Pellicle, exposure original plate with pellicle, exposure method and method for producing semiconductor

Abstract

To provide pellicle frames and pellicles characterized by sufficient ventilation ability, efficient processability of the pellicle frames, and superior adhesion to masks.SOLUTION: The present invention provides a pellicle frame in a frame shape, with an upper end face for placing a pellicle film and a lower end face opposite a photomask. A notch is provided from an outer side to an inner side of the upper end face. The present invention also provides a pellicle including the pellicle frame as a component.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pellicle frame and a pellicle that are attached to a photomask for lithography as a dust guard. [Background technology]

[0002] In recent years, LSI design rules have been miniaturized to the sub-quarter micron level, and as a result, the wavelength of exposure light sources has been shortened. That is, exposure light sources have shifted from g-line (436 nm) and i-line (365 nm) from mercury lamps to KrF excimer lasers (248 nm) and ArF excimer lasers (193 nm), and furthermore, EUV exposure using EUV (Extreme Ultra Violet) light with a dominant wavelength of 13.5 nm is being considered.

[0003] In the manufacture of semiconductors such as LSIs and VLSIs, or liquid crystal display panels, patterns are created by irradiating light onto a semiconductor wafer or an original plate for liquid crystal display. However, if dust is attached to the lithography photomasks and reticles (collectively referred to as "exposure original plates") used in this case, the dust can absorb or bend the light, causing the transferred pattern to be deformed or have rough edges, as well as causing the base to become blackened and dirty, compromising the dimensions, quality, appearance, etc.

[0004] These operations are usually carried out in a clean room, but it is still difficult to keep the exposure master clean at all times. Therefore, a method is generally adopted in which a pellicle is attached to the surface of the exposure master as a dust cover before exposure. In this case, foreign particles do not adhere directly to the surface of the exposure master, but to the pellicle, so if the focus is set on the pattern of the exposure master during lithography, the foreign particles on the pellicle will not affect the transfer.

[0005] The basic structure of this pellicle is that a pellicle film with high transmittance to the light used for exposure is stretched on the upper end surface of the pellicle frame, and an airtight gasket is 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 polymer, etc., which have high transmittance to the light used for exposure (g-line (436 nm) from a mercury lamp, i-line (365 nm), KrF excimer laser (248 nm), ArF excimer laser (193 nm), etc.), but for EUV exposure, ultrathin silicon film and carbon film are being considered as pellicle films.

[0006] There are several restrictions on pellicle frames for EUV exposure due to the nature of the exposure tool. Because the space for arranging the pellicle inside the EUV exposure tool is small, the height of the pellicle must be 2.5 mm or less.

[0007] In addition, since EUV exposure is performed under high vacuum, the EUV pellicle must be able to withstand pressure changes from atmospheric pressure to vacuum, and the ventilation part of the EUV pellicle is required to have a large area. Therefore, Patent Document 2 and Patent Document 3 propose a pellicle frame with a filter that can obtain a large ventilation area. Since the pellicle height is low, it is said that it is preferable to provide the filter parallel to the membrane in order to attach the filter, but if the filter is provided on the upper end surface or lower end surface of the pellicle frame, a bend will occur in the ventilation path. If a bend exists in the ventilation path, a large resistance will occur in the ventilation path, especially when the pressure is returned from high vacuum to atmospheric pressure, and a pressure difference will occur between the inside and outside of the pellicle, leading to a concern that this will lead to damage to the pellicle membrane. There is no problem if the pressure is returned slowly, but it has been found that there are cases where it is required to return from high vacuum to atmospheric pressure more quickly from the viewpoint of workability. In addition, it is difficult to thoroughly clean the ventilation path with a bend when cleaning the pellicle frame, and there was also a concern that foreign matter will remain.

[0008] Patent Document 4 proposes a pellicle in which the mask and pellicle are mechanically fixed together via a pressing spring provided on the pellicle and fasteners called studs on the mask. In this pellicle, a gap of 200 to 300 μm is created between the mask and pellicle to allow ventilation, so the ventilation capacity is sufficient, but when the pellicle is fixed mechanically, metal-to-metal contact always occurs at the connection. There is a concern that metal-to-metal contact may lead to dust generation.

[0009] The specification of Japanese Patent Application No. 2017-197004, previously filed by the applicant of the present application, proposes a pellicle frame with many through holes on the side surface. However, in order to provide a large-area ventilation section using only through holes, it is necessary to open a very large number of through holes, which is difficult and costly to process, especially when manufacturing a pellicle frame using a material that is easily damaged. In addition, it was found that if foreign matter remains in the through holes due to insufficient cleaning, it is difficult to find the foreign matter because visual inspection cannot be performed inside the through holes.

[0010] In addition, the specification of Japanese Patent Application No. 2017-196982, which was previously filed by the applicant of the present application, proposes a pellicle frame having a cutout portion on the lower end surface as a gripping portion of the peeling tool and a ventilation portion. Although the ventilation capacity and processability are sufficient, there is a drawback in that the adhesive portion between the pellicle frame and the mask is reduced. Since the adhesive portion is reduced, there is a concern that the pellicle will fall if used for a long period of time. In order to prevent the pellicle from falling, it is possible to use an adhesive with strong adhesive strength, but the pellicle needs to be peeled off from the mask after use or when a problem occurs with the pellicle. If the adhesive strength is too strong, a strong force is applied to the pellicle when peeling, and there is a high possibility that the pellicle film will be damaged. If the pellicle film is damaged, the mask will be contaminated, so it is difficult to use an adhesive with strong adhesive strength. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2016-200616 A [Patent Document 2] JP 2017-83791 A [Patent Document 3] JP 2016-191902 A [Patent Document 4] International Publication No. 2016 / 124536 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made in consideration of the above circumstances, and aims to provide a pellicle frame and a pellicle using said pellicle frame which, when EUV exposure is performed under high vacuum, can withstand the pressure change from atmospheric pressure to vacuum without causing damage to the pellicle membrane, does not require the installation of a large number of through holes, does not make it difficult to detect foreign matter, does not cause damage to the pellicle membrane even when an adhesive or pressure-sensitive adhesive with strong adhesive strength is used, and is very unlikely to peel off even after long-term use. [Means for solving the problem]

[0013] The inventors discovered that by providing a frame-shaped pellicle frame having an upper end surface on which a pellicle film is provided and a lower end surface facing a photomask, and by providing a cutout portion from the outer surface of the upper end surface of the pellicle frame toward the inner surface, the adhesive portion between the pellicle frame and the pellicle film is reduced, but since there is no need to peel the pellicle film from the pellicle frame, an adhesive or pressure-sensitive adhesive with strong adhesive strength can be used, and further, since the only load applied to the adhesive portion is the pellicle film, the possibility of peeling off even with long-term use is extremely low, and thus the present invention was made.

[0014] Accordingly, the present invention provides the following pellicle frame and pellicle. 1. A frame-shaped pellicle frame having an upper end surface on which a pellicle membrane is provided and a lower end surface facing a photomask, characterized in that at least one cutout portion is provided from the outer surface of the upper end surface toward the inner surface. 2. A pellicle frame according to claim 1, wherein the cutout portion is formed from the outer surface to the inner surface. 3. A pellicle frame according to 1 or 2 above, having a thickness of less than 2.5 mm and made of titanium. 4. A pellicle frame according to 1 or 2 above, having a thickness of less than 2.5 mm and made of crystalline silicon. 5. A pellicle comprising the pellicle frame according to any one of 1 to 4 above as a component. 6. A pellicle as described in 5 above, wherein an adhesive is provided on the upper end surface of the pellicle frame other than the cutout portion. Effect of the Invention

[0015] According to the present invention, it is possible to provide a pellicle frame and a pellicle which have sufficient ventilation capacity, excellent workability as a pellicle frame, and excellent attachment to a mask. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing an example of a pellicle frame of the present invention. [Diagram 2] 13A and 13B show another example of a pellicle frame of the present invention, in which (A) is a plan view from the upper end surface side, and (B) is a front view seen from the outer short side surface side. [Diagram 3] 1 is a schematic diagram showing the appearance of the pellicle of the present invention attached to a photomask. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The pellicle frame of the present invention is a frame-shaped pellicle frame having an upper end surface on which a pellicle membrane is provided and a lower end surface facing the photomask.

[0018] If the pellicle frame is frame-shaped, its shape corresponds to the shape of the photomask on which the pellicle is to be mounted, and is generally a quadrilateral (rectangular or square) frame shape.

[0019] The pellicle frame also has a surface for providing a pellicle membrane (here, the upper end surface) and a surface that faces the photomask when the photomask is attached (here, the lower end surface).

[0020] Typically, a pellicle film is provided on the upper end surface of the pellicle frame via an adhesive or the like, and a pressure sensitive adhesive or the like is provided on the lower end surface for attaching the pellicle to a photomask, but this is not limited to the above.

[0021] There is no limitation on the material of the pellicle frame, and known materials can be used. For EUV pellicle frames, materials with a small thermal expansion coefficient are preferred because they may be exposed to high temperatures. Examples include Si, SiO2, SiN, quartz, invar, titanium, and titanium alloys. Among these, titanium and titanium alloys 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 EUV pellicle is limited to 2.5 mm or less, the thickness of the EUV pellicle frame is smaller than that, that is, less than 2.5 mm.

[0023] Furthermore, the thickness of the pellicle frame for EUV is preferably 1.5 mm or less, taking into consideration the thickness of the pellicle film, mask adhesive, etc.

[0024] The pellicle frame of the present invention has a cutout portion provided from the outer surface to the inner surface of the upper end face of the pellicle frame. There is no limit to the location or number of the cutout portions, but the total area of ​​the opening should be less than 20 mm 2 It is preferable that the thickness is more than 30 mm. 2 More preferably, it is equal to or greater than this.

[0025] Furthermore, a jig hole is usually provided on the side of the pellicle frame for use in handling or peeling the pellicle from the photomask. The size of the jig hole is 0.5 to 1.0 mm in length in the thickness direction of the pellicle frame (diameter in the case of a circle). There is no limitation on the shape of the hole, and it may be circular or rectangular. Furthermore, the jig hole is usually a hole that does not penetrate from the outer side to the inner side, but in addition to the jig hole, an air hole that penetrates from the outer side to the inner side may be provided. In the case of air holes, there is no limitation on the location or number of them.

[0026] A filter may be provided in the cutout formed from the outer surface to the inner surface of the pellicle frame. In that case, the filter may be provided on either the inner surface or the outer surface of the pellicle frame so as to cover the cutout.

[0027] In the pellicle of the present invention, a pellicle membrane is provided on the upper end surface of the pellicle frame as described above via a pressure sensitive adhesive or adhesive. There are no limitations on the material of the pressure sensitive adhesive or adhesive, and any known material can be used. The pressure sensitive adhesive or adhesive is provided on the upper end surface of the pellicle frame other than the cutout portion. In order to firmly hold the pellicle membrane, a pressure sensitive adhesive or adhesive with strong adhesive strength is preferred.

[0028] The material of the pellicle film is not particularly limited, but it is preferable that the material has high transmittance at the wavelength of the exposure light source and high light resistance. For example, an extremely thin silicon film or a carbon film is used for EUV exposure.

[0029] Furthermore, a mask adhesive for attaching a photomask is formed on the lower end surface of the pellicle frame. In general, it is preferable that the mask adhesive is provided around the entire periphery of the pellicle frame.

[0030] The above masking adhesive may be a known adhesive, and an acrylic adhesive or a silicone adhesive may be preferably used. The adhesive may be processed into any shape as required.

[0031] 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, 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 necessary.

[0032] Here, Fig. 1 shows an example of a pellicle frame 1 of the present invention, and in each drawing, 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. In the upper end surface of the pellicle frame 1 in Fig. 1, one notch 10, 10 is provided on each of the upper end surfaces of the short sides, and none is provided on the long side. Note that, normally, a jig hole used to peel the pellicle from the photomask is provided on the long side of the pellicle frame, but this is not shown in Fig. 1.

[0033] Fig. 2 shows an example in which a total of four notches are provided on the upper end surface of the pellicle frame 1, with one notch 10, 10 provided on each of the upper end surfaces of the short sides and another notch 10, 10 provided offset therefrom on the upper end surface of the long side. In Fig. 2, the above-mentioned notches are formed so as to communicate from the outer surface to the inner surface. In Fig. 2, the symbol W indicates the width of the notch, the symbol D indicates the depth of the notch, and the symbol T indicates the height of the notch.

[0034] 3 shows a pellicle 20, in which a pellicle film 2 is adhered and stretched on the upper end surface of a pellicle frame 1 with an adhesive 4. The pellicle 2 is also releasably adhered to a photomask 3 with a pressure sensitive adhesive 5, and protects the pattern surface on the photomask 3. EXAMPLES

[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] Titanium (linear expansion coefficient: 8.4 x 10 -6 (1 / K), density: 4.5g / cm 3 A pellicle frame (outer dimensions: 150 mm × 118 mm × 1.5 mm, frame width: 4.0 mm) was fabricated using a 300-mm thick glass.

[0037] Two jig holes, 1 mm in diameter and 1.2 mm in depth, were drilled on the outer surface of the long side of the pellicle frame, 52 mm away from the center of the side toward the corner. A cutout portion, 90 mm in width, 0.1 mm in height, and 4 mm in depth, was drilled on the upper end surface at the center of each side of the pellicle frame. This cutout portion was formed from the outer surface to the inner surface.

[0038] The pellicle frame was washed, and 100 parts by mass of silicone adhesive (X-40-3264, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed with 1 part by mass of curing agent (PT-56, manufactured by Shin-Etsu Chemical Co., Ltd.) and applied to the upper end surface of the pellicle frame to a width of 1 mm and a thickness of 0.1 mm except for the notched portion. In addition, 100 parts by mass of acrylic adhesive (SK Dyne 1495, manufactured by Soken Chemical Co., Ltd.) was mixed with 0.1 parts by mass of curing agent (L-45, manufactured by Soken Chemical Co., Ltd.) and applied as a mask adhesive to the entire circumference to a width of 1 mm and a thickness of 0.1 mm to the lower end surface of the pellicle frame.

[0039] The pellicle frame was then heated at 90°C for 12 hours to harden the adhesive on the upper and lower surfaces of the pellicle frame. An ultrathin silicon film was then used as the pellicle membrane, and the ultrathin silicon film was pressed against the adhesive on the upper surface of the pellicle frame to complete the pellicle.

[0040] This pellicle was attached to a 150 mm x 150 mm quartz mask as a substitute for a photomask.

[0041] [Example 2] A titanium pellicle frame (external dimensions 150 mm × 118 mm × 1.5 mm, frame width 4 mm) was fabricated.

[0042] Two jig holes, 1 mm in diameter and 1.2 mm in depth, were provided on the outer surface of the long side of the pellicle frame, 52 mm away from the center of the side toward the corner. Two notches, 50 mm in width, 0.1 mm in height, and 4 mm in depth, were provided at 15 mm intervals on the upper end surface of the long side of the pellicle frame. Two notches, 40 mm in width, 0.1 mm in height, and 4 mm in depth, were provided at 15 mm intervals on the upper end surface of the short side of the pellicle frame. These notches were formed from the outer surface to the inner surface.

[0043] The pellicle frame was washed, and 100 parts by mass of silicone adhesive (X-40-3264, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed with 1 part by mass of curing agent (PT-56, manufactured by Shin-Etsu Chemical Co., Ltd.) and applied to the upper end surface of the pellicle frame to a width of 1 mm and a thickness of 1 mm, except for the notched portion. The same silicone adhesive was also applied to the lower end surface of the pellicle frame to a width of 1 mm and a thickness of 1 mm around the entire circumference.

[0044] After that, the pellicle frame was heated at 90° C. for 12 hours to harden the adhesive on the upper and lower end faces of the pellicle frame. Next, an ultrathin silicon film was used as the pellicle film, and the ultrathin silicon film was pressed against the adhesive formed on the upper end face of the pellicle frame to complete the pellicle.

[0045] This pellicle was attached to a 150 mm x 150 mm quartz mask as a substitute for a photomask.

[0046] [Comparative Example 1] A titanium pellicle frame (external dimensions 150 mm × 118 mm × 1.5 mm, frame width 4 mm) was produced. No notches were provided on each side of the pellicle frame, but instead, 20 through holes with a diameter of 0.8 mm were provided on each side as ventilation sections. The rest of the structure was the same as in Example 1.

[0047] [Comparative Example 2] A titanium pellicle frame (outer dimensions: 150 mm x 118 mm x 1.5 mm, frame width: 4 mm) was fabricated. The structure was the same as that of Example 1, except that a cutout was provided on the lower end surface of the center of each side of the pellicle frame.

[0048] The following application stability test, air permeability test, and foreign matter inspection after cleaning were carried out on the pellicles of Examples 1 and 2 and Comparative Examples 1 and 2. The evaluation results are shown in Table 1.

[0049] [Patch stability test] The pellicle attached to the quartz substrate was placed so that the pellicle was located on the bottom, heated to 80°C in an oven, and left for one week, and the presence or absence of the pellicle falling off was confirmed. As a result, only in Comparative Example 2, the pellicle had fallen off.

[0050] [Air permeability test] The pellicle attached to the quartz substrate was placed in a vacuum chamber and heated to 1E-4 (1.0×10 -4 The pressure was then reduced to atmospheric pressure over a period of 2 minutes, and the state of the pellicle membrane was checked. No abnormalities were found in the pellicle membrane in both Examples 1 and 2 and Comparative Examples 1 and 2.

[0051] [Inspection for foreign matter after cleaning] After cleaning the pellicle frame, the surface of the pellicle frame was inspected for foreign matter adhering thereto under fluorescent lighting and in a dark room using focused light. No foreign matter was found in either Examples 1 and 2 or Comparative Examples 1 and 2. In Comparative Example 1, the presence or absence of foreign matter inside the through-holes could not be confirmed by visual inspection, so after cleaning the pellicle frame, the presence or absence of foreign matter inside the through-holes was confirmed using a microscope. Of the 80 through-holes, foreign matter of about 100 μm was confirmed in two places. Furthermore, because visual observation was performed using a microscope, a large amount of foreign matter was attached to the surface of the pellicle frame due to the use of the microscope.

[0052] [Table 1]

[0053] From Table 1 above, it can be seen that in the pellicles of Examples 1 and 2, by using a pellicle frame with a notch at the upper end, foreign body inspection can be easily performed, the attachment stability is good, and there is sufficient ventilation capacity compared to the pellicles of Comparative Examples 1 and 2. [Explanation of symbols]

[0054] 1 Pellicle frame 11 Inner surface of pellicle frame 12 Pellicle frame outer surface 13 Pellicle frame upper end surface 14 Lower end surface of pellicle frame 10 Cutout W Width of cutout D Depth of cutout T Cutout height 20 Pellicle 2. Pellicle membrane 3. Photomask 4 Pellicle membrane adhesive 5 Photomask adhesive

Claims

1. A pellicle membrane; A pellicle including, as a component, a frame-shaped pellicle frame having an upper end surface on the side where the pellicle membrane is provided and a lower end surface which is an end surface opposite to the upper end surface, At least one ventilation part having a recess provided on the upper end surface and extending from an outer surface to an inner surface, The ventilation portion serves as an air passage for ventilating the inside and outside of the pellicle, However, this pellicle is characterized in that a filter having approximately the same shape as the recess is placed inside the recess, and the pellicle has a flat recessed portion on the upper end surface.

2. The pellicle according to claim 1 , further comprising a filter on an inner or outer surface of the pellicle frame so as to cover the recess.

3. 3. The pellicle according to claim 1, wherein the pellicle frame is in the shape of a rectangular frame and has recesses on two opposing sides.

4. 3. The pellicle according to claim 1, wherein the pellicle frame is in the shape of a rectangular frame and has recesses on all four sides.

5. The pellicle according to any one of claims 1 to 4, wherein a mask adhesive is formed on said lower end surface.

6. 6. An exposure master with a pellicle, comprising: the pellicle according to claim 1 attached to an exposure master.

7. 7. An exposure method comprising exposing using the exposure master with a pellicle according to claim 6.

8. A method for manufacturing a semiconductor, comprising exposing using the exposure master with a pellicle according to claim 6.

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