Method for producing multilayer graphene film, production device, multilayer graphene film, method for producing pellicle film using multilayer graphene film, and pellicle film

Abstract

[Problem] To provide: a method for producing a multilayer graphene film that has a desired number of layers, especially ten or more layers, and a large area; a production device; a multilayer graphene film; a method for producing a pellicle film using the multilayer graphene film; and a pellicle film. [Solution] Provided is a method for producing a multilayer graphene film, the method comprising a step A and a step B. The step A includes: a step 1 for bonding a graphene film, which is formed on a base material for film formation, and a graphene support film; a step 2 for etching the graphene film so as to remove the base material for film formation, thereby preparing a graphene film on the graphene support film; and a step 3 for bonding the graphene film on the graphene support film and a separation film. The step B includes: a step 1 for removing the separation film from the graphene film that is prepared in the step A and bonding the graphene film on the graphene support film and a transfer-receiving substrate; and a step 2 for separating the graphene support film.

Description

Multilayer graphene film manufacturing method, manufacturing apparatus, multilayer graphene film, and manufacturing method of pellicle film using multilayer graphene film, pellicle film

[0001] The present invention relates to a method and apparatus for producing a multilayer graphene film, a multilayer graphene film, and a method for producing a pellicle film using the multilayer graphene film, and a pellicle film.

[0002] SP ２ Conductive planar crystals (two-dimensional crystals) made of bonded carbon atoms are called "graphene films." In this specification, the term "graphene film" refers to a single-layer graphene film. Graphene films have a wide range of excellent properties, including very high electron mobility, thermal conductivity, and mechanical strength. In addition to these advantages, they are also extremely thin, making them promising for applications in various fields, such as as an alternative material for transparent conductive films.

[0003] For example, graphene films can absorb light over a very wide wavelength range, which has led to their use in infrared sensors [see Non-Patent Document 1]. Furthermore, development is underway for biosensors [see Non-Patent Document 2] and gas sensors [see Non-Patent Document 3] that take advantage of the fact that molecular adsorption on the graphene film surface causes charge modulation and changes in electrical properties.

[0004] Since graphene films formed by chemical vapor deposition (CVD) are formed on a catalytic metal, they cannot be used for devices in this form, and therefore must be transferred to a substrate.

[0005] For example, Patent Document 1 proposes a technology in which a binder layer is formed on a graphene film on a catalytic metal, the graphene film is fixed to a transfer substrate such as polyethylene terephthalate (PET), and the catalytic metal is then etched away to form a graphene film on the transfer substrate.

[0006] Non-Patent Document 4 reports that a multilayer graphene film formed by repeatedly transferring graphene films onto a silicon oxide substrate exhibits higher mobility than graphene films on a silicon oxide substrate. Demand for multilayer graphene films is increasing due to their potential for various applications, such as improving the output of optical sensors and thermal management. Increasing the number of layers in a graphene film is effective for application to highly sensitive sensors.

[0007] In recent years, graphene films have been attracting attention as an alternative to transparent polymers in thin films (hereafter referred to as pellicles) used to protect photomasks (masters) in semiconductor manufacturing. Pellicles for extreme ultraviolet (EUV) exposure, in particular, require the development of materials with high transmittance and high strength. Furthermore, to achieve higher resolution, thin, durable pellicles are required, and graphene films with 10 or more layers are a promising candidate.

[0008] Various methods for transferring graphene films have been investigated [see Non-Patent Document 5]. Transfer methods using protective films can generally be broadly divided into two categories: dry processes and wet processes. For example, the polymethyl methacrylate (PMMA) method, which uses a wet process, requires the PMMA / graphene film to float on the liquid surface when transferring the graphene film to the receiving substrate, which poses significant challenges for automation. Furthermore, graphene films are extremely thin, with a thickness of just a single atomic layer, making them extremely difficult to handle.

[0009] Patent Document 2 provides a method for forming a graphene film laminate with less damage without using a binder layer such as PMMA. Patent Document 3 provides an apparatus and method for producing a graphene film roll by so-called roll-to-roll transfer of a graphene film using a thermal release film, and a method for manufacturing an element using a graphene film roll. Furthermore, Patent Documents 4 and 5 disclose transfer techniques using PDMS (polydimethylsiloxane). Patent Document 4 discloses a mechanical peeling technique, and Patent Document 5 discloses a bonding technique.

[0010] Japanese Patent Publication No. 2009-298683 Japanese Patent No. 5991520 Japanese Patent No. 5707628 Japanese Patent Publication No. 2022-157508 Japanese Patent Publication No. 2014-034503

[0011] M. Shimatani, S. Ogawa, S. Fukushima, S. Okuda, Y. Kanai, T. Ono, and K. Matsumoto, Applied Physics Express 12, 025001 (2019).S. Ushiba, N. Miyakawa, T. Okino, A. Shinagawa, Y. Oka, M. Kimura, T. Ono, Y. Kanai, K. Inoue and K. Matsumoto, Vacuum and Surface Science 63, 7, 358-363 (2020).F. Schedin, A. K. Geim, S. V. Morozov, E. W. Hill, P. Blake, M. I. Katsnelson and K. S. novoselov, nature materials.6, 652-655 (2007).K. Uemura, T. Ikuta, K. Maehashi, Turbostratic stacked CVD graphene for high performance devices, Jap. J. Appl. Phys. 57 (2018) 030311-1-030311-4.Sooyeoun Oh, Gwangseok Yang, and Jihyun Kim, Journal of Vacuum Science & Technology A 33 (2) 021502 (2015).S. Bae, H. Kim, Y. Lee, X. Xu, J.-S. Park, Y. Zheng, J. Balakrishnan, T. Lei, H. R. Kim, Y. I. Song, Y.-J. Kim, K. S. Kim, B. Ozyilmaz, J.-H. Ahn, B. H. Hong, and S. Iijima, Nature Nanotechnology 5, 574 (2010).T. Kobayashi, M. Bando, N. Kimura, K. Shimizu, K. Kadono, N. Umezu, K. Miyahara, S. Hayazaki, S. Nagai, Y.Mizuguchi, Y. Murakami, and D. Hobara, Applied Physics Letters 102, 023112 (2013).

[0012] As mentioned above, there is a desire to increase the number of layers in multilayer graphene films, but to date, multilayer graphene films with 10 or more layers have not been achieved. Furthermore, in thermal management applications, as semiconductors become more highly integrated and perform better, graphene films with high thermal conductivity are expected to serve as thermally conductive materials that efficiently dissipate heat generated inside devices. When using graphene films for heat dissipation purposes, the number of layers must be adjusted to achieve a heat dissipation effect according to the heat output of the heat source. This also necessitates the development of technology for forming multilayer graphene films.

[0013] If a multilayer graphene film formed with a turbostratic structure that maintains the unique electronic structure of graphene could be produced, it would be expected to have improved electrical and thermal properties and photoresponsive characteristics, potentially leading to industrial applications. Multilayer graphene films can be obtained by mechanically peeling graphite layers from a base material such as graphite. However, the multilayer graphene films obtained by this method are not sufficient for large-scale industrial applications. Furthermore, for industrial applications, devices with large substrates are essential. However, producing large-area multilayer graphene films with 10 or more layers is extremely difficult, and no technology has yet been established. Therefore, a multilayer graphene film with 10 or more layers on a large substrate and a method for producing the same are desired. In particular, graphene with 10 or more layers is desired as a material for thin, highly durable pellicle films.

[0014] Patent Document 2 discloses a method for forming a graphene film laminate with less damage without using a binder layer such as PMMA, but this method requires bonding the graphene film to the transfer substrate in a liquid or vacuum, making it unsuitable for large areas. Patent Document 3 also shows an example of a four-layer stack, but does not provide details about the stacking method. For example, when stacking graphene films manually, stacking 10 or more layers is not practical. Furthermore, the adhesion of the graphene film decreases as the stacking progresses, making it unsuitable for stacking 10 or more layers with conventional methods.

[0015] For these reasons, automated fabrication of multilayer graphene films using conventional wet processes is extremely difficult due to the difficulty in handling the graphene film, and there is a high possibility of defects such as film tearing occurring during the transfer process. On the other hand, when a graphene support film (thermal release film or low-adhesive film) is used, the process after etching and removal of the copper foil, which is the CVD synthesis substrate, is essentially a dry process, making automation highly feasible.

[0016] To date, a 30-inch graphene film using a thermal release film [see Non-Patent Document 6] and a 100-m graphene film using an epoxy resin [see Non-Patent Document 7] have been reported. However, conventional methods using thermal release films have mainly been used to transfer graphene films to soft transfer substrates such as PET films. Due to the poor adhesion between the hard transfer substrate and the graphene film, conventional methods are not suitable for transfer to hard transfer substrates such as wafers. Furthermore, Patent Documents 4 and 5 propose dry transfer using PDMS, but the technology has not yet been established.

[0017] When using the PMMA method, the PMMA must be removed after the graphene film is transferred to the substrate. This requires more than a day to complete the transfer process, which is also an obstacle to industrial use. Therefore, a high-throughput, large-area transfer method is desired.

[0018] In view of the above problems, the present invention aims to provide a manufacturing method and manufacturing apparatus for manufacturing a large-area multilayer graphene film having a desired number of layers, particularly 10 layers or more, which can be transferred not only to soft substrates but also to hard substrates, a multilayer graphene film, a manufacturing method for a pellicle film using the multilayer graphene film, and a pellicle film.

[0019] As a result of extensive research to achieve the above object, the inventors have succeeded in producing a multilayer graphene film with a desired number of layers by automatically transferring a graphene film formed on a film-forming substrate to a transfer substrate multiple times. In particular, they have succeeded in producing a multilayer graphene film having 10 or more layers stacked together and having an interlayer distance of 0.31 to 0.42 nm. Furthermore, they have solved the above problem by using UV ozone in the process of transferring the graphene film formed on the film-forming substrate to the transfer substrate.

[0020] The present invention has been completed based on these findings and is as follows: A method for producing a multilayer graphene film of the present invention is a method for producing a multilayer graphene film by transferring a graphene film formed on a film-formation substrate onto a transfer substrate, the method comprising steps A and B, in which step A includes step 1 of bonding the graphene film formed on the film-formation substrate to a graphene support film, step 2 of etching the graphene film formed on the film-formation substrate on the graphene support film produced in step 1 to remove the film-formation substrate, and step 3 of bonding the graphene film on the graphene support film to a separate film, and step B includes step 1 of removing the separate film from the graphene film on the graphene support film to which the separate film has been bonded, produced in step A, and bonding the graphene film on the graphene support film to the transfer substrate, and step 2 of peeling the graphene support film from the graphene film on the graphene support film on the transfer substrate. Preferably, step B further includes step 3, after step 2, of irradiating the graphene film bonded on the transfer substrate with UV ozone. Furthermore, the graphene film formed on the film-formation substrate in step 1 of step A and / or step 1 of step B and / or the transfer substrate can be evacuated and fixed to a sample stage. Alternatively, the method may include repeating steps A and B multiple times to stack graphene films. In this case, the transfer substrate in step 1 of step B from the second transfer onward is the transfer substrate on which the graphene film from the previous transfer was bonded. The multilayer graphene film of the present invention has 10 or more stacked layers. Preferably, the multilayer graphene film has periodicity in the stacking direction.The multilayer graphene film manufacturing apparatus of the present invention is a manufacturing apparatus for use in a method for manufacturing a multilayer graphene film, and includes: the sample stage for fixing the graphene film formed on the film-formation substrate; a lamination roller for bonding the graphene film formed on the film-formation substrate and the graphene support film; a blower for the graphene film on the graphene support film; a device for bonding the graphene film on the graphene support film and the separate film; the sample stage for fixing the transfer substrate; a lamination roller for bonding the graphene film on the graphene support film and the transfer substrate; and a peeling means for peeling the graphene support film from the graphene film on the transfer substrate. The apparatus further includes a UV ozone irradiation device for irradiating UV ozone onto the graphene film bonded to the transfer substrate. The method for producing a pellicle film of the present invention includes the steps of forming a sacrificial layer on the laminated graphene film side of the multilayer graphene film produced by the method for producing a multilayer graphene film of the present invention, removing the transfer substrate from the multilayer graphene film, connecting a pellicle frame to the laminated graphene film side, and removing the sacrificial layer. The pellicle film of the present invention is composed of the multilayer graphene film of the present invention.

[0021] According to the present invention, it is possible to provide a method and apparatus for producing a large-area multilayer graphene film having a desired number of layers, particularly 10 or more layers, a multilayer graphene film, a method for producing a pellicle film using the multilayer graphene film, and a pellicle film.

[0022] 8 is a schematic diagram of a multilayer graphene film according to an embodiment of the present invention; FIG. 9 is a schematic diagram illustrating a method for producing a multilayer graphene film according to an embodiment of the present invention; FIG. 10 is a photograph of the multilayer graphene film according to the embodiment; FIG. 11 is a Raman spectroscopy spectrum according to the embodiment; FIG. 12 is a plot (a) of the number of layers of the graphene film according to the embodiment of the present invention on the horizontal axis and the half-width of the 2D band on the vertical axis, and FIG. 13 is a plot (b) of the number of layers of the graphene film according to the embodiment of the present invention on the horizontal axis and the peak position of the 2D band on the vertical axis; FIG. 14 is an X-ray diffraction spectrum according to the embodiment; FIG. 15 is a schematic diagram illustrating a step of vapor-depositing a sacrificial layer (camphor layer) on the multilayer graphene film according to an embodiment of the present invention; FIG. 16 is a schematic diagram illustrating a multilayer graphene film on which a camphor layer is formed according to an embodiment of the present invention; FIG. 17 is a schematic diagram illustrating a step of dissolving and removing copper foil from the multilayer graphene film of FIG. 8; FIG. 18 is a schematic diagram illustrating a step of connecting a frame for a pellicle to the laminated graphene film with a camphor layer according to an embodiment of the present invention; FIG. 19 is a schematic diagram illustrating a laminated graphene film with a camphor layer connected to a frame for a pellicle according to an embodiment of the present invention. 12 is a schematic diagram showing a laminated graphene film on a frame for a pellicle according to one embodiment of the present invention. FIG. 13 is a photograph of a laminated graphene freestanding film attached to a 50 mm x 50 mm frame simulating a pellicle frame. FIG. 14 is a Raman spectroscopy spectrum of the laminated graphene freestanding film according to this embodiment. FIG. 15 is a result of fitting the 2D band of FIG. 15 with a Lorentz curve. FIG. 15 is an X-ray diffraction spectrum of the laminated graphene freestanding film (33 layers) according to this embodiment. FIG. 16 is a scanning electron microscope photograph of a portion of the laminated graphene freestanding film (33 layers) according to this embodiment. FIG. 17 is an EDX elemental analysis result of a portion of the laminated graphene freestanding film (33 layers) according to this embodiment. FIG. 18 is an X-ray diffraction spectrum of graphite. FIG. 19 is a photograph of a laminated graphene freestanding film having a diameter of 10 mm and 12 layers (thickness 4 nm).

[0023] The present invention will be described below with reference to the drawings. However, the present invention is not limited thereto. In addition, the term "transfer" in this example refers to a series of processes for transferring graphene on a film-forming substrate to another substrate (transfer-receiving substrate).

[0024] [Structure of Multilayer Graphene Film 100] FIG. 1 is a schematic diagram of the multilayer graphene film 100 of this example. As shown in FIG. 1, the multilayer graphene film 100 is composed of a transfer substrate 101 and a stacked graphene film (hereinafter referred to as a stacked graphene film) 102. To manufacture this multilayer graphene film 100, a graphene film on a copper foil synthesized using a roll-to-roll plasma CVD method described in a non-patent document (R. Kato, S. Minami, Y. Koga, M. Hasegawa, Carbon 96, 1008-1013 (2016)) was used. The method for manufacturing the multilayer graphene film 100 is described in detail below.

[0025] [Method for Manufacturing Multilayer Graphene Film 100] The method for manufacturing the multilayer graphene film 100 of this example will be described in detail with reference to FIG. 2. As described above, the multilayer graphene film 100 is manufactured by transferring a graphene film 102 formed on a film-forming substrate onto a transfer substrate. This manufacturing method includes two steps: step A ( FIGS. 2a and 2b ) in which the graphene film 102 formed on the film-forming substrate (copper foil) is bonded onto a graphene support film, and step B ( FIG. 2c ) in which the graphene film 102 on the graphene support film produced in step A is bonded onto a transfer substrate 101. Step A ( FIGS. 2a and 2b ) and step B ( FIG. 2c ) are performed using a multilayer graphene film manufacturing apparatus.

[0026] Process A consists of three steps, and process B consists of two or three steps. In this example, process A and process B are described as three steps, namely, process 1, process 2, and process 3, but additional steps may be added. Furthermore, process 3 of process B is not an essential step and may be omitted.

[0027] Furthermore, the graphene support film can be, for example, a thermal release film or a weak adhesive film. A thermal release film has the advantage of being easily peeled off when heated, while a weak adhesive film such as an acrylic film (PMMA, etc.) or a silicone film (PDMS, etc.) has the advantage of not requiring the application of heat. In this example, a thermal release film 103 is used as the graphene support film, but the present invention is not limited to this, and an appropriate film can be used depending on the application.

[0028] Step 1 of Process A is a step of bonding a graphene film 102 formed on a film-forming substrate 101 to a thermal release film 103. In this example, copper foil is used as the film-forming substrate, but other materials may also be used. In this step 1, first, the graphene film 102 formed on the copper foil (hereinafter referred to as the copper foil / graphene film 104) and the thermal release film 103 are bonded together using a laminating roller 107 to obtain a film (hereinafter referred to as the thermal release film / copper foil / graphene film 105) in which the thermal release film 103 and the copper foil / graphene film 104 are bonded together. During bonding, the copper foil / graphene film 104 is fixed by vacuum on a sample stage 106. This vacuum fixation prevents oxygen and fine dust from entering between the thermal release film 103 and the copper foil / graphene film 104, thereby facilitating closer adhesion. Furthermore, oxidation of the copper foil / graphene film 104 can be prevented. It is not essential to evacuate the sample stage 106, but it is sufficient if the thermal release film 103 and the copper foil / graphene film 104 can be fixed so as to be in close contact with each other.

[0029] In step 2 of process A, the thermal release film / copper foil / graphene film 105 produced in step 1 is immersed in an etching bath to dissolve and remove the copper foil, thereby producing a graphene film 102 on the thermal release film 103. In this example, the copper foil of the thermal release film / copper foil / graphene film 105 is immersed in an etching bath (not shown) of ammonium persulfate solution. This dissolves and removes the copper foil. After the copper foil removal is complete, the graphene film 102 on the thermal release film 103 (hereinafter referred to as the thermal release film / graphene film 108) is thoroughly washed with water.

[0030] In step 3 of process A, the thermal release film / graphene film 108 and the separation film 109 are bonded together. The separation film 109 is necessary to protect the graphene film. In this example, the thermal release film / graphene film 108 and the separation film 109 were bonded together using an automatic laminating device ( FIG. 2 b) (hereinafter, referred to as the thermal release film / graphene film / separate film 110). The bonding device is not limited to an automatic laminating device, and other devices may also be used. Care must be taken when handling the graphene film / thermal release film 108 to avoid tearing it. After washing with water, excess moisture is removed from the graphene film / thermal release film 108 using a blower 111. The use of the blower 111 also prevents the inclusion of foreign matter. In this manner, the thermal release film / graphene film / separate film 110 was obtained.

[0031] In step 1 of process B (top of FIG. 2c), the thermal release film / graphene film / separation film 110 and the transfer substrate 101 are bonded together. A hard substrate (e.g., a silicon wafer or quartz substrate) can be used as the transfer substrate 101. In this embodiment, the separation film of the thermal release film / graphene film / separation film 110 is removed after unwinding, and the graphene film / thermal release film 108 and the transfer substrate 101 are bonded together using a lamination roller 113. The transfer substrate 101 is fixed by vacuuming on the sample stage 112. Note that, as in step 1 of process A, vacuuming the sample stage 112 is not essential.

[0032] In step 2 of process B (in FIG. 2c ), the thermal release film 103 is thermally peeled from the graphene film / thermal release film 108 on the transfer substrate 101. In this example, the thermal release film 103 was peeled from the graphene film / thermal release film 108 on the transfer substrate 101 by applying heat to the thermal release film 103 using a heater 114, which serves as a heat source. The heater 114 was installed on the thermal release film 103, and its temperature was set to the peeling temperature of the thermal release film 103. This step transfers the graphene film 102 of the graphene film / thermal release film 108 to the transfer substrate 101. The transferred graphene film / transfer substrate is cooled by a cooling mechanism (not shown). Note that if a film other than the thermal release film 108 is used as the graphene support film, a separate peeling means other than the heat source is used. In that case, a cooling mechanism is not required.

[0033] In step 3 of process B (bottom of FIG. 2c ), UV ozone is irradiated onto the graphene film 102 transferred onto the transfer substrate 101. This step is intended to improve the transferability of the graphene film 102 and is not an essential step for the present invention. In this example, the adhesion of the graphene film was improved by irradiating the graphene film 102 transferred onto the transfer substrate 101 with UV ozone using a UV device 115. By performing the above steps A and B, one layer of the graphene film 102 was laminated on the transfer substrate 101. By repeating steps A and B multiple times, a multilayer graphene film 100 ( FIG. 1 ) with a desired number of layers can be obtained. During this process, the transfer substrate 101 in step 1 of process B from the second iteration onward is the transfer substrate 101 to which the graphene film 102 from the previous iteration was bonded. When step 3 of step B is not included, a multilayer graphene film 100 ( FIG. 1 ) having a desired number of layers is obtained by automatically repeating steps 1 and 2 of step A and step B. In this example, the steps are repeated "automatically" in consideration of efficiency, but this does not necessarily have to be "automatic" and may be performed manually.

[0034] In this example, one transfer was completed in approximately 10 minutes, enabling large-area transfer with high throughput. By automatically repeating all of the steps A and B 10 or more times, a multilayer graphene film 100 with 10 or more layers could be produced, and even a multilayer graphene film 100 with 10 or more layers could be produced. Multilayer graphene films with 10 or more layers are expected to be used in highly sensitive sensors and thermal management applications. In particular, graphene with 10 or more layers can be used as a material for thin, highly durable pellicles. The multilayer graphene film 100 will be analyzed below.

[0035] [Characteristics of the Multilayer Graphene Film 100 (Raman Spectroscopy)] The characteristics of the multilayer graphene film 100 are analyzed by Raman spectroscopy. FIG. 3 is a photograph of the multilayer graphene film 100 on a 100 mm diameter sapphire substrate of this example. Transmittance measurements were performed using an NDH5000SPN instrument manufactured by Nippon Denshoku Industries Co., Ltd. The number of layers in the graphene film stack was calculated using the optical absorption rate of 2.3% for one graphene film layer described in a non-patent document (RR Nair, P. Blake, AN Grigorenko, KS Novoselov, TJ Booth, T. Stauber, NMR Peres, and AK Geim: Science 320, 1308 (2008)). The number of layers in the graphene film stack of this example was 104 (stacking ratio 84%).

[0036] The measurement device was an XploRA (registered trademark) model manufactured by Horiba, Ltd. The wavelength of the excitation laser was 532 nm, the spot size of the laser beam was 1 μm in diameter, the spectrometer had 1,200 gratings, the output of the laser source was 9.8 mW, and no attenuator was used. The aperture was 300 μm, the slit was 100 μm, and the objective lens was 100x magnification. The exposure time was 5 seconds, and the spectrum was obtained by integrating five measurements.

[0037] 4 shows the Raman spectrum of the multilayer graphene film 100 automatically transferred onto sapphire. The typical G band and 2D band of the multilayer graphene film 100 were detected. The peak position of the G band was 1584 cm －１ , the peak position of the 2D band is 2696 cm－１ The inset in Figure 4 shows the results of fitting the 2D band with a Lorentzian curve, with a full width at half maximum (FWHM) of 43 cm －１ A narrow single peak was obtained.

[0038] Also, 1352 cm －１ The D band was detected at the position of . The D band consisted of a sharp single peak with a full width at half maximum (FWHM) of 29 cm. －１ The D band is mainly detected due to defects and edges. Furthermore, a non-patent document (AC Ferrari, JC Meyer, V. Scardaci, C. Casiraghi, M. Lazzeri, F. Mauri, S. Piscanec, D. Jiang, KS Novoselov, S. Roth, and AK Geim, Physics Review Letters, 97, 187401 (2006)) shows that the D band can also be detected in graphite with a turbostratic structure. This example shows that the D band detected is a peak due not only to defects and edges but also to the turbostratic structure.

[0039] Figure 5 shows the results of analyzing the full width at half maximum (FWHM) and peak position by fitting the Raman spectrum of the multilayer graphene film 100 that was automatically transferred multiple times with a Lorentz curve. The results shown here are for 17 to 104 layers transferred onto a sapphire substrate and a glass substrate.

[0040] Figure 5(a) shows the change in the FWHM of the 2D band with respect to the number of layers. －１ ) is shown by a dotted line and compared with the multilayer graphene film 100. The FWHM of the multilayer graphene film 100 is 41 cm －１ and the thickness of a single-layer graphene film is about 35 cm －１ 6 cm compared to －１ The value was also equivalent to that of pyrolytic graphite with a turbostratic structure, and remained almost constant up to 100 layers.

[0041] Figure 5(b) shows the transition of the 2D band position with respect to the number of layers. Note that the position of the 2D band of pyrolytic graphite with a turbostratic structure (2699 cm －１ ) is shown by a dotted line in comparison with the multilayer graphene film 100. The 2D band position of the multilayer graphene film 100 is 2695 cm －１ and the 2D band position of the graphene film 100 is 2680 cm －１ 15cm compared to －１ The graphene film 102 was shifted to the high wavenumber side and approached that of pyrolytic graphite having a turbostratic structure. From the above, it was found that the multilayer graphene film 100 produced by automatic multiple transfer in this example had a structure in which the graphene films 102 were stacked in a turbostratic manner.

[0042] [Characteristics of Multilayer Graphene Film 100 (X-Ray Diffraction Spectrum)] The characteristics of the multilayer graphene film 100 were analyzed by X-ray diffraction spectroscopy. The measurement was performed using a horizontal X-ray diffractometer SmartLab (registered trademark) manufactured by Rigaku Corporation under the following analysis conditions: an X-ray source Cu-Kα ray (λ=0.15418 nm), an X-ray generation current of 200 mA, an X-ray generation voltage of 45 kV, and a scan angle 2Θ=10 to 40°. The interlayer distance d was calculated from the diffraction angle obtained by the measurement using Bragg's equation (Equation 1).

[0043]

[0044] Graphene is generally considered to be the basic structure of graphite, a layered material. A non-patent document (K.S. Novoselov, A.K. Geim, S.V. Morozov, D. Jiang, Y. Zhang, S.V. Dubonos, I.V. Grigorieva, and A.A. Firsov: Science, 306 (2004) 666.) reported that graphene could be isolated by peeling graphite with tape. Therefore, it is theoretically possible to fabricate graphite by stacking graphene layers. Therefore, to compare the structure of this multilayer graphene film with that of graphite, we measured the interlayer distance of this multilayer graphene film by X-ray diffraction. Figure 6 shows the X-ray diffraction spectrum of a multilayer graphene film 100 (104 layers) automatically transferred onto sapphire multiple times. A broad peak centered at 2Θ = 24.5° was observed. This indicates that the multilayer graphene film of the present invention has periodicity in the stacking direction due to transfer, which is one of its distinctive features. The angle 2Θ at the peak center obtained by peak fitting this diffraction spectrum was 24.538°±0.032°, and the interlayer distance calculated from this was 0.3625±0.0005 nm (±0.0005 nm is the error in the interlayer distance obtained from the error in peak fitting). Furthermore, the half-width of the X-ray diffraction spectrum was 7.4° (2Θ = 20.8° to 28.2°), which was a very broad peak. The range of the interlayer distance calculated using this half-width was 0.316 nm (2Θ = 28.2°) to 0.426 nm (2Θ = 20.8°). Thus, the interlayer distance of the multilayer graphene film of the present invention was determined to have a characteristic structure with a wide distribution of interlayer distances, ranging from 0.316 nm at the narrowest point to 0.426 nm at the widest point, with 0.3625 nm, the peak of the X-ray diffraction spectrum, being the most likely value.

[0045] Typically, the interlayer distance of graphite is 0.335 nm, while the interlayer distance of turbostratic graphite is 0.344 nm. The interlayer distance of the multilayer graphene film of the present invention is significantly larger than these graphites, which is one of the characteristics of the multilayer graphene film of the present invention. For comparison, Figure 20 shows the X-ray diffraction spectrum of graphite. In this spectrum, the peak position 2Θ = 26.54°, and the interlayer distance calculated from this was 0.3358 nm. The half-width of the peak was 0.19° (2Θ = 26.45° to 26.64°). Using this half-width, the range of the interlayer distance of this graphite was calculated to be 0.3346 nm (2Θ = 26.64°) to 0.3369 nm (2Θ = 26.54°). As described above, the half-width of the X-ray diffraction spectrum of the multilayer graphene film of the present invention shown in FIG. 6 is much larger than that of graphite, and the multilayer graphene film has a structure with a large distribution of interlayer distances, which is one of the characteristics of the multilayer graphene film of the present invention.

[0046] As described above, it was found that the multilayer graphene film 100 of this example, which was produced by the automatic multiple transfer method of the present invention, has a novel structure characterized by having periodicity in the stacking direction by transfer, a larger interlayer distance compared to commonly known graphite and turbostratic graphite, and further having a structure with a larger distribution of interlayer distance compared to these graphites.

[0047] In the X-ray diffraction spectrum of Figure 6, sharp peaks were observed near 2Θ = 20.5°, 28.5°, and 37.5°. These peaks are due to adhesive components contained in the thermal release film used in the transfer process. Furthermore, the possibility of water molecules being mixed in during the water washing process is low because their size is 0.38 nm. Therefore, the median interlayer distance of the multilayer graphene film 100 produced by automated multiple transfer is characterized as being 0.362 nm.

[0048] If the interlayer distance of the multilayer graphene film 100 can be controlled, graphite with different interlayer distances can be obtained, which is expected to lead to various applications that expand the possibilities of graphite, such as filters and molecular storage materials.

[0049] [Method for Manufacturing Pellicle Film] A method for manufacturing a pellicle film using a multilayer graphene film 100 manufactured in the same manner as the method for manufacturing the multilayer graphene film 100 described above will be described with reference to FIGS.

[0050] In this example, a 33-layer multilayer graphene film 100 (thickness: 10 nm) was produced. In this example, a method for producing a pellicle film using multilayer graphene 100 stacked in 33 layers is described, but the pellicle film of the present invention is not limited to this number of layers, and preferably has 10 layers or more. As in the method for producing the multilayer graphene film 100 described above, a heat-release sheet was attached to the graphene surface of copper foil on which single-layer graphene had been synthesized, and the copper foil was etched with an aqueous ammonium persulfate solution (0.5 mol / L) to dissolve only the copper foil.

[0051] This heat-release sheet with single-layer graphene was attached to a copper foil as an original, pressed with a roller to adhere it, and then heated to peel off only the sheet, thereby transferring only the single-layer graphene to the copper foil (transfer substrate 101). The above process was repeated 33 times for the copper foil 101 as a transfer destination, thereby producing a copper foil 101 with a 33-layer laminated graphene film 102. Note that, although copper foil was used as the transfer substrate 101 in this example, because the transfer substrate 101 is a layer to be removed in a later process, other materials that can be dissolved and removed, such as other types of metal foils or resin films, may also be used instead of copper foil.

[0052] First, a sacrificial layer 200 is formed on the laminated graphene film 102 side of the multilayer graphene film 100. The multilayer graphene 100 alone lacks sufficient mechanical strength to withstand the task of fixing it to a large-area frame, and therefore needs to be reinforced with a support film (sacrificial layer) 200. The sacrificial layer 201 is a layer that will be removed in a later process. Any material that can be suitably removed, such as a sublimable material, a water-soluble material, or an organic resin material (a material that decomposes thermally), may be used as the sacrificial layer 200 in this example. In this example, a sublimable material, particularly camphor, is used as the sacrificial layer 200. Camphor completely sublimes at room temperature, leaving no residue, making it suitable as a sacrificial layer and enabling high-precision transfer while minimizing damage to the multilayer graphene film 100.

[0053] 7 is a schematic diagram showing a process of vapor-depositing a sacrificial layer (camphor layer) 200 on the multilayer graphene film 102 side. The multilayer graphene film 100 stacked in 33 layers and solid or powdered camphor 201 were sealed in an airtight container, and the camphor 201 was heated at 160° C. for 10 minutes to evaporate, and then cooled to form a camphor layer 200 (160 μm) on the multilayer graphene film 100. FIG. 8 is a schematic diagram showing the structure of the multilayer graphene film 100 on which the camphor layer 200 was vapor-deposited. In order to avoid damaging the multilayer graphene film 100 with the camphor layer 200 due to its own weight or the surface tension of the water when the film is scooped up onto the perforated pellicle frame 300, and to sublimate all of the camphor 201 without causing cracks or the like in the multilayer graphene film 100 when the camphor 201 is sublimated, the camphor layer 200 needs to be formed to have an appropriate thickness. For example, the film thickness is 160 μm. The thickness of the camphor layer 200 is not limited to that in this embodiment and can be changed as appropriate.

[0054] Next, the copper foil 101 is dissolved and removed from the multilayer graphene film 100. FIG. 9 is a schematic diagram showing the process of dissolving and removing the copper foil 101 from the multilayer graphene film 100 on which the camphor layer 200 has been vapor-deposited. The multilayer graphene film 100 on which the camphor 201 has been vapor-deposited is cut to the size of the pellicle frame 300 to which it will ultimately be attached, and etched using an ammonium persulfate aqueous solution (0.5 mol / L) to dissolve only the copper foil 101. After etching of the copper foil 101 is complete, the etched laminated graphene film 102 with the camphor layer 200 is thoroughly washed with pure water to remove etching residue. Note that in this example, the copper foil 101 is dissolved after cutting to the size of the pellicle frame 300, but the copper foil 101 may be dissolved before cutting.

[0055] After dissolving the copper foil 101, a pellicle frame 300 is connected to the laminated graphene film 102. FIG. 10 is a schematic diagram showing the process of connecting the pellicle frame 300 to the laminated graphene film 102 with the camphor layer 200. As shown in FIG. 10, the laminated graphene film 102 with the camphor layer 200 is floated on the surface of pure water and then scooped up by the frame 300 submerged in water. FIG. 11 is a schematic diagram showing the laminated graphene film 102 with the camphor layer 200 connected to the pellicle frame 300. As shown in FIG. 11, the free-standing structure of the laminated graphene film 102 with the camphor layer 200 was maintained within the frame 300.

[0056] Next, the camphor layer 200 is removed from the laminated graphene film 102 with the camphor layer 200. In this example, the camphor layer 200 is completely sublimated and removed by leaving it in an atmospheric environment at room temperature for 24 hours or more. FIG. 12 shows the laminated graphene film 102 (pellicle film) on the completed pellicle frame 300 after the camphor layer 200 has been removed. As shown in FIG. 12, a free-standing laminated graphene film 102 (pellicle film) was successfully completed. This free-standing laminated graphene film 102 (hereinafter referred to as a free-standing laminated graphene film) will be analyzed below.

[0057] Fig. 13 is a photograph of a 10 mm diameter stacked graphene freestanding film, which is an example of Fig. 12. Transmittance measurement was performed using an NDH5000SP instrument manufactured by Nippon Denshoku Industries Co., Ltd., and the transmittance was found to be 46.4%. The number of graphene film layers calculated using the optical absorptance of 2.3% per graphene film layer described in the aforementioned non-patent document (R.R. Nair, P. Blake, A.N. Grigorenko, K.S. Novoselov, T.J. Booth, T. Stauber, N.M. Peres, and A.K. Geim: Science 320, 1308 (2008)) was 33.

[0058] It is also possible to create even larger freestanding graphene films. Figure 14 shows a photograph of a stacked graphene freestanding film attached to a 50 mm x 50 mm frame that mimics an actual pellicle frame. Note that this film was created separately from the film described in the previous section. Similarly, transmittance measurements were performed, revealing a transmittance of 55.5%, which translates to 26 graphene film layers.

[0059] [Raman Spectroscopy] The Raman spectrometer was an inVia (registered trademark) model manufactured by Renishaw, with an excitation laser wavelength of 532 nm, a laser beam spot size of 1 μm in diameter, 2,400 spectrometer gratings, a laser source output of 50 mW, and a 5% attenuator. The objective lens was set to 100x magnification. The exposure time was 1 second, and a spectrum was obtained by integrating five measurements.

[0060] FIG. 15 shows the Raman spectrum of the stacked graphene freestanding film produced in this example. The G band and 2D band of the graphene film were detected. The peak position of the G band was 1578 cm －１ , the peak position of the 2D band is 2679 cm －１ Figure 16 shows the results of fitting the 2D band with a Lorentzian curve, with a full width at half maximum (FWHM) of 51.3 cm －１ A narrow single peak was obtained.

[0061] Also, 1350 cm －１ The D band was detected at the position of . The D band consisted of a broad single peak with a full width at half maximum (FWHM) of 216 cm －１ The D band is detected mainly due to defects and edges, but as described above, it was shown that the D band detected in this example is a peak caused not only by defects and edges but also by the turbostratic structure.

[0062] [X-ray diffraction spectrum] The measurement was performed using a horizontal X-ray diffractometer SmartLab (registered trademark) manufactured by Rigaku Corporation under the following analysis conditions: X-ray source Cu-Kα ray (λ=0.15418 nm), X-ray generation current 200 mA, X-ray generation voltage 45 kV, and scan angle 2Θ=10 to 40°. The interlayer distance d was calculated from the diffraction angle obtained by the measurement using the above-mentioned Bragg's equation (Equation 1).

[0063] Figure 17 shows the X-ray diffraction spectrum of a freestanding stacked graphene film (33 layers) transferred 33 times onto a washer. After peak separation and background removal, a broad peak centered at 2Θ = 24.254° was confirmed. The most likely interlayer distance calculated from the angle (2Θ = 24.254°) at the center of the peak in the diffraction spectrum was 0.3667 nm.

[0064] The range of the interlayer distance calculated from the half-width of the X-ray diffraction spectrum was 0.2737 nm (2Θ = 32.722°) to 0.5613 nm (2Θ = 15.786°). Normally, the interlayer distance of natural graphite is 0.335 nm, and that of turbostratic graphite is 0.344 nm, as mentioned above. Therefore, the 33-layer stacked graphene freestanding film produced in this study has a novel structure with an interlayer distance different from that of commonly known graphite or turbostratic graphite.

[0065] 18 is a scanning electron microscope photograph of the laminated graphene freestanding film portion transferred 33 times onto the washer of this example. The measurement device used was a Hitachi S-3500N.

[0066] 19 shows the results of EDX elemental analysis using the EMAX (registered trademark) 300 energy dispersive X-ray analyzer attached to the measurement device. The analysis results confirmed that this film was a highly pure freestanding laminated graphene film, as no elements other than C and O were detected. Therefore, a highly pure, optimal freestanding laminated graphene film can be provided as a pellicle material.

[0067] In this example, a 33-layer multilayer graphene film was fabricated and analyzed, but multilayer graphene films with other numbers of layers can also be fabricated. As an example, Figure 21 shows a photograph of a 10 mm diameter freestanding stacked graphene film with 12 layers (thickness: 4 nm). This film has a transmittance of 75.9%, and the number of graphene film layers calculated using the method described above was 12.

[0068] As described above, the present invention can provide a method and apparatus for producing a multilayer graphene film having a desired number of layers, particularly 10 or more layers, and a large area, a multilayer graphene film, a method for producing a pellicle film using the multilayer graphene film, and a pellicle film. The graphene film production method of the present invention can automatically laminate a graphene film having a desired number of layers on any transfer substrate, including not only soft transfer substrates but also hard transfer substrates, thereby providing a multilayer graphene film. Furthermore, if a technology for forming a multilayer graphene film can be developed and the interlayer distance can be controlled, various applications that expand the possibilities of graphite, such as filters and molecular storage materials, are expected.

[0069] The present invention makes it possible to realize various products using multilayer graphene films, such as transparent conductive films for touch panel applications, semiconductor devices or electronic devices such as transistors and integrated circuits, transparent electrodes or electrochemical electrodes requiring large areas, and various highly sensitive sensors.

[0070] The multilayer graphene film and its manufacturing method, manufacturing apparatus, and pellicle film and its manufacturing method in the above-described examples are merely examples, and their configurations can be modified as appropriate without departing from the spirit of the invention.

[0071] 100 Multilayer graphene film 101 Transfer substrate 102 (Laminated) graphene film 103 Thermal release film 104 Graphene film / copper foil 105 Thermal release film / graphene film / copper foil 106 Sample stage 107 Laminating roller 108 Thermal release film / graphene film 109 Separation film 110 Thermal release film / graphene film / separation film 111 Blower 112 Sample stage 113 Laminating roller 114 Heater 115 UV device 200 Sacrificial layer (camphor layer) 201 Camphor 300 Frame for pellicle

Claims

1. A method for producing a multilayer graphene film by transferring a graphene film formed on a film formation substrate onto a transfer substrate, the method comprising: Step A and Step B, wherein Step A comprises: Step 1 of bonding the graphene film formed on the film formation substrate to a graphene support film; Step 2 of etching the graphene film formed on the film formation substrate on the graphene support film produced in Step 1 to remove the film formation substrate, thereby producing a graphene film on the graphene support film; and Step 3 of bonding the graphene film on the graphene support film to a separate film; and Step B comprises: Step 1 of removing the separate film from the graphene film on the graphene support film to which the separate film has been bonded, produced in Step A, and bonding the graphene film on the graphene support film to the transfer substrate; and Step 2 of peeling the graphene support film from the graphene film on the graphene support film on the transfer substrate.

2. The method for producing a multilayer graphene film according to claim 1, characterized in that step B further comprises step 3, after step 2, of irradiating UV ozone onto the graphene film bonded to the transfer substrate.

3. The method for producing a multilayer graphene film according to claim 1 or 2, characterized in that the graphene film formed on the film-formation substrate and / or the transfer substrate in step 1 of step A and / or step 1 of step B is evacuated and fixed to a sample stage.

4. The method for producing a multilayer graphene film according to claim 1 or 2, characterized in that the process A and the process B are repeated multiple times to stack graphene films, and the transfer substrate in process 1 in the second or subsequent process B is the transfer substrate to which the graphene film in the previous process has been bonded.

5. A multilayer graphene film characterized by having 10 or more layers.

6. The multilayer graphene film according to claim 5, characterized in that the multilayer graphene film has periodicity in the stacking direction.

7. A manufacturing apparatus for use in the method for manufacturing a multilayer graphene film according to claim 1, comprising: the sample stage for fixing the graphene film formed on the film formation substrate; a lamination roller for bonding the graphene film formed on the film formation substrate and the graphene support film; a blower used for the graphene film on the graphene support film; a device for bonding the graphene film on the graphene support film and the separate film; the sample stage for fixing the transfer substrate; a lamination roller for bonding the graphene film on the graphene support film and the transfer substrate; and peeling means for peeling the graphene support film from the graphene film on the transfer substrate.

8. The multilayer graphene film manufacturing apparatus according to claim 7, further comprising a UV ozone irradiation device for irradiating UV ozone onto the graphene film bonded to the transfer substrate.

9. A method for manufacturing a pellicle film, comprising the steps of: forming a sacrificial layer on the laminated graphene film side of a multilayer graphene film manufactured by the manufacturing method described in claim 1 or 2; removing the transfer substrate from the multilayer graphene film; connecting a frame for a pellicle to the laminated graphene film side; and removing the sacrificial layer.

10. A pellicle membrane made of the multilayer graphene membrane of claim 5 or 6.

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