Pellicle frame, pellicle, method for producing pellicle, and method for evaluating pellicle frame

Abstract

To provide a pellicle frame capable of suppressing deformation of a photomask.SOLUTION: A pellicle frame includes one end face provided with an adhesive layer which can adhere to a photomask, and the other end face for supporting a pellicle film. The pellicle frame is a rectangular pellicle frame (excluding a pellicle frame including a quartz glass). The torsion amount Δd of the one end face is 10 μm or less. A torsion amount Δd of the one end face indicates a maximum value of a distance between a virtual face which passes three points of four points of four corners of the one end face and remaining one point.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a pellicle frame, a pellicle, a method for manufacturing a pellicle, and a method for evaluating a pellicle frame. [Background technology]

[0002] The miniaturization of semiconductor integrated circuits is being driven by photolithography, which uses a photomask with a pattern formed on one side. A pellicle is attached to the photomask to prevent foreign matter such as dust from adhering to the surface of the photomask. When a pellicle is attached to a photomask, the flatness of the photomask changes, which can cause problems with the pattern printed on the wafer due to focus shift during exposure. Furthermore, changes in the pattern shape can cause problems with the overlay accuracy of the photomask. For this reason, efforts have been made to reduce the TIR (Total Indicator Reading), which indicates the flatness of the pellicle frame, in order to suppress deformation of the photomask.

[0003] Patent Document 1 discloses a pellicle that does not impair the flatness of a photomask even when the pellicle is attached to the photomask. The pellicle disclosed in Patent Document 1 includes a pellicle frame (hereinafter also referred to as a "pellicle frame"). The TIR value of the side of the pellicle frame that is attached to the photomask is 30 μm or less. The TIR value of the pellicle film side of the pellicle frame is 15 μm or less.

[0004] Patent Document 2 discloses a pellicle that can minimize deformation of a photomask even when the pellicle is attached to the photomask without paying particular attention to the flatness of the pellicle frame. The pellicle disclosed in Patent Document 2 has a mask adhesive layer (hereinafter also referred to as a "photomask adhesive layer") for attaching the pellicle to the mask. The photomask adhesive layer has a flat surface. The flat surface of the photomask adhesive layer is 15 μm or less.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-256925 Patent Document 2: Japanese Patent Application Laid-Open No. 2009-025560 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the pellicle disclosed in Patent Document 1 does not take into consideration twisting of the pellicle frame included in the pellicle. The main cause of twisting of the pellicle frame is residual stress generated during the manufacturing of the pellicle frame. Even if the TIR value of the side of the pellicle frame that adheres to the photomask is 30 μm or less, there is a risk of twisting in the pellicle frame. If twisting occurs in the pellicle frame, when forming an adhesive layer for a photomask on the pellicle frame, the pressure (load) for flattening the surface of the adhesive layer for a photomask may not be applied uniformly across the entire adhesive layer for a photomask. As a result, the TIR value of the adhesive layer for a photomask may be high. Therefore, when the pellicle disclosed in Patent Document 1 is attached to a photomask, there is a risk of the photomask being distorted.

[0007] The pellicle disclosed in Patent Document 2 does not take into consideration the thickness of the adhesive layer for the photomask. The thicker the adhesive layer for the photomask, the less the TIR value of the adhesive layer for the photomask is affected by the TIR value of the side of the pellicle frame that adheres to the photomask. Therefore, it is easy to make the TIR value of the adhesive layer for the photomask close to the TIR value of the photomask. However, in recent years, due to the trend toward higher miniaturization of semiconductor integrated circuits, it is expected that the required level of outgassing from adhesive layers for photomasks will become higher, regardless of whether ArF excimer lasers (wavelength: 193 nm) or EUV (Extreme Ultra Violet) light (wavelength: 3 nm to 30 nm) is used. Furthermore, it is expected that the thickness required for adhesive layers for photomasks will become thinner. In particular, when EUV light, which has a shorter wavelength than ArF excimer lasers, is used as the light source for exposure, the exposure is carried out in a vacuum environment. Therefore, there is a strong demand for thinner adhesive layers for photomasks. The required thickness for adhesive layers for photomasks is, for example, 10 μm to 500 μm.

[0008] The present disclosure has been made in consideration of the above circumstances. The problem to be solved by one embodiment of the present disclosure is to provide a pellicle frame, a pellicle, and a method for manufacturing a pellicle that can suppress distortion of a photomask caused by attaching a pellicle. The problem to be solved by another embodiment of the present disclosure is to provide a method for evaluating a pellicle frame that can accurately measure the amount of twist at the end face of the pellicle frame. [Means for solving the problem]

[0009] The means for solving the above problems include the following embodiments. <1> one end surface on which an adhesive layer that can be adhered to a photomask is provided; The other end surface that supports the pellicle membrane A rectangular pellicle frame (excluding pellicle frames containing quartz glass), The twist amount Δd of the one end surface is 10 μm or less, The twist amount Δd of the one end face indicates the maximum value of the distance between an imaginary plane passing through three of the four points at the four corners of the one end face and the remaining point, pellicle frame. <2> The twist amount Δd of the other end surface is 10 μm or less, The twist amount Δd of the other end face indicates the maximum value of the distance between an imaginary plane passing through three of the four points at the four corners of the other end face and the remaining one point. <1> The pellicle frame according to claim 1. <3> containing a metal <1> or <2> The pellicle frame according to claim 1. <4> The material includes at least one selected from aluminum, titanium, stainless steel, carbon-based materials, resins, silicon, and ceramic-based materials. <1> or <2> The pellicle frame according to claim 1. <5> The Young's modulus is 90 GPa or more. <1> or <2> The pellicle frame according to claim 1. <6> The twist amount Δd of the one end surface is 1 μm or more. <1> ~ <5> 10. A pellicle frame according to any one of the preceding items. <7> The TIR value of the one end face is 30 μm or less. <1> ~ <6> 10. A pellicle frame according to any one of the preceding items. <8> The TIR value of the other end surface is 30 μm or less. <1> ~ <7> 10. A pellicle frame according to any one of the preceding items. <9> The aforementioned <1> ~ <8> a pellicle frame according to any one of the above items; The adhesive layer provided on the one end surface; The pellicle membrane supported on the other end surface; A pellicle comprising: <10> The aforementioned <1> ~ <8> a step of preparing a pellicle frame according to any one of the above; a step of applying a coating composition to the one end surface to form a coating layer, heating the coating layer while the coating layer is in contact with the flat surface of the planarizing article, and then baking the coating layer to form the adhesive layer; and The thickness of the adhesive layer is 10 μm or more and 500 μm or less, A method for manufacturing a pellicle, wherein the TIR value of the flat surface is less than 10 μm. <11> The process includes fixing three of the four points at the four corners of the rectangular pellicle frame and applying a force to the remaining point. <10> A method for manufacturing a pellicle according to claim 1. <12> A method for evaluating a rectangular pellicle frame having one end surface on which an adhesive layer capable of adhering to a photomask is provided and the other end surface supporting a pellicle membrane, comprising: measuring the amount of twist Δd of the one end surface, A method for evaluating a pellicle frame, wherein the amount of twist Δd indicates the maximum value of the distance between an imaginary plane passing through three of the four points at the four corners of the one end face and the remaining point. [Effects of the Invention]

[0010] According to the present disclosure, there are provided a pellicle frame, a pellicle, and a method for manufacturing a pellicle that can suppress distortion of a photomask caused by attaching a pellicle. According to the present disclosure, there is provided a method for evaluating a pellicle frame that can accurately measure the amount of twist at the end face of the pellicle frame. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a cross section of a pellicle according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a cross section of a pellicle according to a second embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic cross-sectional view showing a cross section of the pellicle frame with an adhesive layer according to Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In the numerical ranges described in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the value shown in the examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, when there are multiple substances corresponding to each component, the amount of each component means the total amount of the multiple substances unless otherwise specified. In the present disclosure, the term "process" refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. In this disclosure, "(meth)acrylate" means acrylate or methacrylate.

[0013] (1) Pellicle frame The pellicle frame of the present disclosure has one end face on which an adhesive layer capable of adhering to a photomask is provided, and the other end face that supports a pellicle film. The pellicle frame of the present disclosure is a rectangular pellicle frame (excluding pellicle frames containing quartz glass). The twist amount Δd of the one end face is 10 μm or less. The twist amount Δd of the one end face indicates the maximum distance between an imaginary plane passing through three of the four points at the four corners of the one end face and the remaining point.

[0014] In the present disclosure, "the twist amount Δd of the one end face indicates the maximum distance between an imaginary plane passing through three of the four corner points of the one end face and the remaining one point" refers to the maximum value among the following first distance, second distance, third distance, and fourth distance. If the four corner points of the one end face are defined as points C1, C2, C3, and C4, respectively, the first distance indicates the shortest distance between point C4 and an imaginary plane passing through points C1, C2, and C3. The second distance indicates the shortest distance between point C3 and an imaginary plane passing through points C1, C3, and C4. The third distance indicates the shortest distance between point C2 and an imaginary plane passing through points C1, C3, and C4. The fourth distance indicates the shortest distance between point C1 and an imaginary plane passing through points C2, C3, and C4. The methods for measuring the first distance, the second distance, the third distance, and the fourth distance are the same as those in the example.

[0015] Hereinafter, one end face of the pellicle frame on which an adhesive layer that can adhere to a photomask (hereinafter also referred to as "adhesive layer for photomask") is provided will also be referred to as the "end face for photomask," and the other end face that supports the pellicle membrane will also be referred to as the "end face for pellicle membrane."

[0016] The pellicle frame of the present disclosure has the above-described configuration, and therefore, even if the thickness of the photomask adhesive layer is thin (for example, 10 μm to 500 μm), it is possible to make the TIR value of the photomask adhesive layer close to the TIR value of the photomask (preferably less than 10 μm). Generally, the TIR value of a photomask is about several μm. As a result, the pellicle frame of the present disclosure can suppress distortion of the photomask caused by the attachment of the pellicle even if the thickness of the photomask adhesive layer is thin, and can further suppress distortion of the photomask even when the thickness of the photomask adhesive layer is the same. The pellicle frame of the present disclosure has the above-described configuration, and therefore can achieve a higher flatness ratio (e.g., 0.5 or more) than conventional pellicle frames. In other words, the pellicle frame of the present disclosure makes it possible to form a photomask adhesive layer with higher flatness even if the flatness of the photomask end face is not high. The flatness ratio is expressed by the following formula (1). Formula (1): Planarization rate = 1 - (TIR value of adhesive layer for photomask / TIR value of end surface for photomask) In formula (1), the method for measuring the TIR value of the adhesive layer for a photomask is the same as in Examples. The method for measuring the TIR value of the end face for a photomask is the same as in Examples.

[0017] The pellicle frame is rectangular. More specifically, the pellicle frame is a rectangular cylindrical object. The pellicle frame has a through-hole. The through-hole represents a space through which light transmitted through the pellicle film passes to reach the photomask. The pellicle frame may have an air vent. When the pellicle frame is attached to the photomask, the air vent connects the internal space of the pellicle with the external space of the pellicle. The "internal space of the pellicle" refers to the space surrounded by the pellicle and the photomask. The "external space of the pellicle" refers to the space not surrounded by the pellicle and the photomask. The rectangular shape may be a square or a rectangle. A "rectangle" refers to a right-angled quadrilateral. A "square" refers to a shape in which all four sides that make up a rectangle are the same length. A rectangle refers to any rectangular shape other than a square.

[0018] (1.1) Photomask end face The twist amount Δd of the photomask end face is preferably 1 μm or more. As described above, the twist amount Δd of the photomask end face indicates the maximum distance between an imaginary plane passing through three of the four corner points of the end face of the photomask end face and the remaining point. If the twist amount Δd of the photomask end face is 1 μm or more, the manufacturing cost of the pellicle frame can be further reduced. To reduce the twist amount Δd of the photomask end face, for example, as described below, it is necessary to polish the raw material plate, which is the raw material for the pellicle frame, at a relatively low polishing efficiency to cut out the pellicle frame. Therefore, if the twist amount Δd of the photomask end face is 1 μm or more, the yield can be improved compared to when the twist amount Δd of the photomask end face is less than 1 μm. As a result, the manufacturing cost of the pellicle frame can be further reduced. The upper limit of the twist amount Δd of the photomask end face is 10 μm, preferably 8 μm or less, more preferably 6 μm or less, and even more preferably 4 μm or less, from the viewpoint of suppressing distortion of the photomask caused by attaching the pellicle. The lower limit of the twist amount Δd of the photomask end face is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 4 μm or more, from the viewpoint of reducing the manufacturing cost of the pellicle frame. From these viewpoints, the twist amount Δd of the photomask end face is preferably 1 μm to 10 μm, more preferably 2 μm to 8 μm, and even more preferably 3 μm to 6 μm.

[0019] The method for measuring the twist amount Δd of the photomask end face is to place the pellicle frame on a surface plate so that the end face of the pellicle frame (i.e., the photomask end face) (hereinafter also referred to as the "measurement side end face") whose twist amount is to be measured and the other end face of the pellicle frame (i.e., the pellicle film end face) face the surface plate. The heights from the surface plate of each of the four points, which are the four corners of the measurement side end face, are measured using a 3D displacement meter. Next, using the height measurements at the four points, an imaginary plane passing through three of the four points is derived, and the shortest distance (hereinafter also referred to as the "first shortest distance") between the derived imaginary plane and the remaining point is calculated. Since there are four patterns for deriving the imaginary plane from the four points, four first shortest distances are calculated. The maximum of the four first shortest distances is taken as the twist amount Δd of the measurement side end face. Specifically, if the four corners of the measurement-side end face are defined as four points C1, C2, C3, and C4, respectively, the amount of twist Δd of the measurement-side end face is the maximum value among the following first distance, second distance, third distance, and fourth distance. The first distance is the shortest distance between point C4 and an imaginary plane passing through points C1, C2, and C3. The second distance is the shortest distance between point C3 and an imaginary plane passing through points C1, C2, and C4. The third distance is the shortest distance between point C2 and an imaginary plane passing through points C1, C3, and C4. The fourth distance is the shortest distance between point C1 and an imaginary plane passing through points C2, C3, and C4.

[0020] The TIR value of the photomask end face is preferably 30 μm or less. The TIR value of the photomask end face represents the difference between the maximum and minimum height differences between the height of a least-squares plane calculated using a predetermined number of measurement points on the photomask end face and the heights of the plurality of measurement points. If the TIR value of the photomask end face is 30 μm or less, the TIR value of the photomask adhesive layer provided on the photomask end face is likely to be lower, and as a result, when the resulting pellicle is attached to the photomask, distortion of the photomask can be suppressed. The upper limit of the TIR value of the photomask end face is more preferably 25 μm or less, and even more preferably 20 μm or less, from the viewpoint of suppressing the occurrence of twisting of the pellicle film due to twisting of the pellicle frame. The lower limit of the TIR value of the photomask end face is not particularly limited, but is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 3 μm or more, and particularly preferably 4 μm or more. From these viewpoints, the TIR value of the photomask end face is preferably 1 μm to 30 μm, more preferably 2 μm to 25 μm, even more preferably 3 μm to 20 μm, and particularly preferably 4 μm to 15 μm.

[0021] To measure the TIR value of the photomask end face, the pellicle frame is placed on a surface plate so that the end face of the pellicle frame (i.e., the pellicle film end face) that is different from the end face of the pellicle frame (i.e., the photomask end face) (hereinafter also referred to as the "measurement side end face") for which the TIR value of the pellicle frame is to be measured faces the surface plate. The height of each of the measurement points on the measurement side end face from the surface plate is measured using a 3D displacement meter. The measurement points are the four corners of the measurement side end face and points set at 2.5 mm intervals from one of the four corners to another of the four corners on each side between the four corners. However, if the distance between one of the four corners (hereinafter also referred to as a "corner point") and the adjacent point (hereinafter also referred to as the "corner spacing") is 2.5 mm or less, the adjacent point is set so that the corner spacing is less than 2.5 mm. A least-squares plane is calculated using the height measurements of all the specified points. The measurement point with the largest difference in height between the least-squares plane and each of the multiple measurement points located on the opposite side of the surface plate from the least-squares plane is identified as the "first measurement point." The measurement point with the largest difference in height between the least-squares plane and each of the multiple measurement points located on the surface plate side of the least-squares plane is identified as the "second measurement point." The sum of the difference in height from the least-squares plane of the first measurement point and the difference in height from the least-squares plane of the second measurement point is determined as the TIR value.

[0022] (1.2) Pellicle membrane end face The twist amount Δd of the end face for the pellicle membrane is preferably 10 μm or less. The twist amount Δd of the end face for the pellicle membrane represents the maximum distance between an imaginary plane passing through three of the four points at the four corners of the end face for the pellicle membrane and the remaining point. By setting the twist amount Δd of the pellicle membrane end face to 10 μm or less, it is possible to suppress the occurrence of twisting of the pellicle membrane due to twisting of the pellicle frame. As a result, the resulting pellicle can suppress the occurrence of exposure defects due to twisting of the pellicle membrane. The upper limit of the twist amount Δd of the pellicle membrane end face is more preferably 8 μm or less, and even more preferably 6 μm or less, from the viewpoint of suppressing the occurrence of twisting of the pellicle membrane. The lower limit of the twist amount Δd of the pellicle membrane end face is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more, from the viewpoint of reducing the manufacturing cost of the pellicle frame. From these viewpoints, the twist amount Δd of the end face for the pellicle membrane is preferably 1 μm to 10 μm, more preferably 2 μm to 8 μm, and even more preferably 3 μm to 6 μm. The method for measuring the twist amount Δd of the end face for the pellicle film is the same as the method described above (method for measuring the twist amount Δd of the end face for the photomask).

[0023] The TIR value of the pellicle membrane end face is preferably 30 μm or less. The TIR value of the pellicle membrane end face represents the difference between the maximum and minimum height differences between the height of a least-squares plane calculated using a predetermined number of measurement points on the pellicle membrane end face and the heights of each of the plurality of measurement points. If the TIR value of the pellicle membrane end face is 30 μm or less, twisting of the pellicle membrane due to twisting of the pellicle frame can be suppressed. As a result, when the resulting pellicle is attached to a photomask, exposure defects due to twisting of the pellicle membrane can be suppressed. The upper limit of the TIR value of the end face for the pellicle membrane is more preferably 25 μm or less, and even more preferably 20 μm or less, from the viewpoint of suppressing the occurrence of twisting of the pellicle membrane. The lower limit of the TIR value of the end face for the pellicle membrane is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more, from the viewpoint of reducing the manufacturing cost of the pellicle frame. From these viewpoints, the TIR value of the end face for the pellicle membrane is preferably 1 μm to 30 μm, more preferably 2 μm to 25 μm, and even more preferably 3 μm to 20 μm. The method for measuring the TIR value of the end face for the pellicle film is the same as the method described above (method for measuring the TIR value of the end face for the photomask).

[0024] (1.3) Pellicle frame material The pellicle frame of the present disclosure does not include a pellicle frame containing silica glass, which has a Young's modulus of 70 GPa.

[0025] The Young's modulus of the pellicle frame is preferably 90 GPa or more. The pellicle film is supported in a taut state on the pellicle film end surface of the pellicle frame. If the Young's modulus of the pellicle frame is 90 GPa or more, deformation of the pellicle frame due to the tension of the pellicle film can be suppressed. Examples of materials with a Young's modulus of 90 GPa or more include titanium, titanium alloys, silicon, etc. The general Young's modulus of glass is 70 GPa. The Young's modulus of the pellicle frame is measured using a tensile test (JIS G0567J). However, if the pellicle frame is made of resin, the value is measured using a three-point bending test (JIS K7171). Whether the pellicle frame is made of resin or not is determined by whether the material undergoes thermal decomposition at 550°C. There is no particular upper limit to the Young's modulus, but it is preferably 300 GPa, and more preferably 250 GPa.

[0026] The Young's modulus of the pellicle frame is preferably 60 GPa or less. Even if the twist amount Δd of the photomask end face of a pellicle frame having a Young's modulus of 60 GPa or less is equivalent to that of a pellicle frame having a Young's modulus of more than 60 GPa, the occurrence of distortion of the photomask when attached to the photomask can be suppressed. Examples of materials with a Young's modulus of 60 GPa or less include magnesium, magnesium alloys, polyethylene terephthalate (PET) resin, and resin. Young's modulus is measured using a tensile test (JIS G0567J). However, if the pellicle frame is made of resin, the value is measured using a three-point bending test (JIS K7171). Whether the pellicle frame is made of resin or not is determined by whether it undergoes thermal decomposition at 550°C.

[0027] The pellicle frame preferably comprises a metal. The metal may be a pure metal or an alloy. A pure metal is composed of a single metal element. Examples of pure metals include aluminum and titanium. An alloy is composed of multiple metal elements, or a metal element and a non-metal element. Examples of alloys include stainless steel, magnesium alloy, steel, carbon steel, and invar.

[0028] The pellicle frame preferably contains at least one material selected from aluminum, titanium, stainless steel, carbon-based materials, resins, silicon, and ceramic-based materials. The resin may be polyethylene or the like. Examples of ceramic materials include silicon nitride (SiN), silicon carbide (SiC), and alumina (Al2O3).

[0029] (1.4) Configuration The pellicle frame of the present disclosure may be a single item or an assembly. A single item is obtained by cutting out a single raw material plate, as described below. An "assembly" is an item in which multiple components are integrated. Methods for integrating multiple components include a method using a known adhesive or a method using fastening parts. Fastening parts include bolts, nuts, screws, rivets, or pins. When the pellicle frame is an assembly, the materials of the multiple components may be different. When the pellicle frame is an assembly, it is preferable that the component constituting the photomask end face (hereinafter also referred to as the "adhesive layer frame component") has a Young's modulus of 60 GPa or less, and the component constituting the pellicle membrane end face (hereinafter also referred to as the "membrane support frame component") has a Young's modulus of 90 GPa or more. This allows the pellicle frame assembly to suppress deformation of the pellicle frame caused by distortion of the membrane support frame due to the tension of the pellicle membrane. Furthermore, even if the twist amount Δd of the photomask end face of the pellicle frame assembly is equivalent to that of an adhesive layer frame component having a Young's modulus of more than 60 GPa, distortion of the photomask can be suppressed when attached to the photomask.

[0030] (2) Pellicle The pellicle of the present disclosure includes a pellicle frame of the present disclosure, a photomask adhesive layer, and a pellicle film. The photomask adhesive layer is provided on the photomask end surface of the pellicle frame. The pellicle film is supported on the pellicle film end surface of the pellicle frame.

[0031] (2.1) Photomask adhesive layer The pellicle of the present disclosure includes an adhesive layer for a photomask. The photomask adhesive layer enables the pellicle of the present disclosure to be adhered to a photomask.

[0032] The adhesive layer for a photomask is a gel-like viscoelastic material. The adhesive layer for a photomask preferably has viscosity and cohesive strength. "Viscosity" refers to the liquid-like properties of contacting and wetting the adherend, i.e., the photomask. "Cohesive strength" refers to the solid-like properties of resisting peeling from the photomask.

[0033] The glass transition temperature Tg of the adhesive layer for photomasks is preferably greater than −25° C. and less than 10° C. This allows the adhesive layer for photomasks to have adhesive strength in the temperature range in which the pellicle is used (e.g., 20° C. or higher), making the pellicle less likely to peel off from the photomask even when exposed to a high-temperature environment. In order to make it more difficult for the pellicle to peel off from the photomask even when exposed to a high-temperature environment, the lower limit of the glass transition temperature Tg of the adhesive layer for the photomask is preferably above -25°C, more preferably -22°C or higher, even more preferably -20°C or higher, and most preferably -18°C or higher. From the viewpoint of imparting adhesiveness at room temperature, the upper limit of the glass transition temperature Tg of the adhesive layer for photomasks is preferably less than 10°C, more preferably 5°C or lower, and even more preferably 0°C or lower. The glass transition temperature (Tg) of the adhesive layer for photomasks is measured in accordance with JIS K 7112. Specifically, the glass transition temperature (Tg) of the adhesive layer for photomasks is measured using a differential scanning calorimetry (DSC) under conditions of a temperature rise rate of 20°C / min and nitrogen.

[0034] The thickness of the adhesive layer for a photomask is not particularly limited and is preferably 10 μm to 500 μm, more preferably 100 μm to 400 μm, and even more preferably 200 μm to 300 μm. When the thickness of the adhesive layer for a photomask is within the above range, the amount of outgassing from the adhesive layer for a photomask is less likely to have an effect. The thickness of the adhesive layer for photomasks was measured in the same manner as in the examples.

[0035] The TIR value of the photomask adhesive layer is preferably less than 10 μm. The TIR value of the photomask end face represents the difference between the maximum and minimum height differences between the height of a least-squares plane calculated using a predetermined number of measurement points on the photomask end face and the heights of the plurality of measurement points. The TIR value of a photomask is about several μm. If the TIR value of the photomask adhesive layer is less than 10 μm, it is close to the TIR value of the photomask, and therefore, when a pellicle is attached to the photomask, changes in the flatness of the photomask can be suppressed. As a result, distortion of the photomask caused by the attachment of the pellicle can be suppressed. The TIR value of the adhesive layer for photomasks was measured in the same manner as in the examples, as described above.

[0036] The adhesive layer for a photomask is formed, for example, by applying a coating composition, heating, drying, curing, and other processes, as described below.

[0037] (2.2) Pellicle membrane The pellicle of the present disclosure comprises a pellicle membrane. The pellicle film prevents foreign matter from adhering to the surface of the photomask and allows the exposure light to pass through during exposure. Foreign matter includes dust. Examples of exposure light include deep ultraviolet (DUV) light and EUV light. EUV refers to light with a wavelength of 2 nm or more and 30 nm or less.

[0038] The pellicle membrane covers the entire opening on one end face (pellicle membrane end face) of the through-hole in the pellicle frame. The pellicle membrane may be supported directly on one end face of the pellicle frame, or may be supported via a membrane adhesive layer. The membrane adhesive layer may be a cured product of a known adhesive.

[0039] The thickness of the pellicle film is preferably 1 nm or more and 400 nm or less. The material of the pellicle membrane is not particularly limited, and examples thereof include carbon-based materials, SiN, polysilicon, etc. Carbon-based materials include carbon nanotubes (hereinafter also referred to as "CNTs"). In particular, the material of the pellicle membrane preferably includes CNTs. The CNTs may be single-wall CNTs or multi-wall CNTs. The pellicle membrane may have a nonwoven structure, which may be formed, for example, from fiber-shaped CNTs.

[0040] The pellicle membrane may be indirectly supported on the pellicle frame via a pellicle membrane adhesive layer, or may be directly supported on the pellicle frame. Examples of adhesives that can be used to form the adhesive layer for the pellicle film include acrylic resin adhesives, epoxy resin adhesives, polyimide resin adhesives, silicone resin adhesives, inorganic adhesives, double-sided adhesive tapes, polyolefin adhesives, and hydrogenated styrene adhesives. In particular, from the viewpoint of ease of application and curing processing, it is preferable that the adhesive for the pellicle membrane is at least one selected from the group consisting of silicone resin adhesives, acrylic resin adhesives, hydrogenated styrene-based adhesives, and epoxy resin adhesives. In the present disclosure, the pellicle membrane adhesive is a concept that includes not only adhesives but also pressure-sensitive adhesives. The thickness of the adhesive layer for a pellicle film is not particularly limited, and is, for example, 10 μm or more and 1 mm or less.

[0041] (2.4) Exposed master The pellicle of the present disclosure may be provided on an exposure master. The exposure master includes a photomask and a pellicle. The photomask is a master for a circuit pattern. The photomask has a pattern. The pellicle is attached to the surface of the photomask that has the pattern.

[0042] The photomask does not necessarily have to have a support substrate, a reflective layer, and an absorber layer stacked in this order. The absorber layer partially absorbs light (e.g., EUV), forming a desired image on a sensitive substrate (e.g., a semiconductor substrate with a photoresist film). Examples of the reflective layer include a multilayer film of molybdenum (Mo) and silicon (Si). The material of the absorber layer may be a material that is highly absorbing of EUV and other light. Examples of materials that are highly absorbing of EUV and other light include chromium (Cr) and tantalum nitride.

[0043] (2.5) Exposure equipment The pellicle of the present disclosure may be included in an exposure apparatus. The exposure apparatus includes a light source, the above-described exposure master, and an optical system. The light source emits exposure light. The optical system guides the exposure light emitted from the light source to the exposure master. The exposure master is positioned so that the exposure light emitted from the light source passes through the pellicle film and irradiates the photomask. The exposure device is capable of forming fine patterns (e.g., line widths of 32 nm or less) using EUV and other technologies, and can also perform pattern exposure with reduced resolution problems caused by foreign matter, even when using EUV, which is prone to resolution problems caused by foreign matter. The exposure light is preferably EUV. Because EUV has a short wavelength, it is easily absorbed by gases such as oxygen or nitrogen. Therefore, exposure with EUV light is performed in a vacuum environment.

[0044] (2.6) An example of a pellicle Next, an example of a pellicle according to the present disclosure will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view of a pellicle 10A according to a first embodiment of the present disclosure. Figure 2 is a cross-sectional view of a pellicle 10B according to a second embodiment of the present disclosure. In the figures, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0045] (2.6.1) First embodiment A pellicle 10A according to the first embodiment of the present disclosure is used by being attached onto the surface of a photomask 20, as shown in FIG. Pellicle 10A includes pellicle frame 11A, photomask adhesive layer 12, and pellicle film 13. Pellicle frame 11A has photomask end surface S11A and pellicle film end surface S11B. Photomask adhesive layer 12 is provided on photomask end surface S11A. Pellicle film 13 is supported on pellicle film end surface S11B via a known film adhesive layer.

[0046] The pellicle frame 11A is a rectangular cylindrical object. The pellicle frame 11A has a through hole TH. The amount of twist Δd of the photomask end surface S11A of the pellicle frame 11A is 10 μm or less. In the first embodiment, the pellicle frame 11A is an assembled product. The pellicle frame 11A includes an adhesive layer frame member 111 and a membrane support frame member 112. The membrane support frame member 112 is placed on the adhesive layer frame member 111. The adhesive layer frame member 111 and the membrane support frame member 112 are integrated together with a known adhesive. In the first embodiment, the adhesive layer frame member 111 and the membrane support frame member 112 are integrated together with a known adhesive, but they may also be integrated together with fastening parts.

[0047] The frame member 111 for an adhesive layer is a rectangular cylindrical object, similar to the pellicle frame 11A. The frame member 111 for an adhesive layer has a through-hole THA. The through-hole THA constitutes a part of the through-hole TH of the pellicle frame 11A. The frame member 111 for adhesive layer has an end surface S111. The end surface S111 constitutes the end surface S11A for photomask of the pellicle frame 11A. In the first embodiment, the Young's modulus of the frame member 111 for the adhesive layer is 60 GPa or less. Therefore, even if the twist amount Δd of the photomask end surface S11A of the pellicle frame 11A is equivalent to that of a frame member for the adhesive layer having a Young's modulus of more than 60 GPa, the occurrence of distortion of the photomask 20 when the frame member is attached to the photomask 20 can be suppressed.

[0048] The membrane support frame member 112 is a rectangular cylindrical object, similar to the pellicle frame 11A. The membrane support frame member 112 has a through-hole THB. The through-hole THB constitutes a part of the through-hole TH of the pellicle frame 11A. The membrane support frame member 112 has an end surface S112. The end surface S112 constitutes the pellicle membrane end surface S11B of the pellicle frame 11A. In the first embodiment, the Young's modulus of the membrane support frame member 112 is 90 GPa or more, so deformation of the pellicle frame 11A caused by distortion of the membrane support frame member 112 due to the tension of the pellicle membrane 13 can be suppressed.

[0049] Pellicle 10A is suitable for use in exposure using short-wavelength exposure light (e.g., EUV light, light with an even shorter wavelength than EUV light, etc.) When exposure light L is EUV light, exposure is performed in a vacuum atmosphere because EUV light is easily absorbed by gases such as oxygen or nitrogen.

[0050] (2.6.2) Second embodiment A pellicle 10B according to the second embodiment of the present disclosure is used by being attached onto the surface of a photomask 20, as shown in FIG. Pellicle 10B includes pellicle frame 11B, photomask adhesive layer 12, and pellicle film 13. Pellicle frame 11B has photomask end surface S11A and pellicle film end surface S11B. Photomask adhesive layer 12 is provided on photomask end surface S11A. Pellicle film 13 is supported on pellicle film end surface S11B via a known film adhesive layer.

[0051] The pellicle frame 11B is a rectangular cylindrical object. The pellicle frame 11B has a through hole TH. The amount of twist Δd of the photomask end surface S11A of the pellicle frame 11B is 10 μm or less. In the second embodiment, the pellicle frame 11B is a single item.

[0052] The pellicle 10B is suitable for use in exposure using short-wavelength exposure light L. When the exposure light L is EUV light, exposure is performed in a vacuum atmosphere because EUV light is easily absorbed by gases such as oxygen or nitrogen.

[0053] (3) Pellicle manufacturing method The method for manufacturing a pellicle according to the present disclosure includes a preparation step and an adhesive layer formation step, which are described below. The preparation step and the adhesive layer formation step are performed in this order. This allows a pellicle to be obtained in which the TIR value of the adhesive layer for a photomask is closer to that of the photomask, even if the adhesive layer for a photomask is thin.

[0054] (3.1) Preparation process The method of manufacturing a pellicle of the present disclosure includes a preparation step. In the preparation step, a pellicle frame according to the present disclosure is prepared, which allows for the formation of a photomask adhesive layer having a TIR value closer to that of the photomask, even if the photomask adhesive layer is thin. Methods for preparing a pellicle frame include a cutting method. For example, in the cutting method, a raw material plate, which is the raw material for the pellicle frame, is polished by a known method at a relatively low polishing efficiency to cut out the pellicle frame, thereby suppressing residual stress generated in the pellicle frame and reducing the amount of twist Δd of the photomask end face. "Polishing efficiency" is expressed as the amount of polishing (removed thickness) (μm) per unit time (minute). Examples of relatively low polishing efficiency include 1000 nm / min or less, preferably 500 nm / min or less, and more preferably 300 nm / min or less. The raw material plate may be a plate-like object. At least one of the main surfaces of the raw material plate is preferably mirror-finished by a known method so that the TIR value is 30 μm or less, thereby obtaining a pellicle frame having a TIR value of 30 μm or less on at least one of the photomask end face and the pellicle membrane end face.

[0055] (3.2) Straightening process The method for manufacturing a pellicle according to the present disclosure may include a correction step, which is performed after the preparation step and before the adhesive layer forming step. In the correction process, the end face of the pellicle frame is corrected to reduce the amount of twist Δd. Methods for correcting the pellicle frame include fixing three of the four points at the four corners of one end face of the rectangular pellicle frame and applying force to the remaining point (hereinafter also referred to as the "correction method"). Examples of the correction method include a method in which the following (a) and (b) are performed in this order. (a) Place the pellicle frame on the surface plate so that three of the four points at the four corners of one end face of the pellicle frame are in contact with the surface plate. (b) A load is applied to the other end face of the pellicle frame such that the remaining one of the four points at the four corners of one end face of the pellicle frame faces in the direction of the surface plate.

[0056] (3.2) Adhesive layer formation process In the adhesive layer forming step, a coating composition is applied to the end surface of a photomask to form a coating layer, and the coating layer is heated while being in contact with the flat surface of a planarizing article, and then the coating layer is baked to form an adhesive layer for a photomask. The thickness of the adhesive layer for a photomask is 10 μm or more and 500 μm or less. The TIR value of each of the flat surfaces is less than 10 μm. The method for measuring the TIR value of the flat surfaces is the same as in the examples.

[0057] (3.2.1) Coating In the adhesive layer forming step, the coating composition is applied to the end face of the photomask to form a coating layer on the end face of the photomask, thereby obtaining a pellicle frame with a coating layer. The area to which the coating composition is applied is preferably not the entire surface of the photomask end face, but only the center of each side between the four corners of the photomask end face. In other words, the area to which the coating composition is applied preferably does not include the edge of each side between the four corners on the through-hole side of the pellicle frame or the edge of the pellicle frame opposite the through-hole side. This makes it less likely that the photomask adhesive layer will overflow onto the inner and outer wall sides of the pellicle frame when the pellicle is attached to the photomask than if the coating composition were applied to the entire surface of the photomask end face. Therefore, the photomask adhesive layer is less likely to be exposed. As a result, the amount of outgassing can be further reduced. The method for applying the coating composition to the photomask end surface of the pellicle frame is not particularly limited, and examples thereof include a method using a dispenser. The thickness of the coating layer of the coating composition may be such that the thickness of the resulting adhesive layer for photomasks is 10 μm or more and 500 μm or less, and preferably 100 μm or more and 400 μm or less.

[0058] (3.2.2) Flattening In the adhesive layer forming step, the coating layer of the pellicle frame with the coating layer is heated while being in contact with the flat surface of the planarization article. The thickness of the coating layer immediately after the coating composition is applied usually varies depending on the location of the coating layer. By heating the coating layer of the pellicle frame with the coating layer while being in contact with the flat surface of the planarization article, the flatness of the thickness of the coating layer of the pellicle frame with the coating layer can be improved. Hereinafter, the flattening article brought into contact with the coating layer of the pellicle frame with the coating layer will also be referred to as the "first contact article." The method for contacting the coating layer with the flat surface of the planarizing article is not particularly limited, and examples include the inverted placement method and the mounted method. In the mounted method, an adhesive protective film (hereinafter also referred to as a "liner") is attached to the surface of the coating layer, and the coating layer of the pellicle frame with the coated layer is placed downward (in the direction of gravity) so that the coating layer of the pellicle frame with the liner attached comes into contact with the flat surface of the planarizing article. In the inverted placement method, the coating layer of the pellicle frame with the coated layer is placed upward (opposite the direction of gravity) so that the coating layer of the pellicle frame with the liner attached comes into contact with the flat surface of the planarizing article, with the liner attached to the surface of the coating layer. In both the mounted method and the inverted placement method, the planarizing article may also be placed in contact with the pellicle membrane end surface of the pellicle frame with the coated layer. Among these, the mounted method is preferred from the viewpoint of making it easier to heat the coating layer when heated on a hot plate. When the flat surface is brought into contact with the coating layer via the liner, the pressure (load) that is applied uniformly to the entire coating layer is not particularly limited, and is preferably 10 g / cm from the viewpoint of reducing the distortion of the pellicle frame while lowering the TIR value of the photomask adhesive layer. 2 ~1000g / cm 2 , more preferably 100 g / cm 2 ~800g / cm 2 , and more preferably 300 g / cm 2 ~600g / cm 2 is. The TIR value of the flat surface of the planarizing article is less than 10 μm. This allows the TIR value of the photomask adhesive layer to be less than 10 μm. From the viewpoint of forming a photomask adhesive layer with a lower TIR value, the TIR value of the flat surface of the planarizing article is preferably 5 μm or less, more preferably 3 μm or less, and the closer to 0 μm the better. Examples of planarizing articles include glass substrates. The method for heating the coating layer of the pellicle frame with the coating layer in contact with the flat surface via a liner is not particularly limited, and examples include a method using an oven and a method using a hot plate. In the method using an oven, the first contact article is placed in the oven chamber, and the first contact article itself is heated to heat the coating layer. In the method using a hot plate, for example, the first contact article is placed on a hot plate so that the flattening article, which is in contact with the coating layer of the first contact article via the liner, comes into contact with the plate of the hot plate, and the coating layer is heated through the flattening article, thereby heating the coating layer. When the coating layer is heated using an oven, the temperature set inside the oven is preferably 70°C to 130°C, more preferably 80°C to 110°C. The temperature set inside the oven refers to the temperature inside the oven. The time for heating the coating layer using the oven is preferably 10 seconds to 15 minutes, more preferably 1 minute to 10 minutes. When the coating layer is heated using a hot plate, the set temperature of the hot plate is 70°C to 130°C, more preferably 80°C to 110°C. The set temperature of the hot plate refers to the surface temperature of the hot plate. The time for heating the coating layer using the hot plate is preferably 10 seconds to 15 minutes, more preferably 1 minute to 10 minutes.

[0059] (3.2.3) Bake In the adhesive layer forming step, the coating layer is heated to flatten it, and then baked. This removes at least one of the solvent and the residual monomer from the coating layer. As a result, an adhesive layer for a photomask is formed from the coating layer. That is, a pellicle frame with an adhesive layer is obtained. The pellicle frame with an adhesive layer comprises a pellicle frame and an adhesive layer for a photomask. The adhesive layer for a photomask is provided on the end surface of the photomask. The thickness of the adhesive layer for a photomask is 10 μm to 500 μm. The method for measuring the thickness of the adhesive layer for a photomask is the same as in the examples. In the adhesive layer forming step, for example, the planarizing article is removed from the first contact article after heating to obtain a pellicle frame with a coating layer. The obtained pellicle frame with a coating layer is placed on a substrate so that the coating layer of the pellicle frame with a coating layer contacts the substrate via a liner. Hereinafter, the substrate and the pellicle frame with a coating layer placed on the substrate are also referred to as the "second contact article." Note that a substrate may be placed on the coating layer of the second contact article so that the substrate contacts the pellicle membrane end surface of the second contact article. The method for baking the coating layer of the pellicle frame with a coating layer is not particularly limited, and examples thereof include a method using an oven, etc. In the method using an oven, the second contact article is placed inside the oven chamber, and the second contact article itself is heated to bake the coating layer. The temperature and time for baking the coating layer are appropriately selected depending on the type of adhesive, the boiling points of the solvent and the residual monomers, etc. When the coating layer is baked using an oven, the temperature set in the oven is preferably 70°C to 130°C, more preferably 80°C to 120°C. The time for baking the coating layer using an oven is preferably 12 hours to 120 hours, more preferably 24 hours to 72 hours.

[0060] (3.2.4) Coating composition The coating composition contains compounds selected from various polymers, solvents, crosslinking agents, catalysts, initiators, etc. depending on the adhesive layer for the photomask to be formed. The coating composition is a precursor of the adhesive composition. In other words, when the coating composition is cured, it becomes the adhesive composition (adhesive layer for the photomask).

[0061] (3.2.5) Adhesive composition The pressure-sensitive adhesive composition is not particularly limited, and examples thereof include acrylic pressure-sensitive adhesives, silicone pressure-sensitive adhesives, styrene pressure-sensitive adhesives, urethane pressure-sensitive adhesives, olefin pressure-sensitive adhesives, etc. Among these, from the viewpoint of reducing the amount of outgassing generated from the pellicle, an acrylic pressure-sensitive adhesive is preferred as the pressure-sensitive adhesive composition, and from the viewpoint of reducing distortion of the photomask, a styrene pressure-sensitive adhesive is preferred. The styrene-based pressure-sensitive adhesive and the acrylic-based pressure-sensitive adhesive will be described below.

[0062] (3.2.5.1) Styrene-based adhesives The styrene-based pressure-sensitive adhesive contains a styrene-based thermoplastic elastomer (A) and a tackifying resin (B).

[0063] (3.2.5.1.1) Styrenic thermoplastic elastomer (A) The styrene-based pressure-sensitive adhesive contains a styrene-based thermoplastic elastomer (A). The styrene-based thermoplastic elastomer (A) does not contain an ester bond in its molecular structure, which gives it excellent hydrolysis resistance and also contains both soft and hard segments in the same molecular structure, resulting in styrene-based pressure-sensitive adhesives with excellent flexibility and mechanical strength.

[0064] The styrene-based thermoplastic elastomer (A) is a polymer containing structural units derived from styrene. The styrene-based thermoplastic elastomer (A) is preferably a block copolymer of styrene and an olefin other than styrene. The olefin other than styrene is preferably a monomer capable of forming a side chain having a bulky branched structure in the polymer block, more preferably isoprene, 4-methyl-1-pentene, etc., and even more preferably isoprene. The total proportion of styrene-derived structural units contained in the styrene-based thermoplastic elastomer (A) is preferably 35 mass% or less, more preferably 20 mass% or less, based on the total amount of the styrene-based thermoplastic elastomer (A). If the total proportion of styrene-derived structural units is within the above range, compatibility with various additives is unlikely to deteriorate, and the styrene-based thermoplastic elastomer (A) and the additives are unlikely to separate. The styrene-based thermoplastic elastomer (A) preferably contains a triblock copolymer (hereinafter also referred to as "SIS") or a hydrogenated triblock copolymer (hereinafter also referred to as "H-SIS"). SIS has a first polystyrene block, a polyisoprene block containing an isopropenyl group (1-methylethenyl group (-C(=CH2)CH3)) in the side chain, and a second polystyrene block. The term "hydrogenated triblock copolymer" refers to a copolymer in which preferably 90% or more, more preferably 95% or more of the unsaturated bonds in the "polyisoprene block" of the three polymer blocks contained in the SIS have been hydrogenated. The hydrogenation rate is measured using a nuclear magnetic resonance (NMR) spectrometer. The SIS may be a commercially available product, such as "Hybrar 5127" (manufactured by Kuraray Co., Ltd.) or "Hybrar 5215" (manufactured by Kuraray Co., Ltd.). H-SIS may be a commercially available product, such as "Hybrar 7125" (manufactured by Kuraray Co., Ltd.) or "Hybrar 7311" (manufactured by Kuraray Co., Ltd.).

[0065] (3.2.5.1.2) Tackifying resin (B) The styrene-based pressure-sensitive adhesive contains a tackifying resin (B).

[0066] The tackifier resin (B) is preferably compatible with the styrene-based thermoplastic elastomer (A). From the viewpoint of high compatibility with the SIS or H-SIS polyisoprene block, the tackifier resin (B) is preferably rosin and its derivatives, polyterpene resins and their hydrogenated products, terpene-phenol resins and their hydrogenated products, aromatic-modified terpene resins and their hydrogenated products, coumarone-indene resins, aliphatic petroleum resins, alicyclic petroleum resins and their hydrogenated products, aromatic petroleum resins and their hydrogenated products, aliphatic-aromatic copolymer petroleum resins, or dicyclopentadiene petroleum resins and their hydrogenated products. Among these, rosin and its derivatives, polyterpene resins and their hydrogenated products, aliphatic petroleum resins, alicyclic petroleum resins and their hydrogenated products are preferred as the tackifier resin (B), with rosin and its derivatives, aliphatic petroleum resins, alicyclic petroleum resins and their hydrogenated products being more preferred, and hydrogenated alicyclic petroleum resins being particularly preferred. The tackifier resin (B) may be a commercially available product. Commercially available rosin and its derivatives include "Pine Crystal," "Super Ester," and "Tamanol" (all manufactured by Arakawa Chemical Industries, Ltd.). Commercially available polyterpene resins, terpene phenol resins, aromatic-modified terpene resins, and their hydrogenated products include "YS Resin," "YS Polystar," and "Clearon" (all manufactured by Yasuhara Chemical Co., Ltd.). Commercially available aliphatic petroleum resins, alicyclic petroleum resins and their hydrogenated products, aromatic petroleum resins and their hydrogenated products, aliphatic-aromatic copolymer petroleum resins, and dicyclopentadiene petroleum resins and their hydrogenated products include "Arcon" (manufactured by Arakawa Chemical Industries, Ltd.), "Hi-Letz" (manufactured by Mitsui Chemicals, Inc.), "Imarv" (manufactured by Idemitsu Kosan Co., Ltd.), "Quinton" (manufactured by Zeon Corporation), and "Escoretz" (manufactured by Tonex Corporation). The tackifier resin (B) may be used alone or in combination of two or more.

[0067] The blending amount of the tackifier resin (B) is 20 to 150 parts by mass per 100 parts by mass of the styrene-based thermoplastic elastomer (A). When the blending amount of the tackifier resin (B) is within the above range, the styrene-based adhesive is less sticky. Furthermore, when the photomask adhesive layer made of the styrene-based adhesive is peeled off from the photomask, adhesive residue is less likely to occur.

[0068] (3.2.5.1.3) Other ingredients The styrene-based pressure-sensitive adhesive may further contain other components. Examples of other ingredients include softeners and waxes. The softener may be any material that can impart flexibility to the styrene-based thermoplastic elastomer (A), and examples thereof include polybutene, hydrogenated polybutene, unsaturated polybutene, aliphatic hydrocarbons, acrylic polymers, etc. The amount of the softener added is preferably 20 to 300 parts by mass, more preferably 50 to 200 parts by mass, per 100 parts by mass of the styrene-based thermoplastic elastomer (A). The wax is a component that can adjust the hardness of the styrene-based pressure-sensitive adhesive. As the wax, for example, a highly elastic material is preferred, and polyethylene wax, polypropylene wax, etc. are more preferred. The amount of wax added is preferably 20 to 200 parts by mass, more preferably 50 to 100 parts by mass, per 100 parts by mass of the styrene-based thermoplastic elastomer (A).

[0069] (3.2.5.2) Acrylic adhesives The acrylic pressure-sensitive adhesive contains a (meth)acrylic acid alkyl ester copolymer.

[0070] (3.2.5.2.1) (Meth)acrylic acid alkyl ester copolymer The (meth)acrylic acid alkyl ester copolymer is a (meth)acrylic acid alkyl ester monomer; It is preferable to include a copolymer with a monomer having a functional group reactive with at least one of an isocyanate group, an epoxy group, and an acid anhydride (hereinafter also referred to as a "functional group-containing monomer").

[0071] Hereinafter, the copolymer of a (meth)acrylic acid alkyl ester monomer and a functional group-containing monomer will also be referred to as "the copolymer."

[0072] Because the acrylic adhesive contains a (meth)acrylic acid alkyl ester copolymer, the pellicle is less likely to peel off from the photomask even when exposed to a high-temperature environment (e.g., a temperature environment of 60°C or above 60°C), and the occurrence of adhesive residue can be suppressed. "Adhesive residue" refers to at least a portion of the adhesive layer for the photomask remaining on the photomask after the pellicle is peeled off from the photomask.

[0073] The weight average molecular weight (Mw) of the (meth)acrylic acid alkyl ester copolymer is preferably 30,000 or more and 2,500,000 or less, more preferably 50,000 or more and 1,500,000 or less, and even more preferably 70,000 or more and 1,200,000 or less. When the upper limit of the weight-average molecular weight (Mw) of the (meth)acrylic acid alkyl ester copolymer is 2.5 million or less, the solution viscosity can be controlled within a range that facilitates processing even if the solid content of the coating composition is increased. The upper limit of the weight-average molecular weight (Mw) of the (meth)acrylic acid alkyl ester copolymer is preferably 2.5 million or less, more preferably 1.5 million or less, and even more preferably 1.2 million or less. If the lower limit of the weight average molecular weight (Mw) of the (meth)acrylic acid alkyl ester copolymer is 30,000 or more, the pellicle will be less likely to peel from the photomask even when exposed to a high temperature environment (e.g., 60°C), and the occurrence of adhesive residue can be suppressed. The lower limit of the weight average molecular weight (Mw) of the (meth)acrylic acid alkyl ester copolymer is preferably 30,000 or more, more preferably 50,000 or more, and even more preferably 70,000 or more. The weight average molecular weight (Mw) of the (meth)acrylic acid alkyl ester copolymer is measured by GPC (gel permeation chromatography). For example, in general, the weight-average molecular weight (Mw) tends to increase as the monomer concentration during the polymerization reaction increases, and the weight-average molecular weight (Mw) tends to increase as the amount of polymerization initiator decreases and the polymerization temperature decreases. The weight-average molecular weight (Mw) can be controlled by adjusting the monomer concentration, the amount of polymerization initiator, and the polymerization temperature.

[0074] The number average molecular weight (Mn) of the (meth)acrylic acid alkyl ester copolymer is preferably 5,000 or more and 500,000 or less, more preferably 8,000 or more and 300,000 or less, even more preferably 10,000 or more and 200,000 or less, and most preferably 20,000 or more and 200,000 or less. If the upper limit of the number-average molecular weight (Mn) of the (meth)acrylic acid alkyl ester copolymer is 500,000 or less, the solution viscosity can be controlled within a range that allows for easy processing, even if the solids concentration of the coating composition is increased. The upper limit of the number-average molecular weight (Mn) of the (meth)acrylic acid alkyl ester copolymer is preferably 500,000 or less, more preferably 300,000 or less, and even more preferably 200,000 or less. If the lower limit of the number-average molecular weight (Mn) of the (meth)acrylic acid alkyl ester copolymer is 5,000 or more, the pellicle is less likely to peel from the photomask even when exposed to a high-temperature environment (e.g., 60°C), and the occurrence of adhesive residue can be suppressed. The lower limit of the number-average molecular weight (Mn) of the (meth)acrylic acid alkyl ester copolymer is preferably 5,000 or more, more preferably 8,000 or more, even more preferably 10,000 or more, and most preferably 20,000 or more. The method for measuring the number average molecular weight (Mn) of the (meth)acrylic acid alkyl ester copolymer is the same as the method for measuring the weight average molecular weight (Mw) of the (meth)acrylic acid alkyl ester copolymer described above.

[0075] The "weight average molecular weight (Mw) / number average molecular weight (Mn)" (hereinafter also referred to as "Mw / Mn") of the (meth)acrylic acid alkyl ester copolymer is preferably 1.0 or more and 10.0 or less, more preferably 2.5 or more and 9.0 or less, even more preferably 2.5 or more and 8.0 or less, and most preferably 3.0 or more and 7.0 or less. If Mw / Mn is within the above range, the (meth)acrylic acid alkyl ester copolymer can be easily produced, and the occurrence of adhesive residue can be suppressed. If the upper limit of Mw / Mn is 10.0 or less, the occurrence of adhesive residue can be suppressed. The upper limit of Mw / Mn is preferably 10.0 or less, more preferably 9.0 or less, even more preferably 8.0 or less, and most preferably 7.0 or less. If the lower limit of Mw / Mn is 1.0 or more, the (meth)acrylic acid alkyl ester copolymer can be easily produced. The lower limit of Mw / Mn is preferably 1.0 or more, more preferably 2.0 or more, even more preferably 2.5 or more, and most preferably 3.0 or more.

[0076] The (meth)acrylic acid alkyl ester monomer preferably contains a (meth)acrylic acid alkyl ester monomer having an alkyl group having 1 to 14 carbon atoms. Examples of the (meth)acrylic acid alkyl ester monomer having an alkyl group having 1 to 14 carbon atoms include a (meth)acrylic acid ester monomer of a linear aliphatic alcohol and a (meth)acrylic acid ester monomer of a branched aliphatic alcohol. Examples of (meth)acrylic acid ester monomers of linear aliphatic alcohols include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, propyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and lauryl (meth)acrylate. Examples of (meth)acrylic acid ester monomers of branched chain aliphatic alcohols include isobutyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0077] Among these, it is preferable that the (meth)acrylic acid alkyl ester monomer has at least one of an alkyl group having 1 to 3 carbon atoms and an alicyclic alkyl group. Hereinafter, a (meth)acrylic acid alkyl ester monomer having at least one of an alkyl group and an alicyclic alkyl group having 1 to 3 carbon atoms is also referred to as a “high Tg monomer.” “Tg” refers to the glass transition temperature. In order to further reduce the amount of outgassing, the (meth)acrylic acid alkyl ester monomer is more preferably an acrylic acid alkyl ester monomer having an alkyl group or an alicyclic alkyl group having a carbon number of 1 to 3, and even more preferably an acrylic acid alkyl ester monomer having an alkyl group having a carbon number of 1 to 3. When the (meth)acrylic acid alkyl ester monomer is an acrylic acid alkyl ester monomer having an alicyclic alkyl group, from the viewpoint of availability, the number of carbon atoms of the alicyclic alkyl group is preferably 5 to 10. When the (meth)acrylic acid alkyl ester monomer contains a high Tg monomer, the pellicle is less likely to peel off from the photomask even when exposed to a high-temperature atmosphere. Specific examples of high Tg monomers include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, cyclohexyl methacrylate, and dicyclopentanyl methacrylate.

[0078] The content of the (meth)acrylic acid alkyl ester monomer is preferably 80 parts by mass to 99.5 parts by mass, more preferably 85 parts by mass to 99.5 parts by mass, and even more preferably 87 parts by mass to 99.5 parts by mass, relative to 100 parts by mass of the total amount of the monomers constituting the copolymer. If the content of the (meth)acrylic acid alkyl ester monomer is within the range of 80 parts by mass to 99.5 parts by mass, an appropriate adhesive strength can be achieved.

[0079] The functional group-containing monomer is a monomer copolymerizable with the (meth)acrylic acid alkyl ester monomer, and has a functional group reactive with at least one of an isocyanate group, an epoxy group, and an acid anhydride. Examples of functional group-containing monomers include carboxy group-containing monomers, hydroxy group-containing monomers, and epoxy group-containing monomers. Examples of the carboxy group-containing monomer include (meth)acrylic acid, itaconic acid, (meth)acrylic acid itaconic acid, maleic acid, and crotonic acid. Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Examples of epoxy group-containing monomers include glycidyl (meth)acrylate. These may be used alone or in combination of two or more. In particular, from the viewpoints of copolymerizability, versatility, etc., the functional group-containing monomer preferably contains a hydroxy group-containing (meth)acrylic acid having a hydroxyalkyl group having 2 to 4 carbon atoms, or glycidyl (meth)acrylate, which is an epoxy group-containing monomer. Examples of the hydroxy group-containing (meth)acrylic acid having a hydroxyalkyl group having 2 to 4 carbon atoms include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0080] The content of the functional group-containing monomer is preferably, for example, 0.5 to 20 parts by mass relative to 100 parts by mass of the total amount of the monomers constituting the copolymer. From the viewpoint of improving the adhesive strength of the adhesive layer for photomasks, the lower limit of the content of the functional group-containing monomer is more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and particularly preferably 3 parts by mass or more, per 100 parts by mass of the total amount of monomers constituting the (meth)acrylic acid alkyl ester copolymer. In order to ensure that the adhesive strength of the photomask adhesive layer is appropriate, the upper limit of the content of the functional group-containing monomer is more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the total amount of monomers constituting the (meth)acrylic acid alkyl ester copolymer.

[0081] (3.2.5.2.2) Polymerization method The polymerization method for the (meth)acrylic acid alkyl ester copolymer is not particularly limited, and examples thereof include solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations. The (meth)acrylic acid alkyl ester copolymer obtained by these polymerization methods may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

[0082] (3.2.5.2.3) Polymerization solvent The reaction solution contains a polymerization solvent. In solution polymerization, for example, propyl acetate, ethyl acetate, toluene, etc. can be used as a polymerization solvent. This allows the viscosity of the copolymer solution to be adjusted. As a result, the thickness and width of the coating composition can be easily controlled during polymerization. Examples of dilution solvents include propyl acetate, acetone, ethyl acetate, and toluene. The viscosity of the copolymer solution is preferably 1000 Pa·s or less, more preferably 500 Pa·s or less, and even more preferably 200 Pa·s or less. The viscosity of the copolymer solution is the viscosity when the temperature of the copolymer solution is 25° C., and can be measured using an E-type viscometer.

[0083] (3.2.5.2.4) Solution Polymerization An example of solution polymerization is a method in which a polymerization initiator is added to a mixed solution of monomers in a stream of an inert gas such as nitrogen, and the polymerization reaction is carried out at 50° C. to 100° C. for 4 hours to 30 hours.

[0084] Examples of the polymerization initiator include azo polymerization initiators and peroxide polymerization initiators. Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionate)dimethyl, and 4,4'-azobis-4-cyanovaleric acid. Examples of the peroxide polymerization initiator include benzoyl peroxide. The content of the polymerization initiator is preferably 0.01 to 2.0 parts by mass relative to 100 parts by mass of the total amount of all monomers constituting the (meth)acrylic acid alkyl ester copolymer. In solution polymerization, in addition to the polymerization initiator, a chain transfer agent, an emulsifier, etc. may be added to the mixed solution of monomers. As the chain transfer agent, emulsifier, etc., known agents can be appropriately selected and used.

[0085] It is preferable that the amount of polymerization initiator remaining in the photomask adhesive layer is small, which can reduce the amount of outgassing that occurs during exposure. Methods for reducing the amount of polymerization initiator remaining in the adhesive layer for photomasks include minimizing the amount of polymerization initiator added when polymerizing the (meth)acrylic acid alkyl ester copolymer, using a polymerization initiator that is easily thermally decomposed, and heating the adhesive to a high temperature for a long period of time during the adhesive application and drying process to decompose the polymerization initiator during the drying process.

[0086] The 10-hour half-life temperature is used as an index to express the thermal decomposition rate of a polymerization initiator. "Half-life" refers to the time it takes for half of the polymerization initiator to decompose. "10-hour half-life temperature" refers to the temperature at which the half-life is 10 hours. It is preferable to use a polymerization initiator with a low 10-hour half-life temperature. The lower the 10-hour half-life temperature, the more easily the polymerization initiator is thermally decomposed. As a result, it is less likely to remain in the photomask adhesive layer. The 10-hour half-life temperature of the polymerization initiator is preferably 80°C or lower, more preferably 75°C or lower.

[0087] Examples of azo polymerization initiators having a low 10-hour half-life temperature include 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (10-hour half-life temperature: 30°C), 2,2'-azobisisobutyronitrile (10-hour half-life temperature: 65°C), 2,2-azobis(2,4-dimethylvaleronitrile) (10-hour half-life temperature: 51°C), dimethyl 2,2'-azobis(2-methylpropionate) (10-hour half-life temperature: 66°C), and 2,2'-azobis(2-methylbutyronitrile) (10-hour half-life temperature: 67°C). Examples of peroxide polymerization initiators with a low 10-hour half-life temperature include dibenzoyl peroxide (10-hour half-life temperature: 74°C) and dilauroyl peroxide (10-hour half-life temperature: 62°C).

[0088] (3.2.5.2.5) Crosslinking Agent The acrylic adhesive preferably contains a reaction product of a (meth)acrylic acid alkyl ester copolymer and a crosslinking agent, which improves the cohesive strength of the resulting photomask adhesive layer, suppresses adhesive residue when peeling the pellicle from the photomask, and improves adhesive strength at high temperatures (e.g., 60°C or higher). The crosslinking agent has at least one of an isocyanate group, an epoxy group, and an acid anhydride group.

[0089] Examples of crosslinking agents include monofunctional epoxy compounds, polyfunctional epoxy compounds, acid anhydride compounds, metal salts, metal alkoxides, aldehyde compounds, non-amino resin amino compounds, urea compounds, isocyanate compounds, metal chelate compounds, melamine compounds, and aziridine compounds. Among these, the crosslinking agent is more preferably at least one of a monofunctional epoxy compound, a polyfunctional epoxy compound, an isocyanate compound, and an acid anhydride compound, and more preferably an acid anhydride compound, in terms of excellent reactivity with the functional group component of the (meth)acrylic acid alkyl ester copolymer.

[0090] Examples of the monofunctional epoxy compound include glycidyl (meth)acrylate, glycidyl acetate, butyl glycidyl ether, and phenyl glycidyl ether. Examples of polyfunctional epoxy compounds include neopentyl glycol diglycidyl ether, polyethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, phthalic acid diglycidyl ester, dimer acid diglycidyl ester, triglycidyl isocyanurate, diglycerol triglycidyl ether, sorbitol tetraglycidyl ether, N,N,N',N'-tetraglycidyl m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyldiaminodiphenylmethane. Examples of the acid anhydride compounds include aliphatic dicarboxylic acid anhydrides and aromatic polycarboxylic acid anhydrides. Examples of the aliphatic dicarboxylic acid anhydride include maleic anhydride, hexahydrophthalic anhydride, hexahydro-4-methylphthalic anhydride, bicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride, 2-methylbicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride, and tetrahydrophthalic anhydride. Examples of aromatic polycarboxylic acid anhydrides include phthalic anhydride and trimellitic anhydride. Examples of isocyanate compounds include xylylene diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, and their multimers, derivatives, polymers, etc. These may be used alone or in combination of two or more.

[0091] The crosslinking agent may be a commercial product, such as "Rikacid MH-700G" manufactured by New Japan Chemical Co., Ltd.

[0092] The adhesive layer for photomasks contains a reaction product of the copolymer and a crosslinking agent, and the content of the crosslinking agent is preferably 0.01 to 3.00 parts by mass per 100 parts by mass of the total amount of monomers constituting the copolymer. The content of the crosslinking agent is preferably 0.01 to 3.00 parts by mass relative to 100 parts by mass of the total amount of the monomers constituting the copolymer, more preferably 0.10 to 3.00 parts by mass, and even more preferably 0.1 to 2.00 parts by mass, from the viewpoint of obtaining an adhesive layer for photomasks that is less likely to leave adhesive residue. If the upper limit of the crosslinking agent content is 3.00 parts by mass or less, the crosslinking density of the (meth)acrylic acid alkyl ester copolymer will not be too high. Therefore, it is thought that the pressure-sensitive adhesive absorbs the stress applied to the photomask, and the influence of the photomask pressure-sensitive adhesive layer on the flatness of the photomask is mitigated. The upper limit of the crosslinking agent content is preferably 2.00 parts by mass or less, more preferably 1.00 parts by mass or less. On the other hand, if the lower limit of the crosslinking agent content is 0.01 parts by mass or more, the crosslink density will not become too small, so that handling properties during the manufacturing process are maintained and adhesive residue is less likely to remain when the pellicle is peeled off from the photomask. If the content of the crosslinking agent is within the range of 0.01 parts by mass to 3.00 parts by mass, a pellicle can be obtained in which the occurrence of adhesive residue is further suppressed.

[0093] (3.2.5.2.6) Catalyst The coating composition may further contain a catalyst, which can further accelerate the curing of the (meth)acrylic acid alkyl ester copolymer. Examples of the catalyst include amine catalysts. Examples of the amine catalyst include octylate salt of (1,8-diazabicyclo-(5.4.0)undecene-7), triethylenediamine, etc. The amine catalyst may be a product of San-Apro Co., Ltd., such as "DBU," "DBN," "U-CAT," "U-CAT SA1," or "U-CAT SA102." The content of the catalyst is preferably 0.01 to 3.00 parts by mass, and more preferably 0.10 to 1.00 parts by mass, relative to 100 parts by mass of the (meth)acrylic acid alkyl ester copolymer.

[0094] (3.2.5.2.7) Surface modifiers The coating composition preferably does not contain a surface modifier, which can suppress the amount of outgassing.

[0095] (3.2.5.2.8) Additives The coating composition may contain additives such as fillers, pigments, diluents, antioxidants, tackifiers, etc. These additives may be used alone or in combination of two or more.

[0096] (3.2.5.2.9) Dilution solvent The coating composition may contain a dilution solvent, which allows the viscosity of the coating composition to be adjusted. As a result, when the coating composition is applied to the photomask end surface of the pellicle frame, the thickness and width of the coating composition can be easily controlled. Examples of dilution solvents include propyl acetate, acetone, ethyl acetate, and toluene. The viscosity of the coating composition is preferably 50 Pa·s or less, more preferably 10 Pa·s to 40 Pa·s, and even more preferably 20 Pa·s to 30 Pa·s. The viscosity of the coating composition is the viscosity when the temperature of the coating composition is 25°C, and can be measured using an E-type viscometer.

[0097] (3.3) Pellicle membrane formation process The method for manufacturing a pellicle according to the present disclosure may include a pellicle film forming step. The pellicle film forming step may be performed by any known method.

[0098] (4) Evaluation method for pellicle frame The present disclosure provides a method for evaluating a pellicle frame, which has a rectangular end face on which an adhesive layer capable of adhering to a photomask is provided and another end face supporting a pellicle membrane. The evaluation method includes measuring the amount of twist Δd of the one end face. The amount of twist Δd represents the maximum distance between an imaginary plane passing through three of the four corner points of the one end face and the remaining point.

[0099] The pellicle frame evaluation method of the present disclosure has the above-described configuration, and therefore can accurately measure the amount of twist at the end face of the pellicle frame, making it possible to evaluate pellicle frames that are easy to suppress mask distortion.

[0100] The pellicle frame to be measured may or may not contain silica glass. A pellicle frame that does not contain silica glass is similar to the pellicle frame of the present disclosure described above. As mentioned above, "the amount of twist Δd of the one end face indicates the maximum value of the distance between an imaginary plane passing through three of the four points at the four corners of the one end face and the remaining point." To measure the amount of twist Δd of one end face, the pellicle frame is placed on a surface plate so that the end face of the pellicle frame other than the end face whose amount of twist is to be measured (hereinafter also referred to as the "measurement-side end face") faces the surface plate. The heights from the surface plate of each of the four points, which are the four corners of the measurement-side end face, are measured using a 3D displacement meter. Next, using the height measurements at the four points, an imaginary plane passing through three of the four points is derived, and the shortest distance between the derived imaginary plane and the remaining point (hereinafter also referred to as the "first shortest distance") is calculated. Since there are four patterns for deriving an imaginary plane from the four points, four first shortest distances are calculated. The maximum of the four first shortest distances is taken as the amount of twist Δd of the measurement-side end face. Specifically, if the four corners of the measurement-side end face are defined as four points C1, C2, C3, and C4, respectively, the amount of twist Δd of the measurement-side end face is the maximum value among the following first distance, second distance, third distance, and fourth distance. The first distance is the shortest distance between point C4 and an imaginary plane passing through points C1, C2, and C3. The second distance is the shortest distance between point C3 and an imaginary plane passing through points C1, C2, and C4. The third distance is the shortest distance between point C2 and an imaginary plane passing through points C1, C3, and C4. The fourth distance is the shortest distance between point C1 and an imaginary plane passing through points C2, C3, and C4. [Example]

[0101] The present disclosure will be described in more detail below with reference to examples, but the invention of the present disclosure is not limited to these examples.

[0102] The methods for measuring the twist amount Δd and TIR value of the end face of the rectangular pellicle frame for the photomask, the TIR value of the flat surface of the flat plate, the TIR value of the adhesive layer for the pellicle for the photomask, the twist amount Δd and TIR value of the end face of the pellicle film, and the thickness of the adhesive layer for the pellicle for the photomask are as follows.

[0103] <Method for measuring the amount of twist Δd at the end face of a photomask> The amount of twist Δd of the photomask end face is determined as follows. The pellicle frame is placed on a surface plate so that the pellicle film end face of the pellicle frame faces the surface plate. The heights from the surface plate at each of the four corners of the photomask end face are measured using a 3D displacement meter (Keyence Corporation, "WI5000" with "WI-004" sensor head). Next, using the height measurements at the four points, a virtual plane passing through three of the four points is derived, and the shortest distance between the derived virtual plane and the remaining point (hereinafter also referred to as the "first shortest distance") is calculated. Since there are four patterns for deriving the virtual plane from the four points, four first shortest distances are calculated. The maximum of the four first shortest distances is defined as the twist amount Δd of the photomask end face.

[0104] <Method for measuring the TIR value of photomask end faces> The TIR value of the photomask end face is determined as follows. The pellicle frame was placed on the surface plate so that the pellicle film end face of the pellicle frame faced the surface plate. The heights of each of the 204 measurement points on the photomask end face from the surface plate were measured using a 3D displacement meter (Keyence Corporation, "WI5000" with "WI-004" sensor head). The 204 measurement points consisted of four points at the four corners of the photomask end face and 200 points on the four sides between the four corners. In principle, the 200 points refer to the total of points set at 2.5 mm intervals from one corner point to another corner point on each side between the four corners. However, if the distance between one of the four corners (hereinafter also referred to as a "corner point") and its adjacent point (hereinafter also referred to as the "corner spacing") is less than 2.5 mm, the adjacent point to the corner point is set so that the corner spacing is less than 2.5 mm. If the number of measurement points does not reach 204 when using the 2.5 mm spacing and corner spacing described above due to differences in the size of the pellicle frame, the measurement points are determined using the 2.5 mm spacing and the above-mentioned corner spacing concept. A least-squares plane is calculated using height measurements from 204 points. The measurement point with the largest difference in elevation between the least-squares plane and each of the multiple measurement points located on the opposite side of the surface plate from the least-squares plane is identified as the "first measurement point." The measurement point with the largest difference in elevation between the least-squares plane and each of the multiple measurement points located on the surface plate side of the least-squares plane is identified as the "second measurement point." The sum of the elevation difference from the least-squares plane of the first measurement point and the elevation difference from the least-squares plane of the second measurement point is defined as the TIR value.

[0105] <Method for measuring the TIR value of the flat surface of a flat plate> The TIR value of the flat surface of the flat plate is measured in the same manner as the method for measuring the TIR value of the end surface for the photomask, except that the pellicle frame is placed on the surface plate so that the surface opposite the flat surface of the flat plate faces the surface plate, and the surface for measuring the height is changed from the end surface for the photomask to the flat surface.

[0106] <Method for measuring the TIR value of adhesive layers for photomasks> The TIR value of the adhesive layer for the photomask is measured in the same manner as the method for measuring the TIR value of the end face for the photomask, except that the pellicle frame with the adhesive layer is placed on a base plate so that the end face for the pellicle film of the pellicle frame with the adhesive layer faces the base plate, and the height measurement surface is changed from the end face for the photomask to the surface of the adhesive layer for the photomask.

[0107] <Method for measuring the twist amount Δd of the end face of a pellicle membrane> The amount of twist Δd of the end face for the pellicle film is measured in the same manner as the method for measuring the amount of twist Δd of the end face for the photomask, except that the pellicle frame is placed on the base plate so that the end face for the photomask of the pellicle frame faces the base plate, and the height measurement surface is changed from the end face for the photomask to the end face for the pellicle film.

[0108] <Method for measuring the TIR value of the end face of a pellicle membrane> The TIR value of the end face for the pellicle film is measured in the same manner as the method for measuring the TIR value of the end face for the photomask, except that the pellicle frame is placed on the base plate so that the end face for the photomask of the pellicle frame faces the base plate, and the height measurement surface is changed from the end face for the photomask to the end face for the pellicle film.

[0109] <Method for measuring the thickness of adhesive layer for photomasks> The thickness of the adhesive layer for a photomask is determined as follows. The pellicle frame is placed on a surface plate so that the pellicle film end face of the adhesive-coated pellicle frame faces the surface plate. The heights from the surface plate at six measurement points on any one side between the four corners of the photomask end face are measured using a 3D displacement meter (Keyence Corporation, "WI5000," sensor head "WI-004"): In the width direction of the pellicle frame (the short direction of one side of the pellicle frame), four of the six measurement points are points where the adhesive layer is applied, and two of the six measurement points are points where the adhesive layer is not applied. In this example, the photomask adhesive layer is formed only at the center of each side between the four corners of the photomask end face, and is not formed on the edge of each side between the four corners on the through-hole side of the pellicle frame or on the edge opposite the through-hole side of the pellicle frame. Therefore, in this example, of the six measurement points, four points located in the center of the pellicle in the width direction are positions where the photomask adhesive layer is formed on the photomask end face. The remaining two points, located on both edges of the pellicle in the width direction, are positions where the photomask adhesive layer is not formed on the photomask end face. Using the height measurements at six points, the height difference between the highest point of the four points where the photomask adhesive layer is applied (the point where the photomask adhesive layer is thickest) and the lowest point of the two points where the photomask adhesive layer is not applied is calculated. This calculation method is performed along the length of the pellicle (the longitudinal direction of one side of the pellicle frame) using the same concept as for the TIR measurement points on the photomask end face (at 2.5 mm intervals and corner intervals). The height difference is calculated in the same way for each of the remaining three sides between the four corners of the photomask end face. The average of all height differences calculated in this way for all four sides is the thickness of the photomask adhesive layer.

[0110] Example 1 <Preparation process> Example 1 will be described with reference to Fig. 3. Fig. 3 is a schematic cross-sectional view showing a cross section of a pellicle frame 30 with an adhesive layer according to Example 1. As shown in FIG. 3, a rectangular pellicle frame 31 (external dimensions: 151 mm × 119 mm, frame height H: 1.4 mm, frame width W: 4 mm, made of SUS304, mass: 18 g) was prepared. The torsion Δd and TIR value of the photomask end surface S31A of the pellicle frame 31 were measured. The measurement results of the torsion Δd and TIR value of the photomask end surface S31A of the pellicle frame 31 are shown in Table 1. The Young's modulus of SUS304 is 193 GPa.

[0111] <Preparation of Coating Composition> As a coating composition, a styrene-based adhesive was prepared as follows.

[0112] The various components shown below were used as raw materials for the styrene-based adhesive. (Styrene-based thermoplastic elastomer (A)) H-SIS: Styrene-hydrogenated isoprene-styrene block copolymer (product name "Hybrar 7125" (Kuraray Co., Ltd.)) (Tackifying resin (B)) Hydrogenated alicyclic petroleum resin: C9 hydrogenated petroleum resin (product name "Arcon P-100" (manufactured by Arakawa Chemical Industries, Ltd.), softening point: 100±5°C, number average molecular weight (Mn): 610) (softener) Paraffin-based mineral oil (product name "Neovac MR-200" (MORESCO Corporation))

[0113] A raw material mixture was obtained by mixing 100 parts by mass of the styrene-based thermoplastic elastomer (A), 100 parts by mass of the tackifier resin (B), and 60 parts by mass of the softener so that the total weight was 48 g. The resulting raw material mixture was placed in a Labo Plastomill (Toyo Seiki Seisakusho, Ltd., capacity: 60 mL) and then sealed. The mixture was kneaded at 200°C and 100 rpm for 20 minutes to obtain a block coating composition. Approximately 10 g of the block coating composition was placed in a heating tank (internal tank temperature: 200°C) and melted. This resulted in a styrene-based adhesive coating composition.

[0114] <Adhesive layer formation process> The pellicle frame 31 was washed with pure water. The coating composition prepared as described above was applied to the photomask end surface S31A of the pellicle frame 31 using a dispenser to form a coating layer. At this time, the area to which the coating composition was applied was only the center of each side between the four corners of the photomask end surface. In this way, a pellicle frame with a coating layer was obtained.

[0115] A first glass substrate was prepared as a flat plate. The TIR value of the flat surface of the flat plate was 5 μm. A placement method was carried out. Specifically, with a liner attached to the surface of the coating layer, the coating layer of the coated pellicle frame was oriented downward (in the direction of gravity), and the coated pellicle frame was placed on the flat plate so that the coating layer of the liner-attached pellicle frame and the flat surface of the flat plate were in contact via the liner. At this time, a load of 423 g / cm was applied uniformly over the entire coating layer of the coated pellicle frame. 2 A pressure (load) of 1000 kJ / cm was applied to the contact article, and a first contact article was obtained. A first oven ("PVC-211" manufactured by ESPEC) was prepared as a heating device. The first contact article was placed inside the chamber of the first oven. The entire first contact article was heated in the first oven at 80 to 110°C for 5 minutes. Next, the first contact article was removed from the heating device, and the first flat plate was removed from the first contact article to obtain a coated pellicle frame.

[0116] A second glass substrate was prepared as the substrate. The pellicle frame with the coating layer was placed on the substrate so that the coating layer of the pellicle frame with the coating layer was in contact with the substrate via the liner. Hereinafter, an article in which the substrate and the pellicle frame with the coating layer are stacked in this order will also be referred to as the "second contact article." A second oven ("PVC-211" manufactured by ESPEC) was prepared. The second contact article was placed inside the chamber of the second oven. The entire second contact article was baked in the second oven at 80°C for 48 hours. The second contact article was then removed from the chamber of the second oven, and the substrate was removed from the second contact article. This resulted in a pellicle frame 30 with an adhesive layer. During baking, the entire second contact article was baked while applying a load of 18 g, including the weight of the pellicle frame. The thickness of the photomask adhesive layer 32 of the adhesive-layer-attached pellicle frame 30 was 250 μm. The TIR value of the photomask adhesive layer 32 of the adhesive-layer-attached pellicle frame 30 was measured. The measurement results of the TIR value of the photomask adhesive layer 32 of the adhesive-layer-attached pellicle frame 30 are shown in Table 1.

[0117] (Examples 2 to 3, and Comparative Example 1) Except for preparing the pellicle frame shown in Table 1, a pellicle frame 30 with an adhesive layer was obtained in the same manner as in Example 1. Table 1 shows the measurement results of the twist Δd and TIR value of the photomask end surface S31A of the pellicle frame 31, and the TIR value of the photomask adhesive layer 32 of the pellicle frame 30 with an adhesive layer.

[0118] (Comparative Example 2) A pellicle frame 30 with an adhesive layer was obtained in the same manner as in Example 1, except that a pellicle frame shown in Table 1 was prepared and that the entire second contact article was baked while applying a load of 9 g, including the mass of the pellicle frame, during baking. Measurement results of the twist Δd and TIR value of the photomask end surface S31A of the pellicle frame 31, and the TIR value of the photomask adhesive layer 32 of the pellicle frame 30 with an adhesive layer are shown in Table 1. The mass of the titanium pellicle frame 31 was 9 g.

[0119] Example 4 Except for preparing a pellicle frame as shown in Table 1 and heating the first contact article using a hot plate (manufactured by AS ONE Corporation, "EC-1200NR") as described below, a pellicle frame 30 with an adhesive layer was obtained in the same manner as in Example 1. Table 1 shows the measurement results of the twist Δd and TIR value of the photomask end surface S31A of the pellicle frame 31, and the TIR value of the photomask adhesive layer 32 of the pellicle frame 30 with an adhesive layer. In Example 4, the first contact article was heated using a hot plate. Specifically, the first contact article was prepared so that the pellicle frame was placed on the flattened article by the placement method, and the first contact article was placed on the plate of the hot plate so that the flattened article and the plate were in contact with each other, and then heated.

[0120] (Example 5, Comparative Example 3, and Comparative Example 4) A pellicle frame 30 with an adhesive layer was obtained in the same manner as in Example 4, except that the pellicle frame shown in Table 1 was prepared. The results of measuring the twist Δd and TIR value of the photomask end surface S31A of the pellicle frame 31, and the TIR value of the photomask adhesive layer 32 of the pellicle frame 30 with an adhesive layer are shown in Table 1. The Young's modulus of titanium is 106 GPa.

[0121] (Examples 6 and 7) Except for preparing the pellicle frame shown in Table 1, a pellicle frame 30 with an adhesive layer was obtained in the same manner as in Example 1. Table 1 shows the measurement results of the twist Δd and TIR value of the photomask end surface S31A of the pellicle frame 31, and the TIR value of the photomask adhesive layer 32 of the pellicle frame 30 with an adhesive layer.

[0122] [Table 1]

[0123] In Table 1, "Δd" indicates the amount of twist Δd of the end face of the pellicle frame for the photomask. In Table 1, "frame TIR value" indicates the TIR value of the end face of the pellicle frame for the photomask. In Table 1, "adhesive layer TIR value" indicates the TIR value of the adhesive layer for the photomask. In Table 1, "flattening ratio" is expressed by the following formula (1). Formula (1): Planarization rate = 1 - (TIR value of adhesive layer for photomask / TIR value of edge surface for photomask)

[0124] The pellicle frames of Examples 1 to 7 had a twist amount Δd of 10 μm or less at the photomask end surface S31A. Therefore, the TIR value of the photomask adhesive layer 32 of the adhesive-layer-attached pellicle frame 30 was less than 10 μm. The TIR value of the photomask was approximately several μm. In other words, it was found that the pellicle frames of Examples 1 to 7 enable the formation of a photomask adhesive layer 32 with a TIR value closer to that of the photomask, even if the photomask adhesive layer 32 is thin. Thus, when a pellicle using a pellicle frame of Examples 1 to 7 is attached to a photomask, the flatness of the photomask is less likely to change. As a result, it was found that the pellicle frames of Examples 1 to 7 can suppress distortion of the photomask caused by the attachment of a pellicle, even if the photomask adhesive layer 32 is thin.

[0125] In the pellicle frames of Examples 1 to 7, the amount of twist Δd of the photomask end surface S31A was 10 μm or less. Therefore, the flattening rate was 50% or more, which is higher than that of conventional pellicle frames. In other words, it was found that the pellicle frames of Examples 1 to 7 make it possible to form a photomask adhesive layer 32 with higher flatness, even if the flatness of the photomask end surface S31A is not high.

[0126] The pellicle frames of Comparative Examples 1 to 4 had a twist amount Δd of more than 10 μm at the photomask end face. Therefore, the TIR value of the photomask adhesive layer of the pellicle frames with an adhesive layer was more than 10 μm. In other words, it was found that the pellicle frames of Comparative Examples 1 to 4 could not form a photomask adhesive layer with a TIR value closer to that of the photomask if the thickness of the photomask adhesive layer was thin. As a result, when a pellicle using the pellicle frames of Comparative Examples 1 to 4 was attached to a photomask, the flatness of the photomask was likely to change. As a result, it was found that the use of the pellicle frames of Comparative Examples 1 to 4 did not allow for suppression of photomask distortion caused by pellicle attachment.

[0127] The disclosure of Japanese Patent Application No. 2021-148631, filed on September 13, 2021, is incorporated herein by reference in its entirety. All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. one end surface on which an adhesive layer that can be adhered to a photomask is provided; The other end surface that supports the pellicle membrane A rectangular pellicle frame (excluding pellicle frames containing quartz glass), The twist amount Δd of the one end surface is 10 μm or less, The twist amount Δd of the one end face indicates the maximum value of the distance between an imaginary plane passing through three of the four points at the four corners of the one end face and the remaining point.

2. The twist amount Δd of the other end surface is 10 μm or less, The pellicle frame according to claim 1 , wherein the twist amount Δd of the other end face indicates the maximum value of the distance between an imaginary plane passing through three of the four points at the four corners of the other end face and the remaining point.

3. The pellicle frame according to claim 1 or claim 2, comprising a metal.

4. 3. The pellicle frame according to claim 1, comprising at least one material selected from the group consisting of aluminum, titanium, stainless steel, carbon-based materials, resins, silicon, and ceramic-based materials.

5. 3. The pellicle frame according to claim 1, wherein the pellicle frame has a Young's modulus of 90 GPa or more.

6. 3. The pellicle frame according to claim 1, wherein the amount of twist Δd of said one end surface is 1 μm or more.

7. 3. The pellicle frame according to claim 1, wherein the TIR value of said one end face is 30 μm or less.

8. 3. The pellicle frame according to claim 1, wherein the TIR value of the other end face is 30 μm or less.

9. The pellicle frame according to claim 1 or 2; The adhesive layer provided on the one end surface; The pellicle membrane supported on the other end surface; A pellicle comprising:

10. A step of preparing a pellicle frame according to claim 1 or claim 2; a step of applying a coating composition to the one end surface to form a coating layer, heating the coating layer while the coating layer is in contact with the flat surface of the planarizing article, and then baking the coating layer to form the adhesive layer; and The thickness of the adhesive layer is 10 μm or more and 500 μm or less, The method for manufacturing a pellicle, wherein the TIR value of the flat surface is less than 10 μm.

11. The method for manufacturing a pellicle according to claim 10, comprising a step of fixing three of four points at four corners of one end face of the rectangular pellicle frame and applying force to the remaining point.

12. A method for evaluating a rectangular pellicle frame having one end surface on which an adhesive layer capable of adhering to a photomask is provided and the other end surface supporting a pellicle membrane, comprising: measuring the amount of twist Δd of the one end surface; A method for evaluating a pellicle frame, wherein the amount of twist Δd indicates the maximum value of the distance between an imaginary plane passing through three of the four points at the four corners of the one end face and the remaining one point.

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