High-speed air pressure adjustable pellicle for exposure

Abstract

[Problem] To achieve high performance of a filter attached to a ventilation port provided through a pellicle frame so as to satisfy strict use conditions required particularly for EUV exposure. [Solution] A pellicle according to the present invention comprises: a pellicle frame; an extremely thin pellicle film provided on the upper end surface of the pellicle frame; a ventilation port provided in the pellicle frame; and a filter that covers the ventilation port. The filter is composed of: a sheet, a part or the entirety of which is composed of nanofibers and / or carbon nanotubes; and a support that has an opening for supporting the sheet.

Description

[Technical Field]

[0001] The present invention relates to an exposure pellicle capable of high-speed air pressure adjustment that protects exposure masks used in the manufacture of semiconductors, liquid crystals, etc. from foreign matter, and in particular to an EUV pellicle. [Background technology]

[0002] The manufacture of semiconductors and liquid crystal displays uses lithography technology to form circuit patterns using exposure masks. In recent years, especially in semiconductors, circuit patterns have become increasingly miniaturized, from microns to submicrons and even nanometers, and accordingly, exposure light sources have become shorter in wavelength, from g-line (436 nm), i-line (365 nm), KrF excimer laser (248 nm), and ArF excimer laser (193 nm). Recently, even shorter wavelength EUV (extreme ultraviolet; 13.5 nm) exposure has also been considered, and some cutting-edge devices have begun to be put to practical use.

[0003] The manufacturing of semiconductors such as LSIs and VLSIs typically involves coating a wafer with resist, placing it in an exposure machine along with an exposure mask bearing the desired circuit pattern, and then irradiating the exposure mask with light to transfer the circuit pattern onto the wafer. While these operations are typically performed in clean rooms designed to minimize dust, dust from people, machinery, or the environment often adheres to the mask during transportation and placement after mask creation. This dust is transferred along with the circuit pattern, resulting in abnormal circuits, resulting in defective semiconductors and reduced manufacturing yields.

[0004] To prevent this, a common practice is to attach a dust-preventing pellicle to the mask immediately after the mask is made, as in Patent Document 1. This is because if a pellicle is attached to the mask all at once, even if there is dust, the dust will not land directly on the circuit pattern of the mask, and even if it does land on the mask, it will be on the pellicle, so the focus of the exposure light will be on the circuit pattern, and the dust on the pellicle will not be transferred due to "out of focus."

[0005] The basic structure of a pellicle usually consists of a pellicle film that is highly transparent and light-resistant to the exposure wavelength stretched over the upper surface of a metal frame, an airtight seal formed on the lower surface using a relatively light-resistant adhesive such as acrylic or silicone, and a vent filter that adjusts the air pressure difference inside and outside the pellicle after it is attached to the mask.

[0006] These pellicle films have high transmittance and light resistance at the exposure wavelength; for example, nitrocellulose is used for g-line (436 nm), cellulose propionate for i-line (365 nm), and amorphous fluoropolymers for KrF excimer laser (248 nm) and ArF excimer laser (193 nm). In recent years, as the wavelengths have become shorter and smaller, EUV (extreme ultraviolet; 13.5 nm) exposure has also begun to be used. In principle, any material with high transmittance and light resistance to EUV light can be used as a pellicle film material, but in practice, organic materials are no longer resistant, and inorganic materials are generally considered preferable. Among these, single crystal silicon, polycrystalline silicon, amorphous silicon, or their nitrides, oxynitrides, carbides, or metal silicides such as molybdenum silicide are suitable, as they can be formed into uniform films at low cost with good reproducibility, and to further protect these film materials, products with protective films made of SiC, SiO2, Si3N4, SiON, YO3, YN, Mo, Ru, Rh, etc. are also available. In order to obtain high transmittance, films with thicknesses of the above films of submicron or less have been considered, and some are already in practical use.

[0007] Of these, conventional pellicles used under atmospheric pressure, such as g-line (436 nm), i-line (365 nm), KrF excimer laser (248 nm), and ArF excimer laser, generally use nonwoven fabrics for their ventilation filters, made of PET, PTFE, or other materials with fiber diameters ranging from tens to hundreds of microns. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-268464 [Non-patent literature]

[0009] [Non-Patent Document 1] "Electronic Materials", July 1997 issue, p.103 Summary of the Invention [Problem to be solved by the invention]

[0010] Meanwhile, pellicles for EUV (extreme ultraviolet; 13.5 nm) exposure, which are used in vacuum or reduced pressure environments and have recently begun to be used, have been proposed or are currently made of conventional resins such as PET and PTFE, as well as porous sintered metals and ceramics. However, there are virtually no filters that can withstand the dimensional limitations and harsh operating conditions imposed by the exposure tool structure, posing a major obstacle to the practical application of EUV (extreme ultraviolet; 13.5 nm) exposure. Specifically, current filters, which consist of a nonwoven fabric made of thick fibers from resins such as PET and PTFE and a support made of a mesh woven with metal fibers, are inevitably large and thick, often rendering them unusable or limiting the usable area of the exposure mask due to the dimensional limitations. Additionally, they suffer from high pressure loss and easily allow submicron particles, which should be blocked, to pass through. On the other hand, with porous sintered metals and ceramics, making the filtration pores fine and uniform can be technically difficult, as the pores can fuse together during production. In addition, the pores can be larger than the diameter of the dust particles to be blocked, smaller than necessary, or blocked, which can lead to problems such as large pressure loss during ventilation and unstable filter performance.

[0011] On the other hand, EUV exposure tools are extremely expensive, costing tens of billions of yen per unit, and although they are wasteful and not directly useful for production, the unavoidable vacuum pumping and atmospheric pressure return when loading and unloading masks creates significant dead time for the tool and is a factor in increasing costs. Therefore, in order to increase the operating rate of EUV exposure tools even slightly and reduce production costs, it is necessary to shorten these times by speeding up the vacuum pumping and atmospheric pressure return.

[0012] However, due to the light resistance, light transmittance and processability of EUV exposure, the pellicle films currently used for EUV exposure are generally made of extremely thin films of submicron thickness made of single crystal silicon, polycrystalline silicon, amorphous silicon, or rigid inorganic materials such as nitrides, oxynitrides and carbides of these materials.

[0013] For this reason, even with the current high-pressure-loss filters themselves, or even with pellicles that are forcibly miniaturized and attached to the mask due to various dimensional limitations imposed by the structure of the exposure equipment, when the above-mentioned vacuum pumping and atmospheric pressure return are performed at high speed, the pressure loss caused by the rapid inflow and outflow of air inside and outside the pellicle creates localized differences in air density in the space between the mask and the pellicle, resulting in large localized pressure differences. The extremely thin and rigid pellicle film cannot adapt to this pressure difference, and the pellicle film breaks and scatters, contaminating the expensive exposure equipment, making subsequent exposures impossible and causing enormous damage, which is a major bottleneck in EUV exposure technology.

[0014] As a solution to this problem, prior art, such as Patent Document 1, proposes covering the circuit pattern with a mask cover (reticle cover) that doubles as a so-called pellicle membrane and a vent filter to protect it from dust. Indeed, this method eliminates the various dimensional limitations imposed by the exposure tool's structure, since the exposure surface also contributes to the filter area, resulting in a significantly larger filtering area and enabling high-speed evacuation and atmospheric pressure return. However, the high-energy EUV light directly hits the exposed surface and the filter's vent area, which are directly exposed to EUV light. This causes the porous fluororesin (PTFE resin) described above to decompose, even though PTFE has relatively good light resistance, and it cannot withstand even short-term use, preventing its practical application. [Means for solving the problem]

[0015] As a result of the inventors' earnest efforts to solve the above bottlenecks and various problems, they have arrived at the present invention, which is as follows. [1] A pellicle frame; an extremely thin pellicle membrane provided on the upper end surface of the pellicle frame; a vent hole provided in the pellicle frame; a filter that blocks the ventilation hole; Equipped with The filter is a pellicle characterized in that it is composed of a sheet made of at least one of nanofibers and carbon nanotubes, partly or entirely, and a support having openings for supporting the sheet. [2] a pellicle frame; an extremely thin pellicle membrane provided on the upper end surface of the pellicle frame; a vent hole provided in the pellicle frame; a filter that blocks the ventilation hole; Equipped with The pellicle described in [1] above is characterized in that the filter is composed in part or in whole of a nonwoven fabric made of at least one of nanofibers or carbon nanotubes, and a support having openings that supports the nonwoven fabric. [3] The pellicle according to [1] or [2], characterized in that the nonwoven fabric is made of at least nanofibers and / or carbon nanotubes (CNTs) produced by electrospinning. [4] The pellicle according to any one of [1] to [3], wherein the support is flat. [5] The pellicle according to any one of [1] to [4], wherein the support has a honeycomb structure. [6] The pellicle according to any one of [1] to [5], characterized in that the filter, including the nonwoven fabric and the support having the openings, has a "filtration accuracy gradient"* from one surface to the other surface, or from both surfaces to the center. (*"Filtration accuracy gradient" refers to gradually changing the filtration accuracy of the filter media. Generally, it captures particles in stages, from large to small, to prevent sudden clogging.) [7] A pellicle according to any one of [1] to [6], characterized in that the pellicle film has a thickness of 1 μm or less and is made in part or in whole of at least single crystal silicon, polycrystalline silicon, amorphous silicon, or their nitrides, oxynitrides, carbides, or metal silicides. [8] The pellicle according to [7], characterized in that the pellicle membrane is coated with an inorganic compound. [9] The pellicle according to [8], wherein the inorganic compound is any one of SiC, Si3N4, and Y2O3.

[10] The pellicle according to any one of [1] to [9], wherein the surface of the nanofiber or carbon nanotube is coated with SiC or Si3N4.

[11] The pellicle according to any one of [1] to

[10] above, wherein the pellicle is a pellicle for an EUV mask.

[12] An exposure mask with a pellicle, characterized in that the pellicle according to any one of [1] to

[11] is attached to an exposure mask.

[13] A method for manufacturing a pellicle according to any one of [1] to

[12] above, characterized by comprising a step of producing a nonwoven fabric composed of at least one of nanofibers using an electrospinning method or carbon nanotubes using a carbon nanotube method, and a step of producing a filter using this nonwoven fabric and a flat support having an opening.

[14] A method for manufacturing a pellicle, characterized in that the flat support of

[13] has a honeycomb structure.

[15] An exposure method comprising exposing using the pellicle-equipped exposure mask according to

[13] or

[14] above.

[16] A method for manufacturing a semiconductor device, comprising a step of exposing using the pellicle-equipped exposure mask according to

[13] or

[14] . [Effects of the Invention]

[0016] The present invention has made it possible for the first time to achieve extremely thin, compact, and high-performance filters for exposure pellicles, particularly for cutting-edge EUV exposure pellicles, which are subject to strict space restrictions for installation. As a result, perfect pellicle installation, which has been difficult until now, is now possible. Because the filter of the present invention is composed of the nonwoven fabric and its support, it is possible to prevent the intrusion of fine foreign matter of submicron size or less despite extremely small pressure loss. In addition, it is possible to speed up the so-called "pressure adjustment" of vacuuming and returning to atmospheric pressure when inserting and removing a mask. This in turn increases the operating rate of expensive exposure equipment, enabling the production of semiconductors with high performance and significantly reduced production costs. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a vertical cross-sectional view showing an embodiment of a pellicle-equipped exposure mask of the present invention. [Figure 2a] FIG. 1(a) is an illustration of an embodiment of a support used in the present invention having a round flat mesh. [Figure 2b](b) An illustration of an embodiment of a support used in the present invention having a rectangular (square) flat mesh. [Figure 2c] (c) An illustration of an embodiment of a support for use in the present invention having a flat mesh with a honeycomb structure. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0019] As shown in Figure 1, the exposure pellicle 10 of the present invention includes a pellicle frame 3, an extremely thin pellicle membrane 1 provided on the upper surface of the pellicle frame 3 via an adhesive layer 2, and at least one ventilation hole 6 provided in the pellicle frame 3. The ventilation hole is closed with a filter 7 made of a sheet or nonwoven fabric, part of which is made of nanofibers and / or carbon nanotubes (CNTs), and a support with an opening that supports the sheet, and serves to prevent the intrusion of foreign matter.

[0020] However, apart from conventional exposure masks and pellicles, EUV exposure masks, especially EUV pellicles, are only provided with extremely small spaces due to the structure of the EUV exposure equipment. Therefore, EUV pellicle filters must also be small and extremely thin. However, in EUV exposure, which does not tolerate even submicron-sized contaminants, conventional contaminant prevention filters, which consist of a nonwoven fabric with a large fiber diameter and a support made of braided thick fibers with overlapping portions, are no longer able to capture submicron-sized contaminants or fit into the extremely small space.

[0021] The present inventors have conducted extensive research into how to improve this situation, and have arrived at the present invention. Specifically, the present invention improves the situation by using a sheet or nonwoven fabric, part of which is made of nanofibers and / or carbon nanotubes (CNTs), as the fiber, and further by using a flat metal or resin plate, which does not cause overlapping of fibers and is processed to have openings of any shape, as the support for the nonwoven fabric, in combination with these.

[0022] More specifically, the present invention provides (1) a filter material that captures foreign matter of submicron size or smaller using a sheet or nonwoven fabric partially composed of nanofibers and / or carbon nanotubes (CNTs), and (2) a planar plate material made of an ultrathin metal such as SUS or Ni or a resin, with openings provided therein, and combined with an ultrathin support to form a filter. Furthermore, as a countermeasure against a decrease in the strength of the ultrathin support along with a larger opening ratio, (3) the openings are made into a honeycomb structure, if necessary. And (4) the filter is made by passing the nonwoven fabric and the support having openings from one surface to the other, or By implementing (1) to (4) individually or in combination, including providing a "filtration accuracy gradient"* from both surfaces toward the center (*"filtration accuracy gradient" refers to gradually changing the filtration accuracy of the filter material. Generally, it captures particles from large to small in a stepwise manner to prevent rapid clogging), a filter for lithography pellicles has been realized that: 1) allows the entire filter to be made small and extremely thin, making it suitable for use in narrow spaces; 2) prevents the intrusion of extremely small foreign matter of submicron size or less; and 3) reduces pressure loss, allowing for high-speed air pressure adjustment. Of course, implementing (1), (2), (3), and (4) simultaneously maximizes the synergistic effect and is most preferable. The implementation of this invention not only improves the operating rate and productivity of EUV lithography equipment, but also enables significant cost reductions.

[0023] The above-mentioned openings can be formed by physical pressing or chemical etching, but etching is preferred because it allows for more precise processing. While the filter 7 is located outside the outer opening of the vent 6 in Figure 1, it is possible to provide a counterbore for partially or completely embedding the filter 7 in the outer opening of the vent 6, or to provide a chamfer on at least one of the outer or inner openings of the vent 6 to reduce dust generation from the periphery of the pellicle frame 3 and prevent dust generation when the filter 7 comes into contact with the periphery of the vent 6. The pellicle frame 3 is generally frame-shaped (usually rectangular) to match the shape of the mask 5.

[0024] As described in JIS L-0222:2001, the nonwoven fabric refers to "a fiber sheet, web, or batt in which the fibers are oriented in one direction or randomly and are bonded by entanglement and / or fusion and / or adhesion, excluding paper, fiber, knitted fabric, tufts, and carpet felt." In the present invention, the filter does not necessarily have to be a nonwoven fabric, but may be a sheet. It is preferable that the sheet is partially or entirely composed of at least one of nanofibers or carbon nanotubes (CNTs) in a sheet-like form, with the nanofibers or carbon nanotubes (CNTs) entangled.

[0025] Furthermore, the nanofibers and carbon nanotubes (CNTs) constituting part or all of the sheet or nonwoven fabric are at least nanofibers produced by electrospinning, and may be carbon nanotubes (CNTs) produced by any of various CNT synthesis methods.

[0026] Conventional nonwoven fabrics are typically produced using fibers produced by drawing. However, the average fiber diameter is several microns or more, and the individual fiber diameters vary widely depending on the drawing force, resulting in inconsistent foreign particle capture rates and strength. This makes them insufficient for capturing submicron-sized foreign particles, making them unsuitable for the purposes of the present invention. Therefore, the nanofibers of the present invention require the electrospinning method, which allows for relatively consistent nanofiber diameters and facilitates the production of ultrafine fibers, and various CNT production methods. The diameter of the nanofibers of the present invention is not particularly limited as long as it is on the nanometer order, but typically, a diameter of 1 μm or less, in the range of 10 to 950 nm, is preferred. This is because fibers less than 10 nm are too weak and difficult to handle. Furthermore, fibers greater than 950 nm are difficult to remove submicron-sized foreign particles.

[0027] Furthermore, as described above, it is more preferable to gradually change the "filtration accuracy gradient" by gradually varying the nanofibers from one surface of the filter nonwoven fabric and the planar support to the other surface or from both surfaces to the center, either by using thinner and thicker nanofibers or by varying the mesh size of the planar support. This is because a nonwoven fabric containing only thin nanofibers of a uniform diameter may have a high foreign matter capture rate, but its filter strength is weak and it easily tears, making it unsuitable for long-term use. On the other hand, by using relatively thick nanofibers from one surface of the filter nonwoven fabric to the other surface or both surfaces and gradually narrowing the average nanofiber diameter toward the center, or by varying the mesh size of the planar support, the filter strength can be improved, the foreign matter capture rate can be increased, and pressure loss can be reduced. As a result, it is possible to speed up vacuuming and atmospheric pressure return when inserting and removing an exposure mask. This is most preferred because a graded "filtration accuracy gradient" is formed depending on the degree of opening of the thicker nanofibers or planar support, with the thinner nanofibers or planar support acting to remove mainly submicron or smaller foreign matter, while the thicker nanofibers or planar support acting to remove some larger foreign matter, and the thicker nanofibers or planar support complement each other as strength reinforcement materials.

[0028] Furthermore, if necessary, in the present invention, it is possible to intentionally mix 5 to 70 vol.% of fibers larger than several microns in size into the filter, rather than using only nanofibers, in order to further increase the speed of evacuation and atmospheric pressure return, and thereby further increase the strength to withstand the wind pressure. If the content of fibers larger than several microns is less than 5 vol.%, the filter strength is not very strong, and further speed increases are difficult. If the content of fibers larger than several microns is 70 vol.% or more, the strength is improved, but the capture efficiency of fine foreign matter smaller than submicrons is reduced, which is not preferable.

[0029] Furthermore, when mixing nanofibers with thick fibers of several micrometers or more, polymer fibers with high bending strength, such as polypropylene, polyester, and polycarbosilane, are suitable. This is because these fibers function similarly to the rebar in reinforced concrete buildings, protecting the mixed nanofibers and the entire filter from destruction by high wind pressure during high-speed evacuation and atmospheric pressure return. The nanofibers of the present invention, particularly inorganic silica nanofibers and CNTs, have brittle and chemically active surfaces that are easily lost or damaged by atmospheric gases. Therefore, their surfaces may be modified with SiC, Si3N4, or the like.

[0030] The EUV pellicle is attached to the upper surface of the pellicle frame 3 via an adhesive layer 2. The ultrathin pellicle film 1 is made of silicon and has a thickness of less than 1 μm. The pellicle film 1 is frame-shaped (usually rectangular) and conforms to the shape of the mask 5. The silicon pellicle film is preferably made of single-crystal silicon, polycrystalline silicon, amorphous silicon, or their nitrides, oxynitrides, carbides, or metal silicides. This is chosen because thin films of various crystal shapes and compounds have relatively high strength compared to various metals and inorganic compounds, and because they have high EUV transmittance and can be easily and economically produced as high-purity films. It is also preferable to further coat the silicon pellicle film 1 or its nitrides, oxynitrides, carbides, or metal silicides with various inorganic compounds, such as SiC, Si3N4, or YO3, to prevent cracking and corrosion. If the thickness of the pellicle film exceeds 1 μm, the transmittance of the exposure light becomes insufficient, so the thickness is preferably 1 μm or less, and more preferably 100 nm to 1 μm.

[0031] As described above, the air pressure adjusting vent 6 provided in the pellicle frame of the present invention is partially or entirely covered with a filter 7 for preventing the intrusion of foreign matter, which is made of a nonwoven fabric composed of at least one of nanofibers and carbon nanotubes and a support having an opening for supporting the nonwoven fabric. More specifically, the nonwoven fabric is made of at least nanofibers and / or carbon nanotubes (CNTs) made by electrospinning, and the support is flat, and if necessary, a honeycomb-structured filter is used as the support.

[0032] In contrast, conventional nonwoven fabric filters are no longer capable of removing the extremely small particles of dust and other contaminants that are problematic in the ultra-high-resolution, highly detailed circuit patterns of recent years, measuring submicrons to several nanometers in size. While various improvements proposed to date, such as porous sintered metal or ceramic filters, can reduce the size of filters, they are difficult to adjust due to variations in the particle size of the metal or ceramic and in the temperature control during sintering, resulting in poor reproducibility of the contaminant capture rate and pressure loss.

[0033] However, the present invention solves these problems and is suitable not only for conventional pellicles but also for cutting-edge ultra-fine masks, particularly pellicles for EUV masks. Specifically, the filter of the present invention efficiently captures submicron to several nanometer particles, allows the filter to be made small and extremely thin, and minimizes pressure loss during air or gas entry and exit. Therefore, EUV exposure masks equipped with pellicles equipped with this filter can be vacuumed and returned to atmospheric pressure more quickly during entry and exit. As a result, the dead time of EUV exposure equipment can be shortened, the utilization rate of the exposure equipment increased, and production costs can be reduced.

[0034] The opening area of the air pressure adjustment vent 6 is not particularly limited, but is preferably at least 2% of the total area of the lower end face of the pellicle frame. To enable faster evacuation and atmospheric pressure return, a range of 10% to 50% is more preferable, further reducing production costs. However, the upper limit of the opening area depends on the strength of the pellicle frame. Making the opening area too large can cause deformation of the pellicle frame, which can distort the circuit pattern, which is undesirable. Therefore, the upper limit of the opening area should be determined based on the type of pellicle frame.

[0035] The outline of how the pellicle of the present invention is attached to an exposure mask will be explained again with reference to Figure 1. An adhesive 4 is formed on the lower end surface of pellicle frame 3 to attach pellicle 10 to the mask. Furthermore, a liner (not shown) is provided on the lower end surface of adhesive 4 to protect the adhesive surface. When attaching the pellicle to the mask, this liner is removed, exposing the adhesive, which is then attached to the mask for use. [Example]

[0036] The present invention will be specifically explained below by showing examples and comparative examples, but the scope of the present invention is not limited thereto.

[0037] [Example 1] A 150-μm-thick nonwoven fabric with a "graded filtration accuracy" was fabricated by blending conventional 3-μm-average-diameter polypropylene fibers and electrospun 0.15-μm-average-diameter silica fibers (calculated from SEM images) in stages, with average fiber diameters of 0.8 μm at both ends and 0.30 μm in the center. The average fiber diameter was calculated from SEM images. The nonwoven fabric was then sandwiched between the supports, with 2.5 mm x 10 mm openings. The mesh had three patterns (a) round (50.1%), (b) square (57.8%), and (c) honeycomb (55.3%) openings, each 30 μm wide, as shown in Figure 2. The mesh had three patterns: (a) round (50.1%), (b) square (57.8%), and (c) honeycomb (55.3%) openings. The nonwoven fabric was sandwiched between the supports to form a filter. This filter, which combines this nanofiber nonwoven fabric with a meshed flat support, already forms a so-called "filtration accuracy gradient" that captures foreign matter in stages, from large particles to small particles, without causing sudden clogging, even with the nonwoven fabric alone.However, by combining it with the above-mentioned support, an even greater "filtration accuracy gradient" is added, making it possible to capture even more foreign matter and reduce pressure drop, as will be described below.

[0038] The 200 μm high filter fabricated above was used to fabricate 28 vents (total opening area = 450 mm) for adjusting the air pressure of the pellicle frame coated with a 0.1 μm thick molybdenum silicide film as shown in Figure 1. 2 Since it was possible to completely block the area of the pellicle frame (21% of the bottom surface of the pellicle frame, filter installation allowable height = 200 μm; allowable height based on the EUV actual device), this pellicle frame was attached to the exposure mask using adhesive.

[0039] The exposure mask was then loaded into a simulated EUV system. NaCl was then processed with a particle-generating atomizer to generate NaCl particles, which were then classified into 0.01-0.5 μm particles using an electrostatic classifier to create a simulated foreign-matter atmosphere. This simulated foreign-matter atmosphere was then introduced into the simulated EUV system, and simulation experiments were conducted to simulate the mask being inserted and removed, including vacuuming and returning to atmospheric pressure. Specifically, the filter was roughly evaluated based on the following measurements: 1) foreign-matter capture rate, 2) maximum pressure drop, and 3) filter displacement at maximum pressure drop (i.e., strength index) during vacuuming and returning to atmospheric pressure. The foreign-matter capture rate was 100% for all particles between 0.01 and 0.5 μm, and the maximum pressure drop was approximately the same for all three patterns, ranging from 0.5 to 0.6 Pa, at a linear velocity of 0.15 cm / s. Furthermore, the maximum displacement of the filter at maximum pressure loss was 28 μm, 45 μm, and 5 μm for (a) round (opening rate: 50.1%), (b) square (opening rate: 57.8%), and (c) honeycomb structure (opening rate: 55.3%), respectively. All of these are practically usable, but of the three types, the displacement of the honeycomb structure was extremely low, at 1 / 6 to 1 / 7 of that of the round and square shapes, making it possible to adjust the air pressure even faster.

[0040] As a precaution, we also tried using a pellicle frame air pressure adjustment filter with a 0.1 μm molybdenum silicide film in a simulated EUV exposure tool, and the molybdenum silicide pellicle film did not break and was able to withstand the high-speed air pressure adjustment. Furthermore, while conventional filters have been difficult to install completely in pellicles due to limited space, the filters used in this invention can be installed completely, resulting in an exposure pellicle that allows for even faster air pressure adjustment.

[0041] [Comparative Example 1] A nonwoven fabric of the same thickness as in Example 1, 150 μm, was prepared using polypropylene fibers with an average diameter of 3 μm using a conventional nonwoven fabric manufacturing method. For comparison, a square pattern was woven using ultra-fine SUS316 wires with a diameter of 30 μm using a conventional method to create a mesh support of 2.5 mm x 10 mm in size, with an opening rate similar to the 30 μm wire width used in Example 1. Two of these supports were used to sandwich the nonwoven fabric, creating a filter.

[0042] The obtained filter was not a thin, flat filter, but a thick filter having unevenness of peaks and valleys and a thickness of 310 μm.

[0043] This was because the square mesh support was made by weaving ultrafine wires, which inevitably resulted in "mountains and valleys" due to the braiding of the ultrafine wires, i.e., unevenness, making it difficult to make the filter of the present invention small and extremely thin. As a result, an attempt was made to evaluate it as a filter for adjusting the air pressure of a pellicle frame using the same device and conditions as in Example 1, but because the filter was 310 μm thick, it was not possible to attach the filter as it was, making evaluation impossible, and it also could not be used in an actual device.

[0044] Therefore, to at least perform a rough evaluation, we created a sample with the pellicle frame spacing widened to 310 μm, partially modified the EUV simulation device, and attached the above filter to the pellicle frame for a rough evaluation. The results showed that the fiber used was too thick for this purpose, and the nonwoven fabric had a large mesh size. The particle capture rates for the 0.01-0.5 μm range were 27.0% at 0.01 μm, 36.5% at 0.05 μm, 49.4% at 0.10 μm, and 56.0% at 0.5 μm. The pressure loss was 11.5 Pa, both of which were extremely poor for EUV filter performance. Furthermore, a pellicle with a 0.1 μm molybdenum silicide pellicle membrane was attached to an exposure mask for evaluation. When the pressure was adjusted at the same speed as in Example 1, the pellicle membrane burst during the process. Because this is not a flat support, the unevenness of the peaks and valleys makes it impossible to support the entire nonwoven fabric evenly, which is thought to have resulted in a local pressure difference in the space between the exposure mask and the pellicle membrane.

[0045] [Example 2] One end surface was laminated with 50 μm of 100% SiC fibers made from polycarbosilane and having an average diameter of 50 μm. On this end surface, 100 μm of CNTs with an average diameter of 35 nm (0.035 μm) and the same SiC fibers with an average diameter of 50 μm were laminated, with the mixing ratio of the two gradually increasing. A 30 μm thickness of 100% CNTs with an average diameter of 35 nm (0.035 μm) was then laminated to form a nonwoven fabric. This nonwoven fabric had three different "filtration accuracy gradients." A honeycomb-structured support made of a 20 μm thick Ni plate, similar to Example 1 (Figure 2), was then placed on top of the 30 μm thickness of 100% CNTs with an average diameter of 35 nm (0.035 μm). This filter was then fabricated. Furthermore, this filter was used to vent 28 air pressure adjustment holes (total opening area = 321 mm) of the pellicle frame with a 0.15 μm p-Si film as shown in Figure 1. 2 (corresponding to 15% of the lower end surface of the pellicle frame) was sealed, and then the pellicle was attached to an exposure mask with an adhesive. Thereafter, the filter was evaluated using the same equipment and conditions as in Example 1. As a result, the foreign matter capture rate was 100% for all particles between 0.01 and 0.5 μm, the pressure loss was 0.15 Pa at a linear velocity of 0.15 cm / s, no damage to the p-Si pellicle membrane due to the pressure difference occurred, and it was able to withstand the vacuum and atmospheric return when inserting and removing the exposure mask. [Explanation of symbols]

[0046] 1. Pellicle membrane 2. Adhesive 3 Pellicle Frame 4. Adhesive 5. Photomask 6 Ventilation holes 7 Filters 10 Pellicle

Claims

1. a pellicle frame; an extremely thin pellicle film provided on the upper end surface of the pellicle frame; a vent hole provided in the pellicle frame; a filter that blocks the ventilation hole; Equipped with the filter is composed of a sheet made of at least one of nanofibers and carbon nanotubes, a support having openings for supporting the sheet, and The pellicle is characterized in that the support is flat and has a honeycomb structure.

2. a pellicle frame; an extremely thin pellicle film provided on the upper end surface of the pellicle frame; a vent hole provided in the pellicle frame; a filter that blocks the ventilation hole; Equipped with the filter is composed of a nonwoven fabric, partly or entirely made of at least one of nanofibers and carbon nanotubes, and a support having openings for supporting the nonwoven fabric; The pellicle is characterized in that the support is flat and has a honeycomb structure.

3. 3. The pellicle according to claim 1, wherein the filter has a filtration accuracy gradient from one surface, including the nonwoven fabric and the support having the openings, to the other surface, or from both surfaces toward the center.

4. A pellicle according to any one of claims 1 to 3, characterized in that the pellicle film has a thickness of 1 μm or less and is made in part or in whole of at least monocrystalline silicon, polycrystalline silicon, amorphous silicon, or their nitrides, oxynitrides, carbides, or metal silicides.

5. 5. The pellicle according to claim 4, wherein the pellicle membrane is coated with an inorganic compound.

6. The inorganic compound is SiC, Si ３ N ４ , Y ２ O ３ 6. The pellicle according to claim 5, wherein the pellicle is any one of the following:

7. The surface of the nanofiber or carbon nanotube is SiC or Si ３ N ４ The pellicle according to any one of claims 1 to 6, characterized in that it is coated with

8. 8. The pellicle according to claim 1, wherein the pellicle is a pellicle for an EUV mask.

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

10. A method for manufacturing a pellicle according to any one of claims 1 to 8, comprising the steps of: preparing a nonwoven fabric made of at least one of nanofibers produced by an electrospinning method and carbon nanotubes produced by a carbon nanotube method; and preparing a filter using the nonwoven fabric and a flat support having openings; A method for manufacturing a pellicle, wherein the flat support has a honeycomb structure.

11. An exposure method comprising exposing using the pellicle-equipped exposure mask according to claim 9.

12. 10. A method for manufacturing a semiconductor device, comprising the step of exposing using the pellicle-equipped exposure mask according to claim 9.

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