room by irradiating with a spotlight 30 minutes after the ArF laser irradiation (total energy: 4500 J), no flickering due to particles was observed.

[0091] Ion analysis was performed using another mask prepared in the same manner. The mask was immersed in 100 ml of pure water at 90° C. for 3 hours, and then ion analysis was performed on the immersed water. However, sulfate ions were not detected.

[0092] <Example 2>

[0093] The mask frame was prepared in the same manner as in Example 1 except that the thickness of the anodic oxide film (aluminum oxide) was 2.0 μm. Although the anodic oxide film was colored, the color was slightly lighter, and the L value of the mask frame was 32. In addition, the transmittance of the transparent polymer electrodeposition coating in the visible light region measured in the same manner as in Example 1 was 83%.

[0094] When 10 mask frames were similarly prepared and subjected to appearance inspection, all the frames showed no color spots observed when the transparent polymer electrodeposition coating film was uneven or surface abnormalities observed when the transparent polymer electrodeposition coating film was not formed.

[0095] The irradiation rate of the inner side of the frame of the mask prepared in the same manner as in Example 1 was set to 5 mJ / cm 2 / pulse, 500 Hz ArF laser. When the state of the inner side surface of the frame was inspected in a dark room by irradiating with a spotlight 30 minutes after the ArF laser irradiation (total energy: 4500 J), no flickering due to particles was observed.

[0096] It should be noted that it takes 1.2 times as much time to inspect 10 mask frames as compared to Example 1. If the required time is 1.5 times or less as compared to Example 1, it can be said that the throughput is good.

[0097] Ion analysis was performed using another mask prepared in the same manner. The mask was immersed in 100 ml of pure water at 90° C. for 3 hours, and then ion analysis was performed on the immersed water. However, sulfate ions were not detected.

[0098] <Example 3>

[0099] A mask frame was prepared in the same manner as in Example 1 except that the thickness of the anodic oxide film (anodic aluminum) was 3.0 μm. The anodic oxide film was colored black, and the L value of the mask frame was 29. The transmittance of the transparent polymer electrodeposition coating in the visible light region measured in the same manner as in Example 1 was 82%.

[0100] When 10 mask frames were similarly prepared and subjected to appearance inspection, all the frames showed no color spots observed when the transparent polymer electrodeposition coating film was uneven or surface abnormalities observed when the transparent polymer electrodeposition coating film was not formed.

[0101] The irradiation rate of the inner side of the frame of the mask prepared in the same manner as in Example 1 was set to 5 mJ / cm 2 / pulse, 500 Hz ArF laser. When the state of the inner side surface of the frame was inspected in a dark room by irradiating with a spotlight 30 minutes after the ArF laser irradiation (total energy: 4500 J), no flickering due to particles was observed.

[0102] Ion analysis was performed using another mask prepared in the same manner. The mask was immersed in 100 ml of pure water at 90° C. for 3 hours, and then ion analysis was performed on the immersed water. However, sulfate ions were not detected.

[0103] <Example 4>

[0104] A mask frame was prepared in the same manner as in Example 1 except that the thickness of the anodic oxide film (anodic aluminum) was 5.0 μm. The anodic oxide film was colored black, and the L value of the mask frame was 26. The transmittance of the transparent polymer electrodeposition coating in the visible light region measured in the same manner as in Example 1 was 82%.

[0105] When 10 mask frames were similarly prepared and subjected to appearance inspection, all the frames showed no color spots observed when the transparent polymer electrodeposition coating film was uneven or surface abnormalities observed when the transparent polymer electrodeposition coating film was not formed.

[0106] The irradiation rate of the inner side of the frame of the mask prepared in the same manner as in Example 1 was set to 5 mJ / cm 2 / pulse, 500 Hz ArF laser. When the state of the inner side surface of the frame was inspected in a dark room by irradiating with a spotlight 30 minutes after the ArF laser irradiation (total energy: 4500 J), no flickering due to particles was observed.

[0107] Ion analysis was performed using another mask prepared in the same manner. The mask was immersed in 100 ml of pure water at 90° C. for 3 hours, and then ion analysis was performed on the immersed water. However, sulfate ions were not detected.

[0108] <Comparative Example 1>

[0109] The mask frame was prepared in the same manner as in Example 1 except that the thickness of the anodic oxide film (aluminum oxide) was 1.5 μm. Although the anodic oxide film was colored, the color was light (light brown), and the L value of the mask frame was 39. In addition, the transmittance of the transparent polymer electrodeposition coating in the visible light region measured in the same manner as in Example 1 was 82%.

[0110] When 10 mask frames were similarly prepared and subjected to appearance inspection, all the frames showed no color spots observed when the transparent polymer electrodeposition coating film was uneven or surface abnormalities observed when the transparent polymer electrodeposition coating film was not formed.

[0111] The irradiation rate of the inner side of the frame of the mask prepared in the same manner as in Example 1 was set to 5 mJ / cm 2 / pulse, 500 Hz ArF laser. When the state of the inner side surface of the frame was inspected in a dark room by irradiating with a spotlight 30 minutes after the ArF laser irradiation (total energy: 4500 J), no flickering due to particles was observed.

[0112] At this time, since the color of the mask frame is light and the brightness is high, it will be illuminated if a spotlight is shone on it. Compared with Example 1, it takes 1.8 times longer to check 10 mask frames.

[0113] Ion analysis was performed using another mask prepared in the same manner. The mask was immersed in 100 ml of pure water at 90° C. for 3 hours, and then ion analysis was performed on the immersed water. However, sulfate ions were not detected.

[0114] <Comparative Example 2>

[0115] A mask frame was prepared in the same manner as in Example 1 except that the thickness of the anodic oxide film (aluminum oxide) was 10.0 μm. The anodic oxide film was colored black, and the L value of the mask frame was 22. The transmittance of the transparent polymer electrodeposition coating in the visible light region measured in the same manner as in Example 1 was 83%.

[0116] When 10 mask frames were similarly prepared and subjected to appearance inspection, 7 frames showed color spots observed when the transparent polymer electrodeposition coating film was uneven or surface abnormalities observed when the transparent polymer electrodeposition coating film was not formed.

[0117] Using a mask frame without color spots or surface abnormalities, the inner side of the frame was irradiated with 5 mJ / cm2 in the same manner as in Example 1. 2 / pulse, 500 Hz ArF laser. When the state of the inner side surface of the frame was inspected in a dark room by irradiating with a spotlight 30 minutes after the ArF laser irradiation (total energy: 4500 J), no flickering due to particles was observed.

[0118] Ion analysis was performed using another mask prepared in the same manner. The mask was immersed in 100 ml of pure water at 90° C. for 3 hours, and then ion analysis was performed on the immersed water. However, sulfate ions were not detected.

[0119] <Comparative Example 3>

[0120] A mask frame was prepared in the same manner as in Example 1 except that the thickness of the anodic oxide film (anodic aluminum) was 8.0 μm. The anodic oxide film was colored black, and the L value of the mask frame was 23. The transmittance of the transparent polymer electrodeposition coating in the visible light region measured in the same manner as in Example 1 was 82%.

[0121] When 10 mask frames were similarly prepared and subjected to appearance inspection, color spots observed when the transparent polymer electrodeposition coating film was uneven or surface abnormalities observed when the transparent polymer electrodeposition coating film was not formed were observed in 5 frames.

[0122] Using a mask frame without color spots or surface abnormalities, the inner side of the frame was irradiated with 5 mJ / cm2 in the same manner as in Example 1. 2 / pulse, 500 Hz ArF laser. When the state of the inner side surface of the frame was inspected in a dark room by irradiating with a spotlight 30 minutes after the ArF laser irradiation (total energy: 4500 J), no flickering due to particles was observed.

[0123] Ion analysis was performed using another mask prepared in the same manner. The mask was immersed in 100 ml of pure water at 90° C. for 3 hours, and then ion analysis was performed on the immersed water. However, sulfate ions were not detected.

[0124] <Comparative Example 4>

[0125] First, as a mask frame substrate, an aluminum frame having a frame outer dimension of 149 mm×115 mm×4.5 mm and a frame thickness of 2 mm was prepared. The surface of the frame substrate was subjected to the same sandblasting treatment as in Example 1.

[0126] Next, an anodic oxide film (aluminum oxide) was formed on the frame substrate with a film thickness of 6.0 μm by the same sulfuric acid method as in Example 1. The anodic oxide film was colored black in the same manner as in Example 1, and then a sealing treatment was performed. Then, the frame was washed with pure water to complete the mask frame. The L value of the mask frame obtained by the above operation was 24.

[0127] The mask was completed in the same manner as in Example 1 using the obtained mask frame.

[0128] When ion analysis was performed in the same manner as in Example 1 using the produced mask, sulfate ions were detected.

[0129] <Comparative Example 5>

[0130] First, as a mask frame substrate, an aluminum frame having a frame outer dimension of 149 mm×115 mm×4.5 mm and a frame thickness of 2 mm was prepared.

[0131] Next, carbon black (Shimizu Co., Ltd., trade name: Elecoat Color Black) was mixed at a concentration of 10 g / L and filler (Shimizu Co., Ltd., trade name: Elecoat ST Satiner) was mixed at a concentration of 55 g / L in an electrodeposition paint (Shimizu Co., Ltd., Elecoat AM) and the mixed paint was used to apply anion electrodeposition coating to the frame substrate in the same manner as in Example 1. Thus, a polymer layer with a thickness of 9 μm was formed. The frame subjected to the electrodeposition coating was heated at 200°C for 60 minutes to cure the polymer layer. It should be noted that the transmittance of the polymer layer in the visible light region measured in the same manner as in Example 1 was 1-10%. In addition, the L value of the mask frame obtained in this manner was 20-25.

[0132] Using the obtained mask frame, the mask was completed in the same manner as in Example 1.

[0133] The inner side of the frame of the produced mask was irradiated with ArF laser in the same manner as in Example 1. 30 minutes after the ArF laser irradiation (cumulative energy: 4500 J), the state of the inner side of the frame was checked by irradiating a spotlight in a dark room, and flickering caused by particles was observed.

[0134] It can be seen that in the embodiment, not only is there no elution of sulfate ions, but also no particles are generated even when stray light is irradiated to the inner side of the mask frame, which can prevent contamination of the photomask. In addition, the generation of surface defects that are mistaken for foreign matter is suppressed, making it easy to perform appearance inspection.

[0135] Explanation of symbols

[0136] 1. 101 Mask

[0137] 2.102 Mask Frame

[0138] 3.103 Adhesive

[0139] 4.104 Adhesive layer

[0140] 5.105 Photomask

[0141] 6.106 Pattern Area

[0142] 7 Frame base material

[0143] 8 Anodic oxide coating

[0144] 9 Transparent polymer electrodeposition coating.

Claims

1. A mask frame comprising: a frame substrate, an anodic oxide film having a thickness of 2.0 μm or more and less than 5.0 μm formed on the surface of the frame substrate, and a transparent polymer electrodeposition coating film formed on the anodic oxide film, The visible light transmittance of the coating film exceeds 50%. The L value of the anodized film is 35 or less. The L value is an index indicating the brightness of a color when a black body is 0 and an opposite white is 100. The black body is an ideal object that absorbs all wavelengths incident on its surface and neither reflects nor transmits. The above-mentioned anodic oxide film contains sulfate ions. The above-mentioned anodic oxide film is sulfuric acid-resistant aluminum.

2. The mask frame of claim 1, wherein: The coating film does not contain any uneven components.

3. The mask frame of claim 1, wherein: The above coating film does not contain a dye.

4. The mask frame of claim 1, wherein: The transparent polymer electrodeposition coating film covered the anodic oxide film so that when the mask frame was immersed in 100 ml of pure water at 90° C. for 3 hours and the immersed water was subjected to ion analysis, no sulfate ions were detected.

5. The mask frame of claim 2, wherein: The transparent polymer electrodeposition coating film covered the anodic oxide film so that when the mask frame was immersed in 100 ml of pure water at 90° C. for 3 hours and the immersed water was subjected to ion analysis, no sulfate ions were detected.

6. The mask frame of claim 3, wherein: The transparent polymer electrodeposition coating film covered the anodic oxide film so that when the mask frame was immersed in 100 ml of pure water at 90° C. for 3 hours and the immersed water was subjected to ion analysis, no sulfate ions were detected.

7. The mask frame of any one of claims 1, 3, 4 and 6, wherein: The coating film does not contain any uneven component that is unevenly present in the coating film.

8. The mask frame according to any one of claims 2, 5 and 7, wherein: The above-mentioned non-uniform components are in a granular form.

9. The mask frame of claim 1, wherein: The anodic oxide film is subjected to a sealing treatment.

10. The mask frame of claim 1, wherein: The coating film has a visible light transmittance of 80% or more.

11. The mask frame of claim 1, wherein: The frame substrate is made of aluminum or aluminum alloy.

12. The mask frame of claim 1, wherein: The thickness of the anodic oxide film is 3.0 μm or more and less than 5.0 μm.

13. The mask frame of claim 1, wherein: The above-mentioned L value is 30 or less.

14. The mask frame of claim 1, wherein: The coating film has a thickness of 2 μm or more.

15. The mask frame of claim 1, wherein: The coating film has a thickness of 2.0 to 10.0 μm.

16. The mask frame of claim 1, wherein: The resin used for the above coating film is epoxy resin, acrylic resin, amino acrylic resin or polyester resin. 17 . A mask comprising: the mask frame according to claim 1 , and a mask film provided on one end surface of the mask frame.

18. The mask of claim 17, wherein: The mask film is an amorphous fluoropolymer, a silicon film or a graphene film having a film thickness of less than 1 μm.

19. The mask of claim 17, wherein: The mask film is arranged on one end surface of the mask frame via an adhesive.

20. The mask of claim 17, wherein: An adhesive layer is arranged on the other end surface of the mask frame.

21. A method for preparing a mask frame, comprising: The steps of forming an anodic oxide film having a thickness of 2.0 μm or more and less than 5.0 μm on the surface of the frame substrate by a sulfuric acid method, and coloring the anodic oxide film, and a step of forming a transparent polymer electrodeposition coating film on the above-mentioned anodic oxide film, The visible light transmittance of the coating film exceeds 50%. The L value of the anodized film is 35 or less. The L value is an index indicating the brightness of a color when a black body is 0 and an opposite white is 100. The black body is an ideal object that absorbs all wavelengths incident on its surface and neither reflects nor transmits. The above-mentioned anodic oxide film contains sulfate ions. The above-mentioned anodic oxide film is sulfuric acid-resistant aluminum.

22. A photomask with a mask, which is formed by attaching the mask according to claim 17 to a photomask.

23. An exposure method, comprising the step of performing exposure using the photomask with a mask according to claim 22.

24. The exposure method according to claim 23, wherein: The above exposure is exposure using ArF laser.

25. A method for manufacturing a semiconductor device, comprising the step of performing exposure using the photomask with a mask according to claim 22.

26. The method for preparing a semiconductor device according to claim 25, wherein: The above exposure is exposure using ArF laser.

27. A method for producing a liquid crystal display, comprising the step of performing exposure using the photomask with a mask according to claim 22.

28. The method for preparing a liquid crystal display according to claim 27, wherein: The above exposure is exposure using ArF laser.

29. Use of the mask frame according to any one of claims 1 to 16 in preparing a mask, wherein the mask is used for preparing a semiconductor device.

30. Use of the mask frame according to any one of claims 1 to 16 in a mask used in the preparation of a semiconductor device.

31. Use of the mask frame according to any one of claims 1 to 16 for preparing a mask for exposure by ArF laser.

32. Use of the mask frame according to any one of claims 1 to 16 in a mask used for exposure using ArF laser.

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