Pellicle frame for EUV, method for producing the same, and pellicle for EUV

Abstract

To provide a pellicle frame and a pellicle with which, by lowering the reflectance of the inner surface of the pellicle frame with respect to inspection light, scattered light from the frame can be suppressed as much as possible and foreign matter inspectability can be improved, and at the same time, by lowering the reflectance only with respect to the wavelength of the inspection light, restrictions such as coloring of the pellicle frame can be reduced.SOLUTION: The present invention provides a frame-shaped pellicle frame having an upper end surface provided with a pellicle film and a lower end surface facing a photomask, wherein the pellicle frame has, on at least an inner surface thereof, a minimum reflectance of 20% or less at a light source wavelength of 500 to 1000 nm, and a pellicle including the pellicle frame.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pellicle frame attached to a photomask for lithography as dust removal, a pellicle, a method for inspecting a pellicle, an exposure original plate with a pellicle, an exposure method, and a method for manufacturing a semiconductor or a liquid crystal display panel.

Background Art

[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) light with a main wavelength of 13.5 nm is used for EUV exposure is being studied.

[0003] In the manufacture of semiconductors such as LSIs and super LSIs or liquid crystal display panels, light is irradiated onto a semiconductor wafer or an original plate for liquid crystals to form a pattern. In this case, if dust adheres to the lithography mask and reticle (hereinafter collectively referred to as "exposure original plate"), since this dust absorbs light or bends light, the transferred pattern is deformed, the edge becomes rough, and there is a problem that the base is blackened and contaminated, and the dimensions, quality, appearance, etc. are impaired.

[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 pellicle 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 pellicle. Therefore, if the focus is adjusted 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 is such that a pellicle film with a high transmittance to the light used for exposure is stretched on the upper end face of a pellicle frame made of aluminum, titanium, etc., and an airtight gasket is formed on the lower end face. An adhesive layer is generally used for the airtight gasket, and a protective sheet for protecting this adhesive layer is attached. The pellicle film is made of nitrocellulose, cellulose acetate, fluorine-based polymers, etc., which transmit well the light used for exposure (such as g-line (436 nm), i-line (365 nm), KrF excimer laser (248 nm), ArF excimer laser (193 nm), etc. from a mercury lamp). However, for EUV exposure, ultrathin silicon films and carbon films are being studied as pellicle films.

[0006] Since the purpose of the pellicle is to protect the exposure original plate from the attachment of foreign substances, a very high cleanliness is required for the pellicle. Therefore, in the pellicle manufacturing process, it is necessary to inspect whether foreign substances are attached to the pellicle film, pellicle frame, adhesive, and protective sheet before shipment.

[0007] Normally, for the inspection of foreign substances on the pellicle frame, light is focused on the frame in a dark room, and the scattered light from the foreign substances is detected visually. If foreign substances exist on the inner surface of the pellicle frame, the foreign substances can easily fall onto the mask surface due to vibration or air movement. Therefore, recently, in addition to visual inspection, the inspection of the inner surface of the pellicle frame by a foreign substance inspection device has been increasing. Generally, in a foreign substance inspection device, a laser such as a He-Ne laser or a semiconductor laser is irradiated onto the pellicle frame, and the scattered light from the foreign substances is detected by a semiconductor detector (CCD), etc.

[0008] However, there is a problem that there is no means to distinguish between the scattered light from the inner surface of the pellicle frame and the scattered light from foreign substances, and the detector detects the scattered light caused by the pellicle frame, resulting in the inability to perform normal foreign substance inspection.

[0009] In Patent Document 1, it is proposed to improve the inspectability by reducing the reflectance of the inner surface of the pellicle frame for inspection light in the range of 400 to 1100 nm to 0.3% or less. However, in order to reduce the reflectance to 0.3% or less for 400 to 1100 nm, it is necessary to color the frame as black as possible. To achieve this, it is necessary to strictly select the pellicle frame material and the coloring method, and in some cases, it may be difficult to achieve depending on the material.

[0010] In addition, the wavelength ranges of the He-Ne laser and semiconductor laser used for inspection light are limited, such as 640 to 660 nm, etc., and it is not always necessary to reduce the reflectance in the entire wavelength range of 400 to 1100 nm.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] The present invention has been made in view of the above circumstances, and by reducing the reflectance of the inner surface of the pellicle frame with respect to the inspection light, the scattered light from the frame can be suppressed as much as possible, and the foreign matter inspectability can be improved. In addition, by reducing the reflectance only with respect to the wavelength of the inspection light, a pellicle frame with fewer restrictions such as coloring of the pellicle frame, a pellicle using the pellicle frame, and an inspection method for the pellicle are provided.

Means for Solving the Problems

[0013] The inventor has found that by using a frame-shaped pellicle frame having an upper end surface provided with a pellicle film and a lower end surface facing a photomask, and adjusting the minimum reflectance at a light source wavelength of 500 to 1000 nm on the inner surface of the pellicle frame to 20% or less, scattered light from the pellicle frame can be suppressed as much as possible, and by using a specific wavelength with a reflectance of 20% or less as the wavelength of the inspection light, the reflectance is lowered only for the wavelength of this inspection light. Thus, the inventors have found that a pellicle frame with good inspectability can be provided without significant restrictions on surface treatments such as the coloring method of the pellicle frame, and have thus completed the present invention.

[0014] Accordingly, the present invention provides the following pellicle frame, pellicle, pellicle inspection method, photomask with pellicle, exposure method, and method for manufacturing a semiconductor or liquid crystal display panel. 1. A frame-shaped pellicle frame having an upper end surface provided with a pellicle film and a lower end surface facing a photomask, wherein the minimum reflectance at a light source wavelength of 500 to 1000 nm on at least the inner side surface of the pellicle frame is 20% or less. 2. The pellicle frame according to item 1, wherein the minimum reflectance is 10% or less. 3. The pellicle frame according to item 1 or 2, wherein the reflectance at all wavelengths of a light source wavelength of 500 to 1000 nm is 20% or less. 4. The pellicle frame according to item 1 or 2, wherein the reflectance at all wavelengths of a light source wavelength of 500 to 1000 nm is 10% or less. 5. The pellicle frame according to item 1 or 2, wherein the minimum reflectance at a light source wavelength of 500 to 1000 nm on the entire circumferential surface of the pellicle frame is 20% or less. 6. The pellicle frame according to item 1 or 2, wherein the material of the pellicle frame contains titanium or a titanium alloy. 7. The pellicle frame according to item 1 or 2, wherein the material of the pellicle frame contains aluminum or an aluminum alloy. 8. The pellicle frame according to item 1 or 2, wherein the thickness of the pellicle frame is less than 2.5 mm. 9. The pellicle frame according to claim 1 or 2, wherein the thickness of the pellicle frame is less than 1.5 mm. 10. The pellicle frame according to claim 1 or 2, wherein an oxide film is formed on the surface of the pellicle frame. 11. The pellicle frame according to claim 1 or 2, wherein the surface of the pellicle frame is blackened. 12. The pellicle frame according to claim 1 or 2, wherein a scratch-proof treatment is applied to the surface of the pellicle frame. 13. The pellicle frame according to claim 1 or 2, wherein the surface of the pellicle frame is subjected to hand polishing, sandblasting, chemical polishing, or electrolytic polishing. 14. The pellicle frame according to claim 1 or 2, which is a pellicle frame used for an EUV pellicle. 15. A pellicle comprising the pellicle frame according to claim 1 and a pellicle film provided on one end face of the pellicle frame via an adhesive or an adhesive agent. 16. The pellicle according to claim 15, wherein the pellicle film is provided on the upper end face of the pellicle frame. 17. The pellicle according to claim 15 or 16, wherein the pellicle film is a silicon film or a carbon film. 18. The pellicle according to claim 15 or 16, wherein the height of the pellicle is 2.5 mm or less. 19. The pellicle according to claim 15 or 16, which is a pellicle used for EUV lithography. 20. A method for inspecting a pellicle for detecting foreign matter existing in the pellicle according to claim 15 by using a foreign matter inspection machine, wherein a specific wavelength at which the reflectance on at least the inner surface of the pellicle frame is 20% or less is used as the wavelength of the inspection light to detect the foreign matter existing in the pellicle. 21. An exposure original plate with a pellicle, characterized in that the pellicle according to claim 15 is mounted on the exposure original plate. 22. The exposure original plate with a pellicle according to claim 21, wherein the exposure original plate is an exposure original plate for EUV. 23. The exposure original plate with a pellicle according to claim 21, which is an exposure original plate with a pellicle used for EUV lithography. 24. An exposure method characterized in that exposure is performed using the exposed original plate with a pellicle described in the above item 21. 25. The exposure method according to the above item 24, wherein the light source for exposure is an exposure light source that emits EUV light. 26. A method for manufacturing a semiconductor, comprising a step of exposing a semiconductor wafer using the exposed original plate with a pellicle described in the above item 21. 27. The method for manufacturing a semiconductor according to the above item 26, wherein the light source for exposure is an exposure light source that emits EUV light. 28. A method for manufacturing a liquid crystal display panel, comprising a step of exposing an original plate for liquid crystal using the exposed original plate with a pellicle described in the above item 21. 29. The method for manufacturing a liquid crystal display panel according to the above item 28, wherein the light source for exposure is an exposure light source that emits EUV light.

Effect of the Invention

[0015] The pellicle frame, pellicle, and pellicle inspection method of the present invention can suppress scattered light from the pellicle frame as much as possible, and by using, as the wavelength of the inspection light, a specific wavelength at which the reflectance of the pellicle frame is 20% or less, the pellicle frame can be surface-treated so as to reduce the reflectance only for the wavelength of this inspection light. The degree of freedom of this surface treatment is increased, and a pellicle frame convenient for inspection can be provided.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Embodiment for Carrying Out the Invention

[0017] Hereinafter, the present invention will be described in more detail. The pellicle frame of the present invention is a frame-shaped pellicle frame having an upper end surface for providing a pellicle film and a lower end surface facing a photomask.

[0018] If the pellicle frame is in a frame shape, its shape corresponds to the shape of the photomask to which the pellicle is attached. Generally, it is in a rectangular (rectangular or square) frame shape. In addition to the rectangular frame shape, it can be changed to a polygonal frame shape such as a triangular frame shape, a pentagonal frame shape, a hexagonal frame shape, an octagonal frame shape, etc., or a circular frame shape, an elliptical frame shape, etc., corresponding to the shape of the photomask. For polygonal frame shapes such as a rectangular frame shape, the existing corners in a chamfered form such as C-chamfering, R-chamfering, or thread-chamfering are also included.

[0019] In addition, the pellicle frame has a surface for providing the pellicle film (here, the upper end surface), and a surface facing the photomask when the photomask is attached (here, the lower end surface).

[0020] Normally, a pellicle film is provided on the upper end surface of the pellicle frame via an adhesive or the like, and an adhesive or the like for attaching the pellicle to the photomask is provided on the lower end surface, but this is not the only case.

[0021] There is no limitation on the material of the pellicle frame, and known materials can be used. For the pellicle frame for EUV, since it may be exposed to high temperatures, a material with a small coefficient of thermal expansion is preferred. For example, Si, SiO2, SiN, quartz, invar, titanium, titanium alloy, etc. can be mentioned. Among them, titanium and titanium alloy are preferred because of their ease of processing and light weight.

[0022] The dimensions of the pellicle frame are not particularly limited, but since the height of the pellicle for EUV is limited to 2.5 mm or less, the thickness of the pellicle frame for EUV is smaller than that and less than 2.5 mm. In particular, considering the thickness of the pellicle film, mask adhesive, etc., the thickness of the pellicle frame for EUV is preferably 1.5 mm or less.

[0023] The surface of the pellicle frame of the present invention is treated so that the minimum reflectance is 20% or less in the wavelength range of 500 to 1000 nm, at least on its inner surface. In particular, it is preferable that the minimum reflectance in the range of the above light source wavelength is 20% or less on the entire peripheral surface of the pellicle frame, and the surface of the pellicle frame is appropriately treated. There is no particular limitation on the method of this surface treatment. For example, a method of forming an oxide film with a thickness of 100 μm on the surface by anodic oxidation treatment to cause color development in blue by interference color, or a method of performing black nickel plating treatment to blacken it. Also, the frame surface can be blackened by doping carbon into the oxide film.

[0024] Regarding the pellicle frame of the present invention, it is not necessary for the reflectance to be 20% or less for all wavelengths in the above-mentioned wavelength range of 500 to 1000 nm, and it is sufficient if the reflectance is 20% or less for a specific wavelength within the above wavelength range. The specific wavelength mentioned here is the wavelength of the inspection light used in the foreign matter inspection machine, and it is preferable that the reflectance is 20% or less, particularly 10% or less, for this wavelength. Conversely, the inspection light used in the foreign matter inspection machine can also be selected from the reflectance distribution showing the minimum reflectance of the pellicle frame.

[0025] Also, in order to improve the inspectability, a surface treatment for removing scratches such as hand polishing, sandblasting treatment, chemical polishing treatment, electrolytic polishing treatment, etc. may be applied to the surface. By roughening the surface roughness of these surface treatments, scattered light from the pellicle frame can be prevented as much as possible.

[0026] Also, usually, on the side surface of the pellicle frame, a jig hole used for handling and peeling the pellicle from the photomask is provided. The size of the jig hole is such that the length in the thickness direction of the pellicle frame (diameter in the case of a circle) is 0.5 to 1.0 mm. There is no limitation on the shape of the hole, and it may be circular or rectangular.

[0027] Also, a ventilation part is provided in the pellicle frame, and a filter can be provided in the ventilation part to prevent the intrusion of foreign matters.

[0028] 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 a bonding agent. There is no limitation on the material of the adhesive or the bonding agent, and known ones can be used. In order to strongly hold the pellicle film, an adhesive or a bonding agent with strong adhesive force is preferable.

[0029] There is no particular limitation on the material of the above-mentioned pellicle film, but those with high transmittance at the wavelength of the exposure light source and high light resistance are preferable. For example, for EUV exposure, an ultrathin silicon film, a carbon film, etc. are used. Examples of these carbon films include films such as graphene, diamond-like carbon, and carbon nanotubes. The above-mentioned pellicle film is not limited to only a thin film, and those including a support frame for supporting the pellicle film can also be adopted. For example, a method of forming a pellicle film on a silicon wafer and removing the silicon wafer by back etching only at the location used as the pellicle film can be adopted. In this case, the pellicle film can be obtained in a state supported by a silicon frame.

[0030] Furthermore, a mask adhesive for mounting on a photomask is formed on the lower end surface of the pellicle frame. Generally, it is preferable that the mask adhesive is provided over the entire circumference of the pellicle frame.

[0031] As the above-mentioned mask adhesive, known ones can be used, and acrylic adhesives and silicone adhesives can be preferably used. The adhesive may be processed into an arbitrary shape as required.

[0032] A release layer (separator) for protecting the adhesive may be attached to the lower end surface of the mask adhesive. The material of the release layer is not particularly limited, and for example, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), polypropylene (PP), etc. can be used. Further, 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. In addition, the attachment of the pellicle to the photomask can be fixed by physical fixing means other than the mask adhesive. Examples of such fixing means include screws, bolts, nuts, rivets, keys, pins, etc. It is also possible to use the mask adhesive and physical fixing means in combination.

[0033] Here, FIG. 1 shows an example of the pellicle frame 1 of the present invention, reference numeral 11 indicates the inner surface of the pellicle frame, reference numeral 12 indicates the outer surface of the pellicle frame, reference numeral 13 indicates the upper end surface of the pellicle frame, and reference numeral 14 indicates the lower end surface of the pellicle frame. Usually, a jig hole used for peeling the pellicle from the photomask is provided on the long side of the pellicle frame, but it is not particularly shown in FIG. 1.

[0034] FIG. 2 shows the pellicle 10. The pellicle film 2 is adhered and stretched by an adhesive 4 on the upper end surface of the pellicle frame 1. Further, on the lower end surface of the pellicle frame 1, it is detachably adhered to the photomask 3 by an adhesive 5, protecting the pattern surface on the photomask 3.

[0035] The pellicle of the present invention may be used not only as a protection member for suppressing the adhesion of foreign matter to the exposure master in an EUV exposure apparatus, but also as a protection member for protecting the exposure master during storage or transportation of the exposure master. Methods for attaching the pellicle to an exposure master such as a photomask and manufacturing an exposure master with a pellicle include, in addition to the method of attaching with the aforementioned mask adhesive, an electrostatic adsorption method, a method of mechanically fixing, etc.

[0036] The manufacturing method of a semiconductor or a liquid crystal display panel according to this embodiment includes a system for exposing a substrate (a semiconductor wafer or a master for liquid crystal) using the above-mentioned pellicle-attached photomask. For example, in a lithography process, which is one of the manufacturing processes of a semiconductor device or a liquid crystal display panel, in order to form a photoresist pattern corresponding to an integrated circuit or the like on a substrate, the above-mentioned pellicle-attached photomask is placed on a stepper for exposure. Generally, in EUV exposure, a projection optical system in which EUV light is reflected by the photomask and guided to the substrate is used, and these are performed under reduced pressure or in a vacuum. As a result, even if foreign matter adheres to the pellicle in the lithography process, these foreign matters do not form an image on the wafer coated with the photoresist, so that short circuits or disconnections of integrated circuits or the like due to the image of the foreign matter can be prevented. Therefore, by using the pellicle-attached photomask, the yield in the lithography process can be improved.

Example

[0037] Hereinafter, examples and comparative examples will be shown to specifically explain the present invention, but the present invention is not limited to the following examples.

[0038] [Example 1] A titanium pellicle frame (outer dimensions 150 mm × 118 mm × 1.5 mm, frame width 4.0 mm) was fabricated. The titanium frame was immersed in a mixed electrolytic solution of phosphoric acid, sulfuric acid, and hydrogen peroxide, and an oxide film was formed by anodic oxidation under the conditions of a temperature of 25°C, a voltage of 20 V, and a time of 30 minutes, causing a blue interference color to develop. This pellicle frame was washed with a neutral detergent and pure water, and a material obtained by adding 1 part by mass of a curing agent (PT-56 manufactured by Shin-Etsu Chemical Co., Ltd.) to 100 parts by mass of a silicone adhesive (X-40-3264 manufactured by Shin-Etsu Chemical Co., Ltd.) and stirring was applied to the upper end surface of the frame to a width of 1 mm and a thickness of 0.1 mm. Also, as a mask adhesive, a material obtained by adding 0.1 part by mass of a curing agent (L-45 manufactured by Soken Chemical & Engineering Co., Ltd.) to 100 parts by mass of an acrylic adhesive (SK Dyn 1495 manufactured by Soken Chemical & Engineering Co., Ltd.) and stirring was applied to the lower end surface of the frame over the entire circumference to a width of 1 mm and a thickness of 0.1 mm. Subsequently, the pellicle frame was heated at 90°C for 12 hours to cure the adhesives on the upper and lower end surfaces. Subsequently, an ultrathin silicon film was used as the pellicle film and was pressure-bonded to the adhesive formed on the upper end surface of the frame to complete the pellicle.

[0039] [Example 2] After fabricating a titanium frame, anodic oxidation, black dyeing, and sealing treatment were sequentially performed to form a black oxide film on the surface of the frame. Except for the coloring treatment method on the surface of this frame, it was the same as in Example 1.

[0040] [Example 3] After fabricating a frame made of an aluminum alloy, anodic oxidation, black dyeing, and sealing treatment were sequentially performed to form a black oxide film on the surface of the frame. Except for the material and surface treatment of this frame, it was the same as in Example 1.

[0041] [Comparative Example 1] It was the same as in Example 1 except that no surface treatment was performed on the titanium pellicle frame.

[0042] For the pellicles obtained in Examples 1 to 3 and Comparative Example 1, inspection was carried out using a foreign matter inspection apparatus. Further, using the same frame material as in Examples 1 to 3 and Comparative Example 1, reflectance measurements of each sample were carried out using a sample piece obtained by subjecting the material to surface treatment.

[0043] [Reflectance Measurement] A 3 cm × 3 cm sample piece with a thickness of 5 mm was prepared, and samples subjected to the same surface treatment as in Examples 1 to 3 and Comparative Example 1 were prepared. Using a "Spectrophotometer V-780" (manufactured by JASCO Corporation, model name), the reflectance in the range of 500 to 1000 nm was measured. Table 1 shows the measured values of the minimum reflectance and the reflectance at the inspection light (532 nm). The minimum reflectance was specified from the chart obtained from the spectrophotometer. The reason for selecting a 532 nm laser as the inspection light is that such a semiconductor laser is compact and has excellent stability, is easy to use for device integration, and has a track record of use in inspection devices for semiconductors.

[0044] [Foreign Matter Inspection] The obtained pellicle was gripped by a dedicated jig using a jig hole, and 20 μm standard particles were attached to a part of the inner wall surface of the pellicle frame. Together with the jig, the above-mentioned pellicle was placed in an inner surface foreign matter inspection apparatus (manufactured by Shin-Etsu Engineering Co., Ltd.) equipped with a semiconductor laser with a wavelength of 532 nm, and the quality of the foreign matter inspection on the inner wall surface was evaluated according to the following criteria. <Judgment Criteria> 〇: No scattered light was confirmed in the area where no particles were attached, and scattered light was confirmed only in the part where particles were attached. ×: Scattered light was confirmed even in the part where no particles were attached.

[0045] [Table 1]

[0046] The following points can be considered from the results in Table 1 above. When using the pellicle frames of Examples 1 to 3, by setting the reflectance of the pellicle frame at inspection light (532 nm) to 20% or less, it was possible to provide a pellicle with good inspectability by a foreign matter inspection machine. On the other hand, when using the pellicle frame of Comparative Example 1, since scattered light of the frame was confirmed even in a portion where no foreign particles were attached, it could not be said that the inspectability was good.

Explanation of Signs

[0047] 1 Pellicle frame 2 Pellicle film 3 Photomask 4 Pellicle film adhesive 5 Photomask adhesive 10 Pellicle

Claims

【Claim 1】 A frame-shaped pellicle frame having an upper end surface provided with a pellicle film and a lower end surface facing a photomask, wherein a minimum reflectance of a light source wavelength of 500 to 1000 nm on at least an inner surface of the pellicle frame is 20% or less. The pellicle frame is characterized by this.

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