Pellicle membrane and pellicle

Abstract

A pellicle film (100) contains a first fibrous material (1) and a second fibrous material (2). The length L FB1 of the first fibrous material (1) is 20 μm or less, and the length L FB2 of the second fibrous material (2) is at least 100 μm and less than 250 μm. A pellicle (200) is provided with: a support body (30) which has a frame part (31) and an opening (32) surrounded by the frame part (31), and which supports the pellicle film (100); and the pellicle film (100).

Description

[Technical field]

[0001] The present invention relates to a pellicle membrane and a pellicle. [Background technology]

[0002] In a manufacturing process for semiconductor devices and the like, for example, a desired circuit pattern is formed on a substrate such as a semiconductor wafer by applying a photoresist to the substrate, irradiating the substrate with the photoresist through a photomask with light, and removing the photoresist.

[0003] When light is irradiated onto a photomask with foreign matter adhering thereto, the foreign matter may cause problems with the circuit pattern formed on the substrate. For this reason, a pellicle having a pellicle film for capturing foreign matter may be used to prevent foreign matter from adhering to the photomask. The pellicle is placed above the photomask at a distance such that the pellicle film does not come into contact with the photomask.

[0004] In recent years, the use of extreme ultraviolet (EUV) has been considered in order to form finer circuit patterns. EUV refers to light with a wavelength of 1 nm or more and 100 nm or less. Specifically, light rays of about 13.5 nm ± 0.3 nm are beginning to be used as EUV. When EUV is irradiated onto a pellicle film, the EUV passes through the pellicle film, but a portion of the irradiated EUV is absorbed by the pellicle film. The light energy of the absorbed EUV is converted into thermal energy, causing the temperature of the pellicle film to rise. For this reason, the pellicle film is required to have EUV transmittance, heat resistance, durability, and the like.

[0005] For example, Patent Document 1 describes a pellicle film including a carbon nanotube sheet. Patent Document 1 describes that the carbon nanotube sheet in the pellicle film includes bundles formed from a plurality of carbon nanotubes, the bundles have a diameter of 100 nm or less, and the bundles are in-plane oriented in the carbon nanotube sheet. Patent Document 1 also describes that the pellicle film has high EUV transmittance and excellent heat resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2018 / 008594 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to obtain a pellicle membrane with higher performance, a pellicle membrane whose pore characteristics (eg, pore size and opening ratio) are easy to control is desirable.

[0008] An object of the present invention is to provide a pellicle membrane whose void characteristics are easy to control, and to provide a pellicle equipped with said pellicle membrane. [Means for solving the problem]

[0009] [1]. A first fibrous material and a second fibrous material, The length L of the first fibrous material FB1 is 20 μm or less, The length L of the second fibrous material FB2 A pellicle membrane having a thickness of 100 μm or more and less than 250 μm.

[0010] [2]. In the pellicle membrane according to [1], The pellicle membrane is a single layer membrane, A pellicle membrane, wherein the first fibrous material and the second fibrous material are mixed in the single layer membrane.

[0011] [3]. [2] The pellicle membrane according to the present invention, The mass M of the first fibrous material in the monolayer FB1 and the mass M of the second fibrous material FB2 Mass ratio to (M FB1 :M FB2 ) is 10:90 to 90:10, a pellicle membrane.

[0012] [4]. In the pellicle membrane according to [2] or [3], A pellicle membrane, wherein the sum of the mass percentage of the first fibrous material in the monolayer membrane and the mass percentage of the second fibrous material in the monolayer membrane is 90 mass% or more.

[0013] [5]. In the pellicle membrane according to [1], The pellicle membrane is a multi-layer membrane including a first pellicle membrane and a second pellicle membrane, The first pellicle film and the second pellicle film are laminated, the first pellicle membrane includes the first fibrous material; The second pellicle membrane comprises the second fibrous material.

[0014] [6]. [5] The pellicle membrane according to the present invention, The mass M of the first fibrous material in the multilayer film FB1 and the mass M of the second fibrous material FB2 Mass ratio to (M FB1 :M FB2 ) is 50:50 to 80:20.

[0015] [7]. In the pellicle membrane according to [5] or [6], A pellicle membrane, wherein the sum of the mass percentage of the first fibrous material in the multilayer membrane and the mass percentage of the second fibrous material in the multilayer membrane is 90 mass% or more.

[0016] [8]. [5] to [7], wherein the pellicle membrane is The pellicle membrane further comprises a third pellicle membrane, The second pellicle film, the first pellicle film, and the third pellicle film are stacked in this order; The third pellicle membrane includes a third fibrous material having a length of 100 μm or more and less than 250 μm; The second fibrous material and the third fibrous material may be the same or different from each other.

[0017] [9]. [8] The pellicle membrane according to the present invention, The mass M of the first fibrous material in the multilayer film FB1 and a mass M of the second fibrous material. FB2 and the mass M of the third fibrous material FB3 The total mass M FB2 +M FB3 Mass ratio to (M FB1 :(M FB2 +M FB3 ) is 33:67 to 80:20.

[0018]

[10] . [8] or [9], wherein the pellicle membrane A pellicle membrane, wherein the sum of the mass percentage of the first fibrous material, the mass percentage of the second fibrous material, and the mass percentage of the third fibrous material in the multilayer membrane is 80 mass% or more.

[0019]

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

[10] , The length L of the first fibrous material FB1 A pellicle membrane having a thickness of 1 μm or more and 20 μm or less.

[0020]

[12] . [1] The pellicle membrane according to any one of [1] to

[11] , The length L of the second fibrous material FB2 A pellicle membrane having a thickness of 100 μm or more and 200 μm or less.

[0021]

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

[12] , which is self-supporting.

[0022]

[14] . A pellicle comprising: a pellicle membrane according to any one of [1] to

[13] ; and a support having a frame and an opening surrounded by the frame, the support supporting the pellicle membrane.

[0023] According to one aspect of the present invention, it is possible to provide a pellicle membrane whose void characteristics are easily controlled, and to provide a pellicle including the pellicle membrane. [Brief description of the drawings]

[0024] [Figure 1] 1 is a cross-sectional view illustrating a first example of a pellicle membrane according to a first embodiment. FIG. [Diagram 2] A cross-sectional view illustrating a second example of a pellicle membrane according to the first embodiment. [Diagram 3] A cross-sectional view illustrating a schematic diagram of a third example of a pellicle membrane according to the first embodiment. [Figure 4] FIG. 11 is a cross-sectional view illustrating a first example of a pellicle according to a second embodiment. [Diagram 5] FIG. 11 is a cross-sectional view illustrating a schematic diagram of a second example of a pellicle according to a second embodiment. [Figure 6] FIG. 11 is a cross-sectional view illustrating a schematic diagram of a third example of a pellicle according to the second embodiment. [Figure 7] 1 is a scanning electron microscope image of a pellicle membrane according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] [First embodiment] (Pellicle membrane) The pellicle membrane according to this embodiment contains a first fibrous material and a second fibrous material. The length L of the first fibrous material contained in the pellicle membrane according to this embodiment FB1 is 20 μm or less, and the length L of the second fibrous material FB2 is 100 μm or more and less than 250 μm. In this way, the pellicle membrane according to the present embodiment contains a plurality of types of fibrous materials that satisfy different length ranges. When the length of the second fibrous material is 250 μm or more, the mass (or molecular weight) per strand of the second fibrous material becomes large. For example, when the content of fibrous material in the pellicle membrane is constant and a pellicle membrane PF1 in which the length range of the fibrous material is 100 μm or more and less than 250 μm is compared with a pellicle membrane PF2 in which the length range of the fibrous material is 250 μm or more, the light transmittances of the pellicle membrane PF1 and the pellicle membrane PF2 are equivalent, while the number of strands of fibrous material contained in the pellicle membrane PF2 is reduced compared to the pellicle membrane PF1. When the number of strands of fibrous material in the membrane is reduced, the number of points where the fibrous materials contact each other is reduced, and the strength of the pellicle membrane is reduced. Therefore, it is required that the length of the second fibrous material is not excessively long.

[0026] The length of the fibrous material contained in the pellicle membrane corresponds to the length of the fibrous material used to fabricate the pellicle membrane. The length of the fibrous material used to fabricate the pellicle membrane may be a nominal value disclosed by the manufacturer of the fibrous material. The length of the fibrous material used to prepare the pellicle membrane can also be measured by casting a dispersion liquid in which the fibrous material is dispersed at a concentration of 0.001% by mass onto a solid substrate, drying the dispersion liquid, and observing the fibrous material attached to the solid substrate with a microscope such as an AFM (atomic force microscope) or an SEM (scanning electron microscope). When observing the fibrous material with a microscope to measure the length, it is desirable to measure 10 or more pieces of fibrous material that are preferably not bundled on one solid substrate, and to use the average of the measured lengths as the length of the fibrous material. A bundle is a fiber bundle composed of multiple fibrous materials.

[0027] In the pellicle membrane according to the present embodiment, the length L of the first fibrous material is set to 100 μm from the viewpoint of making it easier to control the void characteristics of the pellicle membrane and to ensure the mechanical strength of the pellicle membrane. FB1 However, the thickness is preferably 1 μm or more and 20 μm or less, and more preferably 1 μm or more and 10 μm or less.

[0028] In the pellicle membrane according to the present embodiment, the length L of the second fibrous material is set to 100 μm from the viewpoint of making it easier to control the void characteristics of the pellicle membrane and the optical transparency. FB2 However, it is preferable that the thickness is 100 μm or more and 200 μm or less.

[0029] The pellicle film according to the present embodiment is preferably self-supporting from the viewpoint of further improving the strength of the pellicle film and from the viewpoint of improving the transparency of the pellicle film against the exposure light. The fact that the pellicle film is self-supporting means that the pellicle film is in a state in which it is self-supporting, and that the pellicle film is a film that has self-supporting properties (also called a self-supporting film). In other words, a pellicle film that is self-supporting is a film that can maintain its shape by itself even without a base material, a reinforcing layer, etc.

[0030] The first fibrous material and the second fibrous material contained in the pellicle membrane according to the present embodiment are preferably at least one fibrous material selected from the group consisting of cellulose-based fibrous materials, polymer-based fibrous materials, bio-based fibrous materials, carbon-based fibrous materials, silicon-based fibrous materials, boron-based fibrous materials, and metal-based fibrous materials. The first fibrous material and the second fibrous material may be the same type of material or different types of materials, but the first fibrous material and the second fibrous material are preferably the same type of material.

[0031] Specific examples of fibrous materials contained in the pellicle membrane of this embodiment include cellulose-based fibrous materials, such as nanocellulose fibers; polymer-based fibrous materials, such as fibrous materials containing polymer materials such as polypropylene, polyethylene terephthalate, or polylactic acid; bio-based fibrous materials, such as DNA (deoxyribonucleic acid); silicon-based fibrous materials, such as fibrous materials containing silicon carbide or silicon nitride, or fibrous materials consisting only of silicon atoms (silicon nanotubes); carbon-based fibrous materials, such as carbon nanotubes (sometimes abbreviated as CNT), pitch-based carbon fibers, or PAN-based carbon fibers; boron-based fibrous materials, such as fibrous materials containing boron nitride; and metal-based fibrous materials, such as nanowires containing metal.

[0032] The first and second fibrous materials contained in the pellicle membrane according to this embodiment are preferably each independently a carbon-based fibrous material (i.e., a first carbon-based fibrous material and a second carbon-based fibrous material), and more preferably a carbon nanotube (i.e., a first carbon nanotube and a second carbon nanotube). In the pellicle membrane according to this embodiment, the first carbon-based fibrous material as the first fibrous material and the second carbon-based fibrous material as the second fibrous material may be different types of carbon-based fibrous materials, but are preferably the same type of carbon-based fibrous material.

[0033] The carbon nanotubes contained in the pellicle film according to the present embodiment are not particularly limited, and are preferably at least one selected from the group consisting of multi-walled carbon nanotubes (MWCNT), few-walled carbon nanotubes (FWCNT), double-walled carbon nanotubes (DWCNT), and single-walled carbon nanotubes (SWCNT). In the pellicle film according to the present embodiment, the first carbon nanotube as the first carbon-based fibrous material and the second carbon nanotube as the second carbon-based fibrous material may be the same type of carbon nanotube or different types of carbon nanotubes.

[0034] In this embodiment, the multi-walled carbon nanotube is, for example, a carbon nanotube having 4 to 20 concentric layers and a diameter of 4 to 100 nm. The few-walled carbon nanotube is, for example, a carbon nanotube having 2 or 3 concentric layers and a diameter of 2 to 8 nm. The single-walled carbon nanotube is, for example, a single-walled carbon nanotube with a tube diameter of 0.2 to 5 nm.

[0035] In one aspect of this embodiment, the cross-sectional diameter of the carbon nanotube is 0.2 nm or more and 50 nm or less. In one aspect of this embodiment, the cross-sectional diameter of the carbon nanotubes is 0.5 nm or more, or 1 nm or more. In one aspect of this embodiment, the cross-sectional diameter of the carbon nanotubes is 30 nm or less, or 20 nm or less. In the pellicle membrane according to this embodiment, it is also preferable that the cross-sectional diameters of the first carbon nanotube and the second carbon nanotube each independently satisfy any of the ranges of cross-sectional diameters described above.

[0036] Carbon nanotubes can be obtained by known methods, for example by chemical vapor deposition, laser ablation or arc discharge.

[0037] It is also preferable that the pellicle membrane according to this embodiment is substantially composed of only a fibrous material (preferably, a carbon-based fibrous material, more preferably, a carbon nanotube). Here, "substantially composed of only a fibrous material" means that 98% by mass or more (preferably, 99% by mass or more, more preferably, 99.9% by mass or more) of the pellicle membrane is a fibrous material (preferably, a carbon nanotube). When the pellicle membrane is substantially composed of only a fibrous material (preferably, a carbon-based fibrous material, more preferably, a carbon nanotube), a substance that is not intentionally added to the pellicle membrane and that is mixed in the raw materials or the manufacturing process, an unavoidable impurity, may or may not be contained in the pellicle membrane.

[0038] The pellicle membrane according to this embodiment may be a single layer membrane or a multilayer membrane in which multiple layers are stacked.

[0039] <Single layer film> When the pellicle membrane according to the present embodiment is a monolayer membrane, it is preferable that the first fibrous material and the second fibrous material are mixed in the monolayer membrane. In the present embodiment, it is preferable that the surfaces on both sides of the monolayer membrane in which the first fibrous material and the second fibrous material are mixed are the outermost surfaces of the pellicle membrane.

[0040] In the pellicle membrane according to the present embodiment, in order to easily control the void characteristics of the pellicle membrane, the mass M of the first fibrous material in the single layer membrane is FB1 and the mass M of the second fibrous material FB2 Mass ratio to (M FB1 :M FB2 ) is also preferably 5:95 to 95:5.

[0041] In the pellicle membrane according to the present embodiment, in order to easily control the void characteristics of the pellicle membrane, the mass M of the first fibrous material in the single layer membrane is FB1 and the mass M of the second fibrous materialFB2 Mass ratio to (M FB1 :M FB2 ) is also preferably 7:93 to 93:7.

[0042] In the pellicle membrane according to the present embodiment, in order to easily control the void characteristics of the pellicle membrane, the mass M of the first fibrous material in the single layer membrane is FB1 and the mass M of the second fibrous material FB2 Mass ratio to (M FB1 :M FB2 ) is preferably 10:90 to 90:10.

[0043] In the pellicle membrane according to the present embodiment, in order to easily control the void characteristics of the pellicle membrane, the mass M of the first fibrous material in the single layer membrane is FB1 and the mass M of the second fibrous material FB2 Mass ratio to (M FB1 :M FB2 ) is preferably 5:95 to 45:55, 5:95 to 30:70, 5:95 to 20:80, or 5:95 to 15:85.

[0044] The mass percentage of the first fibrous material in the monolayer film, represented by the following formula (Mathematical Formula 11), is preferably 10 mass % or more and 90 mass % or less. {M FB1 / (M FB1 +M FB2 )}×100 …(Number 11)

[0045] The mass percentage of the second fibrous material in the monolayer film, represented by the following formula (Mathematical Formula 12), is preferably 10 mass % or more and 90 mass % or less. {M FB2 / (M FB1 +M FB2 )}×100 …(number 12)

[0046] In the pellicle membrane of this embodiment, from the viewpoint of making it easier to control the void characteristics, the sum of the mass percentage of the first fibrous material in the monolayer membrane and the mass percentage of the second fibrous material in the monolayer membrane is preferably 90 mass% or more, more preferably 95 mass% or more, and even more preferably 98 mass% or more.

[0047] When the pellicle membrane according to the present embodiment is a monolayer membrane, the monolayer membrane is preferably substantially composed of only the first fibrous material (preferably the first carbon-based fibrous material, more preferably the first carbon nanotube) and the second fibrous material (preferably the second carbon-based fibrous material, more preferably the second carbon nanotube). Here, "substantially composed of only the first fibrous material and the second fibrous material" means that 98% by mass or more (preferably 99% by mass or more, more preferably 99.9% by mass or more) of the monolayer membrane is the first fibrous material (preferably the first carbon-based fibrous material, more preferably the first carbon nanotube) and the second fibrous material (preferably the second carbon-based fibrous material, more preferably the second carbon nanotube). When the pellicle membrane is substantially composed of only the first fibrous material and the second fibrous material, a substance that is not intentionally added to the pellicle membrane and is mixed in the raw material or the manufacturing process may be contained in the pellicle membrane, but it is preferable that it is not contained.

[0048] 1 shows a cross-sectional view that shows a first example of a pellicle membrane according to the first embodiment. The present invention is not limited to the pellicle membrane shown in the figure. In addition, in the drawings in the case where the description is given with reference to the drawings in this specification, some parts are illustrated in an enlarged or reduced size in order to facilitate the description.

[0049] The pellicle membrane 100 shown in FIG. 1 is a single layer membrane. The first fibrous material 1 and the second fibrous material 2 are mixed and mutually dispersed in the pellicle membrane 100, which is a single layer membrane. The fibrous materials in FIG. 1 to FIG. 6 are shown typically, and the present invention is not limited to the shape, number, and state of the illustrated fibrous materials. In the single layer membrane, the first fibrous materials 1 may be in contact with each other, the second fibrous materials 2 may be in contact with each other, or the first fibrous material and the second fibrous material may be in contact with each other.

[0050] <Multilayer film> When the pellicle membrane according to the present embodiment is a multilayer membrane, the pellicle membrane is preferably a multilayer membrane including a first pellicle membrane and a second pellicle membrane. The first pellicle membrane and the second pellicle membrane are preferably laminated. The first pellicle membrane and the second pellicle membrane are preferably in direct contact with each other. The first pellicle membrane preferably contains a first fibrous material, and the second pellicle membrane preferably contains a second fibrous material. In the present embodiment, when the pellicle membrane is a multilayer membrane in which the first pellicle membrane and the second pellicle membrane are laminated, the first pellicle membrane is preferably exposed on one of the outermost surfaces of the multilayer membrane, and the second pellicle membrane is preferably exposed on the other outermost surface.

[0051] In the pellicle membrane according to the present embodiment, in order to easily control the void characteristics, the mass M of the first fibrous material in the multilayer membrane is FB1 and the mass M of the second fibrous material FB2 Mass ratio to (M FB1 :M FB2 ) is also preferably 45:55 to 85:15.

[0052] In the pellicle membrane according to the present embodiment, in order to easily control the void characteristics, the mass M of the first fibrous material in the multilayer membrane is FB1 and the mass M of the second fibrous material FB2 Mass ratio to (M FB1 :M FB2 ) is also preferably 48:52 to 82:18.

[0053] In the pellicle membrane according to the present embodiment, in order to easily control the void characteristics, the mass M of the first fibrous material in the multilayer membrane is FB1 and the mass M of the second fibrous material FB2 Mass ratio to (M FB1 :M FB2 ) is preferably 50:50 to 80:20.

[0054] From the viewpoint of easy control of void characteristics, the mass percentage of the first fibrous material represented by the following formula (Mathematical Formula 21) in the multilayer film is preferably 50 mass % or more and 80 mass % or less. {M FB1 / (M FB1 +M FB2 )}×100 …(Number 21)

[0055] From the viewpoint of easy control of void characteristics, the mass percentage of the second fibrous material represented by the following formula (Mathematical Formula 22) in the multilayer film is preferably 20 mass % or more and 50 mass % or less. {M FB2 / (M FB1 +M FB2 )}×100 …(number 22)

[0056] In the pellicle membrane of this embodiment, from the viewpoint of making it easier to control the void characteristics, the sum of the mass percentage of the first fibrous material in the multilayer membrane and the mass percentage of the second fibrous material in the multilayer membrane is preferably 90 mass% or more, more preferably 95 mass% or more, and even more preferably 98 mass% or more.

[0057] When the pellicle membrane according to the present embodiment is a multilayer membrane, the pellicle membrane preferably further includes a third pellicle membrane containing a third fibrous material having a length of 100 μm or more and less than 250 μm. In this case, the second pellicle membrane, the first pellicle membrane, and the third pellicle membrane are preferably laminated in this order. In the present embodiment, when the second pellicle membrane, the first pellicle membrane, and the third pellicle membrane are laminated in this order to form a multilayer membrane, it is preferable that the second pellicle membrane is exposed on one of the outermost surfaces of the multilayer membrane, and the third pellicle membrane is exposed on the outermost surface of the other. By covering both sides of the first pellicle membrane containing a relatively short first fibrous material with the second pellicle membrane containing a relatively long second fibrous material and the third pellicle membrane containing a third fibrous material, it is expected that the first fibrous material will fall off the pellicle membrane during the manufacture and operation of the pellicle membrane, and the first fibrous material will not become a foreign object. In addition, when the length of the third fibrous material is 250 μm or more, the mass (or molecular weight) per strand of the third fibrous material becomes large, as in the case of the second fibrous material. Therefore, when the content of fibrous material in the pellicle film is constant and a pellicle film PF1 in which the length range of the fibrous material is 100 μm or more and less than 250 μm is compared with a pellicle film PF2 in which the length range is 250 μm or more, the light transmittances of the pellicle film PF1 and the pellicle film PF2 are equivalent, while the number of strands of fibrous material contained in the pellicle film PF2 is reduced compared to the pellicle film PF1. When the number of strands of fibrous material in the film is reduced, the number of points where the fibrous materials contact each other is reduced, and the strength of the pellicle film is reduced. Therefore, it is preferable that the length of the third fibrous material is not excessively long.

[0058] In the pellicle membrane according to the present embodiment, the length L of the third fibrous material is set to 100 nm from the viewpoint of making it easier to control the void characteristics of the pellicle membrane and to make it easier to control the optical transparency. FB3 However, it is preferable that the thickness is 100 μm or more and 200 μm or less.

[0059] The second fibrous material and the third fibrous material are not particularly limited as long as they have a length of 100 μm or more and less than 250 μm, and the second fibrous material and the third fibrous material may be the same as or different from each other.

[0060] The third fibrous material contained in the pellicle membrane according to this embodiment is preferably a fibrous material selected from the group consisting of cellulose-based fibrous materials, polymer-based fibrous materials, bio-based fibrous materials, carbon-based fibrous materials, silicon-based fibrous materials, boron-based fibrous materials, and metal-based fibrous materials, and specific examples of these fibrous materials are the same as those described above. The first fibrous material, the second fibrous material, and the third fibrous material may be the same type of material or different types of materials, but it is preferable that the first fibrous material, the second fibrous material, and the third fibrous material are the same type of material.

[0061] The third fibrous material contained in the pellicle film according to this embodiment is preferably a carbon-based fibrous material (i.e., a third carbon-based fibrous material), and more preferably a carbon nanotube (i.e., a third carbon nanotube). In the pellicle film according to this embodiment, the second carbon-based fibrous material as the second fibrous material and the third carbon-based fibrous material as the third fibrous material may be different types of carbon-based fibrous materials, but are preferably the same type of carbon-based fibrous materials. In the pellicle film according to this embodiment, the second carbon nanotube as the second carbon-based fibrous material and the third carbon nanotube as the third carbon-based fibrous material may be the same type of carbon nanotube, or may be different types of carbon nanotube. For example, the second carbon nanotube and the third carbon nanotube may have the same number of layers constituting the carbon nanotube, or may be different. In addition, for example, the second carbon nanotube may be used as the third carbon nanotube in the third pellicle film.

[0062] When the pellicle membrane according to the present embodiment is a multilayer membrane including a first, second and third pellicle membrane, the mass M of the first fibrous material in the multilayer membrane is preferably set to 100% by weight, from the viewpoint of making it easier to control the void characteristics of the pellicle membrane. FB1 and the mass M of the second fibrous material. FB2 and the mass M of the third fibrous material FB3 The total mass M FB2 +M FB3 Mass ratio to (M FB1 :(M FB2 +M FB3 )) is preferably 33:67 to 80:20.

[0063] When the pellicle membrane according to this embodiment is a multilayer membrane including the first, second and third pellicle membranes, the mass ratio (M FB1 :(M FB2 +M FB3 )) is also preferably 20:80 to 80:20, 25:75 to 75:25, 30:70 to 70:30, 30:70 to 60:40, 30:70 to 50:50, or 30:70 to 40:60.

[0064] When the pellicle membrane of this embodiment is a multilayer membrane including a first pellicle membrane, a second pellicle membrane, and a third pellicle membrane, from the viewpoint of making it easier to control the void characteristics of the pellicle membrane, the sum of the mass percentage of the first fibrous material, the mass percentage of the second fibrous material, and the mass percentage of the third fibrous material in the multilayer membrane is preferably 80 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and even more preferably 98 mass% or more.

[0065] When the pellicle membrane according to the present embodiment is a multilayer membrane, the first pellicle membrane constituting the multilayer membrane is preferably substantially composed of only the first fibrous material (preferably the first carbon-based fibrous material, more preferably the first carbon nanotube), the second pellicle membrane is preferably substantially composed of only the second fibrous material (preferably the second carbon-based fibrous material, more preferably the second carbon nanotube), and the third pellicle membrane is preferably substantially composed of only the third fibrous material (preferably the third carbon-based fibrous material, more preferably the third carbon nanotube). Here, "substantially composed of only the first, second or third fibrous material" means that in each of the first, second or third pellicle membranes, 98% by mass or more (preferably 99% by mass or more, more preferably 99.9% by mass or more) of the membrane is the first, second or third fibrous material. When the first, second or third pellicle membrane consists essentially of the first, second or third fibrous material, respectively, substances that are not intentionally added to the pellicle membrane but are unavoidable impurities that are mixed in during the raw materials or manufacturing process may or may not be contained in the pellicle membrane.

[0066] Fig. 2 is a cross-sectional view showing a schematic diagram of a second example of the pellicle membrane according to the first embodiment. The pellicle membrane 110 shown in Fig. 2 is a multilayer membrane in which a first pellicle membrane 10 containing a first fibrous material 1 and a second pellicle membrane 20 containing a second fibrous material 2 are laminated.

[0067] Fig. 3 is a cross-sectional view showing a schematic diagram of a third example of the pellicle membrane according to the first embodiment. The pellicle membrane 120 shown in Fig. 3 is a multilayer membrane in which a first pellicle membrane 10 containing a first fibrous material 1, a second pellicle membrane 20A containing a second fibrous material 2, and a third pellicle membrane 20B containing a third fibrous material 3 are laminated.

[0068] In the pellicle membrane according to the present embodiment, it is preferable that each fibrous material (first, second, third fibrous material, etc.) is oriented in a direction along the surface of the pellicle membrane (in-plane direction). In other words, it is preferable that the long axis direction of each fibrous material (first, second, third fibrous material, etc.) is the same as the in-plane direction of the pellicle membrane.

[0069] The thickness of the entire pellicle film in this embodiment (meaning the entire monolayer film when the pellicle film is a single layer film, and the entire multilayer film when the pellicle film is a multilayer film) is not particularly limited, and is preferably 3 nm or more and 1000 nm or less. The thickness of the entire pellicle film is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. The thickness of the entire pellicle film is preferably 600 nm or less, and more preferably 300 nm or less. If the thickness of the entire pellicle film is, for example, 3 nm or more and 1000 nm or less, the strength of the pellicle film is further improved and EUV transmittance is easily ensured.

[0070] When the pellicle membrane of this embodiment is a multilayer membrane including a first pellicle membrane, a second pellicle membrane, and a third pellicle membrane, the thicknesses of the first pellicle membrane, the second pellicle membrane, and the third pellicle membrane are each independently preferably 3 nm or more and 200 nm or less, and more preferably 10 nm or more and 200 nm or less.

[0071] The mass per unit area of ​​the entire pellicle membrane is not particularly limited, and is 1 ng / mm 2 More than 30ng / mm 2 The mass per unit area of ​​the entire pellicle membrane is preferably 2 ng / mm 2 It is preferable that the concentration is 4 ng / mm 2 More preferably, the mass per unit area of ​​the entire pellicle membrane is 20 ng / mm 2 It is preferable that the concentration is less than 10 ng / mm 2 It is more preferable that the mass per unit area of ​​the entire pellicle membrane is, for example, 1 ng / mm 2 More than 30ng / mm 2 Less than or equal to 2 ng / mm 2 More than 20ng / mm 2 Less than 4 ng / mm 2 More than 10ng / mm 2If the above condition is met, the strength of the pellicle film is further improved and EUV transmittance can be easily ensured.

[0072] The pellicle membrane according to the present embodiment is preferably a porous structure formed by deposition of a fibrous material. The porous structure formed by deposition of a fibrous material can be manufactured by an example of a preferred method for manufacturing a pellicle membrane described below. If the porous structure is formed by deposition of a fibrous material, the strength of the pellicle membrane is further improved and the variation in EUV transmittance is more easily suppressed.

[0073] (Method of manufacturing pellicle membrane) The method for producing the pellicle membrane is not particularly limited and may be appropriately selected depending on the material used.

[0074] One example of a preferred method for producing a pellicle membrane containing a fibrous material includes, for example, a step (PE1) of dispersing the fibrous material, a step (PE2) of allowing the dispersed fibrous material to settle and deposit on an air-permeable member to obtain a film of the fibrous material formed in a mat shape on the air-permeable member, and a step (PE3) of removing the air-permeable member from the film of the fibrous material to obtain a pellicle membrane.

[0075] <Process PE1> First, in step PE1, a fibrous material is dispersed in a liquid to prepare a fibrous material dispersion in which the fibrous material is dispersed in the liquid. The liquid may be a liquid containing water. The fibrous material dispersion may contain only the fibrous material as a solute, or may contain various additives such as a dispersant that disperses the fibrous material in addition to the fibrous material. The dispersant is, for example, carboxymethylcellulose or sodium taurodeoxycholate. Hereinafter, the fibrous material dispersion may be referred to as an FB dispersion, and the carbon nanotube dispersion in the case where carbon nanotubes are used as the fibrous material may be referred to as a CNT dispersion.

[0076] In the case of manufacturing a pellicle membrane in which the first fibrous material and the second fibrous material are mixed in the membrane, the step PE1 preferably includes a step (PE11) of dispersing the first fibrous material in a first liquid to prepare a first dispersion, a step (PE12) of dispersing the second fibrous material in a second liquid to prepare a second dispersion, and a step (PE13) of mixing and stirring the first dispersion and the second dispersion to prepare a mixed fibrous material dispersion. Hereinafter, the mixed fibrous material dispersion may be referred to as a mixed FB dispersion, and a mixed carbon nanotube dispersion in the case where carbon nanotubes are used as the fibrous material may be referred to as a mixed CNT dispersion. The first liquid and the second liquid may be the same liquid or different liquids, but are preferably the same liquid from the viewpoint of ease of mixing, and both may be liquids containing water.

[0077] When manufacturing a multilayer film in which a first pellicle film containing a first fibrous material and a second pellicle film containing a second fibrous material are laminated, it is preferable that step PE1 includes the above-mentioned steps PE11 and PE12. In addition, when manufacturing a multilayer film in which the first pellicle film, the second pellicle film, and the third pellicle film containing the third fibrous material are laminated, the step PE1 preferably includes, in addition to the above-mentioned steps PE11 and PE12, a step (PE14) of dispersing the third fibrous material in a third liquid to prepare a third dispersion. The first liquid, the second liquid, and the third liquid may be the same or different liquids, and are preferably the same liquid from the viewpoint of ease of preparation of the dispersion, and may all be liquids containing water.

[0078] <Process PE2> Next, in step PE2, the dispersed fibrous material is precipitated and deposited on the breathable member. For example, the FB dispersion liquid prepared in step PE1 is filtered through a filtration membrane as a breathable member, whereby the fibrous material is precipitated and deposited to form a membrane of the fibrous material formed in a mat shape on the filtration membrane. For example, a membrane filter or the like is preferably used as the filtration membrane.

[0079] When manufacturing a pellicle membrane in which the first fibrous material and the second fibrous material are mixed in the membrane, it is preferable that process PE2 includes a process (PE21) of forming a membrane using the mixed FB dispersion liquid prepared in the aforementioned process PE13.

[0080] When manufacturing a multilayer film in which a first pellicle film and a second pellicle film are stacked, it is preferable that process PE2 first includes a step (PE22) of forming a first film using one of the first dispersion liquid and the second dispersion liquid, and a step (PE23) of forming a second film on the previously formed first film using the other of the first dispersion liquid and the second dispersion liquid to form a laminate of the first film and the second film.

[0081] Furthermore, when manufacturing a multilayer film in which a first pellicle film, a second pellicle film, and a third pellicle film are stacked, it is preferable that process PE2 includes a step (PE24) of forming a third film using one of the second dispersion liquid and the third dispersion liquid, a step (PE25) of forming a fourth film using the first dispersion liquid, and a step (PE26) of forming a fifth film using the other of the second dispersion liquid and the third dispersion liquid to form a laminate of the third film, the fourth film, and the fifth film.

[0082] <Process PE3> Next, in step PE3, the filtration membrane is removed from the membrane of the fibrous material formed into a mat shape to obtain a pellicle membrane containing the fibrous material. Before removing the filtration membrane from the membrane of the fibrous material formed into a mat shape, or after removing the filtration membrane from the membrane of the fibrous material formed into a mat shape, a drying step may be performed as necessary.

[0083] The pellicle membrane according to the present embodiment makes it easier to control void characteristics (e.g., void diameter and aperture ratio). The void characteristics are likely to affect foreign matter collection properties and EUV transmittance. Therefore, by using the pellicle membrane according to the present embodiment, it becomes easier to obtain a pellicle that has a good balance between foreign matter collection properties and EUV transmittance.

[0084] The pellicle membrane according to this embodiment includes a first fibrous material and a second fibrous material having different lengths. According to this embodiment, a pellicle membrane having a smaller maximum pore diameter (mesh defects) at any composition ratio of fibrous materials can be provided, compared to a pellicle membrane made of a single type of fibrous material.

[0085] When the pellicle membrane of this embodiment is a single layer membrane, the first fibrous material and the second fibrous material having different lengths are dispersed within the single layer membrane, thereby averaging the mesh structure and suppressing the occurrence of sudden non-uniform shapes (defects).

[0086] In addition, according to the present embodiment, the average pore diameter of the pellicle membrane can be controlled by adjusting the mass ratio of the first fibrous material having a short length to the second fibrous material having a long length in the monolayer membrane. The larger the ratio of the first fibrous material, the smaller the average pore diameter becomes, and the larger the ratio of the second fibrous material, the larger the average pore diameter becomes.

[0087] Furthermore, when the pellicle membrane of this embodiment is a self-supporting single layer membrane, changes in the mesh structure in the thickness direction of the pellicle membrane are suppressed, and a pellicle membrane with a uniform mesh structure can be obtained.

[0088] When the pellicle membrane according to the present embodiment is a single-layer membrane, the single-layer membrane has a simpler membrane-forming process and higher productivity than a multi-layer membrane. For example, when forming a pellicle membrane by filtration, a single-layer membrane can be formed by a single filtration operation, whereas a multi-layer membrane is formed by multiple filtration operations.

[0089] When the pellicle membrane according to the present embodiment is a self-supporting multilayer membrane, a first pellicle membrane containing a first fibrous material having a short length that ensures the membrane strength is formed, so that even if a second pellicle membrane containing a second fibrous material having a long length is combined, the decrease in membrane strength is suppressed. When comparing pellicle membranes having the same content of fibrous material in the membrane, a pellicle membrane having a higher content ratio of the first fibrous material having a short length in the membrane tends to have a higher membrane strength.

[0090] In addition, when the pellicle membrane according to the present embodiment is a self-supporting multilayer membrane, a mesh structure (pore size) having a distribution in the thickness direction of the multilayer membrane can be obtained. Therefore, a multilayer membrane having both the characteristics of the first pellicle membrane and the second pellicle membrane can be obtained.

[0091] Furthermore, since the pellicle membrane of this embodiment contains a first fibrous material and a second fibrous material within a predetermined length range, the opening rate of the voids in the pellicle membrane can be controlled within a certain range at any fibrous material composition ratio.

[0092] In this specification, the aperture ratio of the voids means the ratio of the total area of ​​the voids per unit area of ​​the surface of the pellicle film. The aperture ratio is expressed as a percentage. In a pellicle film, the aperture ratio is related to the light transmittance of the film, and the larger the aperture ratio, the larger the light transmittance of the film tends to be.

[0093] In this specification, the void diameter means the diameter of a hypothetical circle having the same area as the area of ​​the void (that is, the equivalent circle diameter).

[0094] In the void characteristics measured on the surface of the porous structure of the pellicle membrane, the void characteristics of the aperture ratio and the average void diameter may be measured by a method having the following steps (1) to (10). By adopting the following measurement method, a unique threshold value is determined, so that a plausible result is likely to be obtained regardless of the person performing the measurement. The measurement method of the void characteristics is specifically as shown in the examples described later.

[0095] (1) Preparing a pellicle membrane. (2) imaging the surface of the prepared pellicle membrane to obtain image data of the pellicle membrane; (3) setting three or more different thresholds as initial thresholds at equal intervals within a range from a first pixel value to a second pixel value greater than the first pixel value, performing binarization processing based on each of the initial thresholds, and obtaining binarized image data based on the initial thresholds. (4) A step of obtaining an initial measured value by calculating the distribution of void characteristics of voids on the surface of the pellicle membrane by performing blob analysis on the binarized image data based on the initial threshold value. (5) A step of calculating an initial theoretical value of the distribution of void characteristics calculated by a probability density function of a log-normal distribution based on the initial measured value. (6) A step of determining an error between the initial measured value and the initial theoretical value. (7) If the error between the initial actual value and the initial theoretical value is not the smallest, the threshold is reset, a binarization process is performed on the image data based on the reset threshold, binarization process image data based on the reset threshold is obtained, and a re-measurement actual value is obtained by calculating the distribution of void characteristics of voids on the surface of the pellicle membrane by performing blob analysis on the binarization process image data based on the reset threshold. (8) A step of calculating an error between the remeasured theoretical value and the distribution of void characteristics calculated by a probability density function of a log-normal distribution, based on the remeasured actual value. (9) If the error between the actual value of the re-measurement and the theoretical value of the re-measurement is not the smallest, a step of obtaining the actual value of the re-measurement and a step of determining the error between the actual value of the re-measurement and the theoretical value of the re-measurement are repeated until the error between the actual value of the re-measurement and the theoretical value of the re-measurement is smallest. (10) A step of obtaining a distribution of void characteristics as a final actual measurement value, the distribution being calculated based on a threshold value at which the error between the initial actual measurement value and the initial theoretical value, or the error between the re-measured actual measurement value and the re-measured theoretical value, is smallest.

[0096] The threshold value at which the error is minimized is preferably determined by using various known optimization algorithms. For example, in the above steps (4) to (9), the threshold value at which the error is minimized is preferably searched for by using various known optimization algorithms. In this case, after the initial threshold value is determined, a unique threshold value is determined by using the optimization algorithm.

[0097] In the step of acquiring the binarized image data based on the initial threshold value, the initial threshold value is not limited to the above, and may be set to 5 or more different threshold values ​​at equal intervals within a range from a first pixel value to a second pixel value greater than the first pixel value, or may be set to 7 or more different threshold values. The interval between the first pixel value and the second pixel value is preferably 100 or more. The first pixel value is preferably set in a range of 20 to 50. The second pixel value is preferably set in a range of 150 to 240. The equal intervals indicate that the intervals between adjacent threshold values ​​are equal, such as when n threshold values ​​are set as the 3 or more different threshold values, the interval between the nth threshold value and the n-1th threshold value and the interval between the n-1th threshold value and the n-2th threshold value are both equal. Specifically, the initial threshold value may be set to 3 or more and 12 or less different threshold values ​​at equal intervals within a range from a pixel value of 20 to a pixel value of 240. In the step of obtaining the actual value of the remeasurement, the threshold value that is reset is not three or more different threshold values ​​but a single threshold value.

[0098] The void characteristics may be measured, for example, by an apparatus having a program that causes a computer to execute the above steps (1) to (10). The program may be recorded on a recording medium.

[0099] Second Embodiment Next, the configuration of the pellicle according to the second embodiment will be described. In the description of the second embodiment, the same components as those in the first embodiment will be given the same reference numerals or names, and the description will be omitted or simplified. In the second embodiment, for structures and materials that are not specifically mentioned, the same structures and materials as those described in the first embodiment can be used.

[0100] (Pellicle) The pellicle according to this embodiment comprises the pellicle membrane according to the first embodiment and a support.

[0101] (Support) The support supports the pellicle membrane. The support has a frame and an opening surrounded by the frame. The frame has a support surface that supports the pellicle membrane. The opening penetrates from one surface of the support to the other surface. The frame and the opening are both formed in a rectangular shape. In this embodiment, all four corners of the outer shape of the frame are rounded, but the shape of the frame is not limited to such a shape. As the material of the support, a known material can be used, for example, a resin material (polyethylene, etc.), a metal material (aluminum, aluminum alloy, magnesium alloy, stainless steel, titanium, titanium alloy, Invar, etc.), a ceramic material (SiC, SiN, etc.), quartz, and a fiber-reinforced plastic material (carbon fiber-reinforced plastic, glass fiber-reinforced plastic, etc.).

[0102] 4, 5, and 6 are cross-sectional views each showing a first example, a second example, and a third example of a pellicle according to the second embodiment. The present invention is not limited to the pellicles shown in the drawings. In the drawings, some parts are shown enlarged or reduced in size to facilitate the explanation.

[0103] The pellicle 200 shown in FIG. 4 has a pellicle film 100 according to the first embodiment and a support 30. The pellicle film 100 has a first pellicle film surface 101 and a second pellicle film surface 102 opposite to the first pellicle film surface 101. The support 30 has a frame portion 31 and an opening 32 surrounded by the frame portion 31. The frame portion 31 has a support surface 34 facing the pellicle film 100. Specifically, the support surface 34 faces the first pellicle film surface 101 of the pellicle film 100 when supporting the pellicle film 100. The opening 32 penetrates from one surface of the support 30 to the other surface. The frame portion 31 and the opening 32 are both formed in a rectangular shape. In pellicle 200 , the first pellicle film surface 101 side of peripheral portion 103 of pellicle film 100 is attached or fixed to support surface 34 of frame portion 31 , and pellicle film 100 covers opening 32 .

[0104] 5 has a pellicle film 110 according to the first embodiment, and a support 30. The pellicle film 110 has a first pellicle film surface 111 and a second pellicle film surface 112 opposite the first pellicle film surface 111. In the pellicle 210, the first pellicle film surface 111 side of the peripheral portion 113 of the pellicle film 110 (i.e., the second pellicle film 20) is attached or fixed to the support surface 34 of the frame portion 31. Another example of a pellicle according to the second embodiment is a pellicle in which the second pellicle film surface 112 side of the pellicle film 110 (i.e., the first pellicle film 10) is attached or fixed to the support surface 34 of the frame portion of the support 30.

[0105] 6 includes a pellicle film 120 according to the first embodiment and a support 30. The pellicle film 120 includes a first pellicle film surface 121 and a second pellicle film surface 122 opposite the first pellicle film surface 121. In the pellicle 220, the first pellicle film surface 121 side of the peripheral portion 123 of the pellicle film 120 (i.e., the second pellicle film 20A) is attached or fixed to the support surface 34 of the frame portion 31. Another example of a pellicle according to the second embodiment is a pellicle in which the second pellicle film surface 122 side of the pellicle film 120 (i.e., the third pellicle film 20B) is attached or fixed to the support surface 34 of the frame portion of the support 30.

[0106] (Method of manufacturing a pellicle) Next, a method for manufacturing a pellicle according to a second embodiment (hereinafter, may be referred to as the manufacturing method according to the second embodiment) will be described. An example of the manufacturing method of the second embodiment includes a step (P1) of preparing the pellicle membrane according to the first embodiment, a step (P2) of preparing a support having a frame and an opening surrounded by the frame and supporting the pellicle membrane, and a step (P3) of providing the pellicle membrane on the support so as to cover the opening and be supported by the support surface of the frame. If necessary, the method may include a step (P4) of providing an adhesive layer on at least a part of the support surface of the frame.

[0107] In the step (P1) of preparing a pellicle membrane, the pellicle membrane according to the first embodiment may be prepared. In the step (P2) of preparing a support, a support formed in a desired shape using the material constituting the support described above may be prepared by a known method. In the step (P3) of providing a pellicle membrane, the pellicle membrane may be installed by a known method so as to cover the opening and be supported by the support surface of the frame. When an adhesive layer is provided on at least a part of the support surface of the frame, the pellicle membrane is installed via the adhesive layer so as to be supported by the support surface of the frame. When various adhesives are used for the adhesive layer, the step of providing the adhesive layer includes applying an adhesive to the support surface to provide an adhesive layer containing the adhesive. When a fibrous material is used for the adhesive layer, the step of providing the adhesive layer includes applying a dispersion of the fibrous material to the support surface and drying the same to provide an adhesive layer containing the fibrous material, for example.

[0108] The pellicle according to this embodiment is used, for example, by being disposed above the photomask and spaced apart from the photomask so that the first pellicle film surface faces the photomask.

[0109] The pellicle according to this embodiment includes the pellicle membrane according to the first embodiment. Therefore, according to this embodiment, it is possible to provide a pellicle with controlled void characteristics (for example, void diameter and aperture ratio).

[0110] [Modifications of the embodiment] The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention. Although an example of the pellicle membrane according to the first embodiment and the pellicle according to the second embodiment have been described with reference to Figures 1 to 6, the pellicle membrane and pellicle according to the present invention are not limited to these examples of the embodiment.

[0111] The pellicle according to the present invention may adopt various forms as long as the effects of the pellicle membrane according to the first embodiment and the pellicle according to the second embodiment can be obtained. The shapes and dimensions of each part of each member constituting the pellicle membrane according to the first embodiment and the pellicle according to the second embodiment may be determined, for example, according to the dimensions of a photomask (not shown) when the pellicle according to the second embodiment is used.

[0112] Furthermore, for example, the shape of the pellicle membrane attached to the support is often rectangular, but the shape of the pellicle membrane of the present invention is not limited to rectangular, and may be formed according to any desired shape (e.g., the shape of a photomask), such as circular, elliptical, and polygonal.

[0113] Also, for example, the pellicle membrane, which is a multilayer membrane, may include a fourth pellicle membrane containing a fourth fibrous material having a length of 20 μm or less (preferably, 1 μm or more and 20 μm or less). In this case, it is preferable that the first pellicle membrane, the second pellicle membrane, and the fourth pellicle membrane are laminated in this order. The first fibrous material and the fourth fibrous material are not particularly limited as long as they have a length of 1 μm or more and 20 μm or less, and the first fibrous material and the fourth fibrous material may be the same as or different from each other. The fourth fibrous material is preferably a fibrous material selected from the group consisting of cellulose-based fibrous materials, polymer-based fibrous materials, bio-based fibrous materials, carbon-based fibrous materials, silicon-based fibrous materials, boron-based fibrous materials, and metal-based fibrous materials, and specific examples of these fibrous materials are the same as those described above. The first fibrous material, the second fibrous material, and the fourth fibrous material may be the same type of material or different types of materials, but it is preferable that the first fibrous material, the second fibrous material, and the fourth fibrous material are the same type of material. The fourth fibrous material is preferably a carbon-based fibrous material (i.e., a fourth carbon-based fibrous material), and more preferably a carbon nanotube (i.e., a fourth carbon nanotube). For example, the first carbon-based fibrous material as the first fibrous material and the fourth carbon-based fibrous material as the fourth fibrous material may be different types of carbon-based fibrous materials, but it is preferable that they are the same type of carbon-based fibrous material. In addition, the first carbon nanotube as the first carbon-based fibrous material and the fourth carbon nanotube as the fourth carbon-based fibrous material may be the same type of carbon nanotube or different types of carbon nanotube. For example, the first carbon nanotube and the fourth carbon nanotube may have the same number of layers constituting the carbon nanotube, or may be different.

[0114] When the pellicle membrane is a multilayer membrane, the number of pellicle membranes is preferably 2 or 3 as in the above embodiment, but may be a multilayer membrane consisting of 4 or more membranes. Each pellicle membrane constituting the multilayer membrane can be a combination of a membrane containing a long fibrous material and a membrane containing a short fibrous material according to the desired characteristics.

[0115] For example, at least one of a first pellicle membrane consisting essentially of the first fibrous material and a second pellicle membrane consisting essentially of the second fibrous material may be laminated on one or both membrane surfaces of the aforementioned monolayer membrane in which the first fibrous material and the second fibrous material are mixed. Furthermore, for example, the above-mentioned monolayer membrane containing a mixture of the first fibrous material and the second fibrous material may be laminated on one or both sides of the membrane surface of at least one of a first pellicle membrane consisting essentially of the first fibrous material and a second pellicle membrane consisting essentially of the second fibrous material.

[0116] In this specification, the terms 1, 2, 3, 4, and 5 are used to distinguish the elements to which they are attached, and do not limit the order of the elements, unless otherwise specified. In addition, in this specification, a numerical range expressed using "~" means a range including the values ​​written before and after "~". EXAMPLES

[0117] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0118] [Example 1] In Example 1, carbon nanotubes were used as the fibrous material. First, a first dispersion in which a first carbon nanotube is dispersed in water and a second dispersion in which a second carbon nanotube is dispersed in water were prepared. The first carbon nanotube had a length of 1 μm or more and 20 μm or less and an aspect ratio of 1000 or more and 15000 or less, and the second carbon nanotube had a length of 100 μm or more and less than 250 μm and an aspect ratio of 10000 or more and 300000 or less. The first dispersion and the second dispersion each contained carboxymethylcellulose as a dispersant, and the carbon nanotube concentration in each of the first dispersion and the second dispersion was 0.1 ppm by mass, and the dispersant concentration was 10 ppm by mass. Next, the first dispersion liquid and the second dispersion liquid were mixed and stirred to prepare a mixed CNT dispersion liquid, in which the mass ratio of the first carbon nanotubes to the second carbon nanotubes in the mixed CNT dispersion liquid was set to 90:10. Next, the mixed CNT dispersion liquid was filtered using a membrane filter to form a circular pellicle film with a diameter of 2 mm (2 mmΦ) on the membrane filter. The mass per unit area of ​​the entire pellicle film, which is the amount of carbon nanotubes in the pellicle film (the total amount of the first carbon nanotubes and the second carbon nanotubes), was set to 1.0 μg / cm 2 (10ng / mm 2 ) was decided. Next, the entire membrane filter with the pellicle membrane was submerged in water to isolate the pellicle membrane above the water surface. The isolated pellicle membrane was dried to obtain the pellicle membrane of Example 1 (single layer membrane).

[0119] [Example 2] The pellicle film (single layer film) of Example 2 was obtained by film formation in the same manner as in Example 1, except that the mass ratio of the first carbon nanotubes to the second carbon nanotubes in the mixed CNT dispersion was prepared to be 50:50.

[0120] [Example 3] The pellicle film (single layer film) of Example 3 was obtained by film formation in the same manner as in Example 1, except that the mass ratio of the first carbon nanotubes to the second carbon nanotubes in the mixed CNT dispersion was prepared to be 10:90.

[0121] [Example 4] First, the same second dispersion liquid as in Example 1 was filtered using a membrane filter, and a circular second pellicle membrane with a diameter of 2 mm (2 mmΦ) was formed on the membrane filter. Next, the same first dispersion liquid as in Example 1 was poured onto the second pellicle membrane and filtered to form a first pellicle membrane on top of the second pellicle membrane, the first pellicle membrane having approximately the same shape and size as the second pellicle membrane. Next, the entire membrane filter with the pellicle membrane, in which the first pellicle membrane and the second pellicle membrane were laminated, was submerged in water to isolate the pellicle membrane above the water surface. The isolated pellicle membrane was dried to obtain a pellicle membrane (multilayer membrane) according to Example 4. The mass per unit area of ​​the entire pellicle membrane, as the amount of carbon nanotubes in the pellicle membrane (multilayer membrane) according to Example 4 (the total amount of the first carbon nanotubes and the second carbon nanotubes), was 1.0 μg / cm 2 (10ng / mm 2 ) and the mass ratio of the first carbon nanotube to the second carbon nanotube was 80:20.

[0122] [Example 5] The pellicle film (multilayer film) according to Example 5 was obtained by film formation in the same manner as in Example 4, except that the mass ratio of the first carbon nanotubes to the second carbon nanotubes in the multilayer film was 50:50.

[0123] [Example 6] The pellicle film (multilayer film) according to Example 6 has a mass per unit area of ​​the entire pellicle film as the amount of carbon nanotubes in the multilayer film (the total amount of the first carbon nanotubes and the second carbon nanotubes) of 0.8 μg / cm 2 (8ng / mm 2 A film was formed in the same manner as in Example 5, except that the above-mentioned step (1) was changed to the above-mentioned step (1).

[0124] [Example 7] The pellicle membrane (multilayer membrane) of Example 7 was obtained by film formation in the same manner as in Example 5, except that a first pellicle membrane was first formed on a membrane filter using a first dispersion liquid, and then a second pellicle membrane of approximately the same shape and size as the first pellicle membrane was formed on top of the first pellicle membrane using a second dispersion liquid.

[0125] [Example 8] First, the same second dispersion liquid as in Example 1 was filtered using a membrane filter, and a circular second pellicle membrane with a diameter of 2 mm (2 mmΦ) was formed on the membrane filter. Next, the same first dispersion liquid as in Example 1 was poured and filtered to form a first pellicle membrane on the second pellicle membrane, the first pellicle membrane having approximately the same shape and size as the second pellicle membrane. Next, the same second dispersion as in Example 1 was poured as a third dispersion and filtered to form a third pellicle membrane on the first pellicle membrane having approximately the same shape and size as the first pellicle membrane. Next, the entire membrane filter with the pellicle membranes, in which the second pellicle membrane, the first pellicle membrane and the third pellicle membrane were laminated in this order, was submerged in water to isolate the pellicle membranes above the water surface. The isolated pellicle membrane was dried to obtain a pellicle membrane (multilayer membrane) according to Example 8. The mass per unit area of ​​the entire pellicle membrane, as the amount of carbon nanotubes in the pellicle membrane (multilayer membrane) according to Example 8 (the total amount of the first carbon nanotube, the second carbon nanotube, and the third carbon nanotube), was 1.0 μg / cm 2 (10ng / mm 2 ), and the mass ratio of the first carbon nanotube, the second carbon nanotube, and the third carbon nanotube was 33:33:33 (=1:1:1).

[0126] [Reference example 1] First, the same first dispersion liquid as in Example 1 was filtered using a membrane filter to form a circular first pellicle film with a diameter of 2 mm (2 mmΦ) on the membrane filter. The amount of carbon nanotubes in the pellicle film (first carbon nanotube amount) was 1.0 μg / cm 2 (10ng / mm 2 Next, the entire membrane filter with the pellicle membrane was submerged in water, and the pellicle membrane was isolated on the water surface. The isolated pellicle membrane was dried to obtain a pellicle membrane (single layer membrane) according to Reference Example 1.

[0127] [Comparative Example 1] The pellicle membrane (single layer membrane) according to Comparative Example 1 was obtained in the same manner as in Reference Example 1, except that the second pellicle membrane was formed using the same second dispersion liquid as in Example 1 instead of the first dispersion liquid.

[0128] <Formability of pellicle film> In order to evaluate the film-forming properties of the pellicle membrane, in addition to the circular pellicle membrane with a diameter of 2 mm (2 mmΦ) described above, a pellicle membrane with a larger area of ​​1 cm square (1 cm × 1 cm) was produced. Except for changing the film size, the film was produced in the same manner as described above. The evaluation results of the film formability of the pellicle film are shown in Table 1. The evaluation criteria are as follows. "A": A pellicle membrane measuring 1 cm square was successfully produced. "C": It was not possible to produce a pellicle membrane measuring 1 cm square.

[0129] In Examples 1 to 8, a pellicle membrane measuring 1 cm square could be formed, and therefore the evaluation was given an "A" rating. In Comparative Example 1, a pellicle membrane with a size of 1 cm square could not be produced, and therefore the evaluation was rated as "C." The amount of carbon nanotubes in each pellicle membrane of the Examples, Reference Examples, and Comparative Examples was set to 1.0 μg / cm in terms of the light transmittance of the membrane. 2When the length of the first carbon nanotube is adjusted to 1 cm, the pellicle film of Comparative Example 1 contains fewer carbon nanotubes than Example 1, because the pellicle film of Comparative Example 1 uses only the second carbon nanotubes that are longer than the first carbon nanotubes. Therefore, in the pellicle film of Comparative Example 1, there are fewer points where the carbon nanotubes contact each other compared to Example 1, and the strength of the film is lower, which is thought to be why a pellicle film with a size of 1 cm square could not be formed. Note that in Comparative Example 1, a pellicle film of a size (diameter 2 mm) applicable to SEM observation could be formed.

[0130] <Analysis of voids in pellicle membrane> (average pore diameter, maximum pore diameter and opening ratio) The surface of the pellicle film obtained in each example was observed with an SEM (Carl Zeiss, product name: CrossBeam550), and image data of six SEM images was obtained. The imaging conditions were an acceleration voltage of 1 kV and a magnification of 10,000 times. When the pellicle film was a multilayer film, the SEM observation was performed from the second pellicle film side. SEM is an abbreviation for Scanning Electron Microscope. Fig. 7 shows an SEM image of the pellicle film according to Example 5. Fig. 7 is an SEM image of the pellicle film of Example 5 observed from the second pellicle film side. As shown in Fig. 7, the second pellicle film containing the long second carbon nanotubes was observed on the front side, and the first pellicle film containing the short first carbon nanotubes was observed to be formed on the back side.

[0131] From the image data of the obtained SEM image, the pore diameter (pore size) was analyzed as a circle equivalent diameter. First, for one field of view of the image data of the SEM image, the initial binarization threshold was set at 7 points of 40, 60, 80, 100, 120, 140, and 160 at equal intervals of 20 pixel values ​​between pixel value 40 and pixel value 160, and 7 points of binarized processed image data were obtained at each binarization threshold. This operation was performed for image data of 3 or more fields of view. Next, the initial pore diameter distribution based on the initial binarization threshold was measured for the obtained binarized processed image data. Then, a binarization threshold that minimizes the error between the actual pore diameter distribution value and the theoretical pore diameter distribution value was automatically searched for by fitting using Bayesian optimization so that the actual pore diameter distribution value closely approximates (fits) the log-normal distribution. Then, the average pore diameter (average pore diameter), maximum pore diameter (maximum pore diameter), and opening rate were calculated from the pore diameter distribution and the opening rate distribution measured based on the binarization threshold when the error between the actual pore diameter distribution value and the theoretical pore diameter distribution value was minimized.

[0132] The evaluation results of the void characteristics of the pellicle membrane are shown in Table 1. The evaluation criteria are as follows:

[0133] <Evaluation criteria for average pore diameter> "A": The average pore diameter was within the range between Reference Example 1 and Comparative Example 1.

[0134] <Evaluation criteria for aperture ratio> “A”: The aperture ratio was within the range of ±5% of the aperture ratio of Reference Example 1.

[0135] <Evaluation criteria for maximum pore diameter> "A": The maximum pore diameter was 200 nm or less. “B”: The maximum pore diameter was smaller than the maximum pore diameter of Reference Example 1.

[0136] Regarding the notation of the film configuration in Table 1, "1st / 2nd" indicates that the second pellicle film is formed first, and then the first pellicle film is formed, so that the first pellicle film is laminated on the second pellicle film. "2nd / 1st" indicates that the first pellicle film is formed first, and then the second pellicle film is formed, so that the second pellicle film is laminated on the first pellicle film. "3rd / 1st / 2nd" indicates that the second pellicle film is formed first, and then the first pellicle film is formed, and then the third pellicle film is formed, so that the second pellicle film, the first pellicle film, and the third pellicle film are laminated in that order. In addition, in Table 1, carbon nanotubes are abbreviated as "CNT."

[0137] [Table 1]

[0138] As shown in Table 1, when the mass ratio of each carbon nanotube contained in the film was changed in Examples 1 to 8, the average pore diameter of the pellicle membranes of Examples 1 to 8 showed a value between the average pore diameter of the pellicle membrane of Reference Example 1 and the average pore diameter of the pellicle membrane of Comparative Example 1. In other words, it was found that by changing the mass ratio of each carbon nanotube, a pellicle membrane having a desired average pore diameter can be obtained.

[0139] Furthermore, as shown in Table 1, when the mass ratio of each carbon nanotube contained in the film was changed in Examples 1 to 8, no significant difference was observed in the aperture ratio contributing to the light transmittance of the pellicle film (it was at the same level) compared to Reference Example 1. Thus, it was found that even when the mass ratio of each carbon nanotube was changed, a significant fluctuation in the aperture ratio was suppressed, and the light transmittance was guaranteed.

[0140] The maximum pore diameter is an index that reflects the presence of large pores (voids) in the SEM image of the pellicle membrane. As shown in Table 1, the maximum pore diameter of the pellicle membrane of Reference Example 1 was large. On the other hand, the maximum pore diameters of the pellicle membranes of Examples 1 to 8 were sufficiently smaller than that of Reference Example 1, and it was found that large pores were not formed suddenly in the pellicle membrane.

[0141] From the above, a pellicle film having desired void characteristics was obtained by including carbon nanotubes as multiple types of fibrous materials satisfying different length ranges in a single layer film or a multilayer film as in the pellicle films of Examples 1 to 8. Therefore, it was found that the pellicle film according to the present invention makes it easier to control the void characteristics. It is expected that a pellicle film having desired void characteristics can be obtained, similar to the case of using carbon nanotubes, even if a material other than carbon nanotubes is used as the fibrous material. [Explanation of symbols]

[0142] 1...first fibrous material, 2...second fibrous material, 3...third fibrous material, 10...first pellicle membrane, 20...second pellicle membrane, 20A...second pellicle membrane, 20B...third pellicle membrane, 30...support, 31...frame, 32...opening, 34...support surface, 100...pellicle membrane, 101...first pellicle membrane surface, 102...second pellicle membrane surface, 103...periphery, 110...pellicle membrane, 111...first pellicle membrane surface, 112...second pellicle membrane surface, 113...periphery, 120...pellicle membrane, 121...first pellicle membrane surface, 122...second pellicle membrane surface, 123...periphery, 200...pellicle, 210...pellicle, 220...pellicle.

Claims

1. A pellicle membrane, comprising: The pellicle membrane is a single layer membrane, The pellicle membrane contains carbon nanotubes as a first fibrous material and carbon nanotubes as a second fibrous material, the first fibrous material and the second fibrous material are mixed in the monolayer film, The length L of the first fibrous material ＦＢ１ is 20 μm or less, The length L of the second fibrous material ＦＢ２ is 100 μm or more and less than 250 μm, The sum of the mass percentage of the first fibrous material in the monolayer film and the mass percentage of the second fibrous material in the monolayer film is 90 mass% or more. Pellicle membrane.

2. 2. The pellicle membrane according to claim 1, The mass M of the first fibrous material in the monolayer ＦＢ１ and the mass M of the second fibrous material ＦＢ２ Mass ratio to (M ＦＢ１ : M ＦＢ２ ) is 10:90 to 90:

10.

3. The pellicle membrane according to claim 1 or 2, A pellicle membrane, wherein the sum of the mass percentage of the first fibrous material in the monolayer membrane and the mass percentage of the second fibrous material in the monolayer membrane is 95 mass% or more.

4. A pellicle membrane, The pellicle membrane contains carbon nanotubes as a first fibrous material and carbon nanotubes as a second fibrous material, The pellicle film is a multi-layer film including a first pellicle film and a second pellicle film, The first pellicle film and the second pellicle film are laminated, the first pellicle membrane includes the first fibrous material; the second pellicle membrane comprises the second fibrous material; The length LFB1 of the first fibrous material is 20 μm or less; The length LFB2 of the second fibrous material is 100 μm or more and less than 250 μm; The sum of the mass percentage of the first fibrous material in the multilayer film and the mass percentage of the second fibrous material in the multilayer film is 90 mass% or more. Pellicle membrane.

5. The pellicle membrane according to claim 4, The mass M of the first fibrous material in the multilayer film ＦＢ１ and the mass M of the second fibrous material ＦＢ２ Mass ratio to (M ＦＢ１ : M ＦＢ２ ) is 50:50 to 80:

20.

6. The pellicle membrane according to claim 4 or 5, A pellicle membrane, wherein the sum of the mass percentage of the first fibrous material in the multilayer film and the mass percentage of the second fibrous material in the multilayer film is 95 mass% or more.

7. A pellicle membrane, The pellicle membrane contains carbon nanotubes as a first fibrous material, carbon nanotubes as a second fibrous material, and carbon nanotubes as a third fibrous material; The pellicle film is a multi-layer film including a first pellicle film, a second pellicle film, and a third pellicle film, The second pellicle film, the first pellicle film, and the third pellicle film are stacked in this order, the first pellicle membrane includes the first fibrous material; the second pellicle membrane comprises the second fibrous material; the third pellicle membrane comprises the third fibrous material; The length LFB1 of the first fibrous material is 20 μm or less; The length LFB2 of the second fibrous material is 100 μm or more and less than 250 μm; The third fibrous material has a length LFB3 of 100 μm or more and less than 250 μm; the second fibrous material and the third fibrous material are the same or different from each other; The sum of the mass percentage of the first fibrous material, the mass percentage of the second fibrous material, and the mass percentage of the third fibrous material in the multilayer film is 80 mass% or more. Pellicle membrane.

8. The pellicle membrane according to claim 7, The mass M of the first fibrous material in the multilayer film ＦＢ１ and the mass M of the second fibrous material. ＦＢ２ and the mass M of the third fibrous material ＦＢ３ The total mass M ＦＢ２ +M ＦＢ３ Mass ratio to (M ＦＢ１ :(M ＦＢ２ +M ＦＢ３ ) is 33:67 to 80:

20.

9. The pellicle membrane according to claim 7, A pellicle membrane, wherein the sum of the mass percentage of the first fibrous material, the mass percentage of the second fibrous material, and the mass percentage of the third fibrous material in the multilayer membrane is 90 mass% or more.

10. The pellicle membrane according to claim 1, claim 4 or claim 7, The length L of the first fibrous material ＦＢ１ A pellicle membrane having a thickness of 1 μm or more and 20 μm or less.

11. The pellicle membrane according to claim 1, claim 4 or claim 7, The length L of the second fibrous material ＦＢ２ A pellicle membrane having a thickness of 100 μm or more and 200 μm or less.

12. The pellicle membrane according to claim 1, claim 4 or claim 7, A pellicle membrane that is self-supporting.

13. A pellicle membrane according to claim 1, claim 4 or claim 7; A pellicle comprising a support having a frame and an opening surrounded by the frame, the support supporting the pellicle membrane.

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