Pellicle frame, pellicle, exposure original plate with pellicle, exposure method, and method for manufacturing semiconductor

Abstract

[Problem] The invention relates to a dustproof filter used while being attached to a vent hole for rapidly lowering an atmospheric pressure difference abruptly generated between the inside and outside of a pellicle closed space in a frame of a pellicle, especially a pellicle for EUV exposure, and addresses the problem of preventing a decrease in the handleability of the filter due to a reduction in the thickness of the filter which is particularly required these days. [Solution] In a pellicle frame 2 having a vent hole 5 for ventilation between the inside and outside of a pellicle closed space, a filter 3 is provided so as to close at least a part of the vent hole, and the thickness of the entire filter is made larger than the thickness of a filter opening 10 by 0.1 mm or more.

Description

Pericle Frame, Pericle, Photomask with Pericle, Exposure Method, and Semiconductor Manufacturing Method

[0001] The present invention relates to a pericle frame suitably used for a pericle attached to a photomask for lithography as dust removal.

[0002] In recent years, the design rules of LSIs have been miniaturized to sub-quarter microns, and along with this, 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 plates, light is irradiated onto a semiconductor wafer or a master for liquid crystals to create a pattern. In this case, if dust adheres to the photomask for lithography and the reticle (hereinafter, collectively described as "exposure master"), this dust absorbs light or bends light, so that the transferred pattern is deformed, the edge becomes rough, and in addition, the substrate becomes black and dirty, resulting in problems such as dimensional, quality, and appearance being impaired.

[0004] These operations are usually performed in a clean room, but it is still difficult to always keep the exposure master clean. Therefore, a method of performing exposure after attaching a pericle to the surface of the exposure master as dust removal is generally adopted. In this case, foreign matter does not directly adhere to the surface of the exposure master but adheres to the pericle. Therefore, if the focus is set on the pattern of the exposure master 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 provided on the upper end surface of the pellicle frame, and an airtight gasket formed on the lower end surface. An adhesive layer is generally used for the airtight gasket. 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] Furthermore, since EUV lithography is performed under vacuum or equivalent reduced pressure, there is a high possibility that the pellicle film will bend significantly and break when pressure changes occur from atmospheric pressure to vacuum. Therefore, EUV lithography pellicles need to withstand pressure changes from atmospheric pressure to vacuum, and the ventilation area of ​​EUV lithography pellicles is required to be large. Accordingly, EUV lithography pellicles are provided with more ventilation holes than other types of pellicles to mitigate such pressure changes, and the total ventilation area is increased.

[0007] Furthermore, a filter is provided at the opening of this ventilation hole to prevent particles from entering the closed space of the pellicle. However, when a filter is installed in the ventilation hole, the pressure loss from the filter reduces ventilation, and the amount of membrane displacement of the pellicle film increases when the pressure changes from atmospheric pressure to vacuum, which also increases the likelihood of membrane damage. Therefore, pellicles for EUV exposure are required to be equipped with a filter that has low pressure loss and good permeability.

[0008] Patent Document 1 proposes a pellicle using a filter composed of at least one of nanofibers or carbon nanotubes. By using a filter composed of nanofibers or carbon nanotubes with a small fiber diameter, pressure loss can be reduced and foreign matter can be collected with high efficiency. Furthermore, because the fiber diameter is small, the thickness of the filter can also be reduced. While reducing the thickness of the filter is one way to reduce the pressure loss of the filter, the inventors have found that this weakens the strength of the filter, making it more prone to tearing and thus creating handling problems.

[0009] International Publication No. 2023 / 013660

[0010] As mentioned above, since EUV lithography is performed under vacuum or equivalent reduced pressure, there was a concern that the pellicle film would undergo significant displacement during pressure changes from atmospheric pressure to vacuum, or vice versa, potentially leading to film damage within the EUV lithography apparatus.

[0011] To prevent film damage during pressure changes, filters installed in pellicles for EUV lithography require high permeability, and thus the pressure drop of the filter must be minimized. However, the inventors have discovered that reducing the thickness of the filter to minimize pressure drop weakens the strength of the filter itself, resulting in poor handling.

[0012] Therefore, the present invention has been made in view of the above circumstances, and aims to provide a pellicle frame and pellicle using a filter that maintains strength while minimizing pressure loss.

[0013] The inventors of this invention discovered that, rather than improving the overall mechanical strength and filtering function of the filter, which tend to be in a trade-off relationship, it is possible to independently improve filtering function and mechanical strength by separating the components responsible for filtering function and mechanical strength, and thus completed the present invention.

[0014] In other words, the present invention is as follows: [1] A pellicle frame having ventilation holes for ventilating the inside and outside of a closed pellicle space, wherein a filter is provided so as to block at least a part of the ventilation holes, and the total thickness of the filter is 0.1 mm or more thicker than the thickness of the filter opening through which air can pass. [2] The pellicle frame according to [1], wherein the thickness of the filter opening is 0.1 mm or less. [3] The pellicle frame according to [1] or [2], wherein the total thickness of the filter is 0.3 mm or less. [4] The pellicle frame according to any one of [1] to [3], wherein a region 0.1 mm or more thicker than the thickness of the filter opening is provided along the outer edge of the filter. [5] The pellicle frame according to [4], wherein the region 0.1 mm or more thicker than the thickness of the filter opening comprises a filter layer, an adhesive layer, and a base material layer. [6] The pellicle frame according to any one of [1] to [5], wherein the thickness of the pellicle frame is 2.0 mm or less. [7] A pellicle frame according to any one of [1] to [6] above, which is a component of a pellicle for EUV exposure. [8] A pellicle frame according to any one of [1] to [7] above, wherein the pellicle frame base material of the pellicle frame is made of titanium or a titanium alloy. [9] A pellicle characterized in that it comprises a pellicle frame and a pellicle film according to any one of [1] to [8] above.

[10] A pellicle according to [9] above, wherein the film displacement of the pellicle film when the pellicle is exposed to a pressure change from atmospheric pressure to a vacuum, or when the pellicle is exposed to a pressure change from a vacuum to atmospheric pressure, is 1 mm or less.

[11] An exposure master plate with a pellicle, characterized in that the pellicle according to [9] or

[10] is installed on the exposure master plate.

[12] An exposure method characterized by exposure using the pellicle according to [9] or

[10] above.

[13] A semiconductor manufacturing method characterized by having a step of exposure using the pellicle according to [9] or

[10] above.

[0015] According to the present invention, by increasing the overall thickness of the filter, the strength of the filter can be maintained, and deterioration of handling properties can be prevented. Therefore, the thickness of the filter opening can be reduced, and the pressure loss of the filter can be reduced.

[0016] This is a schematic diagram showing one embodiment of the pellicle frame of the present invention and the pellicle frame and pellicle listed in Examples 1 and 2, where (A) is a view from the lower end side, (B) is a view from the outer side of the long side, and (C) is a view from the outer side of the short side. This is a schematic diagram of the filter listed in Example 1, where (A) is a view from the adhesive layer side, and (B) is a side view of an enlarged cross section between A and A' in (A). This is a schematic diagram of the filter listed in Example 2, where (A) is a view from the adhesive layer side, and (B) is a side view of an enlarged cross section between A and A' in (A). This is a schematic diagram of the filter listed in Comparative Example 1, where (A) is a view from the adhesive layer side, and (B) is a side view of an enlarged cross section between A and A' in (A). This is a simplified explanatory diagram for explaining the pressure loss measurement method of the filters listed in Examples 1 and 2 and Comparative Example 1.

[0017] Embodiments of the present invention will be described in detail below with reference to the drawings, but the present invention is not limited to these embodiments. In each drawing, the same or corresponding parts are denoted by the same reference numerals. Furthermore, the photomask (hereinafter sometimes simply referred to as "mask") described below is an example of an exposure master plate, and the same applies to the reticle.

[0018] The pellicle frame of the present invention (hereinafter sometimes simply referred to as "frame") is a frame-shaped pellicle frame having an upper end surface on the side on which the pellicle film is provided and a lower end surface on the side facing the photomask. This pellicle frame comprises at least a pellicle frame base material and a filter as its components. The pellicle frame base material is provided with ventilation holes for ventilation between the inside and outside of the closed pellicle space, which will be described later, and the filter is provided so as to block at least a part of the ventilation holes. Figure 1 is a schematic diagram showing one embodiment of the pellicle frame of the present invention and the pellicle frame and pellicle mentioned in Examples 1 and 2 described later, where (A) is a view from the lower end surface side of the pellicle frame, (B) is a view from the outer side of the long side, and (C) is a view from the outer side of the short side. In Figure 1, the reference numerals are as follows: 1 represents the pellicle, 2 represents the pellicle frame, 3 represents the filter, 4 represents the pellicle film, 5 represents the ventilation holes, 6 represents the mask adhesive layer, and 7 represents the film adhesive layer.

[0019] The pellicle frame is preferably frame-shaped, and its shape preferably corresponds to the shape of the photomask on which the pellicle is attached. Generally, it is a rectangular (especially square or rectangular) frame shape.

[0020] Furthermore, the pellicle frame has a side on which the pellicle film is attached (referred to here as the "upper end surface") and a side on which the photomask faces when the photomask is attached (referred to here as the "lower end surface").

[0021] Typically, a pellicle film is provided on the upper end surface of a pellicle frame via an adhesive, and a mask adhesive layer for attaching the pellicle to a photomask is provided on the lower end surface; however, the pellicle frame of the present invention is not limited to this. Furthermore, by providing a projection facing outward on the pellicle frame and providing a connection mechanism (screw, adhesive, etc.) to the exposure master plate on this projection, the mask adhesive layer can be omitted.

[0022] The material of the pellicle frame base material constituting the pellicle frame of the present invention is preferably a ductile metal. Furthermore, since higher precision is required in EUV lithography than in ArF lithography, the requirements for mask flatness are stringent. It is known that mask flatness is affected by the pellicle. Therefore, in order to minimize the influence of the pellicle on the mask, the material of the pellicle frame base material is preferably lightweight titanium or a titanium alloy. On the other hand, quartz and SiO ２ The pellicle frame base material may be made of inorganic materials such as the above.

[0023] The dimensions of the pellicle frame of the present invention are not particularly limited, but since the height of the pellicle for EUV exposure is limited to 2.5 mm or less, if the pellicle frame of the present invention is a pellicle frame for EUV exposure, the thickness (height) of the EUV exposure pellicle frame will be smaller than that, less than 2.5 mm. In practice, considering the thickness of the pellicle film and mask adhesive layer, the thickness of the EUV exposure pellicle frame is preferably 2.0 mm or less, and more preferably 1.6 mm or less.

[0024] Furthermore, in order for the pellicle to fully perform its function, it is preferable that the height of the pellicle be 1.5 mm or more. In that case, the thickness of the EUV exposure pellicle frame is preferably 1.0 mm or more, taking into account the thickness of the pellicle film, mask adhesive layer, etc.

[0025] The width (top and bottom edges) of the pellicle frame is preferably about 3 to 5 mm, because this width is necessary when attaching the filter, which will be described later, to the top or bottom surface of the pellicle frame.

[0026] Furthermore, the sides of the pellicle frame are typically provided with jig holes used for handling and detaching the pellicle from the photomask, as well as ventilation openings to alleviate the pressure difference between the inside and outside of the pellicle's enclosed space. These ventilation openings are areas through which air can pass and consist of ventilation holes formed to penetrate the pellicle frame. The size of the jig holes and ventilation openings is typically 5 to 1.0 mm in length in the thickness direction of the frame (or diameter in the case of a circular opening), but is not limited to this. There are also no restrictions on the shape of the jig holes and ventilation openings; they can be circular or rectangular.

[0027] Here, the pellicle closed space refers to the space enclosed by the pellicle and the exposure master when the pellicle is attached to the exposure master. This pellicle closed space cannot be created when the pellicle is not attached to the exposure master, but for convenience, we will assume the existence of the exposure master and define the space formed by the pellicle and the exposure master as the pellicle closed space.

[0028] Furthermore, typically, jig holes are holes that do not penetrate from the outer surface to the inner surface of the pellicle frame, while ventilation holes are holes that penetrate from the outer surface to the inner surface of the pellicle frame. Dust filters for particle removal (hereinafter simply referred to as "filters") are provided in the ventilation holes so as to block at least a portion of the ventilation hole.

[0029] In the pellicle frame of the present invention, there are no particular restrictions on the structure or number of the ventilation holes, as long as they allow ventilation between the inside and outside of the closed pellicle space. Therefore, the ventilation holes can be of various forms, including not only ventilation passages having openings on the outer surface and inner surface of the pellicle frame, but also ventilation passages having openings on the outer surface and upper end surface, ventilation passages having openings on the outer surface and lower end surface, ventilation passages having openings on the upper end surface and inner surface, and ventilation passages having openings on the upper end surface and lower end surface. Instead of ventilation holes that penetrate both the outer and inner surfaces, ventilation holes that change direction midway, such as through holes extending from the outer surface to the inner surface of the pellicle frame and then bending towards the upper or lower surface of the pellicle frame to create an opening on the upper or lower surface, or through holes extending from the inner surface to the outer surface of the pellicle frame and then bending towards the upper or lower surface of the pellicle frame to create an opening on the upper or lower surface, make it easy to design a wide opening area on the upper or lower surface. This is an effective technique for thin pellicles such as those used for EUV exposure, which have a height restriction of approximately 2.5 mm or less.

[0030] In EUV lithography, the exposure apparatus is kept under vacuum or a similar reduced pressure state, so the EUV exposure pellicle needs to be able to withstand the pressure change from atmospheric pressure to vacuum. For this reason, the ventilation area of ​​the EUV exposure pellicle is preferably as large as possible, and the filter installed in the ventilation area is preferably one that minimizes pressure loss.

[0031] The filter provided in the ventilation holes of the pellicle frame of the present invention preferably comprises a dustproof filter layer and an adhesive layer for attaching it to the pellicle frame. Furthermore, it may also have a base layer to support the filter layer and an adhesive layer for attaching the base layer to the filter layer. These filter layer and base layer are breathable. In addition, the base layer is preferably provided along the outer edge of the filter layer to increase the overall mechanical strength of the filter (Figure 2), and it can also be provided so as to cover the entire top of the filter layer via the adhesive layer, not just the outer edge of the filter layer (Figure 3). Figures 2 and 3 are schematic diagrams of the filter, where (A) is a view from the adhesive layer side and (B) is a side view of an enlarged cross section between A and A' in (A). The filter can also be installed inside the pellicle frame by making a recess from the outer surface.

[0032] Effective methods for reducing the pressure loss of the aforementioned filter include reducing the thickness of the filter layer and increasing the pore size of the filter layer and substrate layer. Furthermore, since the material and fiber diameter of the filter layer and substrate layer also affect the pressure loss, selecting appropriate materials and fiber diameters can reduce the pressure loss of the filter.

[0033] The material of the filter layer is not particularly limited, but for example, polytetrafluoroethylene (PTFE), stretched polytetrafluoroethylene (ePTFE), polypropylene (PP), polyvinyl alcohol (PVA), polyamide-imide, etc. can be used.

[0034] Furthermore, the material of the base layer is not particularly limited, but polypropylene (PP), polyethylene terephthalate (PET), vinylon, polyether ether ketone (PEEK), etc. can be used.

[0035] The filter layer or substrate layer is preferably a structure in which the fibers of the above-mentioned material are formed into a porous membrane such as a nonwoven fabric. This porous membrane may be in the form of a mesh, not just a nonwoven fabric.

[0036] The overall thickness of the filter is preferably 0.3 mm or less, and more preferably 0.28 mm or less. However, from the viewpoint of ease of handling when the filter is installed on the pellicle, the overall thickness of the filter is preferably 0.15 mm or more, more preferably 0.2 mm or more, and particularly preferably 0.23 mm or more. Here, the overall thickness of the filter refers to the thickness (height) from the top end to the bottom end of the filter. In Figures 2 and 3, W1 corresponds to the overall thickness of the filter. The overall thickness of the filter was measured using a laser displacement meter (Keyence Corporation, multi-color laser coaxial displacement meter CL-3000).

[0037] As shown in Figures 2 and 3, the adhesive layer 9 of the filter 3 is usually formed all the way around along the outer edge of the filter layer 8 or the base layer 11. In the filter, the portion excluding the part in which this adhesive layer is formed (the portion inside the circumferentially formed adhesive layer), that is, the portion through which air can pass, is the filter opening 10, and the larger the opening of this filter, the better the air permeability of the filter.

[0038] In the present invention, it is preferable to achieve both filtering function and mechanical strength by partially thickening the filter while maintaining a thin thickness at the filter opening. For such a filter, it is preferable that the overall thickness of the filter is 0.1 mm or more thicker than the thickness at the filter opening. The difference between the overall thickness of the filter and the thickness at the filter opening is more preferably 0.15 mm or more, and even more preferably 0.2 mm or more. Therefore, it is preferable to select the thicknesses of the filter layer, substrate layer, and adhesive layer such that the overall thickness of the filter is 0.1 mm or more thicker than the thickness at the filter opening.

[0039] Furthermore, the thickness of the filter opening is preferably 0.1 mm or less in order to reduce the pressure drop of the filter and the amount of membrane displacement during pressure changes. A smaller thickness is preferable as it reduces the filter pressure drop. From the viewpoint of handling, the lower limit is preferably about 0.005 mm, and is about 0.01 mm.

[0040] Such a filter can be manufactured, for example, by providing a region that is 0.1 mm or more thicker than the thickness of the filter opening (hereinafter sometimes simply referred to as the "thick region") along the outer edge of the filter. This thick region can be obtained, for example, using the filter layer 8, the adhesive layer 9, and the base material layer 11 as components. In FIGS. 2(B) and 3(B), W2 corresponds to the thick region (note that in FIGS. 2(B) and 3(B), the adhesive layer 9 provided on the lower end surface of the filter is for attaching to the pellicle frame and is not included in the region that is 0.1 mm or more thicker than the thickness of the filter opening).

[0041] Here, the base material layer is not particularly limited as long as it can impart mechanical strength to the filter. For example, tapes or films such as plastics are preferably mentioned.

[0042] As the plastic tape (film), for example, a tape (film) of the material exemplified as the base material layer described above or a tape (film) of the material exemplified as the release layer described later can be used.

[0043] The adhesive for forming the adhesive layer 9 for attaching the filter to the pellicle frame or the base material layer is not particularly limited as long as it can fix the filter to the pellicle frame or the base material layer. Examples include the adhesives exemplified as the mask adhesive described later, as well as urethane adhesives, rubber-based adhesives, and the like. From the viewpoint of workability during attachment, it is preferably an adhesive, but it may also be an adhesive agent.

[0044] The adhesive layer and the base material layer for forming the thick region may be provided on the side facing the pellicle frame of the filter layer, on the opposite side, or on both sides. Also, although the filter function will decrease, a thick region may be partially provided in the filter opening to an extent that it can be put into practical use.

[0045] The pellicle of the present invention is provided with a pellicle film on the upper end surface of the aforementioned pellicle frame via a film adhesive layer 7 (formed by an adhesive or bonding agent). There is no restriction on the material of the adhesive or bonding agent, and known materials can be used. Generally, the adhesive or bonding agent is applied over the entire circumferential direction of the end surface of the pellicle frame with a width equal to or less than the width of the pellicle frame to form a film adhesive layer. The application of the adhesive or bonding agent can be performed, for example, by dipping, spraying, brush coating, an application device using a dispenser, etc. However, application using an application device with a dispenser is preferable in terms of stability, workability, yield, etc.

[0046] Also, there is no restriction on the material of the pellicle film, but it is preferably one with a high transmittance at the wavelength of the exposure light source and high light resistance. For example, for EUV exposure, an ultrathin silicon film, SiN film, carbon film, etc. are used. When it is difficult to handle the pellicle film alone, the film supported by a frame such as silicon can be used as the pellicle film. In that case, the pellicle can be easily manufactured by bonding the area of the frame and the pellicle frame.

[0047] As described above, the pellicle of the present invention uses the pellicle frame of the present invention that reduces the thickness of the filter opening and the pressure loss of the filter as a component, so that when the vacuum device is loaded and unloaded, that is, when the pressure changes from atmospheric pressure to vacuum or from vacuum to atmospheric pressure, it is possible to reduce the displacement of the pellicle film. In order to prevent damage to the pellicle film when the pellicle is exposed to a pressure change from atmospheric pressure to vacuum or when the pellicle is exposed to a pressure change from vacuum to atmospheric pressure, the displacement amount of the pellicle film is preferably 1 mm or less.

[0048] Furthermore, a mask adhesive layer 6 for attaching to a photomask is formed on the lower end surface of the pellicle frame illustrated in Figures 2 and 3. Known mask adhesives can be used to form this mask adhesive layer, and acrylic adhesives and silicone adhesives are preferably used. These adhesives may be processed into any shape as needed. For example, if ventilation holes are provided on the lower end surface of the pellicle frame, and the filter is provided so as to block the opening of the ventilation holes, the mask adhesive layer is provided on the lower end surface excluding the filter portion so as to allow ventilation between the inside and outside of the closed pellicle space.

[0049] A release layer (separator) to protect the adhesive may be attached to the lower end surface of the mask adhesive layer. 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, 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 as needed.

[0050] The following are examples, but the present invention can be implemented in many forms and should not be interpreted as being limited to the contents described in the examples. Furthermore, the numerical values ​​described in the examples are merely examples and do not limit the interpretation of the present invention.

[0051] (Example 1) A titanium pellicle frame 2 (external dimensions 150 mm x 118 mm x 1.5 mm, frame width 4 mm) was fabricated as shown in Figure 1. Twelve ventilation holes 5 were provided on the long sides (six per long side) and eight on the short sides (four per short side) of the pellicle frame 2, extending from the outer surface towards the bottom end. The ventilation holes on the long sides had openings of 9 mm x 0.7 mm on the outer surface side and 9 mm x 2 mm on the bottom end side. The ventilation holes on the short sides had openings of 19 mm x 0.7 mm on the outer surface side and 19 mm x 2 mm on the bottom end side.

[0052] A filter A, as shown in Figure 2, was attached to the opening of a ventilation hole provided on the lower end surface of the frame. As shown in Figure 2(A), filter A is a roughly rounded rectangle and is formed from a nonwoven fabric-like filter layer 8 made of stretched polytetrafluoroethylene (ePTFE), an adhesive layer 9 provided along the outer edges of the upper and lower end surfaces of the filter layer 8, and a base layer 11 provided on the adhesive layer 9 on the upper end surface side of the filter layer 8. The base layer has the same shape as the adhesive layer, the thickness of the filter layer 8 and the filter opening 10 is approximately 0.02 mm, and the overall thickness of the filter 3 is approximately 0.25 mm. Twelve pieces of filter A, with outer dimensions of 10 mm x 2.5 mm and a filter opening of 7.5 mm x 1.5 mm, were attached to the long side to cover the opening on the lower end surface of the ventilation hole. Eight pieces of filter A, with outer dimensions of 20 mm x 2.5 mm and a filter opening of 18 mm x 1.5 mm, were attached to the short side to cover the opening on the lower end surface of the ventilation hole.

[0053] The pellicle frame to which the filter was attached was washed with a neutral detergent and pure water. A mixture of 100 parts by mass of acrylic adhesive (SK Dyne 1499M, manufactured by Soken Chemical Co., Ltd.), 0.1 parts by mass of curing agent (L-45K, manufactured by Soken Chemical Co., Ltd.), and a mixture was added and applied to the entire circumference of the frame to a thickness of 0.1 mm. The pellicle frame was then heated at 100°C for 12 hours to cure the adhesive on the upper and lower ends. Subsequently, an extremely thin silicone film was pressed onto the adhesive formed on the upper end of the frame to complete the pellicle.

[0054] (Example 2) A filter B, as shown in Figure 3, was attached to the opening of a ventilation hole provided on the lower end surface of a pellicle frame 2 similar to that in Example 1. As shown in Figure 3(A), filter B is a roughly rounded rectangle and is formed from a nonwoven fabric filter layer 8 made of polytetrafluoroethylene (PTFE), an adhesive layer 9 provided along the outer edges of the upper and lower end surfaces of the filter layer 8, and a base layer 11 made of polypropylene (PP) provided on the adhesive layer 9 on the upper end surface side of the filter layer 8. The base layer has the same shape as the filter layer, the thickness of the filter layer 8 is approximately 0.02 mm, the thickness of the filter opening 10 is approximately 0.20 mm, and the overall thickness of the filter 3 is approximately 0.30 mm. The thickness of the base layer 11 is approximately 0.08 mm, and the thickness of each adhesive layer 9 is approximately 0.10 mm. Twelve pieces of filter B, with outer dimensions of 10 mm x 2.5 mm and a filter opening of 6 mm x 1.1 mm, were attached to the long side to cover the opening on the lower end surface of the ventilation hole. Eight pieces of filter B, with outer dimensions of 20 mm x 2.5 mm and a filter opening of 18 mm x 1.0 mm, were attached to the short side to cover the opening on the lower end surface of the ventilation hole. The pellicle was completed in the same manner as in Example 1, except for the filters.

[0055] (Comparative Example 1) A filter C, as shown in Figure 4, was attached to the opening of a ventilation hole provided on the lower end surface of a pellicle frame 2 similar to that in Example 1. As shown in Figure 4(A), the filter C is a roughly rounded rectangle and is formed from a nonwoven fabric filter layer 8 made of polyamide-imide and an adhesive layer 9 provided along the outer edge of the lower end surface of the filter layer 8. The thickness of the filter layer 8 and the filter opening 10 is approximately 0.07 mm, and the total thickness of the filter 3 is 0.13 mm. On the long side, twelve of the filter C, with outer dimensions of 10 mm × 2.5 mm and a filter opening of 9 mm × 1.5 mm, were attached to cover the opening on the lower end surface of the ventilation hole. On the short side, eight of the filter C, with outer dimensions of 20 mm × 2.5 mm and a filter opening of 19 mm × 1.5 mm, were attached to cover the opening on the lower end surface of the ventilation hole. The pellicle was completed in the same manner as in Example 1, except for the filter.

[0056] The filters used in Examples 1 and 2 and Comparative Example 1 were evaluated for their handling characteristics and pressure drop measured using the methods described below. Furthermore, the pellicles fabricated in Examples 1 and 2 and Comparative Example 1 were subjected to membrane displacement measurements during pressure changes from atmospheric pressure to vacuum using the methods described below. Table 1 shows the handling characteristics, pressure drop, and maximum membrane displacement of each pellicle filter.

[0057] (Evaluation of filter handling properties) The filters used in Examples 1 and 2 and Comparative Example 1 were attached to a backing sheet, and the edges of the filters were grasped with tweezers and peeled off the backing sheet at a speed of approximately 1 mm / second. If the filter did not tear or break during peeling, it was evaluated as ○, and if the filter tore or the filter layer and adhesive layer separated, or the filter was otherwise damaged, it was evaluated as ×. The results are shown in Table 1.

[0058] (Measurement of filter pressure drop) The pressure drop of the filters used in Examples 1 and 2 and Comparative Example 1 was measured in a cleanroom (temperature 23°C, humidity 55% RH). A simplified diagram illustrating the measurement method is shown in Figure 5. A circular filter with a diameter of 68.8 mm was fixed inside a cylindrical filter fixing jig with an inner diameter of 68.8 mm using an O-ring with an inner diameter of 57 mm. The upstream side of the filter fixing jig was left open, and a particle counter (manufactured by Rion, KC22B) was connected to the downstream side with a rubber tube using a tube fitting from Swagelok. Air was drawn from the downstream side of the filter fixing jig at a flow rate of 0.3 L / min using the particle counter, allowing air to flow through the filter inside the filter fixing jig, and the pressure drop was measured using a differential pressure gauge (manufactured by Nagano Keiki, GC30-101) connected to the top and bottom of the filter fixing jig with tubes. The results are shown in Table 1.

[0059] (Measurement of membrane displacement) The pellicles prepared in Examples 1 and 2 and Comparative Example 1 were attached to a 150 mm x 150 mm quartz glass sheet as a substitute for a photomask. The resulting masked pellicle was placed in a vacuum chamber with the pellicle membrane facing upwards. The pressure was reduced from atmospheric pressure to 5 Pa in 400 seconds, and then returned to atmospheric pressure in three stages over 280 seconds (4000 Pa in 100 seconds, 17000 Pa in 180 seconds, and atmospheric pressure in 280 seconds). The displacement of the pellicle membrane was measured using a laser displacement meter (Keyence Corporation, multi-color laser coaxial displacement meter CL-3000) installed on top of the pellicle membrane. The position of the pellicle membrane before the pressure change was used as the reference position, and the maximum membrane displacement during the pressure changes from atmospheric pressure to 5 Pa and from 5 Pa to atmospheric pressure was recorded. The results are shown in Table 1. The conditions of the multi-color laser coaxial displacement meter used are shown below.

[0060] (Information on the multi-color laser coaxial displacement meter) Controller: CL-3000 Sensor head: CL-PO30 Optical unit: CL-PO30N Measurement method: Displacement sampling setting: 1000us Filter type: Moving average Number of averages: 64

[0061]

[0062] (Results and Discussion) According to the results in Table 1, in the pellicle of Example 1, the overall thickness of the filter was 0.1 mm or more thicker than the thickness of the filter opening, so the filter could be peeled off the backing without tearing, and furthermore, the pressure drop of the filter was small, and the film displacement of the pellicle membrane was made 1 mm or less. On the other hand, in the pellicle of Comparative Example 1, the value obtained by subtracting the thickness of the filter opening from the overall thickness of the filter was less than 0.1 mm, so although the pressure drop and film displacement of the filter were sufficiently small, the handling of the filter was poor. In addition, in the pellicle of Example 2, the value obtained by subtracting the thickness of the filter opening from the overall thickness of the filter was 0.1 mm, and since a filter with a thick filter opening was used, the pressure drop of the filter was somewhat large and the film displacement was 1 mm or more, but the handling of the filter was good. Based on these results, it is considered that making the overall thickness of the filter 0.1 mm or more thicker than the thickness of the filter opening is effective in preventing the decrease in filter handling that occurs when the thickness of the filter is reduced.

[0063] 1. Pellicle 2. Pellicle frame 3. Filter 4. Pellicle membrane 5. Ventilation holes 6. Mask adhesive layer 7. Membrane adhesive layer 8. Filter layer 9. Adhesive layer 10. Filter opening 11. Substrate layer

Claims

1. A pellicle frame having ventilation holes for ventilating the inside and outside of a closed pellicle space, wherein a filter is provided so as to block at least a portion of the ventilation holes, and the total thickness of the filter is 0.1 mm or more thicker than the thickness of the filter opening through which air can pass.

2. The pellicle frame according to claim 1, wherein the thickness of the filter opening is 0.1 mm or less.

3. The pellicle frame according to claim 1, wherein the overall thickness of the filter is 0.3 mm or less.

4. The pellicle frame according to claim 1, wherein a region is provided along the outer edge of the filter that is 0.1 mm or more thicker than the thickness of the filter opening.

5. The pellicle frame according to claim 4, wherein the region that is 0.1 mm or more thicker than the thickness of the filter opening comprises a filter layer, an adhesive layer, and a substrate layer as constituent elements.

6. The pellicle frame according to claim 1, wherein the thickness of the pellicle frame is 2.0 mm or less.

7. The pellicle frame according to claim 1, which is a component of a pellicle for EUV exposure.

8. The pellicle frame according to claim 1, wherein the pellicle frame base material of the pellicle frame is made of titanium or a titanium alloy.

9. A pellicle characterized by comprising a pellicle frame and a pellicle membrane as described in any one of claims 1 to 8.

10. The pellicle according to claim 9, wherein the amount of membrane displacement of the pellicle membrane when the pellicle is exposed to a pressure change from atmospheric pressure to a vacuum, or a pressure change from a vacuum to atmospheric pressure, is 1 mm or less.

11. An exposure master plate with a pellicle, characterized in that the pellicle described in claim 9 is installed on the exposure master plate.

12. An exposure method characterized by exposure using the pellicle described in claim 9.

13. A method for manufacturing a semiconductor, characterized by comprising the step of exposure using the pellicle described in claim 9.

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