pellicle

Abstract

The present invention provides a pellicle, or more particularly, a pellicle for EUV exposure, characterized by comprising a pellicle frame 1 and a bonding or gluing agent 10 applied to an upper end face and a lower end face 1a of said pellicle frame to attach a pellicle film and a photomask, wherein the bonding or gluing agent 10 is formed within a region W1 three-quarters from the outside of each of the upper end face and the lower end face 1a of the pellicle frame 1. The pellicle according to the present invention can prevent a bonding agent for the pellicle film and a gluing agent for the photomask from being directly irradiated with EUV scattered light reaching the inside of the pellicle frame.

Description

Pellicle

[0001] The present invention relates to a pellicle 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 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 the manufacture of liquid crystal display panels, light is irradiated onto a semiconductor wafer or a raw plate for liquid crystals 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") used, since this dust absorbs light or bends light, the transferred pattern is deformed, the edge becomes rough, and in addition, the base is blackened and soiled, resulting in problems such as damage to 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 pellicle 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 pellicle. Therefore, if the focus is set on the pattern of the exposure original plate during lithography, the foreign matter on the pellicle becomes irrelevant to the transfer.

[0005] The basic structure of this pellicle consists of a pellicle frame made of aluminum or titanium, with a pellicle film that has high transmittance to the light used for exposure stretched across its upper surface, and an airtight gasket formed on its lower 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] Unlike conventional transmissive exposure plates, EUV exposure plates are reflective. Ideally, EUV light should enter the exposure plate at an oblique angle, and 100% of the light should be reflected from the surface of the plate. However, in reality, a small amount of scattered light occurs. Therefore, there is a concern that the pellicle may be exposed to EUV light from the inside, and the pellicle needs a structure that is resistant to degradation even when irradiated with EUV light from the inside.

[0007] Generally, a pellicle consists of a pellicle film, a pellicle frame, an adhesive for the pellicle film, and an adhesive for the photomask. Since the pellicle film is designed to be exposed to EUV light, a material with high transmittance to EUV light is selected. Furthermore, the pellicle frame can be made of materials such as metals or ceramics that degrade less when exposed to EUV light, and even if degradation occurs, it is unlikely to be so severe that the pellicle frame dimensions cannot be maintained.

[0008] On the other hand, adhesives for pellicle films and adhesives for photomasks are generally made of resin materials, and therefore it is easy to foresee that they are susceptible to damage from EUV light. Furthermore, it is possible that performance degradation, such as a decrease in adhesive strength, may occur due to damage from EUV light. For this reason, for EUV pellicles, it is necessary to design the pellicle film adhesive and photomask adhesive in a way that makes them less susceptible to damage from EUV light.

[0009] In conventional pellicles, it is common to apply pellicle film adhesive or photomask adhesive across the entire end face of the frame. However, if the pellicle film adhesive or photomask adhesive is present up to the inner edge of the pellicle on one end face of the pellicle frame, EUV scattered light will directly irradiate these adhesives and adhesives.

[0010] Patent Document 1 proposes protecting the adhesive by coating its sides with a material resistant to EUV light. However, it was found that there is a high risk of foreign matter adhering to the adhesive during the coating process, which is performed after the adhesive is applied to the pellicle frame.

[0011] International Publication No. 2018 / 151056

[0012] The present invention has been made in view of the above circumstances, and aims to provide a pellicle that can prevent EUV scattered light reaching the inside of the pellicle frame from directly irradiating the adhesive for the pellicle film and the adhesive for the photomask.

[0013] As a result of diligent research to achieve the above objective, the inventors have found that the above problem can be solved by forming the adhesive or adhesive in a region extending three-quarters of the outer surface of each end face of the upper and lower ends of the pellicle frame, in a pellicle having an adhesive or adhesive applied to the upper and lower ends of the pellicle frame for attaching a pellicle film and a photomask, and thus have made the present invention.

[0014] Accordingly, the present invention provides the following pellicles: 1. A pellicle comprising a pellicle frame and an adhesive or tack for attaching a pellicle film and a photomask to the upper and lower end surfaces of the pellicle frame, characterized in that the adhesive or tack is formed in a region extending three-quarters of the way from the outside of each end surface of the upper and lower end surfaces of the pellicle frame. 2. The pellicle according to 1, wherein grooves or stepped portions are formed along the length of the pellicle frame on one or both sides of the region where the adhesive or tack is applied to the upper and lower end surfaces of the pellicle frame. 3. The pellicle according to 1 or 2, which is for EUV exposure.

[0015] According to the present invention, it is possible to prevent EUV scattered light reaching the inside of the pellicle frame from directly irradiating the adhesive for the pellicle film and the adhesive for the photomask.

[0016] This is a plan view showing a pellicle frame according to one embodiment of the present invention. This is a cross-sectional view of the pellicle frame cut along line A-A in Figure 1, and also a cross-sectional view of the pellicle frame used in Example 1 (with adhesive applied). This is a cross-sectional view of the pellicle frame used in Example 2 (with adhesive applied). This is a cross-sectional view of the pellicle frame used in Example 3 (with adhesive applied). This is a cross-sectional view of the pellicle frame used in Example 4 (with adhesive applied).

[0017] The present invention will be described in more detail below. In the following description, the adhesive for the pellicle film will be simply referred to as "film adhesive," and the adhesive for the photomask will be simply referred to as "mask adhesive." Also, the pellicle frame may be simply referred to as "frame."

[0018] The present invention is characterized by forming a film adhesive or mask adhesive within three-quarters of the outer surface of each end face of the upper and lower end faces of the pellicle frame.

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

[0020] 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").

[0021] There are no restrictions on the material of the pellicle frame; known materials can be used. Examples include Si, SiO2, SiN, quartz, Invar, titanium, titanium alloys, and aluminum alloys, among which metal is preferred due to its ease of processing and light weight.

[0022] The dimensions of the pellicle frame are not particularly limited, but since the height of the EUV pellicle is limited to 2.5 mm or less, the thickness of the EUV pellicle frame is smaller than that, less than 2.5 mm.

[0023] 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.

[0024] 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.

[0025] Furthermore, the pellicle frame is provided with vents to mitigate pressure changes inside and outside the pellicle. There are no restrictions on the shape or number of vents. Filters can be installed in the vents to prevent foreign matter from entering the pellicle. There are no restrictions on where the filters can be installed; they can be on the inside of the pellicle frame, inside the vents, or on the outside of the pellicle frame.

[0026] 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.

[0027] In the pellicle of the present invention, a pellicle film is provided on the upper end surface of the pellicle frame as described above, via an adhesive or bonding agent. There are no particular restrictions on the material of the adhesive or bonding agent; known materials can be used, for example, acrylic adhesives and silicone adhesives can be suitably used. To strongly hold the pellicle film, an adhesive or bonding agent with strong adhesive strength is preferred.

[0028] 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.

[0029] The above-mentioned film adhesive and mask adhesive are provided in the end face region, which extends 3 / 4 of the frame width outwards. By providing them in the end face region, which extends 3 / 4 of the frame width outwards, the risk of scattered EUV light irradiating the film adhesive and mask adhesive can be reduced. The further the film adhesive and mask adhesive are from the inside of the pellicle, the more preferable the position. The width of the adhesive and adhesive used is 3 / 4 or less of the frame width (for example, 3 mm or less for a 4 mm wide frame).

[0030] The thickness of the adhesive or bonding agent is preferably 0.3 mm or less, given that the pellicle thickness is limited to 2.5 mm or less. Furthermore, in order to make it difficult for scattered EUV light to reach the adhesive or bonding agent, the thickness of the adhesive or bonding agent should be as thin as possible, and 0.2 mm or less is particularly preferred.

[0031] It is usually difficult to form adhesives or bonding agents of such thin thickness into a uniform width on the frame end face. Therefore, grooves or steps may be provided at both ends or one end of the area where the adhesive is to be formed. By providing grooves or steps at both ends of the area to be applied in this way, the width of the adhesive can be reliably defined. Even if too much adhesive is applied, the adhesive will spread into the grooves or steps, and will not continue to spread beyond the grooves, thus improving the stability of the width of the applied adhesive.

[0032] The shape of the grooves and steps described above is not particularly limited; they may be recessed or L-shaped, or simply have a depression, and the inner surface (bottom surface) may be flat or curved, such as a hemisphere. The width of the grooves and steps is not particularly limited, but the lower limit is preferably 0.1 mm or more, more preferably 0.3 mm or more, and the upper limit is preferably 3.0 mm or less, more preferably 1.0 mm or less, and even more preferably 0.8 mm or less. The depth of the grooves and steps is not particularly limited, but the lower limit is preferably 0.05 mm or more, more preferably 0.1 mm or more, and the upper limit is preferably 1.3 mm or less, more preferably 0.3 mm or less, and even more preferably 0.2 mm or less.

[0033] 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.

[0034] Here, Figure 1 is a plan view showing an example of the pellicle frame 1 of the present invention. In this pellicle frame 1, a groove 1b is formed on the upper end surface 1a along the entire circumference of the frame in the longitudinal direction. Figure 2 shows a cross-sectional view of the pellicle frame cut along the line A-A in Figure 1. As shown in Figure 2, the application area of ​​the film adhesive 10 or mask adhesive 10 is within the end surface area of ​​3 / 4 of the frame width from the outside, and the formation of the groove 1b limits the application area of ​​the film adhesive 10 or mask adhesive 10 to the upper or lower end surface area W1 from the outside of the frame to the groove. In Figure 2, reference numeral W2 denotes the uncoated area, which is at least within a certain area from the inside of the frame, and the size of the area width satisfies the relationship W2 < W1.

[0035] [Examples 1-4] The present invention will be specifically described below with reference to 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, frame width 4.0 mm) was prepared. Two jig holes, 1 mm in diameter and 1.2 mm in depth, were made on the outer surface of the long side of the pellicle frame, 52 mm away from the center of the side towards the corner. A notch measuring 90 mm in width x 0.1 mm in height x 4 mm in depth was made on the upper end surface of the center of each side of the pellicle frame. This notch is formed from the outer surface to the inner surface. In addition, 0.5 mm diameter through holes were made on the long side at 20 mm intervals around the center. In addition, 0.5 mm diameter through holes were made on the short side at 25 mm intervals around the center. Furthermore, a groove 0.5 mm wide and 0.1 mm deep was made around the entire circumference at a position 2 mm from the outer edge of both end faces. On the outer 2 mm area of ​​the upper end surface, excluding the notched portion, 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 then applied and molded to a thickness of 0.1 mm. Next, on the outer 2 mm area of ​​the lower end surface, a mixture of 100 parts by mass of acrylic adhesive (SK-Dyne 1495, manufactured by Soken Chemical Co., Ltd.), 0.1 part by mass of hardener (L-45, manufactured by Soken Chemical Co., Ltd.), was added and mixed, and then applied and molded around the entire circumference to a width of 2 mm and a thickness of 0.1 mm. Subsequently, an ultra-thin silicone film was used as the pellicle film, and this ultra-thin silicone film was pressed onto the adhesive formed on the upper end surface of the pellicle frame to complete the pellicle. Figure 2 shows a cross-sectional view of the frame (the frame with adhesive applied) in the area without the notched portion. In this embodiment, the pellicle has a distance of 2 mm between the film-side adhesive and the mask-side adhesive from the inside of the pellicle frame, making it difficult for EUV scattered light to reach the adhesive, thus preventing deterioration of the adhesive.

[0037] [Example 2] This example is the same as Example 1, except that a groove with a width of 0.5 mm and a depth of 0.1 mm is provided around the entire circumference at a position 1 mm from the outside of both ends of the frame, and the width of the adhesive is 1 mm. Figure 3 shows a cross-sectional view of the frame (frame with adhesive applied) in the area without a notch. Compared to Example 1, the pellicle of this example has a distance of 3 mm between the film-side adhesive and the mask-side adhesive, which is further from the inside of the pellicle frame. As a result, EUV scattered light is less likely to reach the adhesive, and deterioration of the adhesive can be prevented.

[0038] [Example 3] This example is the same as Example 1, except that a step portion with a depth of 0.1 mm is provided around the entire circumference of the outer 0.5 mm of both ends of the frame, a groove portion with a width of 0.5 mm and a depth of 0.1 mm is provided around the entire circumference at a position 1.5 mm from the outside, and adhesive is placed from a position 0.5 mm to 1.5 mm from the outside, with an adhesive width of 1 mm. Figure 4 shows a cross-sectional view of the frame (frame with adhesive applied) in the area without a notch. In Figure 4, reference numeral 1b indicates the groove portion and reference numeral 1c indicates the step portion. Compared to Example 1, the pellicle of this example has a distance of 2.5 mm between the film-side adhesive and the mask-side adhesive, which is further from the inside of the pellicle frame. As a result, EUV scattered light is less likely to reach the adhesive, and deterioration of the adhesive can be prevented. In addition, in Example 1 there was a concern that the adhesive would overflow onto the outer surface of the frame, but this concern can be reduced in this example.

[0039] [Example 4] A groove with a width of 0.5 mm and a depth of 0.1 mm was provided around the entire circumference of the upper end surface of the frame at positions 0.5 mm and 2 mm from the outside, and a film adhesive was placed from 1 mm to 2 mm from the outside, making the adhesive width 1 mm. In addition, a groove with a width of 0.5 mm and a depth of 0.1 mm was provided around the entire circumference at a position 1 mm from the outside of the lower end surface of the frame, making the mask side adhesive width 1 mm. Except for the above, it is the same as Example 1. Figure 5 shows a cross-sectional view of the frame (frame with adhesive applied) in the area without a notch. In the present invention, as in this Example 4, the film adhesive and the mask adhesive do not have to be placed in the same position.

[0040] 1 Pellicle frame 1a Upper or lower end surface 1b Groove 1c Step 10 Adhesive or bonding agent W1 Coating area W2 Uncoated area

Claims

1. A pellicle comprising a pellicle frame and a pellicle with adhesive or a bonding agent applied to the upper and lower end surfaces of the pellicle frame for attaching a pellicle film and a photomask, characterized in that the adhesive or bonding agent is formed within three-quarters of the outer surface of each end surface of the upper and lower end surfaces of the pellicle frame.

2. The pellicle according to claim 1, wherein grooves or stepped portions are formed along the longitudinal direction of the pellicle frame on one or both sides of the area where the adhesive or tack is applied to the upper and lower end surfaces of the pellicle frame.

3. The pellicle according to claim 1, which is for EUV exposure.

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