Pellicle film and pellicle

Abstract

To provide a pellicle film which can secure EUV permeability, even if the pellicle film has a reduced void structure.SOLUTION: A pellicle film 10 has a porous structure, wherein the pellicle film 10 contains a carbon nanotube, the length of the carbon nanotube is 1 μm or more and 250 μm or less, a weight per unit area of the pellicle film is 0.71 μg / cm2 or more and 1 μg / cm2 or less, an average void diameter of voids, which is measured on the surface of the porous structure, is 30 nm or more and 60 nm or less, an average most adjacent inter-centroid distance between gaps is 50 nm or more and 70 nm or less, and light transmittance at a wavelength of 550 nm of 50% or more and 84.1% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pellicle film and a pellicle.

Background Art

[0002] In a manufacturing process of a semiconductor device or the like, for example, a photoresist is applied to a substrate such as a semiconductor wafer, light is irradiated onto the substrate coated with the photoresist using a photomask, and the photoresist is removed, whereby a target circuit pattern is formed on the substrate.

[0003] When light is irradiated with foreign matter adhering to the photomask, the adhering foreign matter may cause a problem in the circuit pattern formed on the substrate. For this reason, in order to suppress the adhesion of foreign matter to the photomask, a pellicle provided with a pellicle film for capturing foreign matter may be used. The pellicle is disposed above the photomask at a distance where the pellicle film does not contact the photomask.

[0004] In recent years, in order to form a finer circuit pattern, the use of extreme ultraviolet light (EUV) has been studied. EUV refers to light having a wavelength of 1 nm or more and 100 nm or less. As EUV, for example, specifically, light rays of about 13.5 nm ± 0.3 nm are being used. When EUV is irradiated onto the pellicle film, although EUV passes through the pellicle film, a part of the irradiated EUV is absorbed by the pellicle film. The light energy of the absorbed EUV is converted into thermal energy, whereby the temperature of the pellicle film rises. For this reason, the pellicle film is required to have EUV transparency, heat resistance, durability, and the like.

[0005] In a pellicle used in a process of forming a circuit pattern using EUV, carbon nanotubes are being studied as one of the materials used for the pellicle film provided in the pellicle.

[0006] For example, Patent Document 1 discloses a pellicle film containing carbon nanotubes in which at least a part of carbon is replaced by silicon at least on the surface layer side.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] The pellicle film containing carbon nanotubes disclosed in Patent Document 1 is said to be excellent in strength and EUV transmittance. However, Patent Document 1 does not mention the void characteristics on the surface of the pellicle film. Void characteristics are likely to affect foreign matter trapping properties and EUV transmittance. For example, in order to improve EUV transmittance, if the void structure such as the void diameter and the average nearest neighbor center-of-gravity distance between voids is expanded too much, the foreign matter trapping property will decrease. Therefore, it has been required that the pellicle film ensure high EUV transmittance while reducing the void structure.

[0009] An object of the present invention is to provide a pellicle film capable of ensuring EUV transmittance even when having a reduced void structure in a pellicle film containing carbon nanotubes, and a pellicle using the pellicle film.

Means for Solving the Problems

[0010] [1] A pellicle film having a porous structure, the pellicle film contains carbon nanotubes, the average void diameter of the voids measured on the surface of the porous structure is 60 nm or less, and the average nearest neighbor center-of-gravity distance between voids is 70 nm or less, pellicle film.

[0011] [2] In the pellicle film described in [1], wherein the average pore diameter is 20 nm or more and 60 nm or less, Pellicle film.

[0012] [3] In the pellicle film described in [1] or [2], wherein the average nearest neighbor center - of - gravity distance is 40 nm or more and 70 nm or less, Pellicle film.

[0013] [4] In the pellicle film described in any one of [1] to [3], wherein the length of the carbon nanotube is 0.1 μm or more and 1000 μm or less, Pellicle film.

[0014] [5] In the pellicle film described in any one of [1] to [4], wherein the cross - sectional diameter of the carbon nanotube is 0.2 nm or more and 50 nm or less, Pellicle film.

[0015] [6] In the pellicle film described in any one of [1] to [5], wherein the pellicle film is a porous structure formed by deposition of the carbon nanotubes, Pellicle film.

[0016] [7] In the pellicle film described in any one of [1] to [6], A pellicle film having self - standing property.

[0017] [8] A pellicle film according to any one of [1] to [7], a support having a frame portion and an opening surrounded by the frame portion, and supporting the pellicle film, comprising Pellicle.

Advantages of the Invention

[0018] According to one aspect of the present invention, there can be provided a pellicle film capable of ensuring EUV transmittance even when having a reduced void structure in a pellicle film containing carbon nanotubes, and a pellicle using the pellicle film.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0020] (Pellicle film) The pellicle film according to the present embodiment has a porous structure. The pellicle film contains carbon nanotubes, and the average pore diameter of the pores measured on the surface of the porous structure is 60 nm or less, and the average distance between the centers of gravity of the closest adjacent pores is 70 nm or less.

[0021] Since the pellicle film according to the present embodiment has the above configuration and is considered to have a void structure having a large number of relatively small voids, it can be said that it has a reduced void structure. And according to the pellicle film according to the present embodiment, by having a large number of relatively small voids, it is considered that EUV transmittance can be ensured even when having a reduced void structure. Further, according to the pellicle film according to the present embodiment, since it has a reduced void structure, while ensuring the transmittance of EUV transmittance, the foreign matter collection property is also improved. Note that the pellicle film according to the present embodiment has a reduced void structure and is considered to have a void structure of a certain size. Therefore, the transparency of the transmitted light passing through the pellicle film is ensured, and the foreign matter collection property is considered to be improved. As the void structure of a certain size, for example, in the case of the average void diameter, a void structure with an average void diameter of 20 nm or more is exemplified. Further, as the void structure of a certain size, for example, in the case of the average nearest neighbor center-to-center distance, a void structure with an average nearest neighbor center-to-center distance of 40 nm or more is exemplified.

[0022] The means for adjusting the pellicle film to have an average void diameter of the voids measured on the surface of the porous structure of 60 nm or less and an average nearest neighbor center-to-center distance between the voids of 70 nm or less is not particularly limited. For example, in an example of a preferred manufacturing method of the pellicle film described later, the means for adjusting the amount of carbon nanotubes contained in the pellicle film (for example, the amount of carbon nanotubes contained in the carbon nanotube film product which is an intermediate product when forming the pellicle film, or the amount of carbon nanotubes in the carbon nanotube dispersion when forming the carbon nanotube film product) and the dispersion intensity of the carbon nanotubes are mentioned.

[0023] The carbon nanotubes contained in the pellicle film according to the present embodiment are not particularly limited, and it is 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).

[0024] The carbon nanotubes can be obtained by known manufacturing methods such as arc discharge method, laser ablation method, and chemical vapor deposition.

[0025] The length of the carbon nanotube is preferably, for example, 0.1 μm or more and 1000 μm or less. The length of the carbon nanotube is more preferably 0.5 μm or more, and even more preferably 1 μm or more. The length of the carbon nanotube is more preferably 600 μm or less, and even more preferably 400 μm or less.

[0026] The cross-sectional diameter of the carbon nanotube is preferably 0.2 nm or more and 50 nm or less. The cross-sectional diameter of the carbon nanotube is more preferably 0.5 nm or more, and even more preferably 1 nm or more. The cross-sectional diameter of the carbon nanotube is more preferably 30 nm or less, and even more preferably 20 nm or less. In this specification, the cross-sectional diameter may sometimes be simply referred to as the diameter.

[0027] From the viewpoint of facilitating ensuring EUV transmittance, the average pore diameter in the pores measured on the surface of the porous structure of the pellicle film may be, for example, 20 nm or more and 60 nm or less. The average pore diameter may be 25 nm or more, or may be 30 nm or more. The average pore diameter may be 55 nm or less, or may be 50 nm or less.

[0028] In this specification, the pore diameter means the diameter (i.e., the equivalent circle diameter) in a virtual circle obtained by imagining a circle having the same area as the area of the pore.

[0029] From the viewpoint of facilitating ensuring EUV transmittance, the average distance between the centers of gravity of the closest adjacent pores in the pores measured on the surface of the porous structure of the pellicle film is preferably, for example, 40 nm or more and 70 nm or less. The average distance between the centers of gravity of the closest adjacent pores may be 45 nm or more, or may be 50 nm or more. The average distance between the centers of gravity of the closest adjacent pores may be 68 nm or less, or may be 67 nm or less.

[0030] In this specification, the distance between the centers of gravity of the closest adjacent voids is the distance between the center of gravity of one void and the center of gravity of the void that is closest and adjacent to the one void. That is, in the case of adjacent voids, it means the distance from the center of gravity of one void to the center of gravity of the other void.

[0031] That is, the pellicle film according to the present embodiment may have an average void diameter of the voids measured on the surface of the porous structure of 20 nm or more and 60 nm or less, and an average distance between the centers of gravity of the closest adjacent voids of 40 nm or more and 70 nm or less.

[0032] In the void characteristics measured on the surface of the porous structure of the pellicle film, the void characteristics of the average void diameter and the average distance between the centers of gravity of the closest adjacent voids 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, for example, a reasonable result is likely to be obtained regardless of the measurer. The measurement method of the void characteristics is specifically as shown in the examples described later.

[0033] (1) Step of preparing a pellicle film. (2) Step of imaging the surface of the prepared pellicle film to obtain image data of the pellicle film. (3) In the range from the first pixel value to the second pixel value larger than the first pixel value for the image data, a plurality of different threshold values of 3 or more are set at equal intervals as initial threshold values, and binarization processing is performed based on each of the initial threshold values to obtain binarization processing image data based on the initial threshold values. (4) Step of obtaining an initial measured value of calculating the distribution of the void characteristics of the voids on the surface of the pellicle film by performing blob analysis on the binarization processing image data based on the initial threshold values. (5) Step of obtaining an initial theoretical value of the distribution of the void characteristics obtained by the probability density function of the lognormal distribution based on the initial measured value. (6) Step of obtaining the error between the initial measured value and the initial theoretical value. When the error between the initial measured value and the initial theoretical value is not the smallest, the threshold value is reset, and binarization processing is performed on the image data based on the reset threshold value of the reset, and binarized image data based on the reset threshold value is obtained. By performing blob analysis on the binarized image data based on the reset threshold value, a re-measured actual value of the distribution of the void characteristics on the surface of the pellicle film is obtained. (8) A step of obtaining an error between the re-measured actual value and the re-measured theoretical value of the distribution of the void characteristics obtained by the probability density function of the lognormal distribution based on the re-measured actual value. (9) When the error between the re-measured actual value and the re-measured theoretical value is not the smallest, the steps of obtaining the re-measured actual value and obtaining the error from the re-measured theoretical value are repeated until the error between the re-measured actual value and the re-measured theoretical value is the smallest. (10) A step of obtaining the distribution of the void characteristics calculated based on the threshold value when the error between the initial measured value and the initial theoretical value or the error between the re-measured actual value and the re-measured theoretical value is the smallest as the final measured value.

[0034] The threshold value when the error is the smallest is preferably determined by using various known optimization algorithms. For example, in the steps from (4) to (9) above, it is preferable to use various known optimization algorithms to search for the threshold value when the aforementioned error becomes the minimum value. In this case, after determining the initial threshold value, a unique threshold value will be determined by using the optimization algorithm.

[0035] In the step of obtaining the binarized image data based on the initial threshold value, the initial threshold value is not limited to the above, and within the range from the first pixel value to the second pixel value larger than the first pixel value, a plurality of different threshold values of 5 or more may be set at equal intervals, or a plurality of different threshold values of 7 or more may be set. It is preferable that the interval between the first pixel value and the second pixel value is 100 or more. The first pixel value is preferably set in the range of 20 or more and 50 or less. The second pixel value is preferably set in the range of 150 or more and 240 or less. The equal interval means that when n threshold values are set as the plurality of different threshold values of 3 or more, the interval between the nth threshold value and the (n - 1)th threshold value, and the interval between the (n - 1)th threshold value and the (n - 2)th threshold value are equal, indicating that the intervals between adjacent threshold values are equal. Specifically, the initial threshold value can be set as a plurality of different threshold values of 3 or more and 12 or less at equal intervals within the range from the pixel value 20 to the pixel value 240, for example. In addition, in the step of obtaining the actually measured value of the remeasurement, the threshold value to be reset is not a plurality of different threshold values of 3 or more, but one threshold value.

[0036] The void characteristics may be measured, for example, by an apparatus including a program that causes a computer to execute the steps (1) to (10) above. The program may be recorded on a recording medium.

[0037] The thickness of the pellicle film is preferably 3 nm or more and 1000 nm or less. The thickness of the pellicle film is preferably 10 nm or more, and more preferably 20 nm or more. The thickness of the pellicle film is preferably 500 nm or less, and more preferably 300 nm or less. If the thickness of the pellicle film is, for example, 3 nm or more and 1000 nm or less, it becomes easier to ensure EUV transmittance. Also, the operability of the pellicle film is improved.

[0038] The weight per unit area of the pellicle film is not particularly limited. For example, 0.1 μg / cm 2 or more and 20 μg / cm 2The following are preferred. The weight per unit area of the pellicle film is 0.5 μg / cm 2 or more, more preferably 1 μg / cm 2 or more, and even more preferably 15 μg / cm 2 or less, more preferably 10 μg / cm 2 or less, and even more preferably. If the weight per unit area of the pellicle film is, for example, 0.1 μg / cm 2 or more and 20 μg / cm 2 or less, it becomes easier to ensure EUV transmittance.

[0039] The pellicle film according to this embodiment is preferably a porous structure formed by depositing carbon nanotubes. The porous structure formed by depositing carbon nanotubes can be manufactured by an example of a preferred manufacturing method of the pellicle film described later. If it is a porous structure formed by depositing carbon nanotubes, it becomes easier to ensure EUV transmittance.

[0040] From the viewpoint of improving the transparency of the pellicle film to the exposure light, the pellicle film according to this embodiment preferably has self-supporting properties. That the pellicle film has self-supporting properties means that the pellicle film itself is in a self-supporting state, indicating that the pellicle film is a film having self-supporting retention properties (also referred to as a self-supporting film). That is, a pellicle film having self-supporting properties is a film that can maintain its shape by itself without the presence of a substrate or the like.

[0041] (Manufacturing method of pellicle film) The manufacturing method of the pellicle film is not particularly limited. An example of a preferred manufacturing method of the pellicle film includes, for example, a step (P1) of dispersing carbon nanotubes, a step (P2) of sedimenting and depositing the dispersed carbon nanotubes on a breathable member to obtain a carbon nanotube film product formed in a mat shape on the breathable member, and a step (P3) of removing the breathable member from the carbon nanotube film product to obtain a pellicle film.

[0042] First, in step P1, carbon nanotubes are dispersed in a liquid as a dispersion medium to prepare a carbon nanotube dispersion in which the carbon nanotubes are dispersed in the liquid. The liquid may be a liquid containing water. The carbon nanotube dispersion may contain only carbon nanotubes as a dispersoid. The carbon nanotube dispersion may contain various additives such as a dispersant for dispersing the carbon nanotubes in addition to the carbon nanotubes.

[0043] For example, by adjusting the balance between the dispersion intensity when dispersing carbon nanotubes in a liquid in step P1 and the weight per unit area of the carbon nanotubes when producing a carbon nanotube film in step P2, a perlicle film having an average pore diameter of 60 nm or less and an average nearest-neighbor center-to-center distance between pores of 70 nm or less can be easily obtained. For example, specifically, when the weight per unit area of the carbon nanotubes is set to a certain amount or more, it is easy to satisfy the range where the average pore diameter is 60 nm or less. If the weight per unit area of the carbon nanotubes is reduced too much, the average pore diameter tends to exceed 60 nm. Also, for example, when the dispersion intensity is suppressed to a certain range, it is easy to satisfy the range where the average nearest-neighbor center-to-center distance between pores is 70 nm or less. If the dispersion intensity is increased too much, the average nearest-neighbor center-to-center distance between pores tends to exceed 70 nm.

[0044] The weight per unit area of the carbon nanotubes and the dispersion intensity are, for example, in the range of 0.1 μg / cm 2 or more and 20 μg / cm 2 or less, as the amount of carbon nanotubes contained in the carbon nanotube film produced in step P2. Also, when a stirrer is used as a dispersing machine for dispersing the carbon nanotubes, the dispersion intensity is, for example, in the range of a peripheral speed of the stirrer of 10 m / s or more and 60 m / s or less, and the stirring time of the stirrer is, for example, 5 minutes or more and 60 minutes or less.

[0045] Next, in step P2, the dispersed carbon nanotubes are sedimented and deposited onto the air-permeable member. For example, by filtering the carbon nanotube dispersion prepared in step P1 with a filter membrane as the air-permeable member, the carbon nanotubes are sedimented and deposited to form a film-like product of carbon nanotubes in a mat shape on the filter membrane. The filter membrane is preferably, for example, a membrane filter or the like.

[0046] Next, in step P3, the filter membrane is removed from the film-like product of carbon nanotubes formed in a mat shape to obtain a pellicle film containing carbon nanotubes. Before removing the filter membrane from the film-like product of fibers formed in a mat shape, or after removing the filter membrane from the film-like product of fibers formed in a mat shape, a drying step may be provided as necessary. The obtained pellicle film is a self-supporting film.

[0047] (Pellicle) The pellicle according to the present embodiment includes the pellicle film according to the above-described embodiment, a frame portion, and a support body that has an opening surrounded by the frame portion and supports the pellicle film.

[0048] Hereinafter, the pellicle according to the present embodiment will be described with reference to the drawings. In the drawings referred to in this specification for explanation, there are some portions that are illustrated enlarged or reduced for ease of explanation.

[0049] FIG. 1 shows a plan view of the pellicle 100 as viewed from above the surface on which the pellicle film 10 is installed, and FIG. 2 shows a cross-sectional view of the pellicle 100 shown in FIG. 1. The pellicle 100 includes a pellicle film 10 and a support 30 that supports the pellicle film 10. The support 30 includes a frame portion 31 and an opening 32 surrounded by the frame portion 31, and the opening 32 penetrates from one surface to the other surface of the support 30. Both the frame portion 31 and the opening 32 are formed in a rectangular shape, and the four corners of the outer shape of the frame portion 31 are all rounded. The frame portion 31 includes a support surface 33 facing the pellicle film 10. The pellicle film 10 is formed in a rectangular shape and includes a first pellicle film surface 11 facing the support surface 33 of the support 30 and a second pellicle film surface 12 on the side opposite to the first pellicle film surface 11. The peripheral edge 13 of the pellicle film 10 is fixed to a part of the support surface 33 of the frame portion 31 and covers the opening 32 of the support 30.

[0050] The pellicle film 10 is the pellicle film according to the above-described embodiment. As the material of the support 30, for example, resin materials (such as polyethylene), metal materials (such as aluminum, aluminum alloy, magnesium alloy, stainless steel, and titanium), ceramic materials (such as SiC), and fiber-reinforced plastic materials (such as carbon fiber-reinforced plastic) are used.

[0051] In the pellicle film 10, for the sake of clarity, the terms "first pellicle film surface 11" and "second pellicle film surface 12" are used to clarify the positional relationship between the surface facing the support surface 33 of the support 30 and the surface on the opposite side. Therefore, in some cases, both the first pellicle film surface 11 and the second pellicle film surface 12 can be interchanged and used, and the first pellicle film surface 11 and the second pellicle film surface 12 can be used without distinction from each other.

[0052] The above described an example of the pellicle according to the present embodiment with reference to FIGS. 1 and 2. However, the pellicle according to the present embodiment is not limited thereto. The pellicle according to the present embodiment can adopt various forms as long as the effects of the pellicle using the pellicle film according to the above-described present embodiment can be obtained. The shape, dimensions, etc. of each part of each member constituting the pellicle according to the present embodiment may be determined according to, for example, the dimensions of a photomask (not shown) when the pellicle according to the present embodiment is used.

[0053] For example, in the pellicle 100 shown in FIGS. 1 and 2, both the pellicle film 10 and the support 30 are formed in a rectangular shape. The pellicle according to the present embodiment is not limited thereto, and may be formed in any desired shape such as circular, elliptical, and polygonal.

[0054] Also, for example, in the pellicle 100 shown in FIGS. 1 and 2, the peripheral portion 13 of the pellicle film 10 is fixed to a part of the support surface 33 of the support 30. The pellicle 100 is not limited thereto, and the peripheral portion 13 of the pellicle film 10 may be fixed to the entire surface of the support surface 33 of the support.

[0055] Also, for example, in FIGS. 1 and 2, the pellicle film 10 and the support 30 may be fixed by providing an adhesive layer (not shown). The adhesive layer is a layer provided as needed. The material constituting the adhesive layer is not particularly limited, and for example, various adhesives such as acrylic resin, epoxy resin, silicone resin, polyimide resin, and fluororesin, as well as carbon nanotubes, etc. may be used.

[0056] (Method for manufacturing a pellicle) An example of a preferable manufacturing method of the pellicle according to the present embodiment includes a step of preparing a pellicle film according to the present embodiment, a step of preparing a support having a frame portion and an opening surrounded by the frame portion, and supporting the pellicle film, and a step of providing a pellicle film on the support so as to cover the opening and be supported by a support surface of the frame portion. The manufacturing method may include a step of providing an adhesive layer on at least a part of the support surface of the frame portion as necessary.

[0057] For the step of preparing the pellicle film according to the present embodiment, the pellicle film according to the above-described embodiment may be prepared. For the step of preparing the support, a support formed in a target shape may be prepared by using a material constituting the above-described support and by a known method. For the step of providing the pellicle film, the pellicle film may be installed by a known method so as to cover the opening and be supported by the support surface of the frame portion. When an adhesive layer is provided on at least a part of the support surface of the frame portion, the pellicle film is installed so as to be supported by the support surface of the frame portion via the adhesive layer. When various adhesives are used for the adhesive layer, for the step of providing the adhesive layer, an adhesive layer containing an adhesive is provided by applying the adhesive to the support surface. When carbon nanotubes are used for the adhesive layer, for the step of providing the adhesive layer, for example, an adhesive layer containing carbon nanotubes is provided by applying and drying a dispersion liquid of carbon nanotubes to the support surface.

[0058] The pellicle according to the present embodiment is used, for example, above the photomask and spaced apart from the photomask so that the first pellicle film surface faces the photomask. By using the pellicle according to the present embodiment, EUV transmissivity is ensured. Further, since the void structure of the pellicle film according to the present embodiment is reduced, the foreign matter capturing property is enhanced, and the effect of suppressing the adhesion of foreign matter to the photomask is enhanced.

[0059] Note that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within the range that can achieve the object of the present invention are included in the present invention.

Example

[0060] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples at all.

[0061] [Example 1] [Preparation of Pericle Membrane] As carbon nanotubes (hereinafter referred to as CNTs), CNTs with a diameter of 0.2 nm or more and 50 nm or less and a length of 1 μm or more and 250 μm or less were prepared. The prepared CNTs were weighed so that the concentration in the aqueous dispersion of CNTs was 0.02% by mass. Further, as a dispersant, carboxymethyl cellulose (hereinafter referred to as CMC) was weighed so that the concentration in the aqueous dispersion was 0.2% by mass. The weighed CNTs and the weighed CMC were put into water, and using a thin-film swing-type high-speed stirrer (manufactured by Primix Corporation, product name "Filmix"), at a peripheral speed of 40 m / s and a dispersion time of 25 minutes, the CNTs were dispersed in water to prepare an aqueous dispersion of CNTs. The shear rate when the CNTs were dispersed was approximately 4.0×10 5 s -1 . Next, the aqueous dispersion of CNTs was diluted so that the concentration of CNTs became 1 ppm. Next, the aqueous dispersion of diluted CNTs was put into a filter so that the mass of CNTs contained in the pericle membrane (denoted as the mass inside the CNT membrane in Table 1) became 0.71 μg / cm 2 . Next, the aqueous dispersion of CNTs put into the filter was filtered through a membrane filter to form a mat-like CNT film product on the membrane filter. Thereafter, the mat-like CNT film product was peeled off from the membrane filter to prepare a pericle membrane containing CNTs. The pericle membrane was a self-supporting membrane. From the obtained pericle membrane, the average pore diameter and the average distance between the centers of gravity of the nearest neighbors between pores were calculated according to the pore analysis of the pericle membrane described below.

[0062] [Pore Analysis of Pericle Membrane] The surface of the pellicle film obtained in each example was observed with a scanning electron microscope (SEM: Scanning Electron Microscope) (manufactured by Carl Zeiss, CrossBeam550), and the image data of the SEM image was acquired. The imaging conditions were an acceleration voltage of 1 kV and a magnification of 10,000 times. The number of fields of view was set to 3 or more.

[0063] From the image data of the obtained SEM images, the void diameter (pore size) was analyzed with the equivalent circle diameter. First, for one field of view of the image data of the SEM image, the initial binarization threshold was set at seven equally spaced values of 40, 60, 80, 100, 120, 140, and 160 at intervals of 20 in the range from pixel value 40 to pixel value 160. With each binarization threshold, seven sets of binarized image data were obtained. This operation was performed on the image data of 3 or more fields of view. Next, for the obtained binarized image data, the initial void diameter distribution based on the initial binarization threshold was measured. Then, using Bayesian optimization for fitting so that the measured values of the void diameter distribution were well approximated (fitted) by a lognormal distribution, the binarization threshold that minimized the error between the measured values of the void diameter distribution and the theoretical values of the void diameter distribution was automatically searched for. And based on the void diameter distribution and the distribution of the nearest neighbor centroid distance between voids measured with the binarization threshold when the error between the measured values of the void diameter distribution and the theoretical values of the void diameter distribution was minimized, the average void diameter and the average nearest neighbor centroid distance between voids were calculated.

[0064] <Transmittance Evaluation at Wavelength 550 nm> For the pellicle obtained in each example, the light transmittance from wavelength 200 nm to 800 nm was measured using an ultraviolet-visible-near-infrared spectrophotometer (manufactured by Shimadzu Corporation, product name "UV-VIS-NIR SPECTROPHOTOMETER UV-3600"), and the light transmittance (%) at wavelength 550 nm was extracted. For the measurement, the attached large sample chamber MPC-3100 was used, and the measurement was performed without using the built-in integrating sphere.

[0065] It is known that there is a correlation between the light transmittance at a wavelength of 13.5 nm and the light transmittance at a wavelength of 550 nm for a pellicle film containing CNTs (see, for example, Marina, Y., et al., “CNT EUV pellicle tunability and performance in a scanner-like environment,” Proc. SPIE 11609, Extreme Ultraviolet (EUV) Lithography XII, 116090Y, (23 March 2021). Figure 4(a); doi: 10.1117 / 12.2584519). Therefore, it is possible to evaluate the light transmittance at a wavelength of 13.5 nm (i.e., evaluate EUV transmittance) by evaluating the light transmittance at a wavelength of 550 nm. Note that if the light transmittance at a wavelength of 550 nm is 85% or more, it is easy to ensure, for example, a high EUV transmittance (e.g., EUV transmittance of 94% or more). In the pellicle film according to this embodiment, if the light transmittance at a wavelength of 550 nm is 50% or more, the EUV transmittance is also excellent, and it can be determined that a high EUV transmittance is obtained.

[0066] [Examples 2 to 5 and Comparative Examples 1 to 4] According to Table 1, a pellicle film was produced in the same manner as in Example 1 except that the dispersion intensity and the mass of CNTs contained in the pellicle film (mass inside the CNT film) were changed, and void analysis of the pellicle film and evaluation of the transmittance at a wavelength of 550 nm were performed.

[0067]

Table 1

[0068] From the above results, it can be seen that a pellicle film having an average pore diameter of 60 nm or less and an average nearest neighbor center-of-gravity distance between pores of 70 nm or less has excellent transmittance evaluation results at a wavelength of 550 nm. Therefore, according to one embodiment of the present invention, a pellicle film with guaranteed EUV transmittance and a pellicle using the pellicle film can be provided, even though the pore structure is reduced. Further, according to one embodiment of the present invention, since the pore structure is reduced, it is predicted that the foreign matter collection effect is also high. Note that the transmittance at a wavelength of 550 nm in each comparative example is better than that in each example, which is because each comparative example has a relatively large pore structure. And it can be predicted that a comparative example having a relatively large pore structure has a low foreign matter collection effect.

Explanation of Signs

[0069] 10... Pellicle film, 11... First pellicle film surface, 12... Second pellicle film surface, 13... Peripheral portion, 30... Support, 31... Frame portion, 32... Opening, 33... Support surface, 100... Pellicle.

Claims

1. A pellicle film having a porous structure, wherein the pellicle film contains carbon nanotubes, the length of the carbon nanotubes is 1 μm or more and 250 μm or less, The weight per unit area of the pellicle film is 0.71 μg / cm ２ or more and 1 μg / cm ２ or less, the average pore diameter of the pores measured on the surface of the porous structure is 30 nm or more and 60 nm or less, and the average nearest-neighbor center-to-center distance between the pores is 50 nm or more and 70 nm or less, and the light transmittance at a wavelength of 550 nm is 50% or more and 84.1% or less, pellicle film.

2. The pellicle film according to Claim 1, wherein the cross-sectional diameter of the carbon nanotubes is 0.2 nm or more and 50 nm or less, pellicle film.

3. The pellicle film according to Claim 1 or Claim 2, wherein the pellicle film is a porous structure formed by deposition of the carbon nanotubes, pellicle film.

4. The pellicle film according to Claim 1 or Claim 2, which has self-supporting property, pellicle film.

5. The pellicle film according to Claim 1 or Claim 2, and a support having a frame portion and an opening surrounded by the frame portion, for supporting the pellicle film, comprising pellicle.

Images