Method for manufacturing a graphene-coated substrate

Abstract

To inhibit the formation of cracks and wrinkles in a graphene film.SOLUTION: When a graphene film is transferred to cover a conductive pattern formed on a substrate, cracks or wrinkles may appear in the graphene film, resulting in a decrease in charge mobility, a characteristic of graphene. To solve this problem, a conductive pattern is formed on the substrate with a sloping shape so that the top is narrower than the bottom in cross-sectional view, and the graphene film is transferred so that it covers the conductive pattern. This prevents cracks and wrinkles from forming in the graphene film.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a substrate with a graphene film.

Background Art

[0002] Since graphene has a high charge mobility, it is expected to be used as a channel material in next-generation electronic devices. However, at present, it is difficult to directly form a graphene film on an element substrate. Therefore, a graphene film formed on another substrate is peeled off and transferred onto the element substrate. For example, it is known to obtain an electronic device by transferring a graphene film so as to cover metal pads formed on an element substrate and then patterning the graphene film into a desired shape (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When transferring a graphene film so as to cover a conductive pattern formed on a substrate, cracks and / or wrinkles may be formed in the graphene film, and the charge mobility, which is a characteristic of graphene, may decrease.

[0005] On one side, an object is to suppress the formation of cracks and wrinkles in the graphene film.

Means for Solving the Problems

[0006] In one embodiment, the process includes the steps of forming a conductive pattern on a substrate that has a sloping shape such that the upper part is narrower than the lower part when viewed in cross-section, and transferring a graphene film onto the substrate so as to cover the conductive pattern. The step of forming the conductive pattern includes, using a mask layer having openings formed on the substrate as a mask, depositing a deposition material onto the substrate while rotating the substrate and oscillating the substrate around a deposition source, then removing the mask layer, and subsequently flattening the edge portion of the conductive pattern so that the angle with respect to the substrate becomes small. This is a method for manufacturing a graphene-coated substrate. In one embodiment, the method for manufacturing a graphene-coated substrate comprises the steps of: forming a conductive pattern on a substrate having a sloping shape such that the upper part is narrower than the lower part in a cross-sectional view; and transferring a graphene film onto the substrate so as to cover the conductive pattern, wherein the step of forming the conductive pattern includes the steps of: using a mask layer having openings formed on the substrate as a mask, depositing a deposition material onto the substrate while rotating the substrate and moving the substrate back and forth horizontally with respect to a deposition source, then removing the mask layer, and then flattening the edge portion of the conductive pattern so that the angle with respect to the substrate is small. [Effects of the Invention]

[0007] One aspect of this is that it can suppress the formation of cracks and wrinkles in the graphene film. [Brief explanation of the drawing]

[0008] [Figure 1] Figures 1(a) to 1(c) are cross-sectional views (part 1) showing the method for manufacturing a graphene film-coated substrate according to Example 1. [Figure 2] Figures 2(a) to 2(c) are cross-sectional views (part 2) showing the method for manufacturing a graphene film-coated substrate according to Example 1. [Figure 3] Figures 3(a) and 3(b) show the rotation and oscillation of the substrate during the deposition of a conductive film. [Figure 4] Figures 4(a) to 4(d) are cross-sectional views (part 1) illustrating the transfer of a graphene film onto a substrate. [Figure 5] Figures 5(a) and 5(b) are cross-sectional views (part 2) illustrating the transfer of a graphene film onto a substrate. [Figure 6] Figures 6(a) to 6(c) are cross-sectional views (part 1) showing a method for manufacturing a graphene-coated substrate according to a comparative example. [Figure 7] Figures 7(a) and 7(b) are cross-sectional views (part 2) showing a method for manufacturing a graphene film-coated substrate according to a comparative example. [Figure 8] Figures 8(a) and 8(b) show the rotation and horizontal movement of the substrate during the deposition of a conductive film. [Figure 9]Figure 9(a) is a cross-sectional view of the sample used in the simulation, and Figure 9(b) is a graph showing the period of the reciprocating movement of the substrate in the simulation. [Figure 10] Figures 10(a) and 10(b) show the simulation results of the shape of the metal film when a metal film is deposited while the substrate is moved back and forth horizontally. [Figure 11] Figures 11(a) to 11(d) are cross-sectional views showing a method for manufacturing a graphene-coated substrate according to Example 3. [Figure 12] Figure 12 shows the simulation results of the shape of the metal film before and after sputter etching by irradiating the metal film with argon (Ar) ions. [Figure 13] Figures 13(a) to 13(d) are diagrams (part 1) illustrating the method for manufacturing a graphene film-coated substrate according to Example 4. [Figure 14] Figures 14(a) to 14(d) are diagrams (part 2) showing the method for manufacturing a graphene film-coated substrate according to Example 4. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [Examples]

[0010] FIG. 1(a) to FIG. 2(c) are cross-sectional views showing a method for manufacturing a substrate with a graphene film according to Example 1. As shown in FIG. 1(a), a substrate 10 having an insulating film 12 formed on its surface is prepared. The substrate 10 is, for example, a silicon substrate with an oxide film. In this case, the insulating film 12 is a silicon oxide film. The insulating film 12 may be formed not only on the upper surface of the substrate 10 but also on the entire surface. A mask layer 16 having a plurality of openings 14 is formed on the substrate 10. The mask layer 16 includes an upper layer 16a and a lower layer 16b. The upper layer 16a of the mask layer 16 is formed of, for example, a photoresist, and the lower layer 16b is formed of a resin soluble in the developing solution when developing the upper layer 16a. Thus, by performing exposure and development on the upper layer 16a, the lower layer 16b is also dissolved in the developing solution, and as a result, an opening 14 having a larger width in the lower layer 16b than in the upper layer 16a is formed. The reason for making the opening 14 have a shape with a larger width in the lower layer 16b than in the upper layer 16a is to facilitate lift-off, which will be described later.

[0011] As shown in FIG. 1(b), using the mask layer 16 as a mask, a conductive film 18 is formed on the substrate 10 by, for example, a vacuum evaporation method. At this time, while rotating the substrate 10, it is swung to form the conductive film 18 on the substrate 10. FIGS. 3(a) and 3(b) are diagrams showing the rotation and swing of the substrate 10 when forming the conductive film 18. FIG. 3(a) is a plan view showing the rotation of the substrate 10, and FIG. 3(b) is a side view showing the swing of the substrate 10. As shown in FIG. 3(a), during the formation of the conductive film 18 by the vacuum evaporation method, the substrate 10 is rotated around the center 11 of the substrate 10 as the rotation axis as indicated by an arrow 40. As shown in FIG. 3(b), during the formation of the conductive film 18 by the vacuum evaporation method, the substrate 10 is swung in a pendulum shape as indicated by an arrow 42 around the evaporation source 44 located above the substrate 10.

[0012] In vacuum deposition, the deposition material is incident on the substrate 10 with high linearity. Therefore, by oscillating the substrate 10 around the deposition source 44, a portion of the deposition material ejected from the deposition source 44 is blocked by the mask layer 16 at each of the multiple openings 14, preventing it from entering the opening 14. Furthermore, by oscillating the substrate 10 around the deposition source 44 while rotating the substrate 10, a portion of the deposition material is blocked by the mask layer 16 in all directions of the opening 14, preventing it from entering the opening 14. As a result, the conductive film 18 formed in the opening 14 has a shape that slopes upward in cross-sectional view, as shown in Figure 1(b). For example, the conductive film 18 formed in the opening 14 has a curved shape such as an elliptical arc or a circular arc in cross-sectional view. The surface of the conductive film 18 formed in the opening 14 may be represented by a curve from bottom to top in cross-sectional view, by a straight line, or by both a curve and a straight line.

[0013] As shown in Figure 1(c), the mask layer 16 and the conductive film 18 formed on the mask layer 16 are removed by the lift-off method. This forms multiple conductive patterns 20 on the substrate 10, which have a shape that slopes upward in cross-sectional view. That is, multiple conductive patterns 20 are formed on the substrate 10, which have a shape that slopes such that the width W2 at the top is narrower than the width W1 at the bottom in cross-sectional view. The top of the conductive pattern 20 is, for example, curved in cross-sectional view. The top of the conductive pattern 20 may also be, for example, flat in cross-sectional view. The thickness T of the conductive pattern 20 is, for example, about 10 nm to 300 nm. The maximum width W1 of the conductive pattern 20 is, for example, about 10 μm to 100 μm. The spacing H between adjacent conductive patterns 20 is, for example, about 10 μm to 100 μm. The angle θ between the top surface of the substrate 10 and the surface of the conductive pattern 20 is, for example, 20° to 60°. The conductive pattern 20 may be, for example, a wire, an electrode, or something else.

[0014] As shown in Fig. 2(a), a graphene film 30 is transferred onto a substrate 10 so as to directly cover a plurality of conductive patterns 20. The graphene film 30 may be a single layer or multiple layers. On the upper surface of the graphene film 30, a polymer film 32, such as a PMMA (polymethyl methacrylate) resist, is provided. The thickness of the polymer film 32 is, for example, about 100 nm.

[0015] Here, the transfer of the graphene film 30 onto the substrate 10 will be described. Figs. 4(a) to 5(b) are cross-sectional views showing the transfer of the graphene film 30 onto the substrate 10. As shown in Fig. 4(a), a metal film 52 is formed on a substrate 50 by, for example, a sputtering method. The thickness of the metal film 52 is, for example, about 1 nm to 1 mm. The substrate 50 is, for example, a sapphire substrate. The metal film 52 is, for example, a copper film. Note that the substrate 50 and the metal film 52 are not limited thereto. The substrate 50 may be, for example, a silicon substrate with an oxide film. The metal film 52 may be a film formed of a metal that serves as a catalyst for graphene. For example, it may be an iron film, a nickel film, or a cobalt film.

[0016] As shown in Fig. 4(b), a graphene film 30 is formed on the metal film 52. The graphene film 30 is grown on the metal film 52 by, for example, a thermal CVD (Chemical Vapor Deposition) method. In the thermal CVD method, for example, methane gas is used as a source gas, and hydrogen and argon are used as dilution gases. Note that the graphene film 30 may be grown by other methods such as a plasma CVD method or an MBE (Molecular Beam Epitaxy) method. The graphene film 30 may be a single layer or multiple layers. After growing the graphene film 30, the substrate 50 may be placed in a nitrogen atmosphere for degassing treatment.

[0017] As shown in Fig. 4(c), a polymer film 32 is applied onto the upper surface of the graphene film 30. The polymer film 32 is formed over the entire upper surface of the graphene film 30.

[0018] As shown in Figure 4(d), the substrate 50 is immersed in the etching solution 62 in the container 60 to dissolve the metal film 52 in the etching solution 62. This separates the substrate 50 from the graphene film 30, with the substrate 50 sinking to the bottom of the etching solution 62 and the graphene film 30 floating on the surface of the etching solution 62. Because the polymer film 32 is provided on the upper surface of the graphene film 30, even if the graphene film 30 is separated from the metal film 52, the dispersion of the graphene film 30 is suppressed.

[0019] As shown in Figure 5(a), the graphene film 30 floating on the surface of the etching solution 62 is scooped up with another substrate (not shown), the graphene film 30 is washed, and finally the graphene film 30 is floating on the surface of the pure water 66 in the container 64.

[0020] As shown in Figure 5(b), the graphene film 30 floating on the surface of the pure water 66 is scooped up with the substrate 10. As a result, as shown in Figure 2(a), the graphene film 30 covering multiple conductive patterns 20 is transferred onto the substrate 10. A polymer film 32 is provided on the upper surface of the graphene film 30.

[0021] As shown in Figure 2(b), the substrate 10 is immersed in a container containing a solution that dissolves the polymer film 32. This dissolves and removes the polymer film 32 that is attached to the upper surface of the graphene film 30. After that, the substrate 10 and the graphene film 30 are washed with water and then heated with a heating device 68 to dry the substrate 10 and the graphene film 30. The heating device 68 is, for example, a heater.

[0022] As shown in Figure 2(c), by drying the substrate 10 and the graphene film 30, a graphene-coated substrate 100 is obtained in which the graphene film 30 is transferred onto the substrate 10 so as to cover the conductive pattern 20.

[0023] [Comparative Example]

[0024] Figures 6(a) to 7(b) are cross-sectional views showing a method for manufacturing a graphene film-coated substrate according to a comparative example. As shown in Figure 6(a), a mask layer 16 having a plurality of openings 14 is formed on the substrate 10. The mask layer 16 includes an upper layer 16a and a lower layer 16b.

[0025] As shown in Figure 6(b), a conductive film 18 is deposited on the substrate 10 using, for example, a vacuum deposition method, with the mask layer 16 acting as a mask. In the comparative example, the substrate 10 is not rotated or oscillated during the deposition of the conductive film 18. Therefore, the conductive film 18 formed in the opening 14 has a rectangular shape in cross-section.

[0026] As shown in Figure 6(c), the mask layer 16 and the conductive film 18 formed on the mask layer 16 are removed by the lift-off method. As a result, multiple conductive patterns 20a with a rectangular shape in cross-section are formed on the substrate 10.

[0027] As shown in Figure 7(a), the graphene film 30 is transferred onto the substrate 10 so as to directly cover multiple conductive patterns 20a. The graphene film 30 is transferred onto the substrate 10 by the same method as shown in Figures 4(a) to 5(b). Because the spacing between the conductive patterns 20a is large relative to the thickness of the graphene film 30 and the polymer film 32, the graphene film 30 and the polymer film 32 become curved by the conductive patterns 20a.

[0028] As shown in Figure 7(b), the substrate 10 is immersed in a container containing a solution that dissolves the polymer film 32. This dissolves and removes the polymer film 32 that is provided on the upper surface of the graphene film 30. After that, the substrate 10 and the graphene film 30 are washed with water and then heated with a heating device 68 to dry the substrate 10 and the graphene film 30. Because the conductive pattern 20a has a rectangular shape in cross-section, the stress on the graphene film 30 becomes large at the right-angle corners of the conductive pattern 20a. For this reason, for example, during the removal of the polymer film 32 and / or drying with the heating device 68 after the removal of the polymer film 32, cracks may occur in the graphene film 30 at the corners of the conductive pattern 20a, and wrinkles may form as a result. When wrinkles form in the graphene film 30, foreign matter 34 such as water from washing may remain in the wrinkles.

[0029] On the other hand, according to Example 1, as shown in Figure 1(c), a conductive pattern 20 is formed on the substrate 10 with a sloping shape such that the upper part is narrower than the lower part in cross-sectional view. Then, as shown in Figures 2(a) to 2(c), a graphene film 30 is transferred onto the substrate 10 so as to cover the conductive pattern 20. In this way, because the conductive pattern 20 has a shape that slopes upward, the stress on the graphene film 30 that is formed covering the conductive pattern 20 can be reduced. Therefore, it is possible to suppress the occurrence of cracks and wrinkles in the graphene film 30.

[0030] In Example 1, as shown in Figures 2(a) to 2(c), the graphene film 30 is transferred onto the substrate 10 so as to directly cover the conductive pattern 20. In this case, the graphene film 30 is easily affected by the shape of the conductive pattern 20. Therefore, if the conductive pattern 20a is rectangular, as in the comparative example, the stress on the graphene film 30 becomes large at the right-angle corners of the conductive pattern 20a, making it prone to cracks and wrinkles. However, as in Example 1, by making the conductive pattern 20 inclined so that the upper part is narrower than the lower part, the stress on the graphene film 30 can be reduced even when the graphene film 30 is transferred so as to directly cover the conductive pattern 20. Thus, the occurrence of cracks and wrinkles in the graphene film 30 can be suppressed. In Example 1, the graphene film 30 may also be transferred so as to cover the conductive pattern 20 with another thin layer formed along the surface of the conductive pattern 20 sandwiched in between.

[0031] Furthermore, in Example 1, as shown in Figure 1(c), a conductive pattern 20 with a curved upper surface is formed in cross-sectional view. This reduces the stress on the graphene film 30 that covers the conductive pattern 20, thereby suppressing the occurrence of cracks and wrinkles in the graphene film 30.

[0032] In Example 1, as shown in Figure 1(b), a mask layer 16 having an opening 14 formed on the substrate 10 is used as a mask, and a conductive film 18 is deposited by vapor deposition. At this time, as shown in Figures 3(a) and 3(b), the substrate 10 is rotated while the substrate 10 is oscillated around the vapor deposition source 44, and the vapor deposition material is deposited onto the substrate 10. After that, as shown in Figure 1(c), the mask layer 16 is removed to form a conductive pattern 20 on the substrate 10. This makes it easy to form a conductive pattern 20 on the substrate 10 with a sloping shape such that the upper part is narrower than the lower part when viewed in cross-section.

[0033] In Example 1, as shown in Figure 5(b), a polymer film 32 is provided on one side of the graphene film 30, which floats on the surface of pure water 66, and the graphene film 30 is scooped up with the substrate 10. Then, as shown in Figures 2(b) and 2(c), the polymer film 32 is removed to transfer the graphene film 30 onto the substrate 10. In this case, if the conductive pattern 20a is rectangular, as in the comparative example, the stress on the graphene film 30 tends to be large at the right-angle corners of the conductive pattern 20a. However, as in Example 1, by making the conductive pattern 20 inclined so that the upper part is narrower than the lower part, the stress on the graphene film 30 can be reduced even when the polymer film 32 is removed after the graphene film 30 is scooped up with the substrate 10. Therefore, the occurrence of cracks and wrinkles in the graphene film 30 can be suppressed.

[0034] Furthermore, in Example 1, as shown in Figure 2(b), the graphene film 30 is dried using a heating device 68 after the polymer film 32 is removed. In this case, if the conductive pattern 20a is rectangular, as in the comparative example, the stress on the graphene film 30 tends to be large at the right-angle corners of the conductive pattern 20. However, as in Example 1, by shaping the conductive pattern 20 so that the upper part is narrower than the lower part, the stress on the graphene film 30 can be reduced even when the graphene film 30 is dried using the heating device 68. Therefore, the occurrence of cracks and wrinkles in the graphene film 30 can be suppressed.

[0035] In Example 1, the method for transferring the graphene film 30 onto the substrate 10 was shown as scooping up the graphene film 30 floating on the surface of pure water 66 with the substrate 10, but other methods may be used. For example, the graphene film 30 may be transferred onto the substrate 10 using adhesive tape. [Examples]

[0036] In Example 1, a conductive film 18 was deposited on the substrate 10 by rotating the substrate 10 while oscillating it around the deposition source 44. In contrast, in Example 2, the conductive film 18 was deposited on the substrate 10 by rotating the substrate 10 while reciprocating it horizontally relative to the deposition source 44. The other manufacturing steps in Example 2 are the same as in Example 1, so their explanation is omitted.

[0037] Figures 8(a) and 8(b) show the rotation and horizontal movement of the substrate 10 when a conductive film 18 is deposited. Figure 8(a) is a plan view showing the rotation of the substrate 10, and Figure 8(b) is a side view showing the horizontal movement of the substrate 10. As shown in Figure 8(a), during the deposition of the conductive film 18 by vacuum deposition, the substrate 10 is rotated around its center 11 as the axis of rotation, as indicated by arrow 40. As shown in Figure 8(b), during the deposition of the conductive film 18 by vacuum deposition, the substrate 10 is moved back and forth horizontally relative to the deposition source 44 located above the substrate 10, as indicated by arrow 46.

[0038] In this way, by rotating the substrate 10 and moving it back and forth horizontally relative to the deposition source 44, similar to Example 1, a portion of the deposition material emitted from the deposition source 44 is blocked by the mask layer 16 at each of the multiple openings 14 and does not enter the opening 14. As a result, the conductive film 18 formed in the opening 14 has a shape that slopes upward in cross-sectional view, similar to Figure 1(b) of Example 1. After removing the mask layer 16, a conductive pattern 20 is formed on the substrate 10 with a shape that slopes so that the upper width is narrower than the lower width in cross-sectional view, similar to Figure 1(c) of Example 1. The upper part of the conductive pattern 20 is, for example, curved in cross-sectional view.

[0039] [Simulation 1] The shape of the metal film formed within the opening 14 of the mask layer 16 when a metal film is deposited while the substrate 10 is moved back and forth horizontally relative to the deposition source 44 was simulated. Figure 9(a) is a cross-sectional view of the sample used in the simulation. As shown in Figure 9(a), a sample was used in which a mask layer 16 having an opening 14 was formed on the substrate 10. The mask layer 16 had a single-layer structure. The reference position 0 was defined as the position of the deposition source 44 on a perpendicular line to the center of the substrate 10, and the right side of the plane of the paper was defined as the + direction and the left side as the - direction from the reference position 0. The simulation conditions were as follows. The shortest distance L from the evaporation source 44 to the substrate 10 is 17.3 cm. Width of aperture 14: X: 10 μm Mask layer 16 thickness T: 1 μm, 2 μm, 4 μm, 8 μm Horizontal movement range of circuit board 10: ±5cm, ±10cm, ±15cm

[0040] Figure 9(b) is a graph showing the period of the reciprocating movement of the substrate 10 in the simulation. The simulation was performed by calculating the destination 72,000 times each time a particle was irradiated onto the substrate 10 within the simulation range. As shown in Figure 9(b), the period of reciprocating movement was set to 36,000 (one particle irradiation time) regardless of whether the horizontal movement range was ±5 cm, ±10 cm, or ±15 cm.

[0041] Figures 10(a) and 10(b) show the simulation results of the shape of the metal film when a metal film is deposited while the substrate 10 is moved back and forth horizontally. In Figures 10(a) and 10(b), the horizontal axis represents the coordinates relative to the origin, with the center of the opening 14 as the origin, and the vertical axis represents the thickness of the deposited metal film. Figure 10(a) shows the simulation results of the shape of the metal film when the thickness of the mask layer 16 is 4 μm and the horizontal movement range is ±5 cm, ±10 cm, or ±15 cm. Figure 10(b) shows the simulation results of the shape of the metal film when the horizontal movement range is ±10 cm and the thickness of the mask layer 16 is 1 μm, 2 μm, 4 μm, or 8 μm.

[0042] As shown in Figures 10(a) and 10(b), by performing deposition while reciprocating the substrate 10 horizontally relative to the deposition source 44, the shape of the metal film deposited in the opening 14 became inclined upwards. In other words, the shape of the metal film formed in the opening 14 became inclined such that the upper part was narrower than the lower part. This is thought to be because reciprocating the substrate 10 horizontally relative to the deposition source 44 causes the deposition material from the deposition source 44 toward the opening 14 to be blocked by the mask layer 16. As shown in Figure 10(a), the larger the horizontal movement range, the larger the area where the deposition material from the deposition source 44 is blocked by the mask layer 16, and the more inclined the metal film became so that the upper part was narrower. As shown in Figure 10(b), the thicker the mask layer 16, the larger the area where the deposition material from the deposition source 44 is blocked by the mask layer 16, and the more inclined the metal film became so that the upper part was narrower.

[0043] Figures 10(a) and 10(b) show the simulation results when the substrate 10 is moved back and forth horizontally relative to the deposition source 44. However, it is believed that similar results can be obtained when the substrate 10 is oscillated around the deposition source 44. This is because, even when the substrate 10 is oscillated, the deposition material moving from the deposition source 44 toward the opening 14 is still blocked by the mask layer 16.

[0044] According to Example 2, a conductive film 18 is deposited by vapor deposition using a mask layer 16 having openings 14 formed on a substrate 10 as a mask. At this time, as shown in Figures 8(a) and 8(b), the deposition material is deposited on the substrate 10 while the substrate 10 is rotated and moved back and forth horizontally relative to the deposition source 44. After that, the conductive pattern 20 is formed on the substrate 10 by removing the mask layer 16. This makes it easy to form a conductive pattern 20 on the substrate 10 with a sloping shape such that the upper part is narrower than the lower part in cross-sectional view.

[0045] In Example 1, the conductive pattern 20 was formed by depositing a deposition material onto the substrate 10 while rotating the substrate 10 and oscillating the substrate 10 around the deposition source 44. In Example 2, the conductive pattern 20 was formed by depositing a deposition material onto the substrate 10 while rotating the substrate 10 and reciprocating it horizontally relative to the deposition source 44. However, the conductive pattern 20 may be formed by any other method as long as a conductive pattern 20 with a sloping shape on the substrate 10 is formed such that the upper part is narrower than the lower part in cross-sectional view. [Examples]

[0046] Figures 11(a) to 11(d) are cross-sectional views showing a method for manufacturing a graphene film-coated substrate according to Example 3. As shown in Figure 11(a), the same steps as in Figures 1(a) to 1(c) of Example 1 are performed to form a conductive pattern 20 on the substrate 10.

[0047] As shown in Figure 11(b), sputter etching is performed on the conductive pattern 20. For example, physical etching is performed on the conductive pattern 20 by irradiating it with argon (Ar) ions using a sputter etching apparatus or an ion milling apparatus. As a result, the conductive pattern 20 has a flattened edge shape. The angle θ between the top surface of the substrate 10 and the surface of the conductive pattern 20 is, for example, 10° to 20°.

[0048] As shown in Figure 11(c), a graphene film 30 is transferred onto the substrate 10 so as to cover multiple conductive patterns 20. The graphene film 30 is transferred onto the substrate 10 by the same method as shown in Figures 4(a) to 5(b) of Example 1.

[0049] As shown in Figure 11(d), the substrate 10 is immersed in a container containing a solution that dissolves the polymer film 32. This dissolves and removes the polymer film 32 that is provided on the upper surface of the graphene film 30. After that, the substrate 10 and the graphene film 30 are washed with water and then heated using a heating device 68 (not shown in Figure 11) to dry the substrate 10 and the graphene film 30, thereby obtaining a graphene-coated substrate 200.

[0050] [Simulation 2] As in Simulation 1 above, a metal film was deposited by reciprocating the substrate 10 horizontally relative to the deposition source 44, and then the shape of the metal film after sputter etching by irradiating it with Ar ions was simulated. The simulation conditions were as follows. Metal film deposition (see Figures 9(a) and 9(b)) The shortest distance L from the evaporation source 44 to the substrate 10 is 17.3 cm. Width of aperture 14: X: 10 μm Thickness T of mask layer 16: 4 μm Horizontal movement range of circuit board 10: ±10cm Sputter etching of metal films Incidence direction of Ar ions: Incident perpendicular to the substrate 10. Etching amount: The minimum thickness of the metal film after etching is set to 5 nm.

[0051] Figure 12 shows the simulation results of the shape of a metal film before and after sputter etching by irradiating it with Ar ions. In Figure 12, the horizontal axis represents the coordinates relative to the origin, with the center of the metal film as the origin, and the vertical axis represents the thickness of the metal film. As shown in Figure 12, by irradiating the metal film with Ar ions and performing sputter etching, the edges of the metal film were flattened so that the angle with respect to the substrate became smaller.

[0052] According to Example 3, before transferring the graphene film 30, the edges of the conductive pattern 20 are flattened so that the angle with respect to the substrate 10 is reduced. This further suppresses the occurrence of cracks and wrinkles in the graphene film 30.

[0053] In Example 3, the edges of the conductive pattern 20 are flattened by physical etching so that the angle with respect to the substrate 10 is reduced. This makes it easy to flatten the edges of the conductive pattern 20. Note that the flattening of the edges of the conductive pattern 20 is not limited to physical etching, but may be performed by other methods as well.

[0054] In Example 3, when sputter etching the conductive pattern 20, Ar ions may be incident perpendicularly to the substrate 10, or the substrate 10 may be tilted and the Ar ions may be incident at an angle to the substrate 10. When the Ar ions are incident at an angle to the substrate 10, it is preferable to rotate the substrate 10 while incidenting the Ar ions at an angle so that the direction of incidence of the Ar ions is not biased within the substrate 10. [Examples]

[0055] Example 4 shows an example where a graphene element is formed on a substrate. An example is shown where a photosensor is used as the graphene element. Figures 13(a) to 14(d) show the method for manufacturing a graphene-coated substrate according to Example 4. Figures 13(a), 13(c), 14(a), and 14(c) are plan views showing the method for manufacturing a graphene-coated substrate according to Example 4. Figures 13(b), 13(d), 14(b), and 14(d) are cross-sectional views AA of Figures 13(a), 13(c), 14(a), and 14(c).

[0056] As shown in Figures 13(a) and 13(b), the same steps as in Figures 1(a) to 1(c) of Example 1 are performed to form a conductive pattern, namely a source electrode 21a and a drain electrode 21b, on the substrate 10. The source electrode 21a and drain electrode 21b are formed from a metal such as gold.

[0057] As shown in Figures 13(c) and 13(d), the same steps as in Figures 2(a) to 2(c) of Example 1 are performed to transfer the graphene film 30 onto the substrate 10 so as to cover the source electrode 21a and the drain electrode 21b.

[0058] As shown in Figures 14(a) and 14(b), the graphene film 30 is processed into a channel shape to be provided between the source electrode 21a and the drain electrode 21b. The graphene film 30 is processed, for example, by photolithography and etching.

[0059] As shown in Figures 14(c) and 14(d), a source wiring 24a is formed on the substrate 10 to connect one end of the graphene film 30 to the source electrode 21a. A drain wiring 24b is formed on the substrate 10 to connect the other end of the graphene film 30 to the drain electrode 21b. The source wiring 24a and drain wiring 24b are formed from a metal such as gold or copper. The source wiring 24a and drain wiring 24b are formed by depositing a metal film by a method such as sputtering, and then patterning the metal film by an etching method. The source wiring 24a and drain wiring 24b may also be formed by a lift-off method.

[0060] A back gate voltage is applied to the substrate 10, and a source-drain voltage is applied between the source electrode 21a and the drain electrode 21b. This makes it possible to detect the light irradiated onto the graphene film 30.

[0061] According to Example 4, a conductive pattern consisting of a source electrode 21a and a drain electrode 21b is formed on the substrate 10. After transferring a graphene film 30 onto the substrate 10 so as to cover the source electrode 21a and the drain electrode 21b, the graphene film 30 is processed into a channel shape located between the source electrode 21a and the drain electrode 21b. As described in Example 1, cracks and wrinkles in the graphene film 30 are suppressed, resulting in a photosensitive sensor with good characteristics.

[0062] In Example 4, the graphene element formed on the substrate 10 was shown as an example where it is a photosensor, but this is not the only example; the graphene element may be a gas sensor, a transistor, or other types of sensors.

[0063] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0064] 10 circuit boards 11 center 12 Insulating film 14 Opening 16 mask layers 16a upper layer 16b Lower layer 18 Conductive film 20, 20a conductive pattern 21a Source electrode 21b Drain electrode 24a Source Wiring 24b Drain wiring 30 Graphene film 32 Polymer film 34 Foreign object 44 Vapor deposition source 50 circuit boards 52 Metal film 60 containers 62 Etching solution 64 Container 66 Pure water 100, 200 graphene film coated substrates

Claims

1. A process of forming a conductive pattern on a substrate that has a sloping shape such that the upper part is narrower than the lower part when viewed in cross-section, The process includes a step of transferring a graphene film onto the substrate so as to cover the conductive pattern, A method for manufacturing a graphene-coated substrate, comprising the steps of forming the conductive pattern, using a mask layer having openings formed on the substrate as a mask, depositing a deposition material onto the substrate while rotating the substrate and oscillating the substrate around a deposition source, then removing the mask layer, and then flattening the edge portion of the conductive pattern so that the angle with respect to the substrate becomes small.

2. A step of forming a conductive pattern on a substrate that has a sloping shape such that the upper part is narrower than the lower part when viewed in cross-section, The process includes a step of transferring a graphene film onto the substrate so as to cover the conductive pattern, A method for manufacturing a graphene-coated substrate, comprising the steps of forming the conductive pattern, using a mask layer having openings formed on the substrate as a mask, depositing a deposition material onto the substrate while rotating the substrate and moving the substrate back and forth horizontally with respect to a deposition source, removing the mask layer, and then flattening the edge portion of the conductive pattern so that the angle with respect to the substrate becomes small.

3. The method for manufacturing a graphene film-coated substrate according to claim 1 or 2, wherein the step of transferring the graphene film is to transfer the graphene film so as to directly cover the conductive pattern.

4. The method for manufacturing a graphene film-coated substrate according to claim 1 or 2, wherein the step of forming the conductive pattern is to form the conductive pattern whose upper part is curved when viewed in cross-section.

5. The method for manufacturing a graphene film-coated substrate according to claim 1 or 2, wherein the planarization step is performed by physically etching the conductive pattern to flatten the edge portion of the conductive pattern.

6. The method for manufacturing a graphene-coated substrate according to claim 1 or 2, wherein the step of transferring the graphene film involves scooping up the graphene film, which has a polymer film provided on one side and floats on the liquid surface, with the substrate, and then removing the polymer film to transfer the graphene film onto the substrate.

7. The method for manufacturing a graphene-coated substrate according to claim 6, wherein the step of transferring the graphene film includes a step of drying the graphene film with a heating device after removing the polymer film.

8. The step of forming the conductive pattern involves forming the conductive pattern which is the source electrode and the drain electrode. A method for manufacturing a graphene film-coated substrate according to claim 1 or 2, further comprising the step of transferring the graphene film, followed by the step of processing the graphene film into a channel shape located between the source electrode and the drain electrode.

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