Structure and method for manufacturing the same

Abstract

To provide a method for manufacturing a structure which is not damaged by an energy beam or the like including a substrate.SOLUTION: The method includes a step of preparing a pattern forming member having a recess at a position corresponding to a thin film pattern and having self-standing rigidity, a step of disposing a nanosheet made of a two dimensional layered substance on a first main surface, a step of preparing a substrate having a flat and smooth first main surface, a step of bringing the nanosheet into contact with the first main surface of the substrate, and a step of separating the substrate from the surface of the nanosheet.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a structure and a method for manufacturing the same. [Background technology]

[0002] Two-dimensional layered materials, which are materials with layered structures in which atomic layers are bonded 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, structures that incorporate patterned two-dimensional layered materials as part of their structural materials are highly anticipated as they will pave the way for applications such as photonics elements with metamaterial structures and two-dimensional network elements.

[0003] Two-dimensional layered materials can be supplied in the form of nanosheets, which can easily provide unique functions different from those in bulk. The methods for patterning nanosheets to form fine patterns include (1) processing by focused ion beam irradiation, (2) processing by femtosecond laser, (3) processing by cutting the nanosheet along the crystal axis, and (4) processing by lithography and dry etching. However, these methods have the following problems associated with processing.

[0004] (1) 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 the sublimation of atoms due to the sputtering phenomenon and the heat generated by the irradiation, as disclosed in Non-Patent Documents 1 and 2. The problem with this method is that the underlying 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] (2) Femtosecond laser processing is a cutting method that uses a focused and sweeping high-intensity femtosecond laser to sublimate and cut the atoms that make up the nanosheet. This method has problems such as spatial resolution limitations due to the optical limitations caused by the wavelength of the laser light, melting due to heat generation, and the generation of defects.

[0006] (3) A processing method for cutting nanosheets along their crystal axes involves placing oxide nanosheets dispersed in a solvent on a substrate with protrusions and cutting the nanosheets along their crystal axes, 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] (4) Lithography and dry etching are the most common processing methods, but they have the problem of easily causing damage, defects, and contamination to 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 low-defect structure having a functional thin film pattern with unique electronic, optical, and mechanical properties, and a method for manufacturing the structure. The present invention overcomes the problems described in the background section above. [Means for solving the problem]

[0011] The configuration of the present invention to solve the problems is shown below. (Configuration 1) A structure in which a thin film pattern is formed on a first main surface of a substrate, the thin film pattern is made of a two-dimensional layered material, A structure, wherein the defect level of the substrate near the pattern end of the thin film pattern is equal to or lower than the defect level of the substrate at locations other than the pattern end. (Configuration 2) A structure in which a thin film pattern is formed on a first main surface of a substrate, the substrate has uniform in-plane constituent elements, composition ratios, structural states, and defect occurrence states in the bulk and on the surface, and the first main surface is flat and smooth; The thin film pattern is a structure made of a two-dimensional layered material. (Configuration 3) 3. The structure according to claim 1 or 2, wherein the two-dimensional layered material has layers bonded together by van der Waals forces. (Configuration 4) 4. The structure of any one of aspects 1 to 3, wherein the two-dimensional layered material is selected from the group consisting of graphene, transition metal chalcogenides (TMDCs), oxides, and nitrides. (Configuration 5) 5. The structure of claim 4, wherein the transition metal chalcogenide is selected from the group consisting of ZrSe2, TaSe2, TaS2, NbSe2, WSe2, MoTe2, MoSe2, MoS2, GaSe, GaS, SnSe2, and SnS2. (Configuration 6) 6. The structure according to any one of aspects 1 to 5, wherein the thickness of the thin film pattern is from one atomic layer to 200 nm. (Configuration 7) A method for producing the structure according to configuration 1, comprising: a pattern formation member preparation step of preparing a pattern formation member having a first main surface in which at least a part of a location corresponding to the thin film pattern is a recess or hole portion and having rigidity to be self-supporting; a nanosheet arranging step of arranging a nanosheet made of the two-dimensional layered material on the first main surface of the pattern formation member; a substrate preparation step of preparing a substrate having a first main surface that is flat and smooth; a contacting step of mechanically contacting the nanosheet with the first main surface of the substrate; A method for producing a structure, comprising a step of separating the substrate from the surface of the nanosheet. (Configuration 8) 8. The method for producing a structure according to claim 7, wherein the substrate has uniform in-plane constituent elements, composition ratios, structural state, and defect generation state in the bulk and on the surface. (Configuration 9) A method for producing a structure according to configuration 7 or 8, further comprising an energy beam irradiation step of irradiating a desired location of the nanosheet with an energy beam after the nanosheet placement step and before the contact step to form a groove in a portion of the nanosheet. (Configuration 10) 10. The method for manufacturing a structure according to claim 9, wherein the energy beam is a focused helium ion beam. (Configuration 11) A method for manufacturing a structure in which a thin film pattern made of a two-dimensional layered material is formed on a first main surface of a substrate, the method comprising: a pattern formation member preparation step of preparing a pattern formation member having a first main surface with a recess or hole in a location corresponding to the thin film pattern and having rigidity to be self-supporting; a nanosheet arranging step of arranging a nanosheet made of the two-dimensional layered material on the first main surface of the pattern formation member; a substrate preparation step of preparing a substrate having a first main surface that is flat and smooth; a contacting step of mechanically contacting the nanosheet with the first main surface of the substrate; A method for producing a structure, comprising a step of separating the substrate from the surface of the nanosheet. (Configuration 12) 12. The method for producing a structure according to any one of configurations 7 to 11, wherein the separating step is carried out by changing the temperature of the pattern formation member. [Effects of the Invention]

[0012] According to the present invention, a low-defect structure is provided that uses a patterned two-dimensional layered material that has a wide range of physical properties as a metal, semiconductor, and superconductor and is expected to be used in a variety of applications as a functional material, and a method for manufacturing the structure is also provided. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing the configuration of a structure of the present invention. [Figure 2] 1A to 1C are cross-sectional views illustrating steps of a first method for producing a structure of the present invention. [Figure 3] FIG. 1 is a flowchart showing a method for manufacturing a structure according to the present invention. [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] 1A to 1C are cross-sectional views illustrating steps of a second method for producing a structure of the present invention. [Figure 6] 10A to 10C are cross-sectional views illustrating steps of a third method for producing a structure of the present invention. [Figure 7] 1 is a cross-sectional view showing an example of a structure of the present invention. [Figure 8] 1A to 1C are process diagrams illustrating the manufacturing process of a sample in Example 1 using cross-sectional views of essential parts. [Figure 9] 1 is an optical microscope photograph of a pattern formation member having recesses (hole rows) observed from above in Example 1. [Figure 10]1 is an optical microscope photograph taken in Example 1, observed from above, in a state where a graphene nanosheet is formed (covered) on a substrate having recesses (hole rows). [Figure 11] 10A to 10C are process diagrams illustrating the manufacturing process of a sample of Example 2 using cross-sectional views of essential parts. [Figure 12] 10 is a photograph showing an example of a fine patterning process according to Example 2, in which a graphene nanosheet is formed (covered) on a substrate having recesses (hole rows) and observed from above using a scanning helium ion microscope. [Figure 13] (a) is an example of a sample in which a pattern-forming member made of a silicon nitride film is entirely covered with graphene, a two-dimensional layered material, observed with a scanning helium ion microscope before nanofabrication, (b) is an enlarged view of the circled area in (a) after processing, and (c) is an image of the pattern (graphene nanosheet pattern) made of two-dimensional layered material formed on the substrate after transfer, observed with an atomic force microscope (AFM). [Figure 14] (a) shows an example of a sample in which graphene, a two-dimensional layered material, is deposited on the recesses of a pattern-forming member made of a silicon nitride film, processed with a focused helium ion beam and then observed with a scanning helium ion microscope, while (b) shows an example of a nanosheet pattern made of graphene nanosheets formed on a substrate, observed with an AFM. Here, a groove is formed by irradiating a portion of the graphene nanosheet above the hole in the pattern-forming member with a focused helium ion beam. [Figure 15] (a) is a scanning helium ion microscope image of a sample in which graphene, a two-dimensional layered material, is deposited on the recesses of a pattern-forming member made of a silicon nitride film, and shows an example in which a groove is formed by irradiating a portion of the graphene nanosheet above the hole in the pattern-forming member with a focused helium ion beam. (b) is an AFM image of a pattern (graphene nanosheet pattern) made of a two-dimensional layered material formed on a substrate, and (c) is an enlarged image of a portion of it. 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) A structure 101 and a manufacturing method thereof will be described in the first embodiment. The manufacturing method described in the first embodiment is a pattern formation method that forms the basis of the present invention and is particularly suitable for producing standardized products.

[0016] <Structure> As shown in FIG. 1, a structure 101 of the present invention is a structure including a thin film pattern 2 made of a two-dimensional layer formed on a first main surface of a substrate 1.

[0017] There are no particular restrictions on the substrate 1 as long as it is a substrate that has the rigidity to stand on its own, but it is possible to use synthetic quartz, glass, silicon (Si), gallium arsenide (GaAs), gallium oxide (Ga2O3), silicon nitride (SiN x ), silicon oxide (SiO x ), silicon oxynitride (SiO x N y ), ceramics such as SiC, metals such as tungsten (W), and plastics (resins).

[0018] The first main surface of the substrate 1 is preferably flat and smooth. If the first main surface of the substrate 1 is flat and smooth, it becomes possible to obtain the structure 101 having the thin film pattern 2 with few defects and high dimensional accuracy with a high yield.

[0019] Furthermore, it is preferable that the constituent elements, composition ratio, structural state, and defect occurrence state of the bulk and surface of the substrate 1 are uniform within the plane, since this makes use of the characteristic of the present structure 101, that is, the low number of defects. As will be explained in detail in the manufacturing method described later, defects are generally more likely to occur near the edge of the thin film pattern 2, but in the structure 101 of the present invention, due to the characteristics of the manufacturing process, defects are essentially less likely to occur. It is possible to provide a structure 101 with high quality and uniform within the plane.

[0020] The thin film pattern 2 is made of a two-dimensional layered material, and the layers are bonded together by a relatively weak interaction force known as van der Waals force. Examples of two-dimensional interlayer materials include graphene, transition metal chalcogenides (TMDCs), oxides, and nitrides. Examples of transition metal chalcogenides include ZrSe2, TaSe2, TaS2, NbSe2, WSe2, MoTe2, MoSe2, MoS2, GaSe, GaS, SnSe2, and SnS2. The thickness of the thin film pattern 2 is preferably 1 atomic layer or more and 200 nm or less. If it is less than 1 atomic layer, the density is low and defects are likely to occur, and if it exceeds 200 nm, the patterning accuracy of the thin film pattern is likely to decrease.

[0021] <Manufacturing method> A method for forming a structure 101 having a thin film pattern 2 made of a two-dimensional layered material according to the first embodiment will be described with reference to FIG. 2, which shows the manufacturing process using cross-sectional views of the main parts, and FIG. 3, which shows a flowchart.

[0022] The first step is a pattern-forming member preparation step (FIG. 2(a), step S11) for preparing a pattern-forming member (substrate) 11 having recesses 12 formed on a first main surface 13. As will be explained later, the recesses 12 serve as a template for a thin film pattern 2.

[0023] The pattern forming member 11 is not particularly limited as long as it has mechanical strength that makes it difficult to deform, and a desired substrate can be used. For example, the pattern forming member 11 may be a Si substrate, a GaAs substrate, a silicon nitride film (SiN x ) substrate, silicon oxide film (SiO xExamples 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 pattern-forming member 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 convex portions on the silicon substrate.

[0024] 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 to prevent a nanosheet made of a two-dimensional layered material from coming into contact with the bottom of the recess 12 when the sheet is subsequently applied to the first main surface 13 of the pattern-forming member 11; for example, it may be an opening that penetrates the pattern-forming member 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.

[0025] The second step is a nanosheet arrangement step (FIG. 2(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 pattern formation member 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.

[0026] 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.

[0027] The third step is a substrate preparation step (FIG. 2(c), step S13) in which a substrate 1 having a first main surface 13 that is flat and smooth is prepared. Examples of substrate 1 include semiconductor substrates such as silicon (Si), gallium arsenide (GaAs), and gallium oxide (Ga2O3) substrates; composite semiconductor substrates with oxide, nitride, or oxynitride films formed on a semiconductor substrate; insulating film substrates such as silicon oxide (SiO2) and silicon nitride (Si3N4); metal film substrates such as aluminum (Al) and tungsten (W); ceramic substrates such as silicon carbide (SiC); glass substrates such as synthetic quartz; and resin substrates. Specific composite semiconductor substrates include substrates formed on a Si substrate with one or more oxide films selected from the group consisting of SiO2, Ta2O3, HfO2, Al2O3, and HfSiO; nitride films such as Si3N4; and oxynitride films such as SiON. Resin substrates include silicone-based polymer substrates such as polydimethylsiloxane (PDMS) and polypropylene carbonate (PPC), polycarbonate substrates, polypropylene substrates, and polyethylene substrates.

[0028] One of the features of the present invention is that it is possible to process and form patterns without damaging the thin film pattern 2 made of a two-dimensional layered material and the substrate 1. To make the most of this feature, it is preferable that the bulk and surface of the substrate 1 have uniform in-plane constituent elements, composition ratios, structural state, and defect occurrence state. In the processing method of thin film pattern 2 made of two-dimensional layered material described in the background art, the area of ​​the substrate irradiated with energy rays or the like is damaged, making it difficult to fabricate a structure with a uniform substrate state within the plane. On the other hand, in the present invention, by preparing a substrate with a uniform state within the plane, structure 101 with a uniform substrate state within the plane can be easily obtained.

[0029] The fourth step is a contact step in which the first main surface 13 of the substrate 1 is brought into contact with the surface of the nanosheet 20 (FIG. 2(d), step S14).

[0030] The fifth step is a detachment step in which the substrate 1 is detached from the surface of the nanosheet 20 (FIG. 2(e), step S15). Through the first to fifth steps, a structure 101 is fabricated in which a thin film pattern 2 made of a two-dimensional layered material is formed on the substrate 1 on the recesses 12 of the pattern formation member 11 (FIG. 2(f)).

[0031] The key point of the present invention is to separate the nanosheet 20 in the pattern formation region. That is, the key point is to ensure sufficient pattern edge precision without damaging the two-dimensional layered material nanosheet that is transferred and attached as the thin film pattern 2 of the structure 101.

[0032] When a nanosheet 20 is placed on a pattern transfer member 11 having a recess 12 and a substrate 1 is brought into contact with the nanosheet 20, four types of interface states exist at interfaces A to D between the pattern transfer member 11, the nanosheet 20, and the substrate 1, as shown in Figure 4. Here, the nanosheet 20 does not come into contact with anything at interface B above the recess 12, but comes into contact with the substrate 1 at interface D. The conditions under which the nanosheet 21 remains on the convex portions of the pattern transfer member 11 as shown in Figure 2(e), and the nanosheet 20 placed in the concave portions 12 adheres to the substrate 1 to form nanosheet pieces 22, resulting in a clean pattern separation of the nanosheet 20, are expressed as follows (1) to (3): (1) There is a relationship that the interaction between the nanosheet 20 and the substrate 1 at the interface C is smaller than the interaction between the pattern transfer member 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 interface D, interactions such as van der Waals forces act between nanosheet 20 and substrate 1.

[0033] 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, it is easily broken at the point where force is applied, and condition (2) is satisfied. Condition (3) is also satisfied. Therefore, condition (1) is satisfied, and pattern separation and pattern detachment of the nanosheet 20 are carried out as shown in FIG. 2(e).

[0034] As a method for satisfying the condition (1), the first method is to use a substrate 1 having an appropriate adhesive force (adhesion), and the second method is to enhance the interaction at the interface A. Naturally, the first and second methods may be combined.

[0035] The first method is to use a substrate 1 in which at least the outermost layer is made of a material selected from the group consisting of SiO2, Si3N4, Si, SiC, GaAs, Ga2O3, synthetic quartz glass, and crystals such as sapphire and magnesium oxide.

[0036] The second method includes a method using a pattern-forming member 11 made of a material with high adhesive strength (adhesion), such as titanium (Ti), molybdenum (Mo), or PPC (polypropylene carbamide), and a method in which an adhesive layer 3 is formed on at least the surface of the convex portions of the pattern-forming member 11. The adhesive layer 3 can be a layer made of a material selected from the group consisting of titanium (Ti), molybdenum (Mo), epoxy resin, acrylic resin, PPC (polypropylene carbamide), and urethane resin. When a polymer such as PPC is formed on the outermost surface, its adhesive strength can be changed by temperature, so it is preferable to control the temperature of the polymer to obtain an appropriate adhesive strength. The adhesive strength and adhesion strength of the polymer change significantly with temperature, so that the nanosheet 20 made of a two-dimensional layered material in contact with the polymer remains attached to the pattern-forming member 11, while the nanosheet 20 positioned in the recess 12 of the pattern-forming member 11 can be attached to the substrate 1 with sufficient controllability. This high degree of controllability is particularly easily achieved near the softening point of the polymer.

[0037] Examples of methods for forming the adhesion layer 3 include selective CVD (Chemical Vapor Deposition), CVD, sputtering, vapor deposition, ALD (Atomic Layer Deposition), coating, casting, and immersion. Other examples include methods for forming an activated layer on the surface of the pattern-forming member 11 by irradiation with an inert gas (e.g., argon) or ions, or oxygen plasma treatment. Here, from the viewpoint of pattern formation, it is essential that the adhesion layer 3 is formed on the convex portions 13 of the pattern forming member 11, and it may be formed only at the locations of the convex portions 13 of the pattern forming member 11, or it may be formed in the area of ​​the convex portions 13 including some or all of the concave portions. There are no particular limitations on the thickness or formation method of the adhesive layer 3. For example, the thickness can be set to a thickness of several atomic layers or more and 50 nm or less.

[0038] <When an adhesion-reinforcing layer is used> A method for forming a pattern by forming an adhesion layer 3 on the surface of the convex portions of a pattern-forming member 11 will be described with reference to FIG. 5. Note that the only difference between this method and the pattern-forming method described with reference to FIG. 1 is the presence or absence of an adhesion layer 3; the pattern-forming steps conform to the steps described with reference to FIG. 1. Therefore, the pattern-forming steps consist of a substrate preparation step (FIG. 5(a)), a nanosheet placement step (FIG. 5(b)), a substrate preparation step (FIG. 5(c)), a substrate contact step (FIG. 5(d)), and a detachment step (FIG. 5(e)). After the substrate is detached, a substrate upside-down inversion step (FIG. 5(f)) is performed to obtain a structure 101 having a pattern 2 (22) made of a two-dimensional layered material arranged on the upper surface.

[0039] The pattern formation method using the adhesion layer 3 is characterized by an extremely low rate of pattern defect occurrence, since it can achieve the aforementioned relationship of "(1) interaction between the nanosheet 20 and the pattern formation member 11 at interface C < interaction between the substrate 1 and the nanosheet 20 at interface A" with a high degree of tolerance.

[0040] 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.

[0041] (Embodiment 2) The second embodiment is based on the pattern formation method described in the first embodiment and is particularly suitable for forming a customized two-dimensional layered material pattern and / or for forming an ultrafine pattern. The method is characterized in that, in addition to the pattern made of the two-dimensional layered material formed in accordance with the first embodiment, an additional pattern is formed by irradiating with energy rays. The method will be described below with reference to FIG. 6.

[0042] The characteristic step in the second embodiment is the third step, the energy beam irradiation step (FIG. 6(c)), and the other steps conform to the steps shown in FIG. 1 of the first embodiment. The first step is a pattern formation member preparation step (FIG. 6(a)) in which a pattern formation member 11 having recesses 12 formed on a first main surface 13 is prepared. The second step is a nanosheet disposing step (FIG. 6( b )) in which a nanosheet 20 made of a two-dimensional layered material is disposed on the first main surface 13 of the pattern formation member 11 .

[0043] The third step is a characteristic step of the second embodiment shown in FIG. 6(c), and is an energy beam irradiation step. The energy beam 41 can be a focused helium ion beam, a focused gallium beam, an electron beam, or a YAG laser. Among these, a focused helium ion beam is the most suitable beam for forming a fine pattern. This is because of its high spatial resolution and the fact that it does not contaminate the periphery of the irradiated area. The irradiation conditions for a focused helium ion beam are, for example, 10 17 ~1018 ions / cm 2 By irradiation with energy beam 41, the two-dimensional layered material is removed from the irradiated areas, forming a two-dimensional layered material pattern (nanosheet) 23 (FIG. 6(c)).

[0044] The fourth step is a substrate preparation step (FIG. 6(d)) in which a substrate 1 is prepared. The fifth step is a contact step (FIG. 6(e)) in which the first main surface of the substrate 1 is brought into contact with the surface of the nanosheet 23. The sixth step is a separation step (FIG. 6(f)) in which the substrate 1 is separated from the surface of the nanosheet 20. In this step, a desired pattern 26 made of a two-dimensional layered material is attached and transferred onto the substrate 1. After the first to sixth steps, the substrate 1 is turned upside down to provide a structure 102 in which a pattern 2 (26) made of the desired two-dimensional layered material is formed on the upper surface of the substrate 1 (FIG. 6(g)).

[0045] Here, the pattern formation includes a step of irradiating the substrate with energy rays 41, which can cause damage, but the substrate 1 is not irradiated with the energy rays 41, and therefore there is no damage to the substrate 1 due to the irradiation of the energy rays 41. Therefore, although the pattern formation is performed by irradiating the energy rays 41, this method is characterized in that the defect level of the substrate near the edge of the pattern 2 made of a two-dimensional layered material is equal to or lower than the defect level of the substrate 1 in places other than the edge. Furthermore, this method allows irradiation with energy rays 41 without worrying about damage to the device, and therefore makes it possible to form extremely fine patterns with high precision.

[0046] <Applicable> In the structure and manufacturing method of the present invention, a pattern made of a two-dimensional layered material formed on a substrate is formed by a soft attachment method that is less susceptible to mechanical impact forces, and therefore the structure produced is less susceptible to damage during the manufacturing process.

[0047] Therefore, applying the method of the present invention to a substrate that is almost undamaged makes it possible to provide a structure that is almost undamaged. In other words, structure 1001, fabricated using substrate 501, shown in Figure 7(a), in which the bulk and surface constituent elements, composition ratio, structural state, and defect occurrence state are uniform across the surface, reflects the properties of a substrate with uniform constituent elements, composition ratio, structural state, and defect occurrence state across the surface. Characterization using such structure 1001 makes it possible to clarify the detailed properties of a film made of a two-dimensional layered material.

[0048] Patterns of two-dimensional layered materials have the potential to be applied to the formation of photonics elements with metamaterial structures and two-dimensional network structures. The present invention makes it possible to easily fabricate photonic elements 1002, in which two-dimensional layered materials with metamaterial effects for light with wavelengths from submicrometers to micrometers are patterned and arranged, as shown in Figure 7(b). This makes it possible to apply the present invention to novel two-dimensional devices in which nano- and micro-sized heterostructures are locally arranged.

[0049] 7(c), an electronic device 1003 in which a conductive layer or semiconductor layer made of a diffusion layer 602 is formed on a substrate 601, and a two-dimensional layered material layer 603 and a conductive layer 604 are sequentially stacked inside the diffusion layer 601, is a damage-free electronic device that is not damaged by, for example, irradiation with energy rays. In such an electronic device 1003, the electric field effect at the edge of the conductive layer 604 often significantly changes the electrical characteristics of the electronic device 1003, but evaluation using this structure makes it possible to evaluate the characteristics in a damage-free state. [Example]

[0050] 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.

[0051] Example 1 In Example 1, as an example of the first embodiment, an example will be described in which graphene having a thickness of two atomic layers is used as the two-dimensional layered material, and a two-dimensional layered pattern having circular openings with a diameter of approximately 2.5 μm is formed on a substrate made of a polymer.

[0052] First, as a pattern forming member preparation step (step S11), as shown in FIG. 9, a silicon nitride (SiN x A pattern formation member 11a (aperture member) was prepared in which holes (through holes) 12 with a diameter of 2.5 μm were arranged in a staggered pattern on a substrate (FIG. 8(a)).

[0053] Second, in the nanosheet arrangement step (step S12), a nanosheet (graphene sheet, manufactured by NORCADA (USA)) made of graphene with a thickness of two atomic layers was prepared, and the graphene sheet 20 was placed on the substrate 11a (FIG. 8(b)). Here, the size of the graphene sheet was 0.5 mm × 0.5 mm.

[0054] Third, in the substrate preparation step (step S13), a two-layer polymer in which a PPC (polypropylene carbonate) film was formed on a PDMS (polydimethylsiloxane) film was prepared as substrate 1 (FIG. 8(c)).

[0055] Fourth, in a contacting step (step S14), the first main surface of the substrate 1 was brought into contact with the graphene sheet 20, and the substrate 1 was heated to about 81°C by a temperature adjusting means and maintained at that temperature for about 2 minutes (FIG. 8(d), the temperature adjusting means is not shown). The softening point of PPC is 100-140°C.

[0056] Fifth, in the separation step (step S15), the substrate 1 was slowly moved upward to separate the surface of the substrate 1 from the pattern-forming member 11a. At this time, the graphene sheet located at the position of the holes 12 in the pattern-forming member 11a was cut at the edge of the hole 12a, becoming nanosheet pieces 22 that adhered to the surface of the substrate 1 and were separated from the pattern-forming member 11a. Meanwhile, the graphene sheet that had been attached to the surface of the pattern-forming member 11a other than the holes 12 remained on the surface of the pattern-forming member 11a as a graphene pattern 21 of a two-dimensional layered material (FIG. 8(e)). Thereafter, the substrate 1 was turned upside down to obtain a structure 101 in which a disk-shaped thin film pattern of a two-dimensional layered material with a diameter of approximately 2.5 μm was formed in a houndstooth pattern on the substrate 1 (FIG. 8(f)).

[0057] Figure 10 shows the results of optical microscope observation of the thin film pattern (nanosheet piece) 2 (22) formed on the substrate 1. It can be seen that the thin film pattern 2, made of graphene, a type of two-dimensional layered material, formed on the substrate 1 is well formed, with a thickness of two atomic layers. 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.

[0058] Example 2 In Example 2, as an example of the second embodiment, it was verified that a desired pattern can be formed on a two-atom-layer graphene film, which is a two-dimensional layered material, by energy beam irradiation. Here, a focused helium ion beam was used as the energy beam, and the irradiation conditions were set to 10 17 ~10 18 ions / cm 2 It was decided.

[0059] First, as a pattern forming member preparation step, as shown in FIG. 9, a silicon nitride (SiN x A pattern formation member 11a (aperture member) was prepared in which holes (through holes) 12a with a diameter of 2.5 μm were arranged in a staggered pattern on a substrate (FIG. 11(a)).

[0060] Second, in the nanosheet placement step, a nanosheet (graphene sheet, manufactured by NORCADA (USA)) made of graphene with a thickness of two atomic layers was prepared, and the nanosheet 20 was placed on the substrate 11a (FIG. 11(b)). Here, the size of the nanosheet 20 was 0.5 mm × 0.5 mm.

[0061] Third, in the energy beam irradiation step, a desired opening pattern was formed by irradiating an energy beam 41 to form a circular pattern of 2.5 μm diameter two-dimensional layered material arranged in a staggered pattern (FIG. 11(c)). Here, a focused helium ion beam was used as the energy beam 41. The focused helium ion beam device was Orion Plus HIM (Zeiss, USA), and the irradiation conditions were 10 17 ~10 18 ions / cm 2 It was decided.

[0062] Fourth, as a substrate preparation step, a two-layer polymer consisting of a PPC (polypropylene carbonate) film formed on PDMS (polydimethylsiloxane) was prepared as substrate 1 (Figure 11(d)).

[0063] Fifth, in the contacting step, the first main surface of the substrate 1 was brought into contact with the nanosheet (graphene sheet) 23 on which a fine pattern had been formed by irradiation with energy rays 41, and the substrate 1 was then heated to 81°C by a temperature control means and held at that temperature for approximately 2 minutes (FIG. 11(e), the temperature control means is not shown). The softening point of PPC is 100-140°C.

[0064] Sixth, in a detachment step, the substrate 1 was slowly moved upward to detach the surface of the substrate 1 from the pattern formation member 11a. At this time, the graphene sheet located at the position of the hole 12a in the pattern formation member 11a was cut at the edge of the hole 12a, and became nanosheet pieces 26 with openings formed by the irradiation of the energy beam 41. These nanosheet pieces adhered to the surface of the substrate 1 and were detached from the pattern formation member 11a. Meanwhile, the remaining graphene sheet that had been attached to the surface of the pattern formation member 11a remained as a graphene pattern 25 as a two-dimensional layered material on the surface of the pattern formation member 11a (FIG. 11(f)).

[0065] After the first to sixth steps, the substrate 1 was turned upside down (FIG. 11(g)). Through the above steps, a structure 102 was obtained on the substrate 1, in which a pattern 2a made of a two-dimensional layered material was formed, in which a disk-shaped houndstooth-arranged thin film pattern with a diameter of approximately 2.5 μm had fine openings formed by irradiation with energy beam 41.

[0066] A focused helium ion beam was irradiated (drawn) onto the nanosheet 20 in square, semicircular, C-shaped, and circular shapes to form a graphene pattern 23 with square, semicircular, C-shaped, and circular openings. 12, 13(a), (b), 14(a), and 15(a) show examples of the graphene pattern 23 observed from above using a scanning helium ion microscope at the energy beam irradiation step. Here, FIG. 12 is an example of observation at low magnification, FIG. 13(a) is an enlarged example of the location #1 in FIG. 12, and FIG. 13(b) is an example of observation at even greater magnification. FIG. 14(a) is an enlarged example of the location #2 in FIG. 12, and FIG. 15(a) is an example of observation at a magnified part of the location #3 in FIG. 12. The observation conditions were 1×10 14 ~10 16 ions / cm 2 These results show that in the energy beam irradiation step, a good fine pattern can be formed on the two-dimensional layered material (graphene layer) by irradiation (drawing) with the energy beam (focused helium ion beam) 41.

[0067] 13(c), 14(b), 15(b), and 15(c) show examples of thin film pattern 2a, a thin film pattern made of graphene (a two-dimensional layered material), observed with an AFM (Atomic Force Microscope, Dimension Icon, manufactured by Brucker) after fabrication of structure 102 was completed. Here, FIGS. 13(c) and 14(b) show examples of pattern formation at locations corresponding to FIGS. 13(b) and 14(a), respectively, during the energy beam irradiation step. FIG. 15(b) shows the overall pattern of #3, and FIG. 15(c) shows an example of pattern formation at a location corresponding to FIG. 15(a) during the energy beam irradiation step. These results demonstrate that excellent fine patterns can be formed on two-dimensional layered materials (graphene layers) by irradiation (drawing) with energy beams (focused helium ion beams) 41.

[0068] From the above, it was demonstrated that micron-sized fine patterns made of graphene, a two-dimensional layered material, can be easily formed using simple equipment. In addition, focused energy beams offer high flexibility in pattern writing. The pattern formation method in which the general-purpose part (platform) pattern is formed by the method demonstrated in Example 1 and the energy beam irradiation method confirmed in Example 2 is used in combination with this for customized patterns is considered to be a highly productive pattern formation method. [Industrial Applicability]

[0069] 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]

[0070] 1: Circuit board 2: Two-dimensional layered material, graphene 2a: Two-dimensional layered material, graphene 3: Adhesion layer 11: Pattern forming member (substrate) 12: Recess 12a: Hole (through hole) 13: 1st main surface 14: Surface (exposed adhesive surface) 16: Exposed surface of pattern forming member 20: Two-dimensional layered material films, nanosheets, graphene sheets 21: Two-dimensional layered material layer 22: Nanosheet piece 23: Nanosheet (after processing), graphene sheet 25: Two-dimensional layered material, graphene pattern 26: Nanosheet piece 41: Energy rays, focused helium ion beams 101: Structure 102: Structure 501: Circuit board 502: Two-dimensional layered material film pattern 503: Two-dimensional layered material film pattern 601: Substrate 602: Diffusion layer 603: Two-dimensional layered material film layer 604: Conductive layer 1001: Structure 1002: Photonics elements 1003: Electronic Devices

Claims

1. A structure having a thin film pattern formed on a first main surface of a substrate, the thin film pattern is made of a two-dimensional layered material, A structure, wherein the defect level of the substrate near the pattern end of the thin film pattern is equal to or lower than the defect level of the substrate at locations other than the pattern end.

2. A structure having a thin film pattern formed on a first main surface of a substrate, the substrate has uniform in-plane constituent elements, composition ratios, structural states, and defect occurrence states in the bulk and on the surface, and the first main surface is flat and smooth; The thin film pattern is a structure made of a two-dimensional layered material.

3. The structure according to claim 1 or 2, wherein the two-dimensional layered material has layers bonded together by van der Waals forces.

4. The structure according to claim 1 , wherein the two-dimensional layered material is selected from the group consisting of graphene, transition metal chalcogenides (TMDCs), oxides, and nitrides.

5. 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 structure of claim 4, comprising one selected from the group consisting of:

6. 6. The structure according to claim 1, wherein the thickness of the thin film pattern is from one atomic layer to 200 nm.

7. 10. A method for manufacturing the structure of claim 1, comprising: a pattern formation member preparation step of preparing a pattern formation member having a first main surface in which at least a part of a location corresponding to the thin film pattern is a recess or a hole and having rigidity to be self-supporting; a nanosheet disposing step of disposing a nanosheet made of the two-dimensional layered material on the first main surface of the pattern formation member; a substrate preparation step of preparing a substrate having a first main surface that is flat and smooth; a contacting step of mechanically contacting the nanosheet with the first main surface of the substrate; A method for producing a structure, comprising a step of separating the substrate from the surface of the nanosheet.

8. 8. The method for manufacturing a structure according to claim 7, wherein the substrate has uniform in-plane constituent elements, composition ratios, structural state, and defect generation state in the bulk and on the surface.

9. The method for producing a structure described in claim 7 or 8, further comprising an energy beam irradiation step of irradiating a desired location of the nanosheet with an energy beam after the nanosheet placement step and before the contact step to form a groove in a portion of the nanosheet.

10. The method for manufacturing a structure according to claim 9 , wherein the energy beam is a focused helium ion beam.

11. 1. A method for manufacturing a structure having a thin film pattern made of a two-dimensional layered material formed on a first main surface of a substrate, comprising: a pattern formation member preparation step of preparing a pattern formation member having a first main surface with a recess or hole in a location corresponding to the thin film pattern and having rigidity to be self-supporting; a nanosheet disposing step of disposing a nanosheet made of the two-dimensional layered material on the first main surface of the pattern formation member; a substrate preparation step of preparing a substrate having a first main surface that is flat and smooth; a contacting step of mechanically contacting the nanosheet with the first main surface of the substrate; A method for producing a structure, comprising a step of separating the substrate from the surface of the nanosheet.

12. 12. The method for manufacturing a structure according to claim 7, wherein the separating step is performed by changing the temperature of the pattern formation member.

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