Pattern formation method

Abstract

To provide a pattern formation method capable of simply forming a fine pattern made of a two-dimensional layered material with a high quality.SOLUTION: There is provided a pattern formation method, comprising: a substrate preparation step of preparing a substrate having a recess formed on a first main surface; a nanosheet placement step of placing a nanosheet made of a two-dimensional layered material on the first main surface of the substrate; an adhesive body preparation step of preparing an adhesive body; a contact step of contacting the first main surface of the adhesive body with a surface of the nanosheet; and a detachment step of detaching the adhesive body from a surface of the nanosheet.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pattern formation method, and more particularly to a pattern formation method using a two-dimensional layered material. [Background technology]

[0002] Two-dimensional layered materials, which are materials with layered structures in which atomic layers are bound by weak van der Waals forces, have unique electronic, optical, and mechanical properties. For these reasons, two-dimensional layered materials have attracted considerable attention in fields such as gas sensors (disclosed, for example, in Patent Document 1), solar cells, lithium-ion batteries, and field-effect transistors. Furthermore, two-dimensional layered materials processed into patterned shapes are highly anticipated as they will pave the way for applications such as photonics devices with metamaterial structures and two-dimensional network devices.

[0003] Two-dimensional layered materials can be supplied in the form of nanosheets, and methods for patterning these nanosheets to form fine patterns include (1) processing using focused ion beam irradiation, (2) processing using femtosecond lasers, (3) processing by cutting the nanosheet along its crystal axis, and (4) processing using lithography and dry etching. However, these methods have the following problems, and the development of a new method for easily forming submicron-sized fine patterns made of two-dimensional layered materials with high quality has been desired.

[0004] The focused ion beam irradiation processing method involves irradiating a nanosheet with a high-density focused helium ion beam or gallium beam, cutting the nanosheet through a sputtering phenomenon and sublimation of atoms due to the heat generated by the irradiation, as disclosed in Non-Patent Documents 1 and 2. The problem with this method is that the base material is also processed at the same time, causing fusion with the substrate, and the heat generated around the cut edge causes melting of the nanosheet, defects, atomic migration, and deformation.

[0005] The femtosecond laser processing method uses a focused, sweeping beam of a powerful femtosecond laser to sublimate and cut the atoms that make up the nanosheet. This method has problems such as limited spatial resolution due to the optical limitations imposed by the wavelength of the laser light, melting due to heat generation, and the generation of defects.

[0006] A processing method for cutting nanosheets along their crystal axes involves placing an oxide nanosheet dispersed in a solvent on a substrate with protrusions and cutting the nanosheet along its crystal axis, as disclosed in Patent Document 2. This method has the problem that cutting is only possible along the crystal axis direction, making it difficult to form patterns of any desired shape.

[0007] Lithography and dry etching are the most common processing methods, but they have the problem of easily damaging and contaminating the underlying workpiece during resist removal and dry etching. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2021-139833 [Patent Document 2] Japanese Patent Application Publication No. 2023-117549 [Non-patent literature]

[0009] [Non-Patent Document 1] M.Sakurai et al.,Nanotechnology,31(2020)345708. [Non-patent document 2] M.Sakurai et al.,Vacuum,207(2023)111605. Summary of the Invention [Problem to be solved by the invention]

[0010] The problem to be solved by the present invention is to provide a method for easily forming submicron-sized fine patterns made of two-dimensional layered materials with high quality, which avoids the above-mentioned problems associated with conventional methods. [Means for solving the problem]

[0011] The configuration of the present invention to solve the problems is shown below. (Configuration 1) a substrate preparation step of preparing a substrate having a recess formed on a first main surface; a nanosheet disposing step of disposing a nanosheet made of a two-dimensional layered material on the first main surface of the substrate; an adhesive body preparation step of preparing an adhesive body; A contacting step of contacting a first main surface of the adhesive body with a surface of the nanosheet; A detaching step of detaching the adhesive body from the surface of the nanosheet, a pattern in which a layer made of the two-dimensional layered material is formed on the first main surface of the substrate other than the recessed portion; (Configuration 2) 2. The pattern forming method according to claim 1, wherein the adhesive body comprises a pad having a flat first main surface. (Configuration 3) 3. The pattern forming method according to claim 2, wherein the pad is made of a material whose adhesive strength changes depending on the temperature. (Configuration 4) 4. The pattern forming method according to Structure 2 or 3, wherein at least the first main surface of the pad is formed of a polymer. (Configuration 5) 2. The pattern forming method according to configuration 1, wherein a fine pattern is formed on the first main surface of the adhesive body, and the pitch p between the fine patterns is smaller than the minimum space s between the patterns to be formed. (Configuration 6) 2. The pattern forming method according to claim 1, wherein at least the surface of the adhesive body is provided with a thermal release tape or an adhesive tape. (Configuration 7) A pattern forming method according to any one of configurations 1 to 6, wherein the peeling step is carried out by changing the temperature of the adhesive body to control the adhesive force between the nanosheet and the adhesive body. (Configuration 8) 8. The pattern forming method according to claim 7, wherein the temperature reached when the temperature is changed is the softening point temperature of the adhesive body. (Configuration 9) 9. The pattern forming method according to any one of the first to eighth aspects, wherein the two-dimensional layered material has layers bonded together by van der Waals forces. (Configuration 10) 10. The pattern forming method according to any one of aspects 1 to 9, wherein the two-dimensional layered material is one selected from the group consisting of graphene, transition metal chalcogenides (TMDCs), oxides, and nitrides. (Configuration 11) 11. The pattern forming method according to claim 10, wherein the transition metal chalcogenide is one selected from the group consisting of ZrSe2, TaSe2, TaS2, NbSe2, WSe2, MoTe2, MoSe2, MoS2, GaSe, GaS, SnSe2 and SnS2. (Configuration 12) 12. The pattern forming method according to any one of aspects 1 to 11, wherein the thickness of the nanosheet is from one atomic layer to 200 nm. (Configuration 13) 13. The pattern forming method according to any one of configurations 1 to 12, wherein the minimum groove width of the recess is 0.05 μm or more and 10 μm or less. (Configuration 14) 14. The pattern forming method according to any one of aspects 1 to 13, wherein an adhesion-enhancing layer is formed between the substrate and the nanosheet. [Effects of the Invention]

[0012] According to the present invention, there is provided a method for easily forming a submicron-sized fine pattern made of a two-dimensional layered material with high quality. [Brief explanation of the drawings]

[0013] [Figure 1]FIG. 1 is a process chart showing a first process of the present invention using cross-sectional views. [Figure 2] FIG. 1 is a flowchart showing steps of a pattern forming method of the present invention. [Figure 3] FIG. 10 is a process diagram illustrating a fourth process of the present invention using cross-sectional views. [Figure 4] FIG. 1 is an explanatory diagram illustrating the key points of nanosheet pattern formation by the nanosheet piece detachment step in the present invention. [Figure 5] FIG. 2 is a process diagram illustrating a second process of the present invention using cross-sectional views. [Figure 6] FIG. 2 is a process diagram illustrating a third process of the present invention using cross-sectional views. [Figure 7] 1A to 1C are process diagrams illustrating the fabrication process of a sample in Example 1 using cross-sectional views. [Figure 8] Photographs showing an example of a micropatterning process according to an embodiment, where (a) is an example of a substrate 11 having recesses (a group of holes 12 arranged in a matrix) observed from above with an optical microscope, and (b) is an example of a substrate 11 coated with a two-dimensional layered material (graphene nanosheet) 20 observed from above with a scanning helium ion microscope. [Figure 9] (a) and (b) show examples of observations using an optical microscope and a scanning helium ion microscope, respectively, of a sample in which a pattern made of graphene, a two-dimensional layered material, is formed on the convex portions of a silicon nitride substrate. [Figure 10] This is an example of observing the pattern 22 made of graphene adhered and formed on the pad 31a using an optical microscope after the adhesive body detachment step. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, A to B in the text indicates A or more and B or less.

[0015] (Embodiment 1) In the first embodiment, a method for forming a fine pattern made of a two-dimensional layered material by a peeling process using an adhesive will be described with reference to the drawings.

[0016] The method for forming a two-dimensional layered material fine pattern according to the first embodiment comprises the following steps, as shown in the flow chart of FIG.

[0017] The first step is a substrate preparation step (FIG. 1(a), step S11) in which a substrate 11 having a recess 12 formed on a first main surface 13 is prepared. Here, the substrate 11 is not particularly limited as long as it has mechanical strength and is resistant to deformation, and any desired substrate can be used. For example, the substrate 11 may be a Si substrate, a GaAs substrate, a silicon nitride film (SiN x ) substrate, silicon oxide film (SiO x Examples of suitable substrates include a silicon oxynitride (SiON) substrate, a synthetic quartz substrate, a glass substrate, a metal substrate such as tungsten (W), a plastic substrate such as polycarbonate, and a ceramic substrate made of silicon carbide (SiC). The substrate 11 may be made of a single material or may be made of multiple materials, and may include, for example, a silicon substrate having a pattern made of silicon oxide, polysilicon, aluminum, etc. that forms protrusions on the silicon substrate.

[0018] The minimum groove width of the recess 12 is preferably 0.05 μm or more and 10 μm or less, and more preferably 0.2 μm or more and 5 μm or less. A minimum groove width within this range enables stable formation of highly accurate patterns with few defects. In the subsequent nanosheet peeling step (step S15), if the minimum groove width is less than 0.05 μm, it is difficult to peel the nanosheet into the desired shape, and defects are likely to occur. If the minimum width exceeds 10 μm, the nanosheet placed in the pattern area is likely to bend, making it difficult to form a pattern of the two-dimensional layered material in the desired shape. Nanosheet peeling occurs depending on the balance between the mechanical rigidity and contact strength of the nanosheet. Therefore, as the pattern size becomes smaller, the contact strength weakens, and the nanosheet must be made thinner. The depth of the recess 12 is not particularly limited as long as it is deep enough so that when a nanosheet made of a two-dimensional layered material is subsequently deposited on the first main surface 13 of the substrate 11, the sheet does not come into contact with the bottom of the recess 12; for example, it may be an opening that penetrates the substrate 11. It is preferable that the first main surface 13 has a smooth surface and a flat horizontal plane. A smooth and flat surface makes it easier to suppress the occurrence of defects.

[0019] The second step is a nanosheet arrangement step (FIG. 1(b), step S12) in which a nanosheet 20 made of a two-dimensional layered material is arranged on the first main surface 13 of the substrate 11. Here, the nanosheet 20 may be arranged by a normal nanosheet deposition method, but it is preferable to use a deposition method that takes care not to introduce air bubbles or wrinkles.

[0020] The two-dimensional layered material 20 is a layered material in which layers are bonded by van der Waals forces, specifically, one selected from the group consisting of graphene, transition metal chalcogenides (TMDCs), oxides, and nitrides. The transition metal chalcogenides include one selected from the group consisting of ZrSe2, TaSe2, TaS2, NbSe2, WSe2, MoTe2, MoSe2, MoS2, GaSe, GaS, SnSe2, and SnS2. These materials have weak van der Waals forces acting between atomic layers, so they can be separated with high pattern shape precision in the nanosheet separation step (step S15) described below. The thickness of the two-dimensional layered material nanosheet 20 is preferably one atomic layer or more and 200 nm or less. When the thickness of the two-dimensional layered material nanosheet 20 is within this range, it becomes possible to stably form a highly accurate pattern with few defects. That is, if the thickness is less than one atomic layer, the nanosheet is porous, brittle, and prone to defects, while if it exceeds 200 nm, it becomes difficult to cleanly separate the pattern at the edge of the substrate recess 12 during the nanosheet detachment step (step S15), making it difficult to form a highly accurate pattern.

[0021] The third step is an adhesive body preparation step (FIG. 1(c), step S13) in which an adhesive body 31 is prepared. Examples of the adhesive body 31 include a pad whose first main surface is formed of a polymer, a thermal release tape, and a pad whose surface is provided with a thermal release tape or adhesive tape. Here, thermal release tape refers to a tape whose adhesive strength changes depending on the temperature. The range of change in adhesive strength used is suitable for peeling off the unnecessary nanosheet portion. Specifically, an example of the thermal release tape is Ripa Alpha (manufactured by Nitto). An example of the adhesive tape is Scotch Mending Tape (810-1-18D) (3M Japan Ltd.).

[0022] The shape of the pad can be exemplified by a pad with a flat first main surface and a pad with a fine pattern formed on the first main surface (brush-like adhesive body, brush-like pad). In the case of the former flat pad, the surface over which the nanosheet 20 and the pad can be brought into contact with each other with uniform pressure is widened, improving the accuracy of pattern formation within the surface. The latter pad with a fine pattern formed thereon has the advantage that defects such as missing patterns are less likely to occur because the pad flexibly conforms to and adheres to the protrusions of the substrate 11 even when the protrusions are not sufficiently flat or smooth. Here, as shown in FIG. 3, the inter-pattern pitch p of the adhesive body (brush-like adhesive body, brush-like pad) 32 with a fine pattern formed thereon is set much smaller than the minimum space s between the patterns to be formed, for example, by an order of magnitude. The only difference between using the pad 32 with a fine pattern formed on its first main surface and using the pad 31 with a flat first main surface is the pad itself. The pattern formation step using the pad 32 conforms to the pattern formation step using the pad 31 with a flat first main surface shown in FIG. 1. That is, even when using a pad with a fine pattern formed on its first main surface, the pattern formation step consists of a substrate preparation step (FIG. 3(a)), a nanosheet placement step (FIG. 3(b)), an adhesive body preparation step (FIG. 3(c)), an adhesive body contact step (FIG. 3(d)), and a separation step (FIG. 3(e)).

[0023] The pad is preferably made of a material whose adhesive strength changes with temperature, and at least the first main surface of the pad is preferably formed of a polymer. This is because polymers are less likely to scratch the nanosheet 20 when brought into contact with it, and their adhesive strength changes significantly near their softening temperature. Silicone polymers such as polydimethylsiloxane (PDMS) and polypropylene carbonate (PPC) are preferably used as the polymer.

[0024] The softening index is the temperature at which the surface begins to melt, and in the case of silicone rubber (thermal decomposition or melting temperature 160°C to 250°C) whose main component is a silicone polymer such as PDMS or PPC, a temperature of 50 to 90°C should be used.

[0025] The fourth step is a contact step (Figure 1(d), step S14) in which the first main surface of the adhesive body 31 is brought into contact with the surface of the nanosheet 20. There is no particular limit to the contact time, but if a pad is used with temperature control, it can be several minutes. When a soft pad is used, the force applied from above applies local shear stress to the nanosheet at the edge of the pattern, and the resulting defects along the edge induce peeling along the pattern when the pad is removed. If the pad's adhesiveness changes with temperature, fine adjustment of the applied force is possible. The fifth step is a detachment step in which the adhesive body 31 is detached from the surface of the nanosheet 20 (FIG. 1(e), step S15). Through the first to fifth steps, a pattern is formed in which a two-dimensional layered material layer 21 is formed on the first main surface 13 of the substrate 11 other than the recessed portions 12, i.e., on the protruding portions of the substrate 11 (FIG. 1(f)).

[0026] The key point of the present invention is to separate the nanosheet 20 in the non-pattern-forming region. That is, the key point is to remove the unnecessary nanosheet while ensuring sufficient pattern edge precision without damaging the two-dimensional layered material nanosheet that should remain as a pattern.

[0027] When a nanosheet 20 is placed on a substrate 11 having a recess 12 and an adhesive body 31 comes into contact with the nanosheet 20, four types of interface states exist at interfaces A to D between the substrate 11, the nanosheet 20, and the adhesive body 31, as shown in Figure 4. In this state, the nanosheet 20 does not come into contact with anything at interface B above the recess 12, but comes into contact with the adhesive body 31 at interface D. The conditions under which the nanosheet 21 remains on the convex portion of the substrate 11 as shown in Figure 1(e), and the nanosheet 20 placed in the concave portion 12 adheres to the adhesive body 31 to form nanosheet pieces 22, and the nanosheet 20 is neatly separated into a pattern are expressed by the following (1) to (3). (1) There is a relationship that the interaction between the nanosheet 20 and the adhesive body 31 at the interface C is less than the interaction between the substrate 11 and the nanosheet 20 at the interface A. (2) The in-plane strength of the nanosheet 20 is so weak that it can be almost ignored, and it is easily broken. (3) At the interface D, interactions such as van der Waals forces act between the nanosheet 20 and the adhesive body 31.

[0028] When the nanosheet 20 is a thin film made of a two-dimensional layered material, the in-plane strength of the two-dimensional layered material bonded by van der Waals forces is so weak that it can be almost ignored. Therefore, the nanosheet 20 is easily broken at the point where force is applied, and conditions (2) and (3) are satisfied. Therefore, the condition (1) is satisfied, and the pattern separation and pattern detachment of the nanosheet 20 as shown in FIG. 1(e) is carried out.

[0029] As a method for satisfying the condition (1), the first method is to use an adhesive body 31 having a moderate adhesive strength, and the second method is to enhance the interaction at the interface A. Naturally, the first and second methods may be combined.

[0030] The first method is to use the above-mentioned polymer as the adhesive body 31, and in particular to control the temperature of the polymer so as to obtain an appropriate adhesive strength for the adhesive body 31. Alternatively, a heat-release tape or an adhesive tape may be used as the adhesive body 31.

[0031] The second method includes a method using a substrate 11 with high adhesive strength such as titanium (Ti), and a method in which an adhesive or adhesion strengthening material is formed on the surface of the convex portions of the substrate 11. Examples of adhesives and adhesion strengthening materials include titanium (Ti), molybdenum (Mo), epoxy resin, acrylic resin, and urethane resin, as well as methods in which the substrate surface is activated by irradiation with an inert gas (e.g., argon) or ions, or by oxygen plasma treatment.

[0032] The separation step (step S15) is preferably carried out by changing the temperature of the adhesive body 31 to control the adhesive force between the nanosheet 20 and the adhesive body 31. Here, the temperature reached when the temperature is changed is preferably the softening point temperature of the adhesive body 31. By changing the temperature of the adhesive body 31, the adhesive force changes significantly, and the nanosheet 20 made of the two-dimensional layered material arranged in contact with the substrate 11 remains attached to the substrate 11, while the nanosheet 20 arranged in the recess 12 of the substrate 11 can be sufficiently controlled to achieve an appropriate adhesive force that adheres to the adhesive body 31. This controllability is particularly easy to obtain near the softening point of the adhesive body 31. Furthermore, because the adhesive body 31 near its softening point is highly elastic and soft, the two-dimensional layered material that comes into mechanical contact with the adhesive body 31 is less likely to be damaged. Therefore, it is possible to form the two-dimensional layered material that remains as part of the pattern on the structure 31 with no or little damage.

[0033] <When an adhesion-reinforcing layer is used> A method for forming a pattern by forming an adhesion reinforcement material 15 on the surface of the convex portions of a substrate 11 will be described with reference to Figure 5. The only difference between this method and the pattern formation method described using Figure 1 is the presence or absence of an adhesion reinforcement material 15, and the pattern formation steps conform to the steps described using Figure 1. Therefore, the pattern formation steps consist of a substrate preparation step (Figure 5(a)), a nanosheet placement step (Figure 5(b)), an adhesive body preparation step (Figure 5(c)), an adhesive body contact step (Figure 5(d)), and a detachment step (Figure 5(e)).

[0034] First, a substrate 11a is prepared, in which an adhesion-reinforcing layer 15 is formed on the protrusions 13 on the first main surface of the substrate 11. Examples of adhesion-reinforcing layer 15 include titanium (Ti), molybdenum (Mo), epoxy resin, acrylic resin, and urethane resin, as well as methods for activating the substrate surface by irradiation with an inert gas (e.g., argon) or ions, and oxygen plasma treatment. There are no particular limitations on the thickness or formation method of the adhesion-strengthening layer 15. For example, the thickness can be from several atomic layers to 50 nm. Formation methods include selective CVD (Chemical Vapor Deposition), CVD, sputtering, evaporation, ALD (Atomic Layer Deposition), coating, casting, and immersion. From the perspective of pattern formation, it is essential that the adhesion-strengthening layer 15 be formed on the protrusions 13 of the first main surface. It does not matter whether the adhesion-strengthening layer 15 is formed only at the locations of the protrusions 13 of the first main surface or in the region including the protrusions 13 of the first main surface. The pattern formation method of the present application using the adhesion-reinforcing layer 15 can achieve the aforementioned relationship of "(1) interaction between the nanosheet 20 and the adhesive body 31 at interface C < interaction between the substrate 11 and the nanosheet 20 at interface A" with a high degree of tolerance, and is characterized by an extremely low rate of pattern defect occurrence.

[0035] <When using thermal peeling tape> In the pattern forming method of the present invention, a pressure sensitive adhesive or adhesive tape such as a heat peeling tape can be used as the pressure sensitive adhesive. A method for forming a pattern using an adhesive body 33 made of a thermal peeling tape pattern will be described with reference to an example shown in Fig. 6, in which an adhesion-reinforcing layer 15 is used. However, the adhesion-reinforcing layer 15 is not an essential component in this method. It is also possible to follow the pattern formation method shown in Fig. 1, which does not use the adhesion-reinforcing layer 15, and replace the adhesive body 31 with an adhesive body 33 made of a thermal peeling tape pattern.

[0036] The only difference between this method and the pattern formation method described using Figure 5 or Figure 1 is the application of an adhesive body 33 consisting of a thermal release tape pattern, and the pattern formation steps conform to the steps described using Figure 5 or Figure 1. Therefore, the pattern formation steps consist of a substrate preparation step (Figure 6(a)), a nanosheet placement step (Figure 6(b)), an adhesive body preparation step (Figure 6(c)), an adhesive body contact step (Figure 6(d)), and a detachment step (Figure 6(e)).

[0037] The tape-based manufacturing method is a production method that can be efficiently incorporated into assembly line production and is characterized by high productivity. However, with tape, it is generally difficult to consistently obtain a perfectly flat and smooth surface with a slightly wavy surface even when sufficient tension is applied, and it is also difficult to apply a uniform force to a wide opposing area.

[0038] When tape is used as an adhesive in the pattern formation method of the present invention, all that is required is to separate the thin, uncontacted two-dimensional layered pattern at interface B shown in Figure 4. Therefore, the requirements for (a) stable formation of a completely flat and smooth surface and (b) application of uniform force across a wide opposing area are relatively low. In particular, when an adhesion-reinforcing layer 15 is applied, the adhesive strength at interface A shown in Figure 4 is strong, so even if the adhesive strength at interface C fluctuates slightly, nanosheet 20 made of a two-dimensional layered material adheres sufficiently to interface A. By controlling the applied heat and increasing the adhesive strength at interface D, it is possible to stably separate two-dimensional layered patterns with low defects and high precision. Therefore, a method using adhesive or bonding tape, such as thermal peeling tape, as an adhesive provides a simple, high-quality pattern formation method suitable for highly productive flow production, in which a fine pattern made of a two-dimensional layered material is formed on the upper layer.

[0039] As described above, this method allows for the easy and high-quality formation of textured samples with desired patterns formed on their upper surfaces, made of two-dimensional layered materials, including thin films of several layers. The method of the present invention is characterized by the fact that it is possible to cut nanosheets at any angle and form patterns of desired shapes without the lattice defects or deformation at the edges caused by heat generation, as described in the background section. [Example]

[0040] The present invention will be described in more detail below with reference to examples. However, these examples are provided merely to aid in understanding the present invention and are not intended to limit the present invention.

[0041] In the example, graphene with a thickness of two atomic layers is used as the two-dimensional layer material, and silicon nitride (SiN x ) An example will be described in which a two-dimensional layered pattern with circular openings of about 2.5 μm in diameter was formed on a substrate.

[0042] First, as a substrate preparation step (step S11), as shown in FIG. 8(a), a silicon nitride (SiN x A substrate 11b (opening substrate) was prepared, in which holes (through holes) 12a with a diameter of 2.5 μm were arranged in a staggered pattern (FIG. 7(a)).

[0043] Second, in the nanosheet placement step (step S12), a nanosheet (graphene sheet, manufactured by NORCADA (USA)) made of graphene with a thickness of two atomic layers was prepared, and a graphene sheet 20a was placed on the substrate 11b (FIG. 7(b)). For reference, FIG. 8(b) shows an example of the graphene sheet 20 placed on the substrate 11b and observed from above using a scanning helium ion microscope. Here, the size of the graphene sheet is 0.5 mm × 0.5 mm.

[0044] Third, as an adhesive preparation step (step S13), a polymer stamp with a pad made of two layers of polymer, a PPC (polypropylene carbonate) film formed on a PDMS (polydimethylsiloxane) film, was prepared as adhesive 31 (Figure 7(c)).

[0045] Fourth, in the adhesive contact step (step S14), the pad of the polymer stamp was brought into contact with the graphene sheet 20, and the substrate 11b was heated to 81°C by a temperature control means and maintained at that temperature for approximately 2 minutes (FIG. 7(d), the temperature control means is not shown). The softening point of PPC is 100-140°C.

[0046] Fifth, in the adhesive body detachment step (step S15), the polymer stamp was slowly moved upward to detach the surface of the pad from the substrate 11b. At this time, the graphene sheet located at the position of the hole 12a in the substrate 11b was cut at the edge of the hole 12a, becoming nanosheet pieces 22. The nanosheet pieces 22 adhered to the surface of the pad located on the surface side of the adhesive body 31 and were detached from the substrate 11b. On the other hand, the graphene sheet attached to the surface of the substrate 11b other than the hole 12a remained intact on the surface of the substrate 11b as a graphene pattern 21 as a two-dimensional layered material (FIG. 7(e)).

[0047] For reference, Figures 9(a) and 9(b) show examples of graphene pattern 21 formed on substrate 11b, observed from above using an optical microscope and a scanning helium ion microscope, respectively. It can be seen that a pattern made of graphene (a two-dimensional layered material) was formed with good shape, including the edges. Figure 10 also shows the results of optical microscope observation of a graphene pattern (nanosheet piece) 22 attached to the surface of the pad and detached from substrate 11b. This result shows that the disk-shaped pattern 22 made of graphene adheres to the pad (adhesive body 31) without chipping, particularly on the upper left side where the pad of the polymer stamp can be brought into contact with the graphene sheet 20 with uniform pressure. This means that the graphene pattern 21 formed on the substrate 11b also has no pattern defects. From the above, it was demonstrated that micron-sized fine patterns made of graphene, a two-dimensional layered material, can be easily transferred using a simple device. [Industrial Applicability]

[0048] The present invention makes it possible to easily and with high quality form submicron-sized fine patterns made of two-dimensional layered materials, which have a wide range of physical properties as metals, semiconductors, and superconductors and are expected to be used in a variety of applications as functional materials. Therefore, the present invention is expected to be utilized as a technology supporting high-performance devices and to contribute greatly to the development of industry. [Explanation of symbols]

[0049] 11: Circuit board 11a: Substrate (substrate with adhesion-reinforcing layer) 11b: substrate (opening substrate) 12: Recess 12a: Hole (recess) 13: First main surface convex portion 15: Adhesion strengthening layer, titanium (Ti) 20: Two-dimensional layered materials, nanosheets, graphene sheets 21: Two-dimensional layered material, graphene pattern 22: Nanosheet piece, pattern 31: Sticky substance 32: Adhesive, brush-like adhesive, brush-like pad 33: Heat-release tape, adhesive tape

Claims

1. a substrate preparation step of preparing a substrate having a recess formed on a first main surface; a nanosheet disposing step of disposing a nanosheet made of a two-dimensional layered material on the first main surface of the substrate; an adhesive body preparation step of preparing an adhesive body; A contacting step of contacting a first main surface of the adhesive body with a surface of the nanosheet; A detaching step of detaching the adhesive body from the surface of the nanosheet, a pattern in which a layer made of the two-dimensional layered material is formed on the first main surface of the substrate other than the recessed portion;

2. 2. The pattern formation method according to claim 1, wherein the adhesive body comprises a pad having a first main surface that is flat.

3. 3. The pattern forming method according to claim 2, wherein said pad is made of a material whose adhesive strength changes depending on temperature.

4. 4. The pattern forming method according to claim 2, wherein at least the first main surface of said pad is formed of a polymer.

5. 2. The pattern forming method according to claim 1, wherein a fine pattern is formed on said first main surface of said adhesive body, and a pitch p between said fine patterns is smaller than a minimum space s between patterns to be formed.

6. The pattern forming method according to claim 1 , wherein at least the surface of the adhesive body is provided with a thermal release tape or an adhesive tape.

7. The pattern formation method according to claim 1 , wherein the separating step is carried out by changing the temperature of the adhesive body to control the adhesive force between the nanosheet and the adhesive body.

8. 8. The pattern formation method according to claim 7, wherein the temperature reached when the temperature is changed is the softening point temperature of the adhesive body.

9. 9. The pattern formation method according to claim 1, wherein the two-dimensional layered material has layers bonded together by van der Waals forces.

10. 10. The pattern formation method according to claim 1, wherein the two-dimensional layered material is one selected from the group consisting of graphene, transition metal chalcogenide (TMDC), oxide, and nitride.

11. The transition metal chalcogenide is ZrSe ２ , TaSe ２ , TaS ２ , NbSe ２ , WSe ２ , MoTe ２ , MoSe ２ , MoS ２ , GaSe, GaS, SnSe ２ and SnS ２ The pattern forming method according to claim 10, comprising one selected from the group consisting of:

12. 12. The pattern forming method according to claim 1, wherein the nanosheet has a thickness of at least one atomic layer and at most 200 nm.

13. 13. The pattern forming method according to claim 1, wherein the minimum groove width of the recess is 0.05 [mu]m or more and 10 [mu]m or less.

14. The pattern forming method according to claim 1 , wherein an adhesion-reinforcing layer is formed between the substrate and the nanosheet.

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