Carbon nanotube pellicle film, pellicle, exposure original plate, exposure device, and method for producing carbon nanotube pellicle film

Abstract

A carbon nanotube pellicle film according to the present disclosure has a fractal dimension of 2.70 or greater.

Description

Carbon nanotube pellicle film, pellicle, exposure master, exposure device, and method for manufacturing carbon nanotube pellicle film

[0001] The present disclosure relates to a carbon nanotube pellicle film, a pellicle, an exposure master, an exposure apparatus, and a method for manufacturing a carbon nanotube pellicle film.

[0002] The miniaturization of semiconductor integrated circuits is being driven by photolithography. Photolithography uses a transparent substrate (hereinafter referred to as a "photomask") with a pattern formed on one side. A pellicle is attached to the photomask to prevent foreign matter (e.g., dust, etc.) from adhering to the surface of the photomask. The pellicle includes a pellicle film through which exposure light passes and a pellicle frame that supports the pellicle film.

[0003] Patent Document 1 discloses a pellicle film used in extreme ultraviolet lithography using extreme ultraviolet (hereinafter also referred to as "EUV"). The pellicle film disclosed in Patent Document 1 includes a plurality of carbon nanotubes (hereinafter also referred to as "CNTs") that form a network structure. The thickness of the network structure is 3 nm to 100 nm. The network structure has an EUV transmittance of 92% or more. The plurality of CNTs includes at least 50% or more double-walled carbon nanotubes.

[0004] Patent Document 1: International Publication No. 2022 / 060877

[0005] In extreme ultraviolet lithography, EUV exposure is performed by moving a pellicle-attached photomask, which has a pellicle attached to it, at high speed. If the pellicle film is relatively thick, the EUV transmittance may decrease, and EUV exposure may take a long time. On the other hand, if the pellicle film is thin, the pellicle film may be prone to rupture. Therefore, there is a demand for a pellicle film that is less likely to rupture even when thin.

[0006] The present disclosure has been made in consideration of the above circumstances. An object of one embodiment of the present disclosure is to provide a carbon nanotube pellicle film that is resistant to rupture even when the film thickness is thin, a pellicle, an exposure master, an exposure apparatus, and a method for manufacturing a carbon nanotube pellicle film.

[0007] The means for solving the above problems include the following embodiments.

[0008] <1> A carbon nanotube pellicle film having a fractal dimension of 2.70 or more. <2> The carbon nanotube pellicle film according to <1>, comprising a plurality of carbon nanotubes having tube diameters of 0.8 nm to 6.0 nm, wherein the content of the plurality of carbon nanotubes is 30% or more relative to the total amount of the carbon nanotube pellicle film. <3> The carbon nanotube pellicle film according to <1> or <2>, comprising a plurality of single-walled carbon nanotubes, wherein the content of the plurality of single-walled carbon nanotubes is 30% or more relative to the total amount of the carbon nanotube pellicle film. <4> The carbon nanotube pellicle film according to any one of <1> to <3>, wherein the ratio (G / D) is 5 or more, wherein the ratio (G / D) represents the ratio of the G band intensity measured by resonance Raman scattering measurement to the D band intensity measured by resonance Raman scattering measurement. <5> The carbon nanotube pellicle film according to any one of <1> to <4>, wherein the transmittance of extreme ultraviolet light is 88% or more. <6> The carbon nanotube pellicle film according to any one of <1> to <5>, having a maximum stress of 120 MPa or more. <7> The carbon nanotube pellicle film according to any one of <1> to <6>, having a deflection of 200 μm or less when made into a square with sides of 1 cm. <8> A pellicle comprising: a pellicle frame; and the carbon nanotube pellicle film according to any one of <1> to <7>, supported by the pellicle frame. <9> An exposure master comprising: a photomask; and the pellicle according to <8>, attached to the photomask. <10> An exposure apparatus comprising: an extreme ultraviolet light source that emits extreme ultraviolet light as exposure light; an exposure master according to <9>; and an optical system that guides the exposure light emitted from the extreme ultraviolet light source to the exposure master, wherein the exposure master is positioned so that the extreme ultraviolet light emitted from the extreme ultraviolet light source passes through the carbon nanotube pellicle film and is irradiated onto the photomask.<11> A method for producing a carbon nanotube pellicle film according to any one of <1> to <7>, comprising: preparing a carbon nanotube raw material; and forming a dispersion containing the carbon nanotube raw material into a film to produce the carbon nanotube pellicle film, wherein a ratio (G / D) of the carbon nanotube raw material is 160 to 500, and the ratio (G / D) represents a ratio of a G band intensity measured by resonance Raman scattering measurement to a D band intensity measured by resonance Raman scattering measurement. <12> A method for producing a carbon nanotube pellicle film according to <11>, wherein the carbon nanotube raw material contains single-walled carbon nanotubes synthesized by a modified direct injection pyrolysis synthesis method.

[0009] According to one embodiment of the present disclosure, there are provided a carbon nanotube pellicle film that is resistant to rupture even when the film thickness is thin, a pellicle, an exposure master, an exposure apparatus, and a method for manufacturing a carbon nanotube pellicle film.

[0010] Fig. 1 is a diagram showing the configuration of an information processing device used for the calculation process of fractal dimension. Fig. 2 is a flowchart of the calculation process of fractal dimension. Fig. 3 is a schematic diagram showing a measurement device in a bulge test. Fig. 4 is a graph showing the pressure difference between the inside and outside of a pellicle versus elapsed time in a bulge test.

[0011] In this disclosure, numerical ranges indicated using "to" mean ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In numerical ranges described in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the Examples. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, when multiple substances corresponding to each component are present, the amount of each component refers to the total amount of multiple substances unless otherwise specified. In this disclosure, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. In this disclosure, "extreme ultraviolet radiation" (hereinafter also referred to as "EUV") refers to light with a wavelength of 1 nm to 30 nm. The wavelength of EUV is preferably 5 nm to 13.5 nm.

[0012] (1) Carbon Nanotube Pellicle Film The carbon nanotube pellicle film (hereinafter also referred to as "CNT pellicle film") of the present disclosure has a fractal dimension of 2.70 or more.

[0013] "Fractal dimension" refers to a numerical value that represents the complexity of a material surface. Typically, multiple carbon nanotube aggregates (hereinafter also referred to as "CNT aggregates") are present on the surface of a CNT pellicle film. The fractal dimension of a CNT pellicle film represents the degree of variation in the size of multiple CNT aggregates contained on the surface of the CNT pellicle film. If no CNT aggregates are present on the surface of the CNT pellicle film, the fractal dimension of the CNT pellicle film is 2.0. If many small aggregates are present from a microscopic perspective, the complexity of the material surface is high. The fractal dimension tends to be a numerical value close to 3.0. Details of how to measure the fractal dimension will be described later.

[0014] "Carbon nanotube pellicle film" refers to a pellicle film whose main component is carbon nanotubes (hereinafter also referred to as "CNTs"). By "main component," we mean that the CNT content is 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and most preferably 100% by mass, relative to the total amount of the CNT pellicle film.

[0015] The CNT pellicle film of the present disclosure has the above-described configuration, and therefore is less likely to rupture even when the film thickness is thin. This effect is presumed to be due to, but not limited to, the following reasons. A fractal dimension of 2.70 or greater indicates that a relatively large number of small CNT aggregates are present in the CNT pellicle film. When a large number of small CNT aggregates are present in the CNT pellicle film, there is little bias in the density of the CNT fibers in the CNT pellicle film, and variation in Young's modulus from a microscopic perspective is less likely to occur. When there is little variation in Young's modulus from a microscopic perspective, stress is less likely to concentrate in a portion of the CNT pellicle film. As a result, it is presumed that the CNT pellicle film of the present disclosure is less likely to rupture even when the film thickness is thin.

[0016] (1.1) Fractal dimension The fractal dimension of the CNT pellicle film is 2.70 or more. The fractal dimension of the CNT pellicle film may be 2.85 or more from the viewpoint of making the film less susceptible to rupture even when the film thickness is thin. The fractal dimension of the CNT pellicle film may be 3.00 or less. The fractal dimension of the CNT pellicle film may be 2.85 or less. From these viewpoints, the fractal dimension of the CNT pellicle film may be 2.70 to 3.00.

[0017] (1.1.1) Method for Measuring Fractal Dimension The fractal dimension of a CNT pellicle film is a value calculated by the differential box counting method using a photographed image of the CNT pellicle film. The differential box counting method can be described in the following Non-Patent Document 1: Wen Li Lee, Kai Sheng Hsieh, "A robust algorithm for the fractal dimension of images and its applications to the classification of natural images and ultrasonic liver images," Signal Processing, 90, 6 (2010) 1894-1904.

[0018] (1.1.1.1) Two-dimensional image acquisition The surface of the CNT pellicle film is photographed under the following acquisition conditions to acquire acquired image information. The acquired image information includes position information and brightness values ​​for each of multiple pixels that make up a two-dimensional image of the surface of the CNT pellicle film (hereinafter also simply referred to as a "two-dimensional image").

[0019] <Acquisition conditions> Measuring equipment: Confocal laser scanning microscope EVIDENT LEXT OLS5100 Data used: Height distribution of the object surface (jpeg format) Image size: 1024 x 1024 pixels Measurement magnification: 100x Size of one pixel: 0.125 μm x 0.125 μm

[0020] (1.1.1.2) Fractal Dimension Calculation The fractal dimension is calculated by the information processing device 1 using a differential box counting method. The information processing device 1 is, for example, a personal computer. An example of fractal dimension calculation will be described below with reference to FIGS. 1 and 2.

[0021] 1, the information processing device 1 includes a control device 11, a storage unit 12, a communication unit 13, an input unit 14, an output unit 15, and an interface unit 16. The control device 11, the storage unit 12, the communication unit 13, the input unit 14, the output unit 15, and the interface unit 16 are connected to each other via a bus so as to be able to communicate with each other.

[0022] The control device 11 is a central processing unit. The control device 11 executes various programs. The control device 11 controls each unit. That is, the control device 11 reads a program from the storage unit 12 and executes the program. The control device 11 controls the storage unit 12, the communication unit 13, the input unit 14, the output unit 15, and the interface unit 16 by executing the execution program.

[0023] The control device 11 has a processing unit 111. Specifically, the control device 11 functions as the processing unit 111 by executing a control program stored in the storage unit 12. The processing unit 111 performs a calculation process of the fractal dimension (hereinafter, also simply referred to as the "calculation process"). Details of the calculation process will be described later with reference to FIG. 2.

[0024] The storage unit 12 stores various types of data. The storage unit 12 includes a main storage device (e.g., a semiconductor memory) such as a read-only memory (ROM) and a random access memory (RAM), and an auxiliary storage device (e.g., a hard disk drive). The storage unit 12 stores various computer programs executed by the control device 11. The various computer programs include firmware and control programs. The storage unit 12 includes image information 121 and setting information 122.

[0025] The setting information 122 includes a predetermined size value for multiple divided images and a predetermined spacing value for boxes. The "predetermined size value for divided images" indicates the length of one side of a square when an image is divided into multiple squares in the fractal dimension calculation process. The predetermined size value for multiple divided images is 8 pixels to 55 pixels. The "predetermined spacing value for boxes" indicates the spacing between adjacent boxes. The predetermined spacing value for boxes depends on the size of the divided images and is calculated using the following formula (A): Formula (A): h = G × L / M In formula (A), "h" is the predetermined spacing value for boxes. "G" is the luminance range (maximum luminance value to minimum luminance value for the entire image) of the entire two-dimensional image (hereinafter also referred to as the "entire image"). "M" is the size [pixels] of the entire image. "L" is the predetermined size [pixels] of the divided images.

[0026] The communication unit 13 transmits and receives data to and from other information processing devices via the network 2. The communication unit 13 is a communication interface. The network 2 includes, for example, a local area network (LAN) and a public communication network such as the Internet.

[0027] The input unit 14 is used to input various data and includes, for example, a keyboard, a numeric keypad, or a mouse.

[0028] The output unit 15 outputs various data and includes, for example, a display.

[0029] The interface unit 16 is a connection interface with an external storage medium 161 (for example, a USB (Universal Serial Bus) memory or an SD (Secure Digital) card). The interface unit 16 includes, for example, a USB port or a memory card slot. When the external storage medium 161 is connected to the interface unit 16, the external storage medium 161 can constitute a part of the storage unit 12. The external storage medium 161 may store image information 121.

[0030] (1.1.1.2.2) Calculation Processing Next, the calculation processing performed by the processing unit 111 (i.e., the computer) will be described with reference to Fig. 2. The calculation processing by the processing unit 111 starts in response to the input unit 14 accepting a calculation execution instruction from the user.

[0031] Step S11: The processing unit 111 selects one of a plurality of predetermined image division size values ​​as the size of the image division. The process proceeds to step S12.

[0032] Step S12: The processing unit 111 divides the two-dimensional image into squares each having the size of a divided image, and acquires information about a plurality of divided images. The divided image information includes position information and gray values ​​for each of a plurality of pixels that make up the divided image (hereinafter simply referred to as "divided image"). For example, the image may be divided into nine divided images. The process proceeds to step S13.

[0033] Step S13: The processing unit 111 selects one of the pieces of divided image information, and the process proceeds to step S14.

[0034] Step S14: The processing unit 111 constructs a three-dimensional figure in three-dimensional space based on the selected divided image information. The three-dimensional space is composed of an X-axis, a Y-axis, and a Z-axis. The X-axis, Y-axis, and Z-axis are perpendicular to each other. The X-axis and Y-axis represent the position of a pixel. The Z-axis represents the degree of shading of a pixel. The three-dimensional figure is constructed using the position information and shading values ​​of all pixels that make up the divided image. The three-dimensional figure is constructed by, for example, linear interpolation. The process proceeds to step S15.

[0035] Step S15: The processing unit 111 divides the three-dimensional space into boxes. The boxes represent multiple XY planes stacked along the Z-axis direction. The spacing between adjacent XY planes in the Z-axis direction is a predetermined spacing value for the boxes. The process proceeds to step S16.

[0036] Step S16: The processing unit 111 calculates the number of boxes through which the shading curved surface of the three-dimensional figure passes. The process proceeds to step S17.

[0037] Step S17: The processing unit 111 determines whether or not all of the multiple pieces of divided image information have been selected. If the processing unit 111 determines that all of the multiple divided images have been selected (Step S17; Yes), the processing proceeds to Step S18. If the processing unit 111 determines that all of the multiple divided images have not been selected (Step S17; No), the processing returns to Step S13.

[0038] Step S18: The processing unit 111 calculates the total number of boxes for the plurality of pieces of divided image information for the size of the selected divided image. The process proceeds to step S19.

[0039] Step S19: The processing unit 111 determines whether or not all of the plurality of predetermined values ​​have been selected as the size of the divided image. If the processing unit 111 determines that all of the plurality of predetermined values ​​have been calculated (Step S19; Yes), the processing proceeds to Step S20. If the processing unit 111 determines that all of the plurality of predetermined values ​​have not been selected (Step S19; No), the processing returns to Step S11.

[0040] Step S20: The processing unit 111 calculates the fractal dimension based on the sizes of the multiple divided images and the number of boxes for each divided image size. Specifically, the processing unit 111 calculates the slope of the graph (i.e., the fractal dimension) from a log-log graph showing the number of boxes versus the size of the divided image. The method for calculating the slope of the graph is, for example, the least squares method. The processing then ends.

[0041] (1.2) Physical Properties (1.2.1) Transmittance The transmittance of the CNT pellicle film for extreme ultraviolet rays (hereinafter also referred to as "EUV transmittance") is preferably 80% or more, and more preferably 88% or more. When the EUV transmittance is 88% or more, the EUV irradiation time during EUV exposure can be shortened compared to when the EUV transmittance is less than 88%. From the viewpoint of further shortening the EUV irradiation time, the higher the EUV transmittance, the more preferable it is. The EUV transmittance is more preferably 90% or more, even more preferably 92% or more, and most preferably 100%. From these viewpoints, the EUV transmittance may be 88% to 100%.

[0042] (1.2.1.1) Transmittance Measurement Method EUV transmittance is measured using a photodiode. Specifically, EUV transmittance is expressed as the ratio of the current value detected with the CNT pellicle film installed to the current value detected without the CNT pellicle film installed. EUV transmittance tends to decrease linearly as the thickness of the CNT pellicle film increases.

[0043] An example of a method for adjusting the EUV transmittance of the CNT pellicle film to 88% or more is to reduce the film thickness.

[0044] (1.2.2) Deflection Amount When the CNT pellicle membrane is formed into a square with sides of 1 cm, the deflection amount is preferably 200 μm or less. This makes it possible to suppress the deflection amount due to fluctuations in pressure applied to the CNT pellicle membrane and reduce the possibility of membrane rupture due to interference with the exposure device or the surrounding environment. From the viewpoint of suppressing the deflection amount due to fluctuations in pressure applied to the CNT pellicle membrane and reducing the possibility of membrane rupture due to interference with the exposure device or the surrounding environment, the smaller the deflection amount of the CNT pellicle membrane, the more preferable, and more preferably 100 μm or less, and even more preferably 50 μm or less. The deflection amount of the CNT pellicle membrane is not particularly limited, but may be, for example, 0 μm or more or 1 μm or more. From these viewpoints, the deflection amount of the CNT pellicle membrane may be 0 μm to 200 μm, 0 μm to 50 μm, or 1 μm to 50 μm.

[0045] (1.2.2.1) Measurement Method of Deflection The method for measuring the deflection of a CNT pellicle membrane when it is made into a square with sides of 1 cm is as follows. The CNT pellicle membrane is fixed in a bulge test chamber so that the free-standing membrane portion of the CNT pellicle membrane is in a 1 cm x 1 cm square shape. A displacement meter (e.g., the "LJ-V7200" manufactured by Keyence Corporation) is placed outside the chamber facing the CNT pellicle membrane. The chamber is pressurized by flowing 10 sccm of compressed air into the chamber. The deflection amount is the amount of displacement of the center of the free-standing membrane portion in a pressurized state relative to the center of the free-standing membrane portion when no compressed air is flowing into the chamber. The displacement amount is measured with the displacement meter. Note that if the size of the CNT pellicle membrane is larger than 1 cm x 1 cm, the pellicle membrane can be transferred to a frame that will make the free-standing membrane portion 1 cm x 1 cm, and then the deflection amount can be derived by measuring the deflection amount.

[0046] One method for adjusting the deflection of a CNT pellicle membrane to 200 μm or less when the membrane is cut into a square with sides of 1 cm is to reduce the airflow resistance of the CNT pellicle membrane.

[0047] (1.2.3) Maximum Stress The maximum stress of the CNT pellicle film is preferably 55 MPa or more, and more preferably 120 MPa or more.

[0048] "Maximum stress" refers to an index of the mechanical strength of the CNT pellicle film that is independent of the film thickness of the CNT pellicle film. The method for calculating the maximum stress is the same as that described in the Examples.

[0049] A maximum stress of 120 MPa or more indicates excellent mechanical strength of the CNT pellicle film. In EUV exposure, the interior of the exposure device is evacuated before EUV exposure is performed. If the maximum stress of the CNT pellicle film is 120 MPa or more, the CNT pellicle film is less likely to rupture even when stress caused by evacuation acts on the CNT pellicle film. From the viewpoint of improving the mechanical strength of the CNT pellicle film, the higher the maximum stress of the CNT pellicle film, the more preferable, and more preferably 130 MPa or more, even more preferably 140 MPa or more, and even more preferably 280 MPa or more. From the viewpoint of rupturing the CNT pellicle film during film recovery to facilitate film recovery, the maximum stress of the CNT pellicle film is preferably 500 MPa or less, more preferably 400 MPa or less. From these viewpoints, the maximum stress of the CNT pellicle film may be 120 MPa to 500 MPa. The method for measuring the maximum stress of the CNT pellicle film is the same as that described in the Examples.

[0050] Methods for adjusting the maximum stress of the CNT pellicle film to 120 MPa or more include, for example, using an ultra-high pressure homogenizer or a method with a large classification effect (for example, using an angle (solid-angle rotor) method for centrifugation).

[0051] (1.2.4) Ratio of Air Flow Resistance to Film Thickness The ratio of air flow resistance to film thickness (hereinafter also referred to as "ratio (air flow resistance / film thickness)") is not particularly limited. From the viewpoint of high membrane strength and resistance to membrane rupture, the ratio (air flow resistance / film thickness) is preferably 0.014 [Pa cm ２ / (sccm nm)] or more, more preferably 0.020 [Pa cm ２ / (sccm nm)] or more, more preferably 0.030 [Pa cm ２ The ratio (air flow resistance / membrane thickness) is preferably 1.000 [Pa cm / (sccm nm)] or more, from the viewpoint of being able to further reduce the displacement of the membrane under a constant flow rate. ２ / (sccm nm)] or less, more preferably 0.100 [Pa cm ２ / (sccm nm)] or less, more preferably 0.035 [Pa cm２ From these viewpoints, the ratio (air flow resistance / film thickness) is 0.014 [Pa cm ２ / (sccm·nm)] to 1.000 [Pa·cm ２ / (sccm·nm)] is preferred.

[0052] "sccm" indicates standard cubic centimeter per minute. "sccm" is the amount of 1 cm under standard conditions. ３ / min.

[0053] "Air flow resistance" is an index showing the difficulty of air passing through a CNT pellicle membrane. The thicker the CNT pellicle membrane, the higher the air flow resistance tends to be. "Air flow resistance / membrane thickness" is an index showing the difficulty of air passing through a CNT pellicle membrane per unit membrane thickness (1 nm) of the CNT pellicle membrane.

[0054] The method for measuring airflow resistance is as follows. A CNT pellicle membrane is fixed in a chamber for bulge testing so that the free-standing membrane portion of the CNT pellicle membrane is in the shape of a 1 cm x 1 cm square. Compressed air is flowed into the chamber to create a pressurized state inside the chamber, and a pressure ΔP is applied to the free-standing membrane portion of the CNT pellicle membrane. The pressure ΔP represents the pressure difference (P2 - P1) between the pressure outside the chamber (atmospheric pressure) P1 and the pressure inside the chamber P2. The airflow resistance R is calculated using the following formula (X1):

[0055]

[0056] In formula (X1), "ΔP" represents the pressure difference (P2-P1) (Pa), and "A" represents the air permeable area of ​​the CNT pellicle membrane (cm ２ ) (i.e., the area of ​​the free-standing membrane (cm ２ )), and "Q" represents the flow rate (sccm) of compressed air flowing inside the chamber. The pressure P2 inside the chamber can be measured with a differential pressure gauge. The flow rate Q of compressed air flowing inside the chamber can be measured with a flow meter.

[0057] The ratio (air flow resistance / membrane thickness) is 0.015 [Pa cm ２Examples of a method for adjusting the pressure to be equal to or greater than [0.01 / (sccm·nm)] include a method using an ultra-high pressure homogenizer and a method with a large classification effect (for example, a method using an angle (solid-angle rotor) method in centrifugation).

[0058] (1.3) Carbon Nanotubes CNTs may be single-walled carbon nanotubes (hereinafter also referred to as "single-walled CNTs") or multi-walled carbon nanotubes (hereinafter also referred to as "multi-walled CNTs").

[0059] In this disclosure, the term "single-walled carbon nanotube" refers to a single-walled carbon nanotube, and the term "multi-walled carbon nanotube" refers to a multi-walled carbon nanotube.

[0060] A plurality of CNTs usually form a bundle. The number of CNTs forming a bundle is 3 or more, preferably 4 to 100, and more preferably 5 to 50. The CNT pellicle film may also contain CNTs that do not form bundles.

[0061] The CNT tube diameter (i.e., the width of the CNT) may be 0.4 nm to 50 nm. From the viewpoint of suppressing the occurrence of breakage of the CNT pellicle film, the CNT tube diameter is preferably 0.5 nm or more, more preferably 0.6 nm or more, even more preferably 0.7 nm or more, and particularly preferably 0.8 nm or more. From the viewpoint of improving the EUV transmittance of the CNT pellicle film, the CNT tube diameter is preferably 30 nm or less, more preferably 15 nm or less, even more preferably 10 nm or less, and particularly preferably 6 nm or less. From these viewpoints, the CNT tube diameter may be 0.4 nm to 50 nm, 0.4 nm to 15 nm, 0.4 nm to 10 nm, 0.4 nm to 6 nm, or 0.8 nm to 6 nm. When the CNT tube diameter is 6 nm or less, the EUV light transmittance of the pellicle film is improved.

[0062] The length of the CNT is preferably 10 nm or more. When the length of the CNT is 10 nm or more, the CNTs are well entangled with each other, and the mechanical strength of the CNT pellicle film is excellent. The length of the CNT is preferably 10 cm or less, more preferably 1 cm or less, and even more preferably 100 μm or less. From these viewpoints, the length of the CNT is preferably 10 nm to 10 cm, more preferably 10 nm to 1 cm, and even more preferably 10 nm to 100 μm.

[0063] The outer diameter and length of the CNT tube are the arithmetic mean values ​​measured for 20 or more carbon materials (primary particles) by electron microscope observation. As the electron microscope, a scanning electron microscope (SEM), a transmission electron microscope (TEM), or the like can be used.

[0064] From the viewpoint of increasing the mechanical strength of the CNT pellicle film, the effective length of the CNT is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1.0 μm or more. The effective length of the CNT may be 30 μm or less, 20 μm or less, or 10 μm or less.

[0065] The effective length of CNTs is measured by the following method. First, the far-infrared spectrum of the CNT pellicle film is measured using a Fourier transform infrared spectrometer (for example, a Bruker FT-IR spectrometer, Vertex 80v, etc.). Next, the CNT pellicle film is transferred onto a high-resistance (i.e., low-carrier density) Si substrate. According to the methods described in Non-Patent Documents 2 to 4 below, the CNT channel of the "effective length of CNTs," consisting of conductive paths affected by kinks, defects, etc., is estimated from the peak value of the plasmon resonance to evaluate the effective length of the CNTs. The average tube diameter is used to calculate the effective length of the CNTs. The average tube diameter can be determined by determining the average diameter of CNTs imaged with an electron microscope. Non-patent document 2: T. Nakanishi, T. Ando, ​​Optical Response of Finite-Length Carbon Nanotubes, J. Phys. Soc. Japan. 78 (2009) 114708. Non-patent document 3: T. Morimoto, SK Joung, T. Saito, DN Futaba, K. Hata, T. Okazaki, Length-dependent plasmon resonance in single-walled carbon nanotubes, ACS Nano. 8 (2014) 9897-9904. Non-patent document 4: T. Morimoto, T. Okazaki, Optical resonance in far-infrared spectra of multiwalled carbon nanotubes, Appl. Phys. Express. 8 (2015).

[0066] One method for increasing the effective length of CNTs is to use CNTs with few kinks, defects, etc. CNTs with few kinks, defects, etc. may be CNTs with high crystallinity and excellent linearity.

[0067] The CNT pellicle film contains a plurality of carbon nanotubes having a tube diameter of 0.8 nm to 6.0 nm, and it is preferable that the content of the plurality of carbon nanotubes having a tube diameter of 0.8 nm to 6.0 nm is 30% or more of the total amount of the carbon nanotube pellicle film.

[0068] The CNT pellicle film contains multiple single-walled CNTs, and the content ratio of the multiple single-walled CNTs is preferably 30% or more, more preferably 50% or more, and particularly preferably 80% or more, relative to the total amount of the CNT pellicle film. Single-walled CNTs are more flexible than multi-walled CNTs. When the content ratio of multiple single-walled CNTs is 80% or more, the CNT fibers are less likely to be cut. In other words, the ratio (G / D) described below is improved. The content ratio of multiple single-walled CNTs may be 100% or less, 95% or less, or 90% or less.

[0069] (1.4) Ratio (G / D) The ratio (G / D) is preferably equal to or greater than 5. The "ratio (G / D)" indicates the ratio of the G band intensity measured by resonance Raman scattering measurement to the D band intensity measured by resonance Raman scattering measurement of the CNT pellicle film.

[0070] The "ratio of the G band intensity measured by resonance Raman scattering to the D band intensity measured by resonance Raman scattering of a CNT pellicle film" is an index showing the degree of structural defects in each of the multiple CNTs contained in the CNT pellicle film. "Defects" include the introduction of topological defects in the network (mesh) of carbon atoms constituting the CNTs linked by covalent bonds. Topological defects include five-membered rings and seven-membered rings. The "G band" is the main Raman-active mode of the graphite structure and originates from sp2-bonded carbon, which represents the planar structure of the CNT. The "D band" is a mode derived from disorder or defects, such as structural defects or open ends of the CNTs. The higher the ratio (G / D), the fewer structural defects there are in each of the multiple CNTs contained in the CNT pellicle film.

[0071] Extreme ultraviolet lithography uses a photomask with a reflective layer that reflects EUV light, and the photomask and optical system are placed in a vacuum chamber. EUV exposure is performed in a vacuum atmosphere. However, residual gases (e.g., moisture and organic matter) remain in the vacuum chamber, and EUV irradiation can cause carbon film deposition (hereinafter referred to as "contamination") on the surfaces of mirrors and masks included in the optical system. Contamination can lead to reduced throughput and deterioration of transfer performance. As a countermeasure against contamination, instead of disassembling and cleaning the optical system, hydrogen gas is supplied into the vacuum chamber to clean the generated contamination in situ. The hydrogen gas supplied into the vacuum chamber is thought to become hydrogen plasma when irradiated with EUV light. Areas of the CNT surface with structural defects tend to appear as areas that exhibit nonlinearity from a microscopic perspective (hereinafter referred to as "nonlinear portions"). It is believed that the hydrogen plasma primarily promotes etching of the CNTs (that is, decomposing and scraping off the CNTs) starting from the non-linear portions.

[0072] A ratio (G / D) of 5 or greater indicates that the number of structural defects in each of the multiple CNTs contained in the CNT pellicle film is small. When the ratio (G / D) is 5 or greater, etching of the CNTs is less likely to be accelerated during EUV exposure than when the ratio (G / D) is less than 5. In other words, the CNT pellicle film is less likely to be reduced in thickness even when exposed to hydrogen plasma. As a result, the excellent mechanical strength of the CNT pellicle film is maintained. From the viewpoint of maintaining the mechanical strength of the CNT pellicle film, the higher the ratio (G / D), the more preferable it is, more preferably 7 or greater, even more preferably 15 or greater, particularly preferably 25 or greater, and most preferably 37 or greater. The ratio (G / D) may be 100 or less, 37 or less, or 20 or less. From these viewpoints, the ratio (G / D) may be 5 to 20.

[0073] (1.4.1) Measurement method of the ratio (G / D) The ratio (G / D) is measured by resonance Raman scattering measurement using a laser wavelength of 532 nm. For example, the "NRS-5100" manufactured by JASCO Corporation may be used to measure the ratio (G / D). Specifically, Raman imaging measurement is performed at 10 measurement points spaced 1 mm apart on a freestanding CNT pellicle film of 10 mm x 10 mm. The intensity of the D band is measured at a Raman shift of 1300 cm －１ ~1400cm －１ The Raman scattering intensity is the maximum value among ten measured values ​​within the range. The G band intensity is the maximum value among ten measured values ​​within the range of the Raman shift of 1550 cm －１ ~1610cm －１ This is the maximum value among ten measured values ​​of Raman scattering intensity within the range. In general Raman spectroscopy, the Raman spectrum of a CNT pellicle film reflects the average structure of the CNT chains present within the irradiation area where the CNT pellicle film is irradiated with a laser. In a general Raman microscope, the laser irradiation size is approximately 100 μm in diameter. In a CNT pellicle film made of single-walled CNTs and having a thickness of approximately 15 nm, the total length of the single-walled CNTs contained within a spot diameter of 100 μm is estimated to be approximately 1,000 μm to 2,000 μm. Furthermore, assuming the length of one CNT is 1 μm, the total number of CNTs constituting the CNT pellicle film contained within the above-mentioned 100 μm spot diameter is approximately 1,000 to 2,000. From these facts, the structural information obtained by a general Raman microscope reflects the average structural information of 1000 or more CNTs (length 1000 μm or more).

[0074] (1.5) Film Thickness The film thickness of the CNT pellicle film is not particularly limited and may be 2 nm to 200 nm. From the viewpoint of increasing EUV transmittance, the film thickness of the CNT pellicle film is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 40 nm or less, and particularly preferably 30 nm or less. From the viewpoint of the susceptibility to breakage of the CNT pellicle film and the viewpoint of foreign matter shielding properties (i.e., the viewpoint of preventing foreign matter from passing through the CNT pellicle film), the film thickness of the CNT pellicle film is preferably 3 nm or more, more preferably 4 nm or more, and even more preferably 6 nm or more.

[0075] (1.5.1) Film Thickness Measurement Method The film thickness of the CNT pellicle film is determined by transferring the free-standing film portion of the CNT pellicle film onto a silicon substrate and using a reflectance spectroscopic film thickness meter (F50-UV manufactured by Filmetrics, Inc.) In detail, the film thickness is measured as follows.

[0076] The "free-standing portion of the CNT pellicle membrane" refers to the region of the CNT pellicle membrane that is not supported by the pellicle frame. Specifically, the membrane thickness is measured as follows.

[0077] (1.5.1.1) Transfer: The free-standing film portion of the CNT pellicle film of the pellicle, which will be described later, is transferred onto a silicon substrate. Specifically, a solvent is dropped onto the silicon substrate, and the CNT pellicle film of the pellicle is placed facing the silicon substrate, and the pellicle is placed on the substrate. Examples of the solvent include water and organic solvents. The solvent is dried, and the CNT pellicle film is tightly adhered to the silicon substrate without any gaps. The silicon substrate is fixed and the pellicle frame of the pellicle is lifted, separating the free-standing film portion from the pellicle, and the free-standing film portion is transferred to the substrate.

[0078] (1.5.1.2) Measurement of Reflectance Spectrum For each measurement point of the freestanding film portion transferred to the silicon substrate, the reflectance spectrum is measured in the wavelength range of 200 nm to 600 nm at wavelength intervals of 1 nm to 2 nm. To measure the reflectance spectrum, a reflection spectroscopic film thickness meter (for example, manufactured by Filmetrics, model: F50-UV, spot diameter 1.5 mm) is used as the reflectance measurement device. A silicon wafer is used as a reference for measuring the reflection intensity. The reflectance Rs(λ) is calculated using the following formula:

[0079]

[0080] Here, Is(λ) represents the reflection intensity of the free-standing film portion on the silicon substrate at wavelength λ, Iref(λ) represents the reflection intensity of the reference, and Rref(λ) represents the absolute reflectance of the reference. When a silicon wafer is used as the reference, the optical constants of the silicon wafer are known, so Rref(λ) can be calculated. Note that the gain, exposure time, etc. are the same conditions in measuring the reflection intensity of the reference and the free-standing film portion on the silicon substrate. This allows the absolute reflectance of the free-standing film portion on the silicon substrate to be obtained.

[0081] (1.5.1.3) Calculation of Film Thickness Using the optical constants (refractive index: n, extinction coefficient: k) shown in Table 1 as the optical constants of the CNT pellicle film, and using a three-layer model of air layer / CNT pellicle film layer / silicon substrate, the reflectance spectrum in the wavelength range of 225 nm to 500 nm is analyzed by the least squares method to calculate the film thickness at each measurement point of the free-standing film portion. The film thickness at the "measurement position" of the free-standing film portion is the average film thickness at each of the nine measurement points included in the "measurement position" of the free-standing film portion. The shape of the free-standing film portion when viewed from the film thickness direction of the free-standing film portion is rectangular. The diagonal lines of the free-standing film portion are the X-axis and Y-axis. Three measurement points in the X-axis direction are set at intervals such that the distance between the centers of adjacent measurement points is 2 mm, and three measurement points in the Y-axis direction are set at intervals such that the distance between the centers of adjacent measurement points is 2 mm. In other words, three vertical and three horizontal points, a total of nine measurement points, are set as "measurement positions." A method for calculating the film thickness at each measurement point of the free-standing film portion by analyzing the reflectance spectrum in the wavelength range of 225 nm to 500 nm by the least squares method will be described below.

[0082]

[0083] The film thickness of the free-standing film portion is calculated using a three-layer model of air layer / CNT pellicle film layer / silicon substrate, using the following relational expressions (a) to (c).

[0084] The reflectance Rs is the amplitude reflectance r ｓ is expressed by the following formula (a) using

[0085]

[0086] In the above formula (a), * represents a complex conjugate.

[0087] Amplitude reflectance r from the three layers of air layer / CNT pellicle film layer / silicon substrate ｓ is expressed by the following formula (b).

[0088]

[0089] In the above formula (b), r ０１ represents the amplitude reflectance from the interface between the air layer and the free-standing film layer, and r １２ represents the amplitude reflectance from the interface between the free-standing film layer and the silicon substrate, and i represents the imaginary unit. In the above formula (b), δ is the phase difference that occurs when light of wavelength λ makes one round trip within the film, and is expressed by the following formula (c):

[0090]

[0091] In the above formula (c), d represents the film thickness of the free-standing film portion, N represents the complex refractive index (N=n−ik), φ represents the angle of incidence, and i represents the imaginary unit.

[0092] The film thickness of the free-standing film portion is obtained by calculating using the relationship between the above formulas (a) to (c) with the film thickness d as a variable for the reflectance Rs in the wavelength range of 225 nm to 500 nm using the least squares method. The calculated film thickness at the "measurement position" of the free-standing film is regarded as the film thickness of the CNT pellicle film.

[0093] (2) Pellicle The pellicle of the present disclosure comprises a pellicle frame and a CNT pellicle membrane of the present disclosure. The CNT pellicle membrane is supported by the pellicle frame. Because the pellicle of the present disclosure comprises the CNT pellicle membrane of the present disclosure, it exhibits the same effects as the CNT pellicle membrane of the present disclosure.

[0094] The pellicle frame is a cylindrical object. The pellicle frame has an end face (hereinafter referred to as the "pellicle membrane end face") on one side in the thickness direction. The CNT pellicle membrane may be fixed to the pellicle membrane end face via an adhesive layer. The adhesive constituting the adhesive layer is not particularly limited, and examples thereof include acrylic resin adhesives, epoxy resin adhesives, polyimide resin adhesives, silicone resin adhesives, inorganic adhesives, double-sided adhesive tapes, polyolefin adhesives, and hydrogenated styrene adhesives. The concept of adhesive includes not only adhesives but also pressure-sensitive adhesives. The thickness of the adhesive layer is, for example, 10 μm to 1 mm.

[0095] (2.1) Pellicle Frame The pellicle frame has an exposure through-hole. The exposure through-hole indicates a space through which light transmitted through the CNT pellicle film passes to reach the photomask.

[0096] The shape of the pellicle frame in the thickness direction of the pellicle frame is, for example, rectangular. The rectangular shape may be a square or oblong.

[0097] The pellicle frame may have a vent hole formed, for example, in a side surface of the pellicle frame. When the pellicle frame is attached to the photomask, the vent hole connects the internal space of the pellicle with the external space of the pellicle.

[0098] The rectangular pellicle frame has four sides when viewed in the thickness direction. The length of one longitudinal side is preferably 200 mm or less. The size of the pellicle frame is standardized depending on the type of exposure apparatus. A pellicle frame with a longitudinal length of one side of 200 mm or less satisfies the standardized size for EUV exposure. The length of one lateral side is preferably 5 mm to 180 mm, more preferably 80 mm to 170 mm, and even more preferably 100 mm to 160 mm. The height of the pellicle frame (i.e., the length of the pellicle frame in the thickness direction) is preferably 3.0 mm or less, more preferably 2.4 mm or less, and even more preferably 2.375 mm or less. This allows the pellicle frame to satisfy the standardized size for EUV exposure. The height of the pellicle frame standardized for EUV exposure is, for example, 2.375 mm. The mass of the pellicle frame is not particularly limited, but is preferably 20 g or less, more preferably 15 g or less. This makes the pellicle frame suitable for use in EUV exposure.

[0099] The material of the pellicle frame is not particularly limited, and examples thereof include quartz glass, metal, carbon-based material, resin, silicon, and ceramic-based material. The metal may be a pure metal or an alloy. A pure metal is composed of a single metal element. Examples of pure metals include aluminum and titanium. An alloy is composed of multiple metal elements, or a metal element and a non-metal element. Examples of alloys include stainless steel, magnesium alloy, steel, carbon steel, and invar. Examples of resins include polyethylene. Examples of ceramic-based materials include silicon nitride (SiN), silicon carbide (SiC), and alumina (Al ２ O ３ ) etc.

[0100] The structure of the pellicle frame may be a single item or an assembly. A single item is obtained by cutting out a single raw material plate. An "assembly" is an item in which multiple components are integrated. Methods for integrating multiple components include using a known adhesive or using fastening parts. Fastening parts include bolts, nuts, screws, rivets, or pins. When the pellicle frame is an assembly, the multiple components may be made of different materials.

[0101] (2.2) Adhesive Layer The pellicle may further include an adhesive layer. The adhesive layer enables the pellicle to be adhered to a photomask. The pellicle frame has an end face (hereinafter referred to as the "photomask end face") on the other side of the thickness direction. The adhesive layer is formed on the photomask end face. The adhesive layer is a soft, gel-like solid. The adhesive layer preferably has fluidity and cohesion. "Fluidity" refers to the property of wetting the adherend, i.e., the photomask. "Cohesion" refers to the property of resisting peeling from the photomask. The adhesive layer is made of an adhesive resin. The adhesive resin is not particularly limited, and examples include acrylic adhesives, silicone adhesives, styrene adhesives, urethane adhesives, and olefin adhesives. The thickness of the adhesive layer is not particularly limited, and is preferably 10 μm to 500 μm.

[0102] (3) Exposure Master The exposure master of the present disclosure includes a photomask and the pellicle of the present disclosure. The pellicle of the present disclosure is attached to the photomask. Since the exposure master of the present disclosure includes the pellicle of the present disclosure, it exhibits the same effects as the pellicle of the present disclosure.

[0103] The method for attaching a photomask to a pellicle (hereinafter referred to as the "attachment method") is not particularly limited, and examples include a method using the adhesive layer described above, a method using fastening parts, and a method utilizing the attractive force of a magnet or the like.

[0104] The photomask has a support substrate, a reflective layer, and an absorber layer. The support substrate, reflective layer, and absorber layer are preferably stacked in this order. In this case, the pellicle is attached to the side of the photomask where the reflective layer and absorber layer are provided. The absorber layer partially absorbs EUV light, thereby forming a desired image on a sensitive substrate (e.g., a semiconductor substrate with a photoresist film). Examples of the reflective layer include a multilayer film of molybdenum (Mo) and silicon (Si). The material of the absorber layer may be a material that has high absorption of EUV light and the like. Examples of materials that have high absorption of EUV light and the like include chromium (Cr) and tantalum nitride.

[0105] (4) Exposure Apparatus The exposure apparatus of the present disclosure includes an extreme ultraviolet light source that emits extreme ultraviolet light as exposure light, an exposure master of the present disclosure, and an optical system that guides the exposure light emitted from the EUV source to the exposure master. The exposure master is positioned so that the extreme ultraviolet light emitted from the extreme ultraviolet light source passes through the carbon nanotube pellicle film and irradiates the photomask. The exposure apparatus of the present disclosure achieves the same effects as the exposure master of the present disclosure. Furthermore, because the exposure apparatus of the present disclosure has the above configuration, it can form finer patterns (e.g., line widths of 32 nm or less) and can perform pattern exposure with reduced resolution defects due to foreign matter.

[0106] As the extreme ultraviolet light source, a known extreme ultraviolet light source can be used. As the optical system, a known optical system can be used.

[0107] (5) Manufacturing Method of Carbon Nanotube Pellicle Film The manufacturing method of a CNT pellicle film of the present disclosure is a method for manufacturing a CNT pellicle film of the present disclosure. This manufacturing method includes: preparing a carbon nanotube raw material (hereinafter also referred to as "CNT raw material") (hereinafter also referred to as "preparation step"); and forming a film of a dispersion containing the carbon nanotube raw material to produce the carbon nanotube pellicle film (hereinafter also referred to as "film formation step"). The ratio (G / D) of the carbon nanotube raw material is 160 to 500. The "ratio (G / D)" indicates the ratio of the G band intensity measured by resonance Raman scattering measurement to the D band intensity measured by resonance Raman scattering measurement. The preparation step and film formation step are performed in this order.

[0108] The method for producing a CNT pellicle film according to the present disclosure has the above-described configuration, and therefore can produce a carbon nanotube pellicle film that is resistant to rupture even when the film is thin. This effect is presumably due to, but not limited to, the following reasons: Because the ratio (G / D) of the carbon nanotube raw material is high, there are fewer defects in the CNTs, which improves mechanical strength.

[0109] The method for manufacturing a CNT pellicle according to the present disclosure may further include at least one of a mixing step, a dispersion step, and a purification step in addition to the preparation step and the film formation step.

[0110] Hereinafter, a description will be given of a case where the method for producing a CNT pellicle film according to the present disclosure includes a preparation step, a mixing step, a dispersion step, a purification step, and a film-forming step. The preparation step, mixing step, dispersion step, purification step, and film-forming step are performed in this order.

[0111] (5.1) Preparation Step In the preparation step, a CNT raw material is prepared.

[0112] The method for preparing the CNT raw material is not particularly limited, and examples include methods of obtaining commercially available products and methods of synthesizing carbon nanotube raw materials (hereinafter also referred to as "CNT raw materials"). Examples of commercially available products include eDIPS manufactured by Meijo Nano Carbon Co., Ltd., ZEONANO manufactured by Zeon Nano Technology Co., Ltd., and TUBALL manufactured by OCSiAl. Methods for synthesizing CNT raw materials include the enhanced direct injection pyrolytic synthesis (hereinafter also referred to as the "eDIPS method"), the super-growth method, and the laser ablation method. Among the above methods, the eDIPS method is preferred as a method for synthesizing CNT raw materials. The DIPS method is a gas-phase flow method. Specifically, in the DIPS method, a hydrocarbon-based solution containing a catalyst (or catalyst precursor) and a reaction accelerator is atomized by spraying and introduced into a high-temperature heating furnace, thereby synthesizing single-walled CNTs in a flowing gas phase. The e-DIPS method is a gas-phase flow method that is an improvement over the DIPS method. Specifically, the "e-DIPS method" focuses on the particle formation process in which ferrocene, used as a catalyst, has different particle diameters upstream and downstream in a reactor. Unlike the DIPS method, which uses only an organic solvent as a carbon source, the e-DIPS method is relatively susceptible to decomposition in the carrier gas. In other words, it is a method in which the growth point of single-walled CNTs is controlled by mixing a second carbon source that is likely to act as a carbon source. For details, production can be carried out with reference to Non-Patent Document 5. An example of a commercially available CNT raw material synthesized by the eDIPS method is "MEIJO eDIPS" manufactured by Meijo Nanocarbon Co., Ltd. Non-Patent Document 5: Saito et al., J. Nanosci. Nanotechnol., 8 (2008) 6153-6157

[0113] The main component of the CNT raw material may be single-walled CNTs or multi-walled CNTs. The ratio of the main component of the CNT raw material to the total amount of the CNT raw material may be 30 to 100, 40 to 100, or 80 to 100. The tube diameter of the CNT raw material may be 1 nm to 7 nm, 1 nm to 5 nm, 1 nm to 4 nm, or 1 nm to 3 nm. The average tube diameter of the CNT raw material may be 1.2 nm to 5.0 nm, 1.2 nm to 2.5 nm, 2.0 nm to 4.0 nm, 2.0 nm to 3.0 nm, 2.5 nm to 3.0 nm, or 3.1 nm to 4.0 nm. The length of the tubes of the CNT raw material may be 100 nm or more, 150 nm or more, 160 nm or more, 180 nm or more, 500 nm or less, 450 nm or less, or 400 nm or less.

[0114] The ratio (G / D) of the CNT raw material is 160-500, may be 170-190, may be 190-390, or may be 130-140.

[0115] The carbon nanotube raw material preferably contains single-walled carbon nanotubes synthesized by a modified direct injection pyrolysis synthesis method, and more preferably is single-walled carbon nanotubes synthesized by a modified direct injection pyrolysis synthesis method.

[0116] (5.2) Mixing Step In the mixing step, the CNT raw material and the solvent are mixed with a weak mixing force to disperse the CNTs while suppressing damage to the CNTs, thereby preparing a first dispersion.

[0117] The method for mixing the CNT raw material and the solvent is not particularly limited, and examples thereof include a method using a magnetic stirrer, a method using cavitation (e.g., ultrasonic dispersion, etc.), a method of mechanically applying shear force (e.g., a ball mill, a roller mill, a vibration mill, a kneader, a homogenizer, etc.), and a method using turbulence (e.g., a jet mill, a Nanomizer, etc.).

[0118] The solvent is not particularly limited, and examples thereof include organic solvents, water, etc. Examples of organic solvents include isopropyl alcohol, ethanol, toluene, xylene, ethylbenzene, n-methylpyrrolidone, N,N-dimethylformamide, propylene glycol, and methyl isobutyl ketone.

[0119] In addition to the CNT raw material and solvent, a dispersant may be mixed. The dispersant can disentangle the thick bundles contained in the CNT raw material. Examples of dispersants include flavin derivatives, sodium cholate, sodium deoxycholate, sodium dodecylbenzenesulfonate, polyacrylic acid, sodium polyacrylate, polyfluorene (poly(9,9-dioctylfluorenyl-2,7-diyl)), and sodium dodecyl sulfate.

[0120] The content of the CNT raw material is not particularly limited, and from the viewpoint of uniformly dispersing the CNT raw material in the first dispersion, it is preferably 0.0005% by mass to 1% by mass, and more preferably 0.001% by mass to 0.5% by mass, relative to the total amount of the first dispersion.

[0121] (5.3) Dispersion Step In the dispersion step, a homogenizer is used to disperse the first dispersion to produce a second dispersion. This allows the CNT raw material in the first dispersion to be uniformly dispersed. As a result, the CNT pellicle film of the present disclosure can be easily obtained.

[0122] The homogenizer is not particularly limited, and examples thereof include an agitation type homogenizer and an ultra-high pressure homogenizer.

[0123] An "agitation homogenizer" is a device that uniformly disperses components in a liquid material by rotating an agitation blade at high speed. The agitation homogenizer may be any known dispersing machine. The rotation speed of the agitation blade is not particularly limited, and is preferably 1,000 rpm to 20,000 rpm, more preferably 2,000 rpm to 19,000 rpm. The processing time is preferably 1 minute to 5 hours, more preferably 5 minutes to 4 hours.

[0124] An "ultra-high pressure homogenizer" is a device that applies high pressure to a liquid material to uniformly disperse the components (e.g., particles) in the liquid material. The ultra-high pressure homogenizer may be a known dispersing machine. The ultra-high pressure homogenizer may be a nozzle type or a valve type, and is preferably a nozzle type from the viewpoint of uniformly dispersing the CNT raw material in the first dispersion. In the nozzle type, high pressure is applied to the liquid material, causing the liquid materials to collide with each other, thereby dispersing the components of the liquid material. The nozzle type may be an H-shaped nozzle.

[0125] The pressure of the dispersion treatment is not particularly limited, but is preferably 10 MPa or more, more preferably 15 MPa to 100 MPa, and even more preferably 20 MPa to 90 MPa. The number of dispersion treatments may be one or more. The more dispersion treatments are performed, the more likely structural defects may occur in the CNTs. In other words, the ratio (G / D) of the CNT pellicle film may decrease. Therefore, the number of dispersion treatments is preferably one to ten times, and more preferably two to nine times.

[0126] (5.4) Purification Step In the purification step, the second dispersion is subjected to a purification treatment to produce a third dispersion. This removes the highly agglomerated fibrous CNTs contained in the second dispersion. As a result, the CNT pellicle film of the present disclosure can be more easily obtained.

[0127] Examples of purification methods include methods of precipitating aggregates contained in the dispersion (e.g., standing, filtration, membrane separation, and centrifugation (including ultracentrifugation)). Centrifugal treatment is preferably used. In centrifugation, the rotation speed is preferably 1,000 rpm to 30,000 rpm. Examples of centrifugation methods include a swing rotor method in which centrifugation is performed with the container held horizontally, and an angle rotor method in which centrifugation is performed with the container tilted at a certain angle. From the viewpoints of achieving a high aggregate removal effect, increasing the ratio of airflow resistance to membrane thickness, and making it easier to increase the maximum pressure, the angle rotor method is preferred. In the angle rotor method, in order to enhance the centrifugal effect and make it easier to remove aggregates, the angle at which the container is tilted with respect to the direction of gravity is preferably 1° to 100°, and preferably 10° to 60°. From the viewpoints of preventing membrane rupture and reducing airflow resistance, the angle rotor method is preferred.

[0128] (5.5) Film Forming Step In the film forming step, the third dispersion is formed into a sheet-like film to produce the CNT pellicle film of the present disclosure.

[0129] An example of a method for forming the third dispersion into a sheet-like film is a method in which the second dispersion is applied to a substrate and the solvent is removed by drying or the like. Examples of the application method include blade coating, slit coating, spin coating, and dip coating, which are also known methods. The drying method is not particularly limited and may be any known method, such as a method in which the solvent is dried by leaving the film to stand at room temperature or a method in which the solvent is dried by heating. If necessary, the dispersant in the second dispersion may be removed by washing the CNT pellicle film with a solvent that dissolves the dispersant.

[0130] The present disclosure will be described in more detail below with reference to examples, but the invention of the present disclosure is not limited to these examples.

[0131] [1] Pellicle membrane [1.1] Example 1 A pellicle membrane was prepared as follows.

[0132] [1.1.1] Preparation Step Product A was prepared as a CNT raw material. Product A was single-walled CNTs (crude CNTs, tube diameter: 1 nm to 4 nm, average tube diameter: 3.0 nm, tube length: 100 nm or more, percentage of single-walled CNTs: 40% to 100%, ratio (G / D): 170 to 190) synthesized by the improved direct injection pyrolysis synthesis method (eDIPS method). The single-walled CNTs contained CNT aggregates.

[0133] [1.1.2] Mixing Step To 30 mg of the CNT raw material, 70 mL of isopropyl alcohol and 30 mL of ethanol were added, and further 30 mg of polyacrylic acid was added as an additive. The mixture was stirred using a magnetic stirrer at 1000 rpm (revolutions per minute) for 18 hours to obtain a first dispersion.

[0134] [1.1.3] Dispersion step: A stirring homogenizer ("HF93" manufactured by SMT Co., Ltd.) was prepared as a dispersing machine. The first dispersion was dispersed using the stirring homogenizer at 13,000 rpm for 60 minutes. This gave a second dispersion.

[0135] [1.1.4] Purification Step The second dispersion was centrifuged at 23,000 rpm for 96 minutes at 10°C using a swing rotor (JS-24.15, Beckman Coulter, Inc.) of a high-speed centrifuge (JXN-30, Beckman Coulter, Inc.). The supernatant was then recovered from the first dispersion after the centrifugation process, yielding a third dispersion. The precipitate contained CNT aggregates and clump-like CNT.

[0136] [1.1.5] Film Formation Process The third dispersion was spin-coated onto a 4-inch silicon substrate (roughness Ra: 0.15 nm) at a rotation speed of 600 rpm to form a carbon nanotube film (also referred to as a "CNT film") on the silicon substrate. This resulted in a silicon substrate with a CNT film. The CNT film was washed with water to remove the polyacrylic acid in the CNT film and then dried. Next, the silicon substrate with the CNT film was immersed in water. In the water, the CNT film peeled off from the silicon substrate and floated on the water surface. The silicon substrate was removed from the water, leaving the CNT film in the water. The CNT film floating on the water surface was scooped up with a silicon frame. The silicon frame had a square opening with a side length of 1 cm. This resulted in a CNT pellicle film with a mesh structure. The area of ​​the free-standing CNT pellicle film (i.e., the area of ​​the opening in the silicon frame) was 1 cm. ２ It was.

[0137] [1.2] Example 2 A CNT pellicle film with a network structure was obtained in the same manner as in Example 1, except that the CNT raw material in the preparation step was changed from Product A to Product B. Product B was single-walled CNT (crude CNT, tube diameter: 1 nm to 5 nm, average tube diameter: 3.1 nm, tube length: 100 nm or more, proportion of single-walled CNT: 30% to 100%, ratio (G / D): 190 to 390) synthesized by the improved direct injection pyrolysis synthesis method (eDIPS method).

[0138] [1.3] Comparative Example 1 A CNT pellicle film having a network structure was obtained in the same manner as in Example 1, except that the CNT raw material in the preparation step was changed from Product A to Product C. Product C was single-walled CNT (crude CNT, tube diameter: 1 nm to 3 nm, average tube diameter: 1.7 nm, tube length: 100 nm or more, proportion of single-walled CNT: 50% to 100%, ratio (G / D): 130 to 140) synthesized by the improved direct injection pyrolysis synthesis method (eDIPS method).

[0139] [2] Measurement The film thickness and other properties of the CNT pellicle films of Example 1, Example 2, and Comparative Example 1 were measured by the methods described below. The measurement results are shown in Table 2.

[0140] [2.1] Fractal dimension, etc. The fractal dimension, tube diameter, film thickness, ratio (G / D), and EUV transmittance were measured by the methods described above.

[0141] [2.2] Airflow Resistance, etc. Measurements were made using a bulge test of the CNT pellicle membrane. As shown in Figure 3, the CNT pellicle membrane 10 was fixed in a chamber 20 for the bulge test. The free-standing membrane portion of the CNT pellicle membrane 10 was fixed so that it formed a square shape with sides measuring 1 cm. A displacement meter (Keyence Corporation's "LJ-V7200") was placed outside the chamber 20, facing the CNT pellicle membrane 10. Compressed air F was flowed into the chamber 20, creating a pressurized state inside the chamber 20, and a pressure ΔP was applied to the free-standing membrane portion of the CNT pellicle membrane 10. The pressure ΔP applied to the CNT pellicle membrane 10 is expressed as the difference between the pressure outside the chamber 20 (atmospheric pressure) P1 and the pressure inside the chamber 20, P2. The pressure inside the chamber 20, P2, was measured using a differential pressure gauge 21. The flow rate of the compressed air flowing into the chamber 20 is controlled by a flow meter (not shown), thereby adjusting ΔP.

[0142] As shown in Figure 4, the air flow rate flowing into the chamber 20 was increased by 10 sccm at one-minute intervals until the CNT pellicle film 10 broke. The differential pressure ΔP generated during this process was recorded. ａｉｒ The vertical axis shows the differential pressure ΔP×flow area (in Examples 1 to 4, the flow area is 1 cm ２ ), and the horizontal axis is the air flow rate V ａｉｒ The slope when (i.e., differential pressure ΔP × flow area / air flow rate V ａｉｒ The airflow resistance is calculated by dividing the airflow resistance by the membrane thickness to obtain the airflow resistance / membrane thickness.

[0143] [2.2.1] Airflow Resistance The airflow resistance of the CNT pellicle membrane was measured using the method described above.

[0144] [2.2.2] Ratio (Airflow Resistance / Film Thickness) The measured value of the airflow resistance was divided by the film thickness of the CNT pellicle film 10 to obtain the ratio (airflow resistance / film thickness).

[0145] [2.2.3] Deflection Amount The deflection amount of the CNT pellicle film when cut into a square with sides of 1 cm was measured using the method described above.

[0146] [2.2.4] Maximum Pressure The value of the differential pressure ΔP immediately before the CNT pellicle film 10 broke was defined as the "maximum pressure."

[0147] [2.2.5] Maximum Stress The membrane stress immediately before the CNT pellicle membrane 10 was broken was defined as the maximum stress σ. The maximum stress σ was calculated using the following formula (X2). The allowable range of the maximum stress σ is 50 MPa or more.

[0148]

[0149] In formula (X2), "ΔP" represents the pressure difference (P2-P1) (Pa), "a" represents 1 / 2 (m) of the short side length of the free-standing membrane portion (i.e., "a" represents 0.005 m), "d" represents the deflection amount (m) of the CNT pellicle membrane, and "t" represents the membrane thickness (m) of the CNT pellicle membrane.

[0150]

[0151] "Ratio (G / D)" in Table 2 indicates the ratio (G / D) of the CNT pellicle film.

[0152] [3] Results In Comparative Example 1, the fractal dimension of the CNT pellicle film was not 2.70 or more. Therefore, the maximum stress was less than 100 MPa. As a result, it was found that the CNT pellicle film of Comparative Example 1 was not a "carbon nanotube pellicle film that is resistant to film rupture even when the film thickness is thin."

[0153] In Examples 1 and 2, the fractal dimension of the CNT pellicle films was 2.70 or more. Therefore, the maximum stress was 100 MPa or more. As a result, it was found that the CNT pellicle films of Examples 1 and 2 were "carbon nanotube pellicle films that are resistant to rupture even when they are thin."

[0154] The disclosure of Japanese Patent Application No. 2024-127770, filed on August 2, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A carbon nanotube pellicle film having a fractal dimension of 2.70 or more.

2. A carbon nanotube pellicle film according to claim 1, comprising a plurality of carbon nanotubes having a tube diameter of 0.8 nm to 6.0 nm, the content of said plurality of carbon nanotubes being 30% or more of the total amount of the carbon nanotube pellicle film.

3. A carbon nanotube pellicle film according to claim 1, comprising a plurality of single-walled carbon nanotubes, the content of said plurality of single-walled carbon nanotubes being 30% or more of the total amount of the carbon nanotube pellicle film.

4. A carbon nanotube pellicle film as described in claim 1, wherein the ratio (G / D) is 5 or more, and the ratio (G / D) represents the ratio of the intensity of the G band measured by resonance Raman scattering measurement to the intensity of the D band measured by resonance Raman scattering measurement.

5. The carbon nanotube pellicle film according to claim 1, which has a transmittance of 88% or more for extreme ultraviolet rays.

6. The carbon nanotube pellicle film according to claim 1, wherein the maximum stress is 120 MPa or more.

7. The carbon nanotube pellicle film according to claim 1, which has a deflection of 200 μm or less when cut into a square with sides of 1 cm.

8. A pellicle comprising: a pellicle frame; and a carbon nanotube pellicle film according to any one of claims 1 to 7, supported by the pellicle frame.

9. An exposure master comprising: a photomask; and the pellicle according to claim 8 attached to the photomask.

10. An exposure apparatus comprising: an extreme ultraviolet light source that emits extreme ultraviolet light as exposure light; an exposure master according to claim 9; and an optical system that directs the exposure light emitted from the extreme ultraviolet light source to the exposure master, wherein the exposure master is positioned so that the extreme ultraviolet light emitted from the extreme ultraviolet light source passes through the carbon nanotube pellicle film and is irradiated onto the photomask.

11. A method for producing a carbon nanotube pellicle film according to claim 1, comprising: preparing a carbon nanotube raw material; and forming a dispersion containing the carbon nanotube raw material into a film to produce the carbon nanotube pellicle film, wherein the ratio (G / D) of the carbon nanotube raw material is 160 to 500, and the ratio (G / D) represents the ratio of the intensity of the G band measured by resonance Raman scattering measurement to the intensity of the D band measured by resonance Raman scattering measurement.

12. The method for producing a carbon nanotube pellicle film according to claim 11, wherein the carbon nanotube raw material comprises single-walled carbon nanotubes synthesized by a modified direct injection pyrolysis synthesis method.

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