Pellicle frame, pellicle, and method for releasing pellicle

Abstract

The present invention provides: a pellicle frame 1 that is a metal quadrangular frame-shaped body composed of four side parts 11, 11, 11, 11 and four corner parts 12, 12, 12, 12, and that is used in EUV lithography, the pellicle frame being characterized in that the width W2 of each of the corner parts 12 in a top view is wider than the width W1 of each of the side parts 11 in a top view; a pellicle that includes the pellicle frame as a constituent element; and a method for releasing the pellicle from an exposure original plate. According to the present invention, it is possible to suppress deflection of a pellicle frame when releasing a pellicle from an exposure original plate, and to reduce the risk of breakage of a pellicle film.

Description

Pericle Frame, Pericle, and Method for Peeling Off Pericle

[0001] The present invention relates to a pericle frame, a pericle, and a method for peeling off a pericle, which are attached to a photomask for lithography as dust removal means.

[0002] In recent years, the design rules of LSIs have been miniaturized to sub-quarter microns, and accordingly, the short wavelength of exposure light sources has been progressing. That is, the exposure light source has shifted from g-line (436 nm) and i-line (365 nm) by a mercury lamp to KrF excimer laser (248 nm), ArF excimer laser (193 nm), etc., and further, EUV (Extreme Ultra Violet) exposure using EUV light with a main wavelength of 13.5 nm is being studied.

[0003] In the manufacture of semiconductors such as LSIs and super LSIs or in the manufacture of liquid crystal display panels, light is irradiated onto a semiconductor wafer or a raw plate for liquid crystal to form a pattern. In this case, if dust adheres to the photomask for lithography and the reticle (hereinafter collectively referred to as the "exposure original plate"), this dust absorbs or bends light, resulting in problems such as the transferred pattern being deformed, the edge being rough, and the substrate being blackened and soiled, which impairs dimensions, quality, appearance, etc.

[0004] These operations are usually carried out in a clean room, but it is still difficult to always keep the exposure original plate clean. Therefore, a method of performing exposure after attaching a pericle to the surface of the exposure original plate as dust protection is generally adopted. In this case, foreign matter does not directly adhere to the surface of the exposure original plate but adheres to the pericle. Therefore, if the focus is set on the pattern of the exposure original plate during lithography, the foreign matter on the pericle becomes irrelevant to the transfer.

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

[0006] Due to the limitations of the exposure equipment, there are restrictions on the thickness of the pellicle frame used for EUV exposure. Because the space for pellicle placement within the EUV exposure equipment is small, the height of the pellicle must be less than 2.5 mm. Considering the thickness of the pellicle film, the thickness of the adhesive or bonding agent applied to the upper and lower ends of the frame, and the deflection of the pellicle film caused by pressure changes inside and outside the pellicle, the thickness of the pellicle frame must be thinner than 2.5 mm.

[0007] The pellicle attached to the exposure master plate is replaced if any problems occur, such as the adhesion of foreign matter. Generally, the pellicle is removed from the exposure master plate by inserting a peeling jig into peeling holes provided in the pellicle frame and lifting it. Conventional pellicle frames used in semiconductor manufacturing typically have jig holes in two locations on the outer surface of the opposite long sides.

[0008] As mentioned earlier, ultrathin silicon films and carbon films are being considered as pellicle films for EUV lithography. Films made of these materials tend to break into tiny fragments when damaged, and these fragments scatter, contaminating the surrounding environment. Furthermore, because these tiny fragments scatter, it is difficult to pinpoint the contaminated area. On the other hand, conventional pellicle films for semiconductors and liquid crystals, such as those made of ArF and KrF, are made of fluororesin and cellulose, and are ductile, resulting in an extremely low risk of breakage. Therefore, reducing the risk of pellicle film breakage is a challenge unique to pellicles for EUV lithography.

[0009] The greatest force is applied to the pellicle film when it is detached from the photomask. In EUV lithography, the pellicle film has poor durability against EUV light, so it needs to be detached more frequently than in conventional ArF or KrF lithography. If the pellicle needs to be replaced frequently and the pellicle film is damaged each time, contaminating the exposure master such as the photomask, it will take time to regenerate the exposure master, resulting in very poor production efficiency.

[0010] Furthermore, in EUV lithography, a pellicle with minimal bending and high mechanical strength is required when peeling it off.

[0011] Generally, pellicle peeling is performed by inserting a peeling pin into a jig hole, which is a non-through hole located on the outer surface of the pellicle frame, and pulling the pellicle up in the direction in which the pellicle film is located. For large pellicles with a side length of 500 mm or more, as described in Patent Document 1, it has been proposed to provide peeling holes near the corners of the square to facilitate pellicle peeling (Patent Document 1). However, even if peeling holes are provided near the corners in addition to the two peeling holes on each long side of the pellicle frame, in the case of frames with a thickness of less than 2.5 mm, the deflection of the frame becomes large, and there is a risk of damage to the pellicle film, especially at the corners.

[0012] Patent Document 2 proposes a pellicle frame made of a sintered body designed so that the corners are wider than the straight sections. However, even if the width of the corners is increased, the sintered body lacks ductility, which increases the risk of damage to the pellicle frame when peeling the pellicle from the exposure plate. Furthermore, if the adhesive between the pellicle and the exposure plate is strong, when attempting to peel the pellicle by inserting a peeling pin into a jig hole, the frame near the jig hole may be damaged, making it impossible to peel the pellicle.

[0013] Patent documents 3 and 4 propose frame designs for liquid crystal pellicles with the aim of preventing the pellicle frame from bending inward due to the tension of the pellicle film. These patent documents relate to inventions concerning liquid crystal pellicles, and the liquid crystal pellicle film is made of fluororesin or cellulose. Since these materials are ductile, the pellicle film will not break or scatter.

[0014] Japanese Patent Publication No. 2006-301525, Japanese Patent Publication No. 2016-177120, Japanese Patent Publication No. 2002-333703, Japanese Patent Publication No. 2015-081968

[0015] The present invention has been made in view of the above circumstances, and aims to provide a pellicle frame that can suppress the bending of the pellicle frame when peeling the pellicle from the exposure master plate, thereby reducing the risk of damage to the pellicle film.

[0016] As a result of diligent research to achieve the above objective, the inventors have discovered that, in an EUV pellicle frame which is a rectangular frame made of metal, the corners of the rectangular frame are made thicker in a top view than the four sides of the rectangular frame, that is, the width of the corners in a top view is made wider than the width of the four sides in a top view, thereby suppressing the bending of the pellicle frame when peeling the pellicle from the exposure plate, preventing damage to the pellicle film and enabling smooth peeling work, thus leading to the present invention.

[0017] Accordingly, the present invention provides the following pellicle frame, pellicle, and method for peeling off a pellicle: 1. A pellicle frame for use in EUV lithography, which is a rectangular frame made of metal, the rectangular frame being composed of four sides and four corners, and characterized in that the width of the corners when viewed from above is wider than the width of the sides when viewed from above. 2. The pellicle frame according to 1, wherein the ratio of the width of the corners (a) to the width of the sides (b) is (a) / (b) = 1.2 / 1 to 2 / 1. 3. The pellicle frame according to 1 or 2, wherein the sides of the sides have a number of through holes. 4. The pellicle frame according to 1 or 2, wherein the sides of the sides have jig holes for inserting a peeling jig to peel the pellicle from the exposure plate. 5. A pellicle characterized by including the pellicle frame according to 1 or 2 as a component. 6. A method for peeling a pellicle from an exposure master plate to which the pellicle described in item 5 above is attached, characterized in that a peeling jig is inserted into a jig hole or through hole formed on the side surface of the pellicle frame, and the pellicle is peeled from the exposure master plate by moving the peeling jig toward the upper end surface of the pellicle frame in this state.

[0018] According to the present invention, it is possible to provide an EUV pellicle frame and pellicle that have a low risk of damage to the pellicle film when the pellicle is replaced.

[0019] This is a perspective view showing one embodiment of the pellicle frame of the present invention. This is a plan view of the pellicle frame of Figure 1, viewed from above. This is a schematic diagram showing the pellicle frame of Example 1, where (A) is a plan view viewed from above, (B) is a side view viewed from the short side outer surface, and (C) is a side view viewed from the long side outer surface. This is a plan view of the pellicle frame of Example 2, viewed from above. This is a plan view of the pellicle frame of Example 3, viewed from above. This is a plan view of the pellicle frame of Comparative Example 1, viewed from above. This is a diagram showing the process of peeling a pellicle representing one embodiment of the present invention from a photomask, where (A) is a plan view viewed from above, and (B) is a schematic cross-sectional view.

[0020] The present invention will be described in more detail below. The pellicle frame of the present invention is a frame-shaped pellicle frame having an upper end surface on which a pellicle film is provided and a lower end surface facing a photomask.

[0021] The pellicle frame of the present invention is rectangular (or square) in shape. However, it does not need to be a perfectly rectangular frame; each side of the rectangular frame may have a partially protruding portion. For example, when using an image alignment function to position the pellicle frame, the frame needs structurally distinctive markers. In this case, partially protruding portions may be provided on the outside or inside of the sides to serve as alignment markers. Furthermore, it is preferable to provide the protruding portions on the outside of the frame so as not to obstruct the exposure area.

[0022] Furthermore, the pellicle frame has a surface for attaching the pellicle film (referred to here as the "upper end surface") and a surface that faces the photomask when the photomask is attached (referred to here as the "lower end surface").

[0023] The upper and lower ends, inner and outer surfaces of the pellicle frame do not need to be flat; grooves, steps, and chamfers may be added as needed.

[0024] Typically, a pellicle film is attached to the upper end surface of the pellicle frame via an adhesive, and an adhesive for attaching the pellicle to the photomask is attached to the lower end surface.

[0025] The pellicle frame of the present invention is made of metal. There are no restrictions on the type of metal, and known metals can be used. For pellicle frames used in EUV applications, materials with a low coefficient of thermal expansion are preferred because they may be exposed to high temperatures. Examples include Invar, titanium, titanium alloys, and aluminum alloys, among which titanium, titanium alloys, and aluminum alloys are preferred from the viewpoint of ease of processing and lightweight.

[0026] The dimensions of the pellicle frame are not particularly limited, but since the height of the EUV pellicle is limited to less than 2.5 mm, the thickness of the EUV pellicle frame is smaller than that, less than 2.5 mm.

[0027] Furthermore, the thickness of the pellicle frame for EUV is preferably 1.5 mm or less, taking into account the thickness of the pellicle film, photomask adhesive, etc.

[0028] Typically, the sides of the pellicle frame are provided with jig holes used for handling and separating the pellicle from the photomask. The size of the jig holes is usually 0.5 to 1.0 mm in length in the thickness direction of the pellicle frame (or diameter in the case of a circular frame). There are no particular restrictions on the shape of the jig holes; they can be circular or rectangular. Typically, the jig holes are not holes that penetrate from the outer surface to the inner surface of the pellicle frame.

[0029] The pellicle frame of the present invention may have through-holes for ventilation to prevent the pellicle membrane from bending when there are pressure changes inside and outside the pellicle. The size of these through-holes is 0.5 to 1.0 mm in length in the thickness direction of the pellicle frame (diameter in the case of a circular frame). There are no particular restrictions on the shape of the through-holes; for example, they may be circular or rectangular. The through-holes penetrate from the outer surface to the inner surface of the pellicle frame. There are no particular restrictions on the number or arrangement of the through-holes, but it is preferable to evenly distribute the through-holes on each side of the pellicle frame. By evenly distributing the through-holes, the airflow inside the pellicle frame during pressure fluctuations can be effectively mitigated. Filters may be provided at or inside the openings of the through-holes.

[0030] To suppress the deflection of the pellicle membrane during pressure changes inside and outside the pellicle, it is preferable that the opening area of ​​the through-hole be 1% or more of the surface area of ​​the inner surface of the frame. For example, in the case of Embodiment 1 of the present invention described later, the opening area is 28 mm². 2 The inner surface area of ​​the pellicle frame is 756 mm². 2 As a result, the aperture ratio is 3.7%. In the case of Example 4, the opening area is 100 mm². 2 The inner surface area of ​​the pellicle frame is 743 mm². 2This results in an opening ratio of 13.5%. A larger opening ratio improves breathability and suppresses the bending of the pellicle membrane. However, if the opening ratio is increased too much, the strength of the pellicle frame decreases, making the pellicle frame more prone to bending when the pellicle is peeled off. For this reason, the upper limit of the opening ratio is preferably 30% or less, more preferably 20% or less, and even more preferably 15% or less.

[0031] As shown in the embodiments described later, we assume through-holes with the same diameter running from the outer surface to the inner surface of the pellicle frame, but the through-holes may be locally smaller or larger. If the diameter of the through-holes is not uniform, the point with the smallest diameter will be the rate-limiting point when considering air resistance. Therefore, it is necessary to calculate the opening ratio using the smallest area that is the rate-limiting point. For example, in the case of a through-hole where the opening shape on the inner surface of the pellicle frame is a circle with a diameter of 0.8 mm and the opening shape on the outer surface of the pellicle frame is a circle with a diameter of 0.5 mm, the opening area of ​​the through-hole should be calculated using a circle with a diameter of 0.5 mm.

[0032] Furthermore, through-holes may be used for peeling the pellicle. By inserting a peeling jig into the numerous through-holes and performing peeling at multiple points, the force applied to the pellicle frame can be distributed, thereby suppressing the bending of the pellicle frame.

[0033] The pellicle frame of the present invention is characterized in that the width of the corner portion is wider than the width of the side portion. This "width" refers to the width of the pellicle frame when viewed from the upper or lower end surface, as shown in Figure 1. With a rectangular frame shape like a pellicle frame, strain tends to concentrate at the corner portion when peeling off the pellicle, making the pellicle film prone to damage. By making the width of the corner portion thicker than the width of the side portion, the strength of the corner portion can be increased, deformation of the pellicle frame can be prevented, and the risk of damage to the pellicle film can be reduced as much as possible.

[0034] Regarding the corner portion in the present invention, there are no particular restrictions on the shape of the corner portion as long as the width of the corner portion is greater than the width of the side portion. For example, the corner portion in the present invention may be a right angle or an R-shape (the corner of the frame is rounded). Specific embodiments of the corner portion include an embodiment in which one of the outer and inner corner portions is a right angle and the other has an R-shape, or an embodiment in which both sides have an R-shape and their radii of curvature are different. For example, when both sides have an R-shape, the ratio of the radius of curvature of the outer corner portion to the radius of curvature of the inner corner portion can be set so that the inner radius of curvature is larger than the outer radius, preferably 1:2 to 1:10, more preferably 1:3 to 1:6, and even more preferably 1:4 to 1:5. Furthermore, an R-shape corner portion is preferred because it allows for the removal of burrs that can cause foreign matter and also facilitates foreign matter inspection.

[0035] The ratio of the width of the corner portion (a) to the width of the side portion (b) is preferably (a) / (b) = 1.2 / 1 to 2 / 1, as this increases the strength of the corner portion and more effectively suppresses deformation of the pellicle frame and damage to the pellicle film. The value of (a) / (b) above is more preferably 1.4 / 1 to 1.8 / 1, and even more preferably 1.5 / 1 to 1.6 / 1. If the value of (a) / (b) above is too large, the inner corner portion will be formed to protrude further inward in order to make the inner corner portion wider, and as a result, the frame in that portion will block the irradiation of the exposure, causing problems in pattern formation on the exposure plate.

[0036] Furthermore, there are no particular restrictions on the material of the pellicle film, but it is preferable to use a material that has high transmittance at the wavelength of the exposure light source and high light resistance. For example, for EUV exposure, ultrathin silicon films or carbon films are usually used. In particular, the pellicle frame of the present invention is effective for silicon-based films, which are prone to damage to the pellicle film.

[0037] The pellicle film does not need to be made of only one material. For example, one method for producing an ultrathin silicon film involves first forming a self-supporting pellicle film layer on a silicon wafer, and then etching the portion of the silicon wafer that will become the self-supporting film, thereby producing an ultrathin silicon self-supporting film supported by the frame of the silicon wafer. In such a case, in this invention, the frame of the silicon wafer is also included in the definition of the pellicle film.

[0038] In the pellicle of the present invention, a pellicle film is provided on the upper end surface of the pellicle frame via an adhesive or bonding agent. Generally, it is preferable that the adhesive or bonding agent be provided around the entire circumference of the pellicle frame. There are no restrictions on the material of the adhesive or bonding agent; known materials can be used, and acrylic adhesives or silicone adhesives can be suitably used. The adhesive or bonding agent may be processed into any shape as needed. To strongly hold the pellicle film, an adhesive or bonding agent with strong adhesive strength is preferred.

[0039] Furthermore, an adhesive for attaching the photomask is formed on the lower end surface of the pellicle frame. Generally, it is preferable that the photomask adhesive be provided around the entire circumference of the pellicle frame. Known adhesives can be used as the photomask adhesive, and acrylic adhesives and silicone adhesives are preferably used. The adhesive may be processed into any shape as needed.

[0040] A release layer (separator) may be attached to the lower end surface of the photomask adhesive to protect the adhesive. The material of the release layer is not particularly limited, but for example, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), polypropylene (PP), etc. may be used. In addition, if necessary, a release agent such as a silicone-based release agent or a fluorine-based release agent may be applied to the surface of the release layer.

[0041] The method for peeling a pellicle according to the present invention is to insert a peeling jig into a jig hole or through hole provided on the side surface of the pellicle frame, and in this state, move the peeling jig in the direction of the upper end surface of the pellicle frame, thereby peeling the pellicle from the photomask to which the pellicle is attached. At this time, when peeling the pellicle, strain tends to concentrate on the corner portions. However, since the width of the corner portion of the pellicle frame of the present invention is thicker than the width of the side portion, the strength of the corner portion is increased, deformation of the pellicle frame can be prevented, and the risk of damage to the pellicle film can be reduced.

[0042] When moving the peeling jig in the direction of the upper end surface of the pellicle frame, if the portion of the pellicle frame that contacts the peeling jig is flat, it is preferable that the peeling jig has a flat plate shape. The peeling jig is preferably shaped according to the shape of the portion of the pellicle frame that contacts the peeling jig. For example, if the portion of the pellicle frame that contacts the peeling jig is a normal circular hole, it is preferable to use an oval columnar peeling pin corresponding to the circular hole. By doing so, the contact area between the jig hole or through hole and the peeling pin becomes larger, and it becomes difficult for the pellicle frame to be damaged.

[0043] Here, FIGS. 1 and 2 show an example of the pellicle frame 1 of the present invention, which is a rectangular frame-shaped body presenting a rectangle when viewed from above. In each drawing, reference numeral 11 indicates the side portion of the pellicle frame, and reference numeral 12 indicates the corner portion of the pellicle frame. The side portions 11 of the pellicle frame consist of four, and are composed of two long side portions 11a and two short side portions 11b. And as shown in FIG. 2, the width W2 of the corner portion 12 in a top view is formed wider than the width W1 of the side portion 11 in a top view.

[0044] Also, FIG. 7 is a diagram showing a state in which a pellicle is peeled off from a photomask. Reference numeral 10 indicates the pellicle, and a pellicle film 2 is adhered and stretched on the upper end surface of the pellicle frame 1 by an adhesive 4. Further, on the lower end surface of the pellicle frame, it is detachably adhered to the photomask 3 by an adhesive 5 to protect the pattern surface on the photomask 3. Then, when peeling the pellicle 10 from the photomask 3, a peeling jig (peeling pin) 7 is inserted into a plurality of through holes 20 or jig holes 30 formed on the outer surface of the pellicle frame 1, and the peeling jig is moved in the direction of the upper end surface of the pellicle frame, whereby the pellicle is peeled off from the photomask to which the pellicle is attached.

[0045] [Examples 1 to 4, Comparative Example 1] Hereinafter, examples and a comparative example will be shown to specifically explain the present invention, but the present invention is not limited to the following examples.

[0046] [Example 1] The pellicle frame of Example 1 is made of titanium and has the shape shown in the plan view and side view of FIGS. 3(A) to (C). That is, in Example 1, a pellicle frame (outer dimensions 150 mm × 118 mm × 1.5 mm, frame width 4.0 mm) in which the inside and outside of the corner portion are formed at right angles was produced. The width of the corner portion in a top view is 5.7 mm, and the width of the side portion in a top view is 4.0 mm.

[0047] In the above embodiment, two jig holes measuring 1 mm in diameter and 1.2 mm in depth were provided on the outer surface of the long side of the pellicle frame, spaced 104 mm apart from the center of the side. Reference numeral 30 in Figure 3(C) indicates the jig holes. Note that the spacing between jig holes described below refers to the distance between the centers of the holes. Furthermore, as shown in Figure 3(C), one through hole measuring 0.8 mm in diameter was provided at a spacing of 7 mm from the jig hole toward the corner. Reference numeral 20 in Figure 3(C) indicates the through hole. Furthermore, as shown in Figure 3(C), thirteen through holes measuring 0.8 mm in diameter were provided between the jig holes 30 at a spacing of 7 mm apart, symmetrically from the center of the side. Therefore, there are a total of 15 through holes 20 on one long side of the pellicle frame. On the other hand, as shown in Figure 3(B), thirteen through holes 20 with a diameter of 0.8 mm were provided on the short side of the pellicle frame at intervals of 7 mm, symmetrically from the center of the side. Therefore, there are a total of 56 through holes in the entire pellicle frame.

[0048] The above-mentioned pellicle frame was cleaned, and a mixture of 100 parts by mass of silicone adhesive (product name "X-40-3264" manufactured by Shin-Etsu Chemical Co., Ltd.), 1 part by mass of hardener (product name "PT-56" manufactured by Shin-Etsu Chemical Co., Ltd.), and a mixture was applied to the entire circumference of the upper end surface of the pellicle frame to a thickness of 0.1 mm. On the lower end surface of the pellicle frame, a mixture of 100 parts by mass of acrylic adhesive (product name "SK-Dyne 1495" manufactured by Soken Chemical Co., Ltd.), 0.1 parts by mass of hardener (product name "L-45" manufactured by Soken Chemical Co., Ltd.), and a mixture was applied to the entire circumference of the lower end surface of the pellicle frame to a thickness of 0.1 mm.

[0049] Subsequently, the pellicle frame was heated at 90°C for 12 hours to cure the adhesive applied to the upper and lower surfaces of the pellicle frame. Next, an ultra-thin silicone film was pressed onto the adhesive formed on the upper surface of the pellicle frame to complete the pellicle of Example 1.

[0050] [Example 2] The pellicle frame of Example 2 is made of titanium and has the shape (plan view) shown in Figure 4. Specifically, in Example 2, a pellicle frame (outer dimensions 150 mm × 118 mm × 1.5 mm, frame width 4.0 mm) was manufactured with the inside of the corners formed with R5 (radius of curvature 5 mm) and the outside formed at a right angle. The width of the top view of the corners is 7.7 mm, and the width of the top view of the edges is 4.0 mm. Except for the shape of the corners, the pellicle frame was manufactured in the same manner as in Example 1.

[0051] [Example 3] The pellicle frame of Example 3 is made of titanium and has the shape (plan view) shown in Figure 5. Specifically, in Example 3, a pellicle frame (outer dimensions 150 mm × 118 mm × 1.5 mm, frame width 4.0 mm) was manufactured with the inside of the corners formed with R5 (radius of curvature 5 mm) and the outside with R1 (radius of curvature 1 mm). The width of the top view of the corners is 7.3 mm, and the width of the top view of the edges is 4.0 mm. Except for the shape of the corners, the pellicle frame was manufactured in the same manner as in Example 1.

[0052] [Example 4] The pellicle frame of Example 4 is made of titanium. In Example 4, a pellicle frame (external dimensions 150 mm x 118 mm x 1.5 mm, frame width 4.0 mm) was fabricated with the inner corners formed with R5 (radius of curvature 5 mm) and the outer corners with R1 (radius of curvature 1 mm). The width of the top view of the corners is 7.3 mm, and the width of the top view of the edges is 4.0 mm. Note that a schematic diagram of the pellicle frame of Example 4 is not specifically shown.

[0053] In the above embodiment, two jig holes measuring 1 mm in diameter and 1.2 mm in depth were provided on the outer surface of the long side of the pellicle frame, spaced 104 mm apart from the center of the side. Furthermore, three through holes measuring 0.8 mm in diameter were provided at intervals of 2.2 mm from the jig holes toward the corner. Between the jig holes, 45 through holes measuring 0.8 mm in diameter were provided at intervals of 2.2 mm, symmetrically from the center of the side. Therefore, there are a total of 51 through holes on one long side of the pellicle frame. On the other hand, 49 through holes measuring 0.8 mm in diameter were provided on the short side of the pellicle frame at intervals of 2 mm, symmetrically from the center of the side. Therefore, there are a total of 200 through holes on the entire pellicle. The subsequent steps are the same as in Embodiment 1.

[0054] [Comparative Example 1] The pellicle frame of Comparative Example 1 is made of titanium and has the shape (plan view) shown in Figure 6. Specifically, in Comparative Example 1, a pellicle frame (outer dimensions 150 mm × 118 mm × 1.5 mm, frame width 4.0 mm) was manufactured with the inside of the corners formed with R1 (radius of curvature 1 mm) and the outside with R5 (radius of curvature 5 mm). The width of the top view of the corner portion is 4.0 mm, and the width of the top view of the edge portion is 4.0 mm. Except for the shape of the corner portion, a pellicle frame similar to that of Example 1 was manufactured.

[0055] [Peel Test] The pellicles prepared in Examples 1-3 and Comparative Example 1 were attached to a 6-inch square quartz photomask with a load of 1 kg for 30 seconds and left at room temperature for one day. The four corners of the quartz substrate were fixed, and 0.5 mm diameter peel pins were inserted from the outside of the pellicle frame into four through holes on each side (see Figure 7). The locations of the four through holes into which the peel pins were inserted are the black-filled parts of the through holes indicated by reference numeral 20 in Figure 7(B). Then, the peel pins were pulled up in the upward direction (the direction of the pellicle film) at 0.1 mm / second to peel off the pellicle. The above pellicle peel test was performed five times, and the condition of the pellicle film after peeling was checked (Peel Test 1). For Example 3, the same peel test was performed an additional 50 times, and the condition of the pellicle film after peeling was checked (Peel Test 2). The results of these peel tests 1 and 2 are shown in Table 1 below.

[0056]

[0057] The results in Table 1 show that using the pellicle frame of this embodiment can reduce the risk of damage to the pellicle film during pellicle peeling. Furthermore, the results of peeling test 2 show that the risk of damage to the pellicle film can be reduced to less than 10%.

[0058] In addition to the structure and effects of the pellicle frame of the present invention, it is also possible to further reduce the risk of damage to the pellicle film by appropriately adjusting the peeling conditions according to the design of the pellicle and the type of adhesive, such as the peeling speed when peeling the pellicle from the photomask, the number of through holes in the pellicle frame used for peeling, and the temperature during peeling.

[0059] 1 Pellicle frame 11 Side section 11a Long side section 11b Short side section 12 Corner section 20 Through hole 30 Jig hole W1 Width of side section when viewed from above W2 Width of corner section when viewed from above

Claims

1. A pellicle frame made of metal, having a rectangular frame shape, the rectangular frame shape being composed of four sides and four corners, and used for EUV lithography, characterized in that the width of the corners when viewed from above is wider than the width of the sides when viewed from above.

2. The pellicle frame according to claim 1, wherein the ratio of the width of the corner portion (a) to the width of the side portion (b) is (a) / (b) = 1.2 / 1 to 2 / 1.

3. The pellicle frame according to claim 1, wherein the side surface of the edge portion has a number of through holes.

4. The pellicle frame according to claim 1, wherein the side surface of the edge portion has a jig hole for inserting a peeling jig in order to peel the pellicle from the exposure master plate.

5. A pellicle characterized by including the pellicle frame described in claim 1 as a component.

6. A method for peeling a pellicle from an exposure master plate to which the pellicle described in claim 5 is attached, characterized in that a peeling jig is inserted into a jig hole or through hole formed on the side surface of the pellicle frame, and the pellicle is peeled from the exposure master plate by moving the peeling jig toward the upper end surface of the pellicle frame in this state.

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