Pellicle frame, and pellicle

Abstract

Provided is a pellicle frame that is a frame 1 having a rectangular frame shape and having removal holes formed from the outer surface toward the inner surface and that is characterized in that, in the vicinity of each of the four corners, one or more removal holes 3 are present in each of regions L2, L4 which are located within 10%, from the respective corners, of the outer lengths L1, L3 of the respective sides, and at least one removal hole 3 is present at a location in each of the four sides other than the vicinity of the corners. According to a pellicle that employs the pellicle frame, it is possible to: prevent deflection of the frame during removal work as much as possible; separate the pellicle from an exposure original plate without causing damage to the pellicle film; and satisfactorily and reliably perform pellicle replacement.

Description

Pericle Frame and Pericle

[0001] The present invention relates to a pericle frame and a pericle attached as a foreign matter removal device to a photomask for lithography.

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

[0003] In the manufacture of semiconductors such as LSIs and super LSIs or the manufacture of liquid crystal display panels, light is irradiated onto a semiconductor wafer or a raw plate for liquid crystals to create 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 light or bends light, resulting in problems such as the transferred pattern being deformed, the edges being rough, and the substrate being blackened and soiled, which damages the dimensions, quality, appearance, etc.

[0004] These operations are usually performed 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 as dust protection on the surface of the exposure original plate 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 adjusted to the pattern on 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] Here, due to the limitations of the exposure equipment, there are restrictions on the pellicle thickness. 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 that occurs when pressure changes occur inside and outside the pellicle, the thickness of the pellicle frame for EUV exposure must be thinner than 2.5 mm.

[0007] Furthermore, the pellicle attached to the exposure master plate can be replaced if any problems occur, such as the adhesion of foreign matter. As shown in Figure 6, the pellicle is removed from the exposure master plate by inserting a peeling jig into the peeling hole provided in the pellicle frame and lifting it. Conventional pellicle frames used in semiconductor manufacturing generally have a shape in which jig holes are provided in two places on the outer surface of the opposing long sides. Examples of conventional pellicle frames include the pellicle frames described in Patent Documents 1 to 3 below.

[0008] Japanese Patent Publication No. 2007-298870, Japanese Patent Publication No. 2006-301523, Japanese Patent Publication No. 2016-177120

[0009] In the case of pellicle frames for EUV exposure, when attempting to peel the pellicle from the exposure plate using the peeling holes provided at two locations on the long side, the thinness of the frame caused bending, as shown in Figure 6, for example, resulting in damage to the pellicle film and the generation of foreign matter.

[0010] Furthermore, for large pellicles with side lengths of 500 mm or more, it has been proposed to provide peeling holes near the corners to facilitate pellicle peeling. However, even with peeling holes provided near the corners in addition to the two peeling holes on each long side, it was found that in the case of frames with a thickness of less than 2.5 mm, the frame flexes significantly, as shown in Comparative Example 1 described later, resulting in damage to the film.

[0011] On the other hand, for pellicle frames made of sintered bodies, a frame shape has been proposed in which the corners are wider than the frame width. However, in the case of frames with a thickness of less than 2.5 mm, as shown in Comparative Example 2 later, it was found that simply widening the corners was not enough to suppress the bending of the entire frame, resulting in damage to the film.

[0012] The present invention has been made in view of the above circumstances, and aims to provide a pellicle frame that, even when the frame thickness is less than 2.5 mm, does not cause damage to the pellicle film due to frame bending during the pellicle peeling process, and allows for good and reliable replacement of the pellicle, as well as a pellicle using the pellicle frame.

[0013] The inventors of the present invention conducted diligent studies to achieve the above objectives and, as a result, discovered that by optimizing the position, number, and arrangement of the peeling holes in the pellicle frame, it is possible to prevent the frame from bending as much as possible during the peeling process, thereby enabling the pellicle to be peeled from the exposure master without damaging the pellicle film, and allowing for good and reliable pellicle replacement. Thus, the present invention was completed.

[0014] Accordingly, the present invention provides the following pellicle frame and a pellicle using the pellicle frame. 1. A rectangular frame-shaped frame having peeling holes provided from the outer surface of the frame toward the inner surface, wherein at least one peeling hole is present near each of the four corners in a region within 10% of the outer length of each side from each corner, and at least one peeling hole is present on each of the four sides other than near the corners. 2. The pellicle frame according to 1, wherein the peeling holes have a depth of at least half the thickness of the frame in the outward-inward direction. 3. The pellicle frame according to 1 or 2, wherein the thickness of the corners in the outward-inward direction is greater than the thickness of each side in the outward-inward direction. 4. The pellicle frame according to any one of 1 to 3, wherein the thickness of the frame in the front-back direction is less than 2.5 mm. 5. A pellicle comprising the pellicle frame according to any one of 1 to 4 and a pellicle film provided on the upper end surface of the pellicle frame via an adhesive. 6. The pellicle according to 5, wherein the pellicle film is mainly composed of Si. 7. A pellicle according to claim 5 or 6, used for EUV exposure.

[0015] According to the pellicle frame and pellicle of the present invention, bending of the frame during the peeling process can be prevented as much as possible, allowing the pellicle to be peeled from the exposure master without damaging the pellicle film, and enabling good and reliable pellicle replacement.

[0016] Figure 1 is a three-view drawing consisting of a top view, a front view, and a side view showing the pellicle frame of Example 1 according to the present invention. Figure 2 is a three-view drawing consisting of a top view, a front view, and a side view showing the pellicle frame of Example 2 according to the present invention. Figure 3 is a three-view drawing consisting of a top view, a front view, and a side view showing the pellicle frame of Comparative Example 1. Figure 4 is a three-view drawing consisting of a top view, a front view, and a side view showing the pellicle frame of Comparative Example 2. Figure 5 is a three-view drawing consisting of a top view, a front view, and a side view showing the pellicle frame of Comparative Example 3. Figure 6 is an explanatory diagram showing how damage occurs to the pellicle film when peeling a pellicle using a conventional pellicle frame from an exposure master.

[0017] The present invention will be described in more detail below. The pellicle frame of the present invention is a rectangular frame-shaped pellicle frame having an upper end surface on which a pellicle film is provided and a lower end surface facing a photomask.

[0018] The pellicle frame can be a rectangular frame and is designed to correspond to the shape of the photomask on which the pellicle is attached. The corners (edges) of the pellicle frame may be sharp (pointed), or they may be chamfered, such as with R-chamfering or C-chamfering, to create other shapes such as curved shapes.

[0019] Furthermore, the pellicle frame has a surface for attaching the pellicle film (referred to here as the upper end surface) and a surface that contacts the photomask when the photomask is attached (referred to here as the lower end surface). In this invention, the thickness direction between the upper end surface and the lower end surface is referred to as the "front-back direction," and the thickness direction between the outer and inner surfaces of the frame shape is referred to as the "outer-inner direction."

[0020] On the upper end surface of the pellicle frame, a pellicle film is usually attached via adhesive, similar to the pellicle frame in Figure 6, and on the lower end surface, an adhesive is provided for attaching the pellicle to the photomask (exposure plate). However, the method of attaching the pellicle film and attaching it to the photomask is not limited to using adhesives or glues, and any appropriate method can be adopted.

[0021] The dimensions of the pellicle frame are not particularly limited, but if the height of the EUV pellicle is limited to 2.5 mm or less, the thickness of the EUV pellicle frame must be smaller than that, so it is preferable that it be less than 2.5 mm. In particular, considering the thickness of the pellicle film and the adhesive for the photomask, the thickness of the EUV pellicle frame is preferably 1.5 mm or less. Furthermore, the lower limit of the thickness of the pellicle frame is preferably 1.0 mm or more.

[0022] There are no restrictions on the material of the pellicle frame, and known materials can be used. However, especially 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 Si, SiO2, SiN, SiON, quartz, Invar, titanium, titanium alloys, and aluminum alloys. Among these, titanium, titanium alloys, and aluminum alloys are preferred due to their ease of processing and light weight. Furthermore, from the viewpoint of a low coefficient of thermal expansion, materials with a linear expansion coefficient of 10 × 10⁻¹⁰ are preferred. -6 The metal is preferably (1 / K) or less, and more preferably selected from titanium or a titanium alloy. If necessary, a single or multiple coating may be applied to the surface of the pellicle frame.

[0023] For example, as shown in Figure 1, the pellicle frame 1 is typically provided with a jig hole 2 on its side, which is used for handling and peeling the pellicle from the photomask. The size of the jig hole is approximately 0.5 to 1.0 mm in length (or diameter in the case of a circular hole) in the front-to-back direction of the frame. There are no restrictions on the shape of the hole; it can be circular or rectangular. Typically, the jig hole does not penetrate from the outer surface to the inner surface, but it may be made to penetrate and used as a ventilation hole. In this invention, a separate peeling hole 3 is provided for the peeling operation used to peel the pellicle from the photomask. Therefore, the jig hole 2 can be used exclusively for handling and not for peeling, and in some cases, the peeling hole 3 can also be used as a jig hole for handling, making it possible to omit the jig hole altogether.

[0024] In addition to the jig holes 2 and peeling holes 3 described above, ventilation holes may be provided to prevent the membrane from bending when there are pressure changes inside and outside the pellicle. There are no restrictions on the shape, number, or location of the ventilation holes. Notches may be provided on the end faces to serve as ventilation holes. Filters may be provided in the ventilation holes as needed. The jig holes described above are usually holes that do not penetrate from the outer surface to the inner surface, but they can also be made to penetrate and used as ventilation holes.

[0025] For example, as shown in Figure 1, the pellicle frame 1 of the present invention is provided with peeling holes 3 on its side, in addition to the jig holes 2 mentioned above, for peeling the pellicle from the photomask. The size of the peeling holes 3 is 0.5 to 1.0 mm in length (or diameter in the case of a circular shape) in the front-to-back direction of the frame. There are no restrictions on the shape of the holes; they can be circular or rectangular. The peeling holes 3 may be holes that do not penetrate from the outer surface to the inner surface, or they may be penetrated and used as ventilation holes.

[0026] These peeling holes 3 are located near the four corners of the pellicle frame 1, with at least one hole in each of the four sides within a range L2, L4 of 10% of the outer length L1, L3 from the corner end of each side, and at least one hole outside the vicinity of the corners of each of the four sides (in Figure 1, there are three on the long side and two on the short side). To explain "within 10% of the outer length of the side" in more detail, for example, in the case of a frame side with an outer length of 100 mm, it refers to a range of 10 mm from the corner end. The more peeling holes 3 there are, the better the frame deflection can be suppressed, so it is preferable, and although there are no particular limitations, it is preferable that there be four or more peeling holes 3 on one frame side.

[0027] The depth of the peeling hole 3 is preferably at least half the thickness of the frame in the inward and outward directions. If it is less than half the thickness of the frame in the inward and outward directions, as shown in Figure 6, only the outside of the frame will be supported during peeling, which will cause the frame to bend near the corners and make the pellicle film more susceptible to damage.

[0028] Furthermore, especially with frame materials that have a low Young's modulus, such as aluminum, it is preferable, although not particularly limited, to partially increase the thickness (thicken) of the corners of the frame in the outward and inward directions. With a square frame shape like a pellicle frame, strain tends to concentrate at the corners when peeling off the pellicle, making the pellicle film prone to damage. For example, by setting the radius of the corners so that the thickness (thicken) of the corners in the outward and inward directions is thicker than that of each side, the risk of pellicle film damage can be reduced.

[0029] The pellicle frame of the present invention has a pellicle film attached to its upper end surface via an adhesive and is used as a pellicle. This pellicle is then peelably attached to a photomask (exposure plate) via an adhesive provided on the lower end surface of the pellicle frame, thereby protecting the patterned surface on the photomask.

[0030] While there are no restrictions on the material of the pellicle film, it is preferable to use a material with high transmittance at the wavelength of the exposure light source and high light resistance. For example, ultrathin silicon films and carbon films are used for EUV exposure, but the pellicle frame of the present invention is particularly effective against silicon-based films, which are prone to film damage and are mainly composed of Si.

[0031] There are no restrictions on the adhesive used to attach the pellicle film; any adhesive that can reliably adhere the pellicle film to the upper surface of the pellicle frame is acceptable, and can be appropriately selected from known adhesives. In this case, a strong adhesive is preferably used to firmly hold the pellicle film in place. Alternatively, a strong adhesive can be used as the adhesive for attaching the pellicle film 2.

[0032] The adhesive used on the lower end surface of the pellicle frame to attach the pellicle to the photomask (exposure plate) is preferably provided around the entire circumference of the lower end surface of the pellicle frame. Any known adhesive can be appropriately selected and used, with acrylic adhesives, silicone adhesives, rubber adhesives, etc., being suitably used. The adhesive may be processed into any shape as needed.

[0033] A release layer (separator) may be attached to the lower end surface of the adhesive, that is, the surface of the adhesive that comes into contact with the photomask (exposure plate), 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.

[0034] The pellicle frame and pellicle of the present invention are not particularly limited, but can be suitably used in EUV exposure. In that case, they can be used not only as protective members to prevent foreign matter from adhering to the exposure plate in the EUV exposure apparatus, but also as protective members to protect the exposure plate during storage and transportation.

[0035] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0036] [Example 1] A titanium pellicle frame (external dimensions 150 mm x 118 mm x 1.5 mm, thickness in the inner and outer directions of the frame, 4.0 mm) was prepared. As shown in Figure 1, two jig holes 2 with a diameter of 1 mm and a depth of 1.2 mm were made on the outer surface of the long side of the pellicle frame at a centrally distributed position of 104 mm. Furthermore, five peeling holes 3 with a diameter of 0.8 mm and a depth of 3 mm were made at a centrally distributed interval of 32.5 mm. Four peeling holes 3 with a diameter of 0.8 mm and a depth of 3 mm were made on the short side of the pellicle frame at a centrally distributed interval of 32.5 mm. The radius of the corners was set to R1 on the inside and R5 on the outside.

[0037] The pellicle frame was cleaned, and on the upper end surface of the frame, a mixture of 100 parts by mass of silicone adhesive (X-40-3264, manufactured by Shin-Etsu Chemical Co., Ltd.), 1 part by mass of hardener (PT-56, manufactured by Shin-Etsu Chemical Co., Ltd.), was added and mixed, and applied to the entire width except for the notched areas to a thickness of 0.1 mm. On the lower end surface of the frame, as a mask adhesive, a mixture of 100 parts by mass of acrylic adhesive (SK-Dyne 1495, manufactured by Soken Chemical Co., Ltd.), 0.1 parts by mass of hardener (L-45, manufactured by Soken Chemical Co., Ltd.), was added and mixed, and applied to the entire circumference to a thickness of 0.1 mm across the entire width.

[0038] Next, the pellicle frame was heated at 90°C for 12 hours to cure the adhesive on the upper and lower end surfaces. Then, an ultra-thin silicone film was pressed onto the adhesive formed on the upper end surface of the frame to complete the pellicle.

[0039] As a substitute for a photomask, a 150 mm x 150 mm quartz mask was prepared. After attaching the pellicle to this mask, a peeling jig was inserted into each peeling hole 3 and lifted at a speed of 0.1 mm / s. This allowed the ultra-thin silicon film to be peeled off without damage.

[0040] [Example 2] As shown in Figure 2, the pellicle frame was manufactured in the same manner as in Example 1, except that the corner radius was set to outer R1 and inner R3, and it was made of aluminum alloy (JIS A7075).

[0041] Similar to Example 1, after attaching this pellicle to a quartz mask, a peeling jig was inserted into each peeling hole 3 and lifted at a speed of 0.1 mm / s, allowing the ultrathin silicon film to be peeled off without damage.

[0042] [Comparative Example 1] A titanium pellicle frame (outer dimensions: 150 mm × 118 mm × 1.5 mm, frame outer-inner direction thickness: 4.0 mm) was prepared. As shown in Fig. 3, two jig holes 2 with a diameter of 1 mm × depth of 1.2 mm were provided on the outer surface of the long side of the pellicle frame at a position 104 mm by central distribution, and further two peeling holes with a diameter of 0.8 mm × depth of 3 mm were provided at a position 10 mm from the corner ends of the frame. No jig holes or peeling holes were provided on the short sides. The R shape of the frame corners was R1 on the inner side and R5 on the outer side. A pellicle was produced in the same manner as in Example 1 except for the frame shape.

[0043] Similar to Example 1, after attaching this pellicle to a quartz mask, a peeling jig was inserted into each peeling hole and lifted at a speed of 0.1 mm / s. As a result, the frame started to peel from the corners, the frame deflected greatly at the center of the frame, and the ultra-thin silicon film was damaged.

[0044] [Comparative Example 2] A titanium pellicle frame (outer dimensions: 150 mm × 118 mm × 1.5 mm, frame outer-inner direction thickness: 4.0 mm) was prepared. As shown in Fig. 4, two jig holes with a diameter of 1 mm × depth of 1.2 mm were provided on the outer surface of the long side of the pellicle frame at a position 104 mm by central distribution, and no peeling holes were provided. Also, no jig holes or peeling holes were provided on the short sides. The R shape of the frame corners was R3 on the inner side and R1 on the outer side. A pellicle was produced in the same manner as in Example 1 except for the frame shape.

[0045] Similar to Example 1, after attaching this pellicle to a quartz mask, a peeling jig was inserted into each peeling hole and lifted at a speed of 0.1 mm / s. As a result, the frame deflected greatly at the center of the frame, and the ultra-thin silicon film was damaged.

[0046] [Comparative Example 3] A titanium pellicle frame (outer dimensions: 150 mm × 118 mm × 1.5 mm, frame outer-inner direction thickness: 4.0 mm) was prepared. As shown in Fig. 5, two jig holes with a diameter of 1 mm and a depth of 1.2 mm were provided on the outer surface of the long side of the pellicle frame at positions 104 mm from the center by centering. Further, three peeling holes 3 with a diameter of 0.8 mm and a depth of 3 mm were provided at intervals of 25 mm from the center by centering. Four peeling holes with a diameter of 0.8 mm and a depth of 3 mm were provided on the short side of the pellicle frame at intervals of 25 mm from the center by centering. No peeling holes were provided within 10% of the outer dimension length of the side from the corner for both the long side and the short side. The R shape of the corner was R3 on the inner side and R1 on the outer side. A pellicle was produced in the same manner as in Example 1 except for the frame shape.

[0047] Similar to Example 1, after attaching this pellicle to a quartz mask, a peeling jig was inserted into each peeling hole and lifted at a speed of 0.1 mm / s. As a result, the frame bent significantly at the corners of the frame and the ultra-thin silicon film was damaged.

[0048] From the results of Example 1, 2 and Comparative Examples 1 - 3 above, it was confirmed that even for a pellicle frame with a thickness less than 2.5 mm, by providing peeling holes for peeling operations at predetermined positions near the corners of the frame and at the center of each side, the risk of damage to the pellicle film during pellicle peeling can be kept low.

[0049] 1 Pellicle frame 2 Jig hole 3 Peeling hole L1, L3 Outer dimension length of each side L2, L4 Region within 10% of the outer dimension length of the side from the corner

Claims

1. A rectangular frame-shaped pellicle frame having peeling holes provided from the outer surface of the frame toward the inner surface, wherein at least one peeling hole exists near each of the four corners, within a region within 10% of the outer length of each side from each corner, and at least one peeling hole exists on each of the four sides outside of the vicinity of the corners.

2. The pellicle frame according to claim 1, wherein the peeling hole has a depth of at least half the thickness of the frame in the inward and outward directions.

3. The pellicle frame according to claim 1, wherein the thickness of the corners in the inward and outward directions is greater than the thickness of each side in the inward and outward directions.

4. The pellicle frame according to claim 1, wherein the thickness of the frame in the front-to-back direction is less than 2.5 mm.

5. A pellicle comprising a pellicle frame as described in claim 1 and a pellicle film provided on the upper end surface of the pellicle frame via an adhesive.

6. The pellicle according to claim 5, wherein the pellicle film is mainly composed of Si.

7. The pellicle of claim 5 used for EUV exposure.

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