Method for manufacturing carbon nanotube self-supporting film and method for manufacturing pellicle

Abstract

The present invention provides: a method for manufacturing a carbon nanotube self-supporting film characterized in that a carbon nanotube film 1 is formed on a membrane filter 10, the thickness of an outer circumferential portion 1b of the carbon nanotube film is made thicker than the thickness of a carbon nanotube of an inner diameter portion 1a, a first frame-shaped member 2 is connected to the outer circumferential portion 1b of the carbon nanotube film, and the carbon nanotube film 1 is separated from the membrane filter 10; and a method for manufacturing a pellicle in which, after the carbon nanotube self-supporting film 1 is manufactured, a second frame-shaped member 3 having a frame size smaller than that of the first frame-shaped member 2 is used, the carbon nanotube self-supporting film 1 is a pellicle film 1c, and the second frame-shaped member 3 is a pellicle frame. The present invention makes it possible to stably manufacture a carbon nanotube film as a self-supporting film of a pellicle.

Description

Method for manufacturing carbon nanotube self-supporting film and method for manufacturing pellicle

[0001] The present invention relates to a method for manufacturing a carbon nanotube self-supporting film and a method for manufacturing a pellicle, which are used as a pellicle film of a pellicle used for removing dust from a lithography mask used when manufacturing semiconductor devices such as LSIs and super LSIs, liquid crystal display panels, and the like.

[0002] The development of an exposure technique called photolithography has enabled high integration of semiconductor integrated circuits.

[0003] Currently, the commercialized exposure process uses exposure equipment utilizing the 193 nm ArF wavelength band to progress the transfer process and form fine patterns on the wafer. However, since there are limitations in forming fine patterns of 32 nm or less, various methods such as immersion lithography, double exposure, phase transition, and optical phase correction have been developed. However, it is difficult to realize circuit line widths of 32 nm or less that are further miniaturized with exposure techniques using the ArF wavelength. Therefore, extreme ultraviolet (hereinafter referred to as EUV) photolithography technology using EUV light with a short wavelength of 13.5 nm as the main exposure wavelength compared to the 193 nm wavelength is attracting attention as a next-generation process.

[0004] On the other hand, in the photolithography process, a photomask is used as a master plate for patterning, and the pattern on the photomask is transferred to the wafer. At this time, if impurities such as particles and foreign substances adhere to the photomask, the exposure light is absorbed or reflected by the impurities, and the transferred pattern is damaged, leading to a decrease in the performance and yield of the semiconductor device.

[0005] Therefore, a method of attaching a pellicle to the photomask is employed to prevent impurities from adhering to the surface of the photomask. The pellicle is placed on the upper surface of the photomask, and even if impurities adhere to the pellicle, during the photolithography process, the focus coincides with the pattern on the photomask, so dust or foreign matter on the pellicle will not be focused and will not be transferred to the pattern. Recently, with the miniaturization of circuit line widths, the size of impurities that can affect pattern damage has also decreased, and the role of the pellicle in protecting the photomask has become even more important.

[0006] When the pellicle is constructed as a single film, applying a material with a low extinction coefficient to extreme ultraviolet light at 13.5 nm as the pellicle film makes it easy to ensure the transmittance of the pellicle film, but it is extremely difficult to ensure excellent mechanical and thermal properties.

[0007] The pellicle film for EUV pellicles is typically manufactured by laminating silicon nitride (SiN) or the like on a silicon wafer substrate. On the other hand, development is underway on pellicles using carbon nanotube films as a material with high transmittance to EUV light and high resistance to EUV. Patent documents 1 and 2 below disclose EUV pellicles using carbon nanotube films.

[0008] However, when using carbon nanotube membranes as pellicle membranes, it is difficult to stably produce self-supporting membranes.

[0009] International Publication No. 2014 / 142125, International Publication No. 2018 / 008594

[0010] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a carbon nanotube self-supporting membrane and a pellicle, which can stably produce the carbon nanotube membrane as a self-supporting membrane for a pellicle when the carbon nanotube membrane is used as the pellicle membrane.

[0011] The inventors of the present invention have conducted extensive research to achieve the above objectives and have discovered that a self-supporting carbon nanotube membrane can be stably manufactured by forming a carbon nanotube membrane on a membrane filter, making the thickness of the outer periphery of the carbon nanotube membrane greater than the thickness of the carbon nanotubes in the inner diameter portion, connecting a first frame-like member to the outer periphery of the carbon nanotube membrane, and separating the carbon nanotube membrane from the membrane filter. This has led to the completion of the present invention.

[0012] Accordingly, the present invention provides the following methods for manufacturing a carbon nanotube self-supporting membrane and a pellicle: 1. A method for manufacturing a carbon nanotube self-supporting membrane, characterized by forming a carbon nanotube membrane on a membrane filter, making the thickness of the outer periphery of the carbon nanotube membrane thicker than the thickness of the carbon nanotubes in the inner diameter portion, connecting a first frame-shaped member to the outer periphery of the carbon nanotube membrane, and separating the carbon nanotube membrane from the membrane filter. 2. The method for manufacturing a carbon nanotube self-supporting membrane according to claim 1, wherein the thickness of the outer periphery of the carbon nanotube is 20 nm or more thicker than the thickness of the carbon nanotubes in the inner diameter portion. 3. The method for manufacturing a carbon nanotube self-supporting membrane according to claim 1 or 2, wherein the thickness of the inner diameter portion of the carbon nanotube membrane is 10 to 100 nm. 4. The method for manufacturing a carbon nanotube self-supporting membrane according to claim 1 or 2, wherein the carbon nanotube membrane has a transmittance of 90% or more to radiation having a wavelength of 13.5 nm. 5. A method for manufacturing a pellicle, characterized by forming a carbon nanotube film on a membrane filter, making the thickness of the outer periphery of the carbon nanotube film thicker than the thickness of the carbon nanotubes in the inner diameter portion, connecting a first frame-shaped member to the outer periphery of the carbon nanotube film, separating the carbon nanotube film from the membrane filter to produce a self-supporting carbon nanotube film on the first frame-shaped member, then using a second frame-shaped member having a frame size smaller than the first frame-shaped member to connect the second frame-shaped member and the self-supporting carbon nanotube film, and then separating a portion of the self-supporting carbon nanotube film from the first frame-shaped member, thereby obtaining a pellicle in which the self-supporting carbon nanotube film is a pellicle film and the second frame-shaped member is a pellicle frame.

[0013] According to the method for producing a carbon nanotube self-supporting membrane of the present invention, a carbon nanotube self-supporting membrane can be stably produced when the carbon nanotube membrane is used as a pellicle membrane. Furthermore, even when producing a pellicle membrane that is extremely thin and difficult to transfer, the manufacturing method of the present invention can be used to reliably and stably produce a pellicle membrane and pellicle using a carbon nanotube self-supporting membrane.

[0014] This is a schematic diagram showing the formation of a carbon nanotube film on a membrane filter in a method for manufacturing a carbon nanotube self-supporting film according to one embodiment of the present invention, where (A) is a plan view and (B) is a front view. This is a schematic diagram showing the connection of a first frame-shaped member to the outer periphery of a carbon nanotube film in a method for manufacturing a carbon nanotube self-supporting film according to one embodiment of the present invention, where (A) is a plan view and (B) is a front view. This is a schematic diagram showing the separation of a carbon nanotube film from a membrane filter in a method for manufacturing a carbon nanotube self-supporting film according to one embodiment of the present invention, where (A) is a plan view and (B) is a front view. This is a schematic diagram showing the connection of a second frame-shaped member to a carbon nanotube self-supporting film in a method for manufacturing a carbon nanotube self-supporting film according to one embodiment of the present invention, where (A) is a plan view and (B) is a front view. This is a schematic diagram showing the separation of a part of a carbon nanotube self-supporting film from a first frame-shaped member in a method for manufacturing a carbon nanotube self-supporting film according to one embodiment of the present invention, where (A) is a plan view and (B) is a front view. In a method for manufacturing a self-supporting carbon nanotube film according to one embodiment of the present invention, the self-supporting carbon nanotube film is a pellicle film, and the second frame-shaped member is a pellicle frame. This is a schematic diagram showing the pellicle, where (A) is a plan view and (B) is a front view.

[0015] (1-1. Method for Manufacturing Self-Standing Pellicle Films) The method for manufacturing self-standing pellicle films, more specifically carbon nanotube self-standing films, used for pellicles in EUV photolithography will be explained below with reference to the drawings.

[0016] (1-1-1. Formation of Carbon Nanotube Film) First, as shown in Figures 1(A) and 1(B), a carbon nanotube film 1 is formed on the membrane filter 10. In this embodiment, it is preferable to use carbon nanotubes that have been formed on the membrane filter 10 by a suspended catalyst CVD (Chemical Vapor Deposition) method, in which a metal catalyst is present in the reaction system, carbon monoxide is used as the carbon raw material, and carbon dioxide is added as the oxidizing agent.

[0017] Specific examples of metal catalysts include metal complexes of Fe, Co, Ni, Mo, or combinations thereof.

[0018] The concentration of carbon dioxide is preferably 0.1% to 1.0% relative to the concentration of carbon monoxide.

[0019] Under a metal catalyst, the reaction temperature for carbon monoxide and the reaction temperature for carbon dioxide are preferably between 700°C and 1000°C.

[0020] The thickness of the inner diameter portion 1a of the carbon nanotube film 1 obtained by the above method is preferably 10 nm to 100 nm, more preferably 10 nm to 70 nm, even more preferably 10 nm to 50 nm, and most preferably 10 nm to 30 nm. On the other hand, the thickness of the outer peripheral portion 1b of the carbon nanotube film 1 is preferably 20 nm or more thicker than the thickness of the inner diameter portion 1a. As will be described later, when connecting the first frame-shaped member 2 to the outer peripheral portion 1b of the carbon nanotube film 1, the thickness of the outer peripheral portion 1b of the carbon nanotube film 1 is made thicker than the thickness of the inner diameter portion 1a, thereby ensuring the strength of the carbon nanotube film 1 at the connection point with the first frame-shaped member 2, preventing damage to the carbon nanotubes, and allowing the carbon nanotube film 1 to be easily separated from the membrane filter 10. The thinner the carbon nanotube film 1 is, the lower its strength becomes. Therefore, when connecting the carbon nanotube film 1 to the first frame-shaped member 2 and separating it from the membrane filter 10, the carbon nanotubes are more likely to be damaged, making it difficult to form a self-supporting film.

[0021] The outer peripheral portion 1b of the carbon nanotube film 1 refers to the region that contacts the first frame-shaped member 2, and the inner diameter portion 1a of the carbon nanotube film 1 refers to the region excluding the outer peripheral portion 1b.

[0022] The thickness of the carbon nanotube film 1 can be evaluated using a step meter, such as a stylus-type surface profile analyzer (Veeco: Dektak 150). Alternatively, the step difference between the carbon nanotube film 1 (e.g., 10 mm x 10 mm in size) transferred to a substrate (e.g., a silicon wafer) and the substrate can be measured using a step meter, and this value or the average of these values ​​may be used as the thickness of the carbon nanotube film.

[0023] The membrane filter 10 may be either hydrophobic or hydrophilic. Its components may include nitrocellulose, PTFE, polycarbonate, PVDF, etc. While the membrane filter is generally circular, its shape is not particularly limited. The thickness of the membrane filter is not particularly limited, but is preferably between 50 μm and 1000 μm, and more preferably between 100 μm and 500 μm from a handling standpoint. Furthermore, the pore size of the membrane filter is preferably between 0.1 μm and 1.0 μm, and more preferably between 0.2 μm and 0.5 μm from a handling standpoint.

[0024] (1-1-2. Connection to Frame-Shaped Member) Next, as shown in Figures 2(A) and 2(B), the first frame-shaped member 2 is connected to the outer periphery 1b of the carbon nanotube film 1. For example, stainless steel is used for the first frame-shaped member 2. However, the first frame-shaped member is not limited to stainless steel, and metal materials such as brass, aluminum, aluminum alloys (5000 series, 6000 series, 7000 series, etc.), copper, organic resin materials such as fluororesin, acrylic resin, epoxy resin, or ceramic materials such as boron nitride, silicon nitride, or aluminum oxide may be used. Furthermore, the first frame-shaped member 2 has a frame shape when viewed from above. In this case, the first frame-shaped member 2 may be annular, rectangular, or polygonal.

[0025] Furthermore, when connecting the carbon nanotube film 1 and the first frame-shaped member 2, an adhesive may be used. The adhesive may be a liquid that has been cured, or it may be in the form of a film. Organic resin materials such as silicone resin, acrylic resin, or epoxy resin can be used as the adhesive.

[0026] As shown in Figures 3(A) and 3(B), after connecting the carbon nanotube membrane 1 and the first frame-shaped member 2, the carbon nanotube membrane 1 can be separated from the membrane filter 10 by moving the first frame-shaped member 2 away from the membrane filter 10. In other words, a self-supporting carbon nanotube membrane 1 can be obtained on the first frame-shaped member 2.

[0027] (1-2. Method for Manufacturing Pellicle) Next, the method for manufacturing pellicle will be explained using the drawings.

[0028] First, as shown in Figures 4(A) and 4(B), the second frame-shaped member 3 and the carbon nanotube self-supporting film 1 are superimposed. The second frame-shaped member 3 is smaller than the first frame-shaped member 2 when viewed from above. The second frame-shaped member 3 is used as a pellicle frame. For this reason, a known pellicle frame can be used for the second frame-shaped member 3. The material of the second frame-shaped member 3 is not particularly limited, but aluminum or aluminum alloys (5000 series, 6000 series, 7000 series, etc.), titanium, stainless steel, silicon, etc. are preferred. At this time, an adhesive may be provided in the portion of the second frame-shaped member 3 that is in contact with the carbon nanotube self-supporting film 1. The material of the adhesive is not particularly limited, but it is preferably an organic resin material such as silicone resin, acrylic resin, or epoxy resin, and more preferably an organic resin material that is resistant to EUV light.

[0029] Next, the carbon nanotube self-supporting membrane 1 and the second frame-shaped member 3 are connected using an adhesive, and then, as shown in Figures 5(A) and 5(B), a portion of the carbon nanotube self-supporting membrane 1 is separated from the first frame-shaped member 2. As a result, as shown in Figures 6(A) and 6(B), a pellicle 20 having a pellicle membrane 1c which is a portion of the carbon nanotube self-supporting membrane 1 is manufactured.

[0030] Subsequently, the outer portion of the carbon nanotube self-supporting film 1 that protrudes from the second frame-shaped member 3 may be removed by trimming as appropriate.

[0031] The present invention will be described in detail below with reference to examples, but this is not intended to limit the present invention.

[0032] [Example 1] Carbon monoxide was used as the carbon source, and carbon dioxide was added to the carbon monoxide at a concentration of 0.8% to obtain the carbon raw material gas. Ferrocene was used as the metal catalyst, and carbon monoxide was supplied to the reaction system as the carrier gas. The carbon raw material gas and ferrocene were reacted at a flow rate ratio of 3:1 at 850°C for 20 minutes to obtain carbon nanotubes (CNTs) on a membrane filter (φ293 mm).

[0033] Subsequently, additional CNTs were deposited on the outer periphery of the CNT (the region outside of φ240 mm), resulting in a CNT where the outer periphery 1b is thicker than the inner diameter 1a.

[0034] The CNTs formed on the membrane filter were transferred to an annular first frame-shaped member (outer diameter: 293 mm, inner diameter: 260 mm) to obtain a CNT film.

[0035] A portion of the obtained CNT film (a region where the inner and outer diameters are mixed) was transferred onto a silicon wafer processed to a size of 10 mm x 10 mm, and the film thickness was measured using a stylus-type surface shape analyzer (Veeco: Dektak150). The film thicknesses of the inner and outer diameters were 14 nm and 34 nm, respectively.

[0036] [Example 2] A CNT film was prepared in the same manner as in Example 1, except that the film thickness of the inner diameter portion and the outer circumference portion were deposited to be 22 nm and 43 nm, respectively.

[0037] [Example 3] A CNT film was prepared in the same manner as in Example 1, except that the film thickness of the inner diameter portion and the outer circumference portion were 31 nm and 52 nm, respectively.

[0038] [Comparative Example 1] A CNT film was prepared in the same manner as in Example 1, except that the film thickness of the inner diameter portion and the outer circumference portion were 14 nm and 29 nm, respectively.

[0039] [Comparative Example 2] A CNT film was prepared in the same manner as in Example 1, except that the film thickness of the inner diameter portion and the outer circumference portion were 22 nm and 41 nm, respectively.

[0040] [Comparative Example 3] A CNT film was prepared in the same manner as in Example 1, except that the film thickness of the inner diameter portion and the outer circumference portion were deposited to be 31 nm and 40 nm, respectively.

[0041]

[0042] Table 1 above shows the evaluation results for the fabrication of CNT self-supporting films in Examples 1-3 and Comparative Examples 1-3. The results for each example show that CNT self-supporting films can be manufactured more stably compared to Comparative Examples 1-3. From the above results, it can be seen that the present invention allows for the more stably manufactured CNT self-supporting films than the conventional technology.

[0043] 1. Carbon nanotube membrane (self-supporting membrane) 1a. Inner diameter portion of carbon nanotube membrane 1b. Outer circumference portion of carbon nanotube membrane 1c. Pellicle membrane 2. First frame-shaped member 3. Second frame-shaped member 10. Membrane filter

Claims

1. A method for producing a carbon nanotube self-supporting membrane, characterized by forming a carbon nanotube membrane on a membrane filter, making the thickness of the outer periphery of the carbon nanotube membrane greater than the thickness of the carbon nanotubes in the inner diameter portion, connecting a first frame-shaped member to the outer periphery of the carbon nanotube membrane, and separating the carbon nanotube membrane from the membrane filter.

2. The method for producing a carbon nanotube self-supporting film according to claim 1, wherein the thickness of the outer periphery of the carbon nanotube is 20 nm or more thicker than the thickness of the inner diameter of the carbon nanotube.

3. The method for producing a carbon nanotube self-supporting film according to claim 1, wherein the thickness of the inner diameter portion of the carbon nanotube film is 10 to 100 nm.

4. The method for producing a carbon nanotube self-supporting film according to claim 1, wherein the carbon nanotube film has a transmittance of 90% or more to radiation having a wavelength of 13.5 nm.

5. A method for manufacturing a pellicle, characterized by forming a carbon nanotube film on a membrane filter, making the thickness of the outer periphery of the carbon nanotube film thicker than the thickness of the carbon nanotubes in the inner diameter portion, connecting a first frame-shaped member to the outer periphery of the carbon nanotube film, separating the carbon nanotube film from the membrane filter to produce a self-supporting carbon nanotube film on the first frame-shaped member, then using a second frame-shaped member having a frame size smaller than the first frame-shaped member to connect the second frame-shaped member and the self-supporting carbon nanotube film, and then separating a portion of the self-supporting carbon nanotube film from the first frame-shaped member, thereby obtaining a pellicle in which the self-supporting carbon nanotube film is a pellicle film and the second frame-shaped member is a pellicle frame.

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