Easy-to-adjust air pressure pellicle for exposure

Abstract

To provide a pellicle for exposure in which, in order to deal with a reduction in the maximum allowable foreign matter size required especially for EUV exposure and a severe air pressure fluctuation to which the pellicle film is exposed, the performance of a filter attached to a vent hole penetrating through a pellicle frame is improved.SOLUTION: A pellicle of the present invention comprises a pellicle frame 3, a pellicle film 1 provided on the upper end surface of the pellicle frame, a vent hole 6 provided in the pellicle frame, and a filter 7 closing the vent hole. The filter has a non-woven fabric partially or wholly composed of at least one of nanofibers and carbon nanotubes.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an exposure pellicle that protects exposure masks used in the manufacture of semiconductors, liquid crystal, etc. from foreign matter and has an easily adjustable air pressure, and in particular to a pellicle for EUV masks that has an easily adjustable air pressure. [Background technology]

[0002] The manufacture of semiconductors and liquid crystal displays involves the use of lithography technology to form circuit patterns using exposure masks (also simply called "masks"). In recent years, especially in semiconductors, circuit patterns have become finer, 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 use it.

[0003] In general, the manufacturing of the above-mentioned semiconductors, such as LSI and VLSI, involves coating a wafer with resist, placing the wafer together with an exposure mask on which the desired circuit pattern is drawn, in an exposure machine, irradiating the exposure mask with light, and transferring the circuit pattern to the wafer. Usually, these operations are carried out in a clean room where dust is minimized, but even so, dust from the human body, equipment, or the environment often adheres to the mask when it is moved or placed after the mask is made. This dust is transferred together with the circuit pattern, resulting in abnormal circuits, which results in defective semiconductors and reduced manufacturing yields.

[0004] Therefore, as a preventative measure, it is common to attach a dust-proof pellicle onto the mask immediately after the mask is created, as described in Non-Patent Document 1. This is because, if a pellicle is attached to the mask all at once, even if dust is present and flies in, it is blocked by the pellicle and cannot reach the circuit pattern of the mask, and even if it lands on the pellicle film, it is at a distance from the mask surface, so by adjusting the focus of the exposure light onto the circuit pattern, the dust on the pellicle is not transferred due to "out of focus."

[0005] The basic structure of a pellicle usually consists of a metal frame, a pellicle film that is highly transparent and light-resistant to the exposure wavelength and is stretched across the upper surface of the frame using an adhesive, an adhesive layer made of a relatively light-resistant material such as acrylic or silicone formed on the lower surface of the frame to be attached to the mask, air vents drilled into the frame to adjust the air pressure difference between the inside and outside of the pellicle after it is airtightly attached to the mask, and a filter to cover the outer opening of the air vent.

[0006] The pellicle film has high transmittance and high light resistance at the exposure wavelength, and for example, nitrocellulose is used for g-line (436 nm), cellulose propionate is used for i-line (365 nm), and amorphous fluoropolymer is used for KrF excimer laser (248 nm) and ArF excimer laser (193 nm). Recently, the wavelength has become shorter as the size is further reduced, and EUV (extreme ultraviolet; 13.5 nm) exposure has also begun to be used. Any material that has high transmittance and high light resistance to EUV light can be used as the pellicle film material, but in reality, single crystal silicon, polycrystalline silicon, amorphous silicon, or nitrides, oxynitrides, or carbides thereof are usually suitable because they can be formed uniformly at low cost with good reproducibility. Furthermore, a protective film such as SiC, SiO2, Si3N4, SiON, Y2O3, YN, Mo, Ru, and Rh may be provided to protect these film materials. In order to obtain high transmittance, inorganic material films having a thickness of submicron or less have been investigated, and some of them are already in practical use.

[0007] Of these, in 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 (193 nm), the ventilation hole filters generally use nonwoven fabrics made of PET, PTFE, or other materials with fiber diameters ranging from tens to hundreds of μm (Patent Document 1). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2005-268464 A [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] On the other hand, in pellicles for EUV (extreme ultraviolet: 13.5 nm) exposure, which are used in vacuum or reduced pressure and have recently begun to be put to practical use, conventional filters for the ventilation holes made of resins such as PET and PTFE, as well as porous sintered metals and ceramics, have been used or proposed in some cases, but there are almost no filters that can withstand the harsh conditions of use, which is a major obstacle to the practical use of EUV (extreme ultraviolet: 13.5 nm) exposure. That is, conventional non-woven filters made of resins such as PET and PTFE have the disadvantage that the fiber diameter is thick, the pressure loss is high, and even submicron-sized particles that should be blocked can easily pass through. For porous sintered metals and ceramics, making the filtration holes fine and consistent is technically difficult because the holes are prone to fusion with each other during production. Holes larger than the diameter of the particles to be blocked, holes smaller than necessary, or blocked holes are mixed together, which causes problems such as large pressure loss during ventilation and unstable filter performance.

[0011] On the other hand, EUV exposure tools are particularly expensive, costing tens of billions of yen each, and although they are wasteful and not directly useful for production, the vacuuming and atmospheric pressure return required for the insertion and removal of masks, which are essential for their operation, result in dead time for the operation of the exposure tool and are a factor in increasing costs. Therefore, in order to reduce production costs, there is a demand to speed up the vacuuming and atmospheric pressure return and increase the operating rate of EUV exposure tools even if only slightly.

[0012] However, the pellicle film currently used for EUV exposure is generally made of extremely thin single crystal silicon, polycrystalline silicon, amorphous silicon, or rigid inorganic material films such as nitrides, oxynitrides, or carbides of these materials, each of which is submicron thick, in terms of EUV light resistance, light transmittance, and processability. Therefore, when the above-mentioned vacuuming or atmospheric pressure return is performed at high speed, the sudden inflow and outflow of air causes localized air density in the space enclosed by the combined mask and pellicle, resulting in a large localized pressure difference between the inside and outside of the space. The extremely thin and rigid pellicle film cannot follow this pressure difference, and the pellicle film breaks and scatters, contaminating the expensive exposure machine, making subsequent exposure impossible and causing enormous damage, which is a major bottleneck in EUV exposure technology.

[0013] As a countermeasure to this problem, in the prior art, for example, Patent Document 1 proposes covering the circuit pattern with a mask cover (reticle cover) that also serves as a so-called pellicle film and a vent filter to protect it from dust. Indeed, this method includes the exposed surface as the filter area, and can be made extremely large, so it is possible to perform vacuuming and atmospheric pressure return at high speed, but on the other hand, although a porous fluororesin, specifically PTFE, has been proposed to ensure the filter's vents, EUV light is ultraviolet light with an extremely short wavelength (extreme ultraviolet light: 13.5 nm), so the irradiated energy is extremely large and organic matter decomposes in a short time. Even PTFE, which has relatively good light resistance, has a major problem in that it cannot withstand long-term use with EUV light. [Means for solving the problem]

[0014] 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; A pellicle membrane provided on an upper end surface of the pellicle frame; An air vent provided in the pellicle frame; A filter that blocks the ventilation hole; Equipped with The filter is a pellicle, the pellicle comprising a sheet, a part or the whole of which is made of at least one of nanofibers and carbon nanotubes. [2] A pellicle frame; and A pellicle membrane provided on an upper end surface of the pellicle frame; An air vent provided in the pellicle frame; A filter that blocks the ventilation hole; Equipped with The filter is a pellicle, a part or the whole of which comprises a nonwoven fabric composed of at least one of nanofibers and carbon nanotubes. [3] The pellicle described in [2], wherein the filter has a nonwoven fabric composed in part or in whole of the filter of nanofibers and carbon nanotubes. [4] The pellicle described in any one of [1] to [3], characterized in that 5 to 70 vol% of the fibers constituting the filter are fibers having an average fiber diameter of several μm or more and several hundred μm or less. [5] The pellicle according to any one of [1] to [4], wherein the filter is inserted, in whole or in part, into the air hole. [6] The pellicle described in any one of [1] to [5], characterized in that the air vent has a countersink at its outer opening, and the filter is embedded in part or in whole in the countersink. [7] The pellicle described in any one of [1] to [6] above, wherein at least one of the outer opening or the inner opening of the air hole is chamfered. [8] The pellicle described in any one of [1] to [7], characterized in that the total opening area of ​​the air holes is 2% or more of the total area of ​​the lower end face of the pellicle frame. [9] The pellicle described in [8], characterized in that the total opening area of ​​the air vents is greater than or equal to 10% and less than or equal to 50% of the total area of ​​the lower end surface of the pellicle frame.

[10] The pellicle described in any one of [1] to [9], wherein the filter has a filtration accuracy gradient in which the average fiber diameter gradually decreases from one surface to the other surface, or from both surfaces to the center. "Filtration accuracy gradient": This refers to gradually changing the filtration accuracy of the filter material. In general, this is done by gradually capturing particles from larger to smaller ones to prevent sudden clogging.

[11] The pellicle described in any one of [1] to

[10] , wherein the filter contains fibers having an average fiber diameter of several μm or more and several hundred μm or less, and the proportion of the fibers decreases stepwise from one surface to the other surface, or from both surfaces to the center.

[12] The pellicle described in

[10] or

[11] , characterized in that the filter is made by stacking and combining multiple nonwoven fabric sheets, each of which is made of fibers having different average fiber diameters.

[13] A pellicle according to any one of [1] to

[12] , characterized in that the pellicle film has a thickness of 1 μm or less and is made in part or in whole of single crystal silicon, polycrystalline silicon, amorphous silicon, or a nitride, oxynitride, or carbide thereof.

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

[13] , wherein the pellicle membrane is coated with an inorganic compound.

[15] The pellicle described in

[14] , wherein the inorganic compound is any one of SiC, Si3N4, or Y2O3.

[16] The pellicle described in any one of [1] to

[15] , wherein all or a part of the surface of the nanofiber is covered with SiC or Si3N4.

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

[16] , wherein the pellicle is for an EUV mask.

[18] A pellicle frame; and An air vent provided in the pellicle frame; A filter that blocks the ventilation hole; Equipped with The filter is a pellicle frame with a filter, the filter having a sheet the entirety or a part of which is made of at least one of nanofibers and carbon nanotubes.

[19] A pellicle frame; and An air vent provided in the pellicle frame; A filter that blocks the ventilation hole; Equipped with The pellicle frame with a filter is characterized in that the filter has a nonwoven fabric, a part or the whole of which is composed of at least one of nanofibers and carbon nanotubes.

[20] An exposure mask with a pellicle, comprising: an exposure mask having the pellicle according to any one of [1] to

[17] attached thereto.

[21] A method for producing a pellicle according to any one of [1] to

[17] , comprising the step of producing the nanofibers by electrospinning.

[22] An exposure method comprising exposing using the pellicle-equipped exposure mask described in

[20] above.

[23] A method for manufacturing a semiconductor device, comprising the step of exposing using the pellicle-attached exposure mask described in

[20] . Effect of the Invention

[0015] According to the present invention, it is possible to perform vacuum drawing and atmospheric pressure return more quickly when a mask is moved into or out of a cutting-edge EUV exposure device that transfers ultra-fine patterns, as well as various ordinary pellicles, thereby increasing the operating rate of expensive exposure equipment and significantly reducing productivity costs. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing a vertical cross-sectional structure of an exposure mask with a pellicle in one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the pellicle 10 of the present invention includes a pellicle frame 3, an extremely thin pellicle film 1 provided on the upper end surface of the pellicle frame 3 via an adhesive layer 2, and at least one vent hole 7 provided in the pellicle frame 3. The vent hole is blocked by a filter 7 for preventing the intrusion of foreign matter, the filter 7 having a nonwoven fabric composed of at least one of nanofibers or carbon nanotubes (CNTs) in part or in whole. In FIG. 1, the filter 7 is located outside the outer opening of the vent hole 6, but this does not exclude a mode in which the filter 7 is partially or entirely inserted into the vent hole 6. In addition, a counterbore for embedding the filter 7 in part or in whole in the outer opening of the vent hole 6 is also possible, and at least one of the outer opening or inner opening of the vent hole 6 may be chamfered 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 hole 6. The pellicle frame 3 is frame-shaped (usually rectangular) corresponding to the shape of the mask 5. The nonwoven fabric, as described in JIS L-0222:2001, means "a fiber sheet, web, or batt in which the fibers are oriented in one direction or randomly and are bonded to each other by entanglement and / or fusion and / or adhesion, excluding paper, woven fabric, knitted fabric, tufts, and crepe (pile) 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 shape, and the nanofibers or carbon nanotubes (CNTs) are entangled.

[0018] The pellicle film 1 is made of extremely thin silicon, and is made of single crystal silicon, polycrystalline silicon, amorphous silicon, or their nitrides, oxynitrides, or carbides. This is selected because the strength of thin films of various crystal shapes and compounds is relatively high compared to various metals and inorganic compounds, and high-purity films can be easily and economically produced. Carbon films such as graphene, diamond-like carbon, and carbon nanotubes are also effective for EUV exposure. It is preferable to coat these pellicle films 1 with various inorganic compounds such as SiC, Si3N4, and Y2O3 for the purpose of preventing cracking and corrosion. If it is difficult to handle the pellicle film alone, a pellicle film supported by a frame such as silicon can be used. In that case, the pellicle can be easily manufactured by bonding the frame area and the pellicle frame.

[0019] If the thickness of the pellicle film 1 exceeds 1 μm, the amount of transmitted exposure light becomes insufficient, so the thickness is preferably 1 μm or less, and more preferably 100 nm to 1 μm.

[0020] In the present invention, as described above, the ventilation holes 6 provided in the pellicle frame are partially or entirely blocked by a filter 7 for preventing the intrusion of foreign matter, which has a nonwoven fabric made of at least one of nanofibers or carbon nanotubes (including both nanofibers and carbon nanotubes). As described above, conventional nonwoven fabric filters are no longer capable of removing foreign matter such as dust that is problematic in recent ultra-high definition and highly fine circuit patterns of submicrons to several nm. On the other hand, porous sintered metal or ceramic filters are difficult to adjust the pore size distribution during firing, and the pores are blocked, or it is difficult to adjust the thickness, resulting in problems such as high pressure loss and lack of reproducibility. The arrangement, number, and shape of the ventilation holes are not particularly limited and may take various forms. The ventilation hole is preferably provided so as to connect the outer space and the inner space of the pellicle. As shown in FIG. 1, the ventilation hole provided penetrating from the outer surface to the inner surface of the pellicle frame is easy to manufacture. On the other hand, instead of the ventilation hole penetrating the outer surface and the inner surface, the direction of the through hole extending from the outer surface of the pellicle frame toward the inner surface may be bent toward the upper end surface or the lower end surface of the pellicle frame midway to provide an opening at the upper end surface or the lower end surface of the pellicle frame. Also, the direction of the through hole extending from the inner surface of the pellicle frame toward the outer surface may be bent toward the upper end surface or the lower end surface of the pellicle frame midway to provide an opening at the upper end surface or the lower end surface of the pellicle frame. In this way, the ventilation hole whose direction is changed midway makes it easy to design the opening area at the upper end surface or the lower end surface to be large, and is an effective technology for thin pellicles such as pellicles for EUV exposure, which have a pellicle height of about 2.5 mm or less.

[0021] However, as in the present invention, by blocking the air hole 6 with a filter 7 for preventing the intrusion of foreign matter, which has a nonwoven fabric partially or entirely composed of at least one of nanofibers and carbon nanotubes, the above problem is solved, and the present invention is suitable for not only conventional pellicles, but also state-of-the-art ultra-fine masks, particularly pellicles for EUV masks. That is, since foreign matter of submicrons to several nm is highly efficiently collected by the filter adopted in the present invention, the filter can be made thinner, and in addition, due to the ultra-fine fiber diameter, the pressure loss when air or gas enters and exits is reduced, and due to the synergistic effect, it is possible to speed up evacuation and atmospheric pressure return when inserting and removing the mask. As a result, it is possible to shorten the dead time in the operation of the exposure device, increase the operating rate of the exposure device, and reduce production costs.

[0022] In this case, when one of the openings is the upper end face or the lower end face of the pellicle frame, the total opening area of ​​the vent hole 6 is preferably 2% or more of the total area of ​​the pellicle frame end face having the opening, but more preferably 10% or more in order to enable faster evacuation and atmospheric pressure return, which allows further reduction in production costs. However, the upper limit of the total opening area of ​​all the vent holes depends on the strength of the pellicle frame, and if it is too large, the pellicle frame will deform, and as a result, the circuit pattern will also be distorted, which is not preferable. Therefore, the upper limit of the total opening area should be determined depending on the type of pellicle frame, but due to the difficulty of processing a high-strength pellicle frame, if it exceeds 50%, it is likely to lose the rationality of being able to support increased processing costs regardless of the type. Therefore, the total opening area is preferably 50% or less, more preferably 45% or less, and particularly preferably 35% or less. Here, this total opening area means the ratio of the area of ​​all the openings provided on the end face to the total area of ​​the pellicle frame end face having the opening.

[0023] In addition, in the manufacturing method of ordinary nonwoven fabrics, fibers made by a drawing method are generally used, but the average fiber diameter is as thick as several μm or more, and each fiber diameter also becomes thinner or thicker depending on the drawing force, resulting in a wide distribution, so that the capture rate and strength of foreign matter are not constant. Therefore, it is not suitable for the nanofibers in the present invention and cannot be used. Therefore, in the present invention, the nanofibers are optimally made by the so-called electrospinning method, which makes these relatively constant, and nonwoven fabrics made by the electrospinning method and / or the well-known CNT manufacturing method are optimal. As is well known, the electrospinning method is a method in which a polymer solution, which is the raw material of the nanofibers, is poured into a syringe, and then a high voltage is applied to charge the polymer solution, causing an electrostatic explosion, thereby making nanofibers. The conditions for carrying out this method are not particularly limited, and may be set appropriately depending on the type of polymer material, etc.

[0024] The material of the nanofiber is not particularly limited, and examples thereof include organic polymers (polypropylene, polyester, polycarbosilane, polyethylene, nylon, polyacetate, polyacrylic, polystyrene, polyvinyl chloride, etc.), inorganic polymers (silica, alumina, titania, zirconia, etc.), natural polymer compounds (cellulose, chitin, etc.), carbon materials, etc. In this specification, the term "nanofiber" refers to a fibrous material having an average fiber diameter of the nano order.

[0025] In the present invention, the average fiber diameter of the nanofibers and carbon nanotubes is not further limited, but is usually preferably 1 μm or less and in the range of 10 to 950 nm. This is because fibers less than 10 nm are too weak and difficult to handle, and fibers more than 950 nm are difficult to remove nano-order foreign matter, which has become a recent problem.

[0026] In the present invention, rather than using nanofibers and / or carbon nanotubes for all the fibers in the filter, it is preferable to intentionally mix in only 5 to 70 vol% of fibers having a size of several μm or more and several hundred μm or less (for example, about 1 μm to 300 μm) among the fibers constituting the filter in order to increase the strength so as to withstand the wind pressure when the vacuum is drawn or the atmospheric pressure is returned at high speed. This is because if the fibers having a size of several μm or more and several hundred μm or less are less than 5 vol%, the strength is low and the speed cannot be increased very much, and if the fibers have a size of more than 70 vol%, the collection rate of fine foreign matter of submicron or less begins to decrease even if the strength is high.

[0027] In the present invention, nanofibers, particularly inorganic silica nanofibers and CNTs, have brittle and active surfaces and are therefore easily lost or damaged depending on the atmospheric gas. Therefore, the surfaces of these nanofibers may be slightly modified by coating them with SiC, Si3N4, or the like.

[0028] In the present invention, the filter preferably has a filtration accuracy gradient in which the average fiber diameter decreases stepwise from one surface to the other surface, or from both surfaces to the center. In this way, the formation of a filtration accuracy gradient improves the strength of the filter, increases the foreign matter collection rate, and reduces pressure loss. As a result, it is possible to speed up the evacuation and atmospheric pressure return when entering and leaving the mask. In a more preferred embodiment, the nonwoven fabric of the filter is preferably provided with a filtration accuracy gradient by changing the mixing ratio of nanofibers and thick fibers having a diameter of several μm or more to several hundred μm or less stepwise from one surface to the other surface, or from both surfaces to the center, so that the average fiber diameter decreases stepwise. This is because a nonwoven fabric composed only of nanofibers has a high foreign matter collection rate but has a weak filter strength, and may easily break and not withstand long-term use.

[0029] In addition, when nanofibers are mixed with thick fibers of several μm or more to several hundred μm or less, the thick fibers have bending strength and are preferably polymer fibers such as polypropylene, polyester, polycarbosilane, etc. This is because these fibers play a role similar to that of the reinforcing bars in reinforced concrete, and can prevent the mixed nanofibers and the entire filter from being destroyed by the wind pressure when vacuuming at high speed or when returning to atmospheric pressure.

[0030] A method for producing a filter having a graded filtration accuracy is to stack and combine multiple nonwoven fabric sheets, each composed of fibers having different average fiber diameters, appropriately selected so as to achieve the desired gradient. After stacking, coating the sides with adhesive can prevent dispersion. When embedding the filter in a countersink, it is preferable to coat the sides of the countersink with adhesive.

[0031] The method of mounting the filter thus prepared so as to cover the vent hole drilled in the pellicle frame is the same as that of a conventional filter. For example, adhesive is applied around the outer opening of the vent hole in a square frame or ring shape, etc., according to the shape of the filter, and the filter is attached to this. If there is a countersink, applying adhesive to the side of the countersink will fix the filter and prevent it from scattering.

[0032] A method for mounting the pellicle of the present invention on a mask will be described with reference to Figure 1. An adhesive layer 4 for mounting the pellicle 10 on a photomask 5 is formed on the lower end surface of the pellicle frame 3. Furthermore, a liner (not shown) for protecting the adhesive surface is provided on the lower end surface of the adhesive layer 4. When mounting the pellicle 10 on the photomask 5, this liner is removed and the adhesive layer 4 is exposed and attached to the photomask 5 for use. EXAMPLES

[0033] The present invention will be specifically described below with reference to examples and comparative examples, but the scope of the present invention is not limited thereto.

[0034] [Example 1] Polypropylene fibers with an average fiber diameter of 5 μm used in current filters were mixed with silica nanofibers with an average fiber diameter of 0.3 μm created by electrospinning to create 28 nonwoven filters with a thickness of 500 μm, each with a "filtration accuracy gradient" of 0.95 μm average fiber diameter at both ends and 0.35 μm average fiber diameter in the center. The average fiber diameter was calculated from SEM images. Next, as shown in FIG. 1, the nonwoven fabric filter 7 was used to close the 28 vent holes 6 (total opening area = 450 mm ) of the pellicle frame 3 on which the pellicle membrane 1 made of p-Si (polysilicon) with a thickness of 0.1 μm was stretched. 2 (21%) of the total area of ​​the lower end face of the pellicle frame was blocked one by one, and then the pellicle 10 was attached to an exposure mask 5 via an adhesive layer 4. Then, this exposure mask was mounted in a simulated EUV device, and NaCl was treated with a fine particle generating atomizer to generate NaCl fine particles, which were then classified into 0.01 to 0.5 μm NaCl fine particles using an electrostatic classifier to create a simulated foreign matter atmosphere. While introducing this simulated foreign matter atmosphere into the simulated EUV device, a simulation experiment was carried out of evacuation and atmospheric pressure return, simulating the insertion and removal of the mask. After evacuation, the foreign matter capture rate and differential pressure during atmospheric pressure return were measured to provide a rough evaluation of the nonwoven fabric filter. As a result, the foreign matter capture rate was 100% for all particles between 0.01 and 0.5 μm. The differential pressure was 0.5 Pa at a linear velocity of 0.15 cm / s. The p-Si pellicle membrane was also able to withstand shocks caused by pressure changes without being damaged.

[0035] [Comparative Example 1] As a comparative example using the current filter product, 28 nonwoven fabric filters were created that were composed only of polypropylene fibers with an average fiber diameter of 5 μm as in Example 1 above, and had no gradient in filtration accuracy over the entire 500 μm thickness, with a uniform thickness. Thereafter, using the same apparatus and conditions as in Example 1, the above nonwoven fabric filter was used as the filter for the same pellicle frame, and after evacuation, the foreign matter capture rate and differential pressure were measured when the pressure was returned to atmospheric pressure, to evaluate the above nonwoven fabric filter. As a result, the foreign object capture rate for particles around 0.01 μm was 94.0%, for particles around 0.05 μm was 93.5%, for particles around 0.10 μm was 94.8%, and for particles around 0.5 μm was 95.3%. The pressure difference was 20.5 Pa at a linear velocity of 0.15 cm / s, but the extremely thin p-Si pellicle membrane burst midway because the pressure difference was too large, indicating that the current filter is unsuitable for this simulated EUV device.

[0036] [Example 2] Only polyester fibers with an average fiber diameter of 3 μm were laminated to a thickness of 50 μm on one end surface. Carbon nanotubes (CNTs) with an average fiber diameter of 35 nm (0.035 μm) and the above polyester fibers with an average fiber diameter of 3 μm were laminated to a thickness of 400 μm on this end surface while gradually changing the degree of mixing of the two, and then only CNTs with an average fiber diameter of 35 nm were laminated to a thickness of 50 μm on the other end surface, thereby producing 28 nonwoven fabric filters with a filtration accuracy gradient in the middle. Furthermore, with these nonwoven fabric filters, a total of 28 vent holes 6 (total opening area = 321 mm2) of a pellicle frame 3 on which a 0.1 μm p-Si membrane pellicle membrane 1 was stretched were used as shown in Figure 1. 2 (corresponding to 15% of the total area of ​​the lower end face of the pellicle frame) was covered, and then the pellicle 10 was attached to an exposure mask 5 via an adhesive layer 4. Thereafter, the nonwoven fabric filter was evaluated using the same device 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 differential pressure was 0.2 Pa at a linear velocity of 0.15 cm / s, the p-Si pellicle membrane was not damaged by the differential pressure, and was able to withstand the vacuum pumping and return to atmospheric pressure when inserting and removing the exposure mask. [Explanation of symbols]

[0037] 1 Pellicle membrane 2 Adhesive layer 3 Pellicle Frame 4 Adhesive layer 5. Photomask 6 Ventilation holes 7 Filters 10 Pellicle

Claims

1. A pellicle frame; A pellicle membrane provided on an upper end surface of the pellicle frame; An air vent provided in the pellicle frame; A filter that blocks the ventilation hole; Equipped with The filter is a sheet made of nanofibers in part or in whole. having A pellicle, characterized in that all or a part of the surface of the nanofiber is covered with SiC or Si 3 N 4 .

2. A pellicle frame; A pellicle membrane provided on an upper end surface of the pellicle frame; An air vent provided in the pellicle frame; A filter that blocks the ventilation hole; Equipped with The filter has a nonwoven fabric partly or entirely composed of nanofibers, A pellicle, characterized in that all or a part of the surface of the nanofiber is covered with SiC or Si 3 N 4 .

3. 3. The pellicle according to claim 2, wherein the filter comprises a nonwoven fabric, part or all of which is composed of nanofibers and carbon nanotubes.

4. 4. The pellicle according to claim 1, wherein 5 to 70 vol % of the fibers constituting the filter are fibers having an average fiber diameter of several μm or more and several hundred μm or less.

5. 5. The pellicle according to claim 1, wherein the filter is inserted, in part or in whole, into the air hole.

6. 6. The pellicle according to claim 1, wherein the vent hole has a countersink at its outer opening, and the filter is embedded in part or in whole in the countersink.

7. 7. The pellicle according to claim 1, wherein the vent hole has at least one of its outer opening and inner opening chamfered.

8. 8. A pellicle as described in any one of claims 1 to 7, characterized in that the total opening area of ​​the air vents is 2% or more of the total area of ​​the lower end surface of the pellicle frame.

9. 9. The pellicle according to claim 8, wherein the ratio of the total opening area of ​​the air vents to the total area of ​​the lower end surface of the pellicle frame is 10% or more and 50% or less.

10. The pellicle described in any one of claims 1 to 9, characterized in that the filter has a filtration accuracy gradient in which the average fiber diameter gradually decreases from one surface to the other surface, or from both surfaces to the center.

11. The pellicle described in any one of claims 1 to 10, characterized in that the filter contains fibers having an average fiber diameter of several μm or more and several hundred μm or less, and the proportion of the fibers gradually decreases from one surface to the other surface, or from both surfaces to the center.

12. 12. The pellicle according to claim 10 or 11, wherein the filter is formed by stacking and combining a plurality of nonwoven fabric sheets each made of fibers having different average fiber diameters.

13. A pellicle according to any one of claims 1 to 12, characterized in that the pellicle film has a thickness of 1 μm or less, and is made in part or in whole of single crystal silicon, polycrystalline silicon, amorphous silicon, or a nitride, oxynitride, or carbide thereof.

14. The pellicle according to any one of claims 1 to 13, characterized in that the pellicle membrane is coated with an inorganic compound.

15. The inorganic compound is SiC, Si ３ N ４ , or Y ２ O ３ The pellicle according to claim 14, characterized in that it is any one of the above.

16. The pellicle according to any one of claims 1 to 15, characterized in that the pellicle is a pellicle for an EUV mask.

17. A pellicle frame; An air vent provided in the pellicle frame; A filter that blocks the ventilation hole; Equipped with The filter has a sheet partly or entirely made of nanofibers, A pellicle frame with a filter, characterized in that all or a part of the surface of the nanofiber is covered with SiC or Si 3 N 4 .

18. A pellicle frame; An air vent provided in the pellicle frame; A filter that blocks the ventilation hole; Equipped with The filter has a nonwoven fabric, a part or the whole of which is made of nanofibers, A pellicle frame with a filter, characterized in that all or a part of the surface of the nanofiber is covered with SiC or Si 3 N 4 .

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

20. A method for producing a pellicle according to any one of claims 1 to 16, comprising the step of producing the nanofibers by electrospinning.

21. 20. An exposure method comprising exposing using the pellicle-equipped exposure mask according to claim 19.

22. 20. A method for manufacturing a semiconductor device, comprising the step of exposing using the pellicle-attached exposure mask according to claim 19.

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