Method for manufacturing heterost multilayer devices

Abstract

To provide a manufacturing method of a hetero-layered device capable of efficiently manufacturing thereof with an atomic membrane of the desired size.SOLUTION: A disclosed manufacturing method of a hetero-layered device includes: a step of forming a first atomic membrane formed of layered materials over a first substrate; a step of patterning a first atomic membrane; a step of forming a mask over the first atomic membrane for partially exposing the first atomic membrane and the first substrate; a step of forming a second atomic membrane of a layered material different from that of the first atomic membrane over the second substrate; a step of bringing exposed areas of the first atomic membrane and the first substrate into close contact with the second atomic membrane; and a step of removing a part of the second atomic membrane together with the mask.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The disclosed technology relates to a method for manufacturing a hetero-layered device. [Background Art]

[0002] The following techniques are known as technologies related to the patterning of electronic materials. For example, Patent Document 1 describes a method including the step of forming a film of an electronic material on a substrate, in which a fluoropolymer is used to protect a region of the electronic material during the patterning process.

[0003] Patent Document 2 describes forming a single-layer transition metal dichalcogenide on a substrate so as to be in contact with a single-layer graphene film at a lateral edge. [Prior Art Literature] [Patent Literature]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2012 / 0280216 [Patent Document 2] U.S. Patent Application Publication No. 2019 / 0165107 [Summary of Invention] [Problem to be Solved by Invention]

[0005] Graphene and transition metal chalcogenide (TMDC), which are layered substances having a thickness of one or several atoms, have excellent optical properties, diverse electrical properties, and flexibility, and thus applications to transparent conductive films and flexible devices have been attempted. Recently, the fabrication of hetero-layered devices combining two or more types of layered substances has been actively conducted. In hetero-layered devices, phenomena derived from the unique electronic states at the heterointerface have been observed.

[0006] A method for manufacturing heteromultilayer devices using continuous films obtained by synthesis techniques such as chemical vapor deposition (CVD) has not yet been established. Therefore, currently, heteromultilayer devices are manufactured by stacking flake-like atomic films 200A and 200B exfoliated from bulk crystals, as shown in Figure 1A (plan view) and Figure 1B (cross-sectional view). The exfoliated atomic films are obtained by physically peeling them from the bulk crystal using adhesive tape. However, the thickness (number of layers) and shape of the atomic films obtained by this method are random, and the size of the resulting exfoliated atomic films is small, only a few tens of microns. Furthermore, it is difficult to efficiently manufacture heteromultilayer devices using this method.

[0007] The disclosed technology has been made in view of the above points and aims to enable the efficient fabrication of heteromultilayer devices having atomic films of a desired size. [Means for solving the problem]

[0008] A method for manufacturing a heterostacked device according to the disclosed technology includes the steps of: forming a first atomic film made of a layered material on a first substrate; patterning the first atomic film; forming a mask on the first atomic film that partially exposes the first atomic film and the first substrate; forming a second atomic film made of a layered material different from the first atomic film on a second substrate; bringing the exposed portions of the first atomic film and the first substrate into close contact with the second atomic film; and removing a portion of the second atomic film together with the mask. [Effects of the Invention]

[0009] The disclosed technology enables the efficient fabrication of heteromultilayer devices having atomic films of a desired size. [Brief explanation of the drawing]

[0010] [Figure 1A] This is a plan view showing an example of the configuration of a heterost multilayer device. [Figure 1B]This is a cross-sectional view along the line 1B-1B in Figure 1A. [Figure 2] This is a cross-sectional view showing an example of the configuration of a heterostacked device according to an embodiment of the disclosed technology. [Figure 3A] This is a cross-sectional view showing an example of a method for manufacturing a heterost multilayer device according to an embodiment of the disclosed technology. [Figure 3B] This is a cross-sectional view showing an example of a method for manufacturing a heterost multilayer device according to an embodiment of the disclosed technology. [Figure 3C] This is a cross-sectional view showing an example of a method for manufacturing a heterost multilayer device according to an embodiment of the disclosed technology. [Figure 3D] This is a cross-sectional view showing an example of a method for manufacturing a heterost multilayer device according to an embodiment of the disclosed technology. [Figure 3E] This is a cross-sectional view showing an example of a method for manufacturing a heterost multilayer device according to an embodiment of the disclosed technology. [Figure 3F] This is a cross-sectional view showing an example of a method for manufacturing a heterost multilayer device according to an embodiment of the disclosed technology. [Figure 3G] This is a cross-sectional view showing an example of a method for manufacturing a heterost multilayer device according to an embodiment of the disclosed technology. [Figure 3H] This is a cross-sectional view showing an example of a method for manufacturing a heterost multilayer device according to an embodiment of the disclosed technology. [Figure 4] This figure shows an example of a method for forming a first atomic film on a first substrate by atmospheric pressure CVD. [Figure 5A] This figure shows an example of a method for forming a first atomic film on a first substrate 11 by transfer. [Figure 5B] This figure shows an example of a method for forming a first atomic film on a first substrate 11 by transfer. [Figure 5C] This figure shows an example of a method for forming a first atomic film on a first substrate 11 by transfer. [Figure 5D] This figure shows an example of a method for forming a first atomic film on a first substrate 11 by transfer. [Figure 5E]It is a diagram illustrating an example of a method for forming a first atomic film on a first substrate by transfer. [Figure 6] It is a microscopic image showing a pattern of graphene formed on a substrate. [Figure 7A] It is a cross-sectional view illustrating an example of a method for manufacturing a heterolaminated device according to a comparative example. [Figure 7B] It is a cross-sectional view illustrating an example of a method for manufacturing a heterolaminated device according to a comparative example. [Figure 7C] It is a cross-sectional view illustrating an example of a method for manufacturing a heterolaminated device according to a comparative example. [Figure 7D] It is a cross-sectional view illustrating an example of a method for manufacturing a heterolaminated device according to a comparative example. [Figure 7E] It is a cross-sectional view illustrating an example of a method for manufacturing a heterolaminated device according to a comparative example. MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, an example of an embodiment of the disclosed technology will be described with reference to the drawings. In each drawing, the same or equivalent components and portions are denoted by the same reference signs, and overlapping descriptions are omitted.

[0012] Figure 2 is a cross-sectional view illustrating an example of the configuration of a heterolaminated device 1 according to an embodiment of the disclosed technology. The heterolaminated device 1 includes a first substrate 11, a first atomic film 21 provided on the first substrate 11, and a second atomic film 22 formed on the first substrate 11 with a portion overlapping a part of the first atomic film 21. Each of the first atomic film 21 and the second atomic film 22 has a portion that does not overlap the other atomic film.

[0013] The first substrate 11 is not particularly limited, and may be, for example, a silicon substrate with a thermal oxide film in which a thermal oxide film such as SiO2 is provided on a surface thereof. The first substrate 11 may also be a sapphire substrate or a magnesium oxide substrate.

[0014] The first atomic film 21 and the second atomic film 22 are layered materials having a thickness of one or several atoms. The materials of the first atomic film 21 and the second atomic film 22 are different from each other. The materials of the first atomic film 21 and the second atomic film 22 are not particularly limited, but are atomic films made of layered materials such as graphene, layered chalcogenides, hBN (hexagonal boron nitride), phospholene, silicene, germanene, and stanene. Examples of layered chalcogenides include transition metal dichalcogenides containing chalcogens (S, Se, Te) and transition metals (Mo, Nb, W, Ta, Ti, Zr, Hf, V, etc.), group 13 chalcogenides containing chalcogens and group 13 elements (Ga, In, Tl), group 14 chalcogenides containing chalcogens and group 14 elements (Ge, Sn, Pb), and bismuth chalcogenides composed of chalcogens and bismuth.

[0015] The heterolayer device 1 has a first electrode 31 connected to a first atomic film 21 and a second electrode 32 connected to a second atomic film 22. The first electrode 31 is connected only to the first atomic film 21 of the two atomic films 22, and the second electrode 32 is connected only to the second atomic film 22 of the two atomic films 21. The materials of the first electrode 31 and the second electrode 32 are not particularly limited, but metals such as Au, Ag, Cu, and Al can be used, for example.

[0016] The manufacturing method for the heterostacked device 1 will be described below. Figures 3A to 3H are cross-sectional views showing an example of the manufacturing method for the heterostacked device 1.

[0017] First, a first atomic film 21 is formed on the first substrate 11 (Figure 3A). The first atomic film 21 may be formed directly on the first substrate 11 by a synthesis method such as chemical vapor deposition (CVD), or the first atomic film 21 formed on a substrate other than the first substrate 11 may be transferred onto the first substrate 11.

[0018] An example of a method for directly forming a first atomic film 21 on a first substrate 11 by chemical vapor deposition (CVD) is described below. In this method, precursors that serve as raw materials for the first atomic film 21 are reacted in a vacuum, an inert gas atmosphere, or an inert gas atmosphere containing hydrogen, to deposit the constituent elements of the first atomic film 21 on the first substrate 11.

[0019] For example, when synthesizing a metal chalcogenide film as the first atomic film 21, the precursor may be the elemental element constituting the target metal chalcogenide film, or a compound containing it (oxide, chloride, fluoride, hydride, organic compound, etc.). It is desirable to select the precursor according to the type of metal chalcogenide film to be synthesized. The metal chalcogenide film may be synthesized from one type of precursor containing all the elements that constitute it, or from multiple types of precursors. The precursor may be a solid (crystalline, amorphous), liquid, or gas. When using a solid or liquid as the precursor, it is desirable to vaporize it by heating or other means. The amount of evaporation of the precursor depends on the temperature, pressure, amount of precursor (weight, volume), and the vapor pressure inherent to the precursor, so it is desirable to adjust each parameter appropriately according to the required thickness and area of ​​the metal chalcogenide film during synthesis. Furthermore, it is desirable to adjust the heating temperature of the substrate when synthesizing the metal chalcogenide film according to the type, thickness, area, and quality of the target metal chalcogenide film. The pressure used during synthesis can be either atmospheric pressure or reduced pressure.

[0020] The arrangement of the first substrate 11 and precursors during the synthesis of the first atomic film 21 should be appropriately adjusted according to the configuration and shape of the CVD apparatus and the synthesis conditions. Figure 4 shows an example of a method for forming a MoS2 film 21A, which is an example of the first atomic film 21, on the first substrate 11 by atmospheric pressure CVD using a quartz tubular furnace 50. Molybdenum trioxide (MoO3) 51 and sulfur (S) 52 are used as precursors.

[0021] In a furnace filled with an Ar atmosphere, approximately 100-1000 sccm of Ar gas is continuously introduced from upstream as a carrier gas. The substrate temperature is maintained at 500-1000°C, the temperature of molybdenum trioxide (MoO3) 51 (1-100 mg) placed upstream of the first substrate 11 is maintained at 300-600°C, and the temperature of sulfur (S) 52 (10-1000 mg) placed further upstream is maintained at 100-200°C. As in this example, when using two types of precursors, it is desirable to independently control the evaporation rate of each precursor by setting the optimal heating temperature considering the vapor pressure of each precursor. This also makes it possible to adjust the stoichiometric ratio (elemental composition ratio) of the metal chalcogenide film, which is the first atomic film 21. Furthermore, considering that each precursor reacts and precipitates with each other in the gas phase, it is desirable to appropriately set the distance and arrangement between the first substrate 11 and each precursor.

[0022] Next, an example of a method for forming the first atomic film 21 on the first substrate 11 by transfer will be described with reference to Figures 5A to 5E. For example, the first atomic film 21 is formed on a substrate 13 different from the first substrate 11 by CVD (Figure 5A). The method for forming the first atomic film 21 by CVD is as described above. Note that the substrate 13 is an example of the "third substrate" in the disclosed technology.

[0023] Next, a support substrate 14 is formed on the surface of the first atomic film 21 (Figure 5B). A polymer or a commercially available resist can be used as the material for the support substrate 14. The resist is applied to a thickness of approximately 0.1 to 100 μm by spin coating. After that, the resist is dried by heat treatment at approximately 25°C to 200°C.

[0024] Next, the first atomic film 21 is peeled off together with the support substrate 14 (Figure 5C). By immersing the substrate 13 in the etchant, the etchant penetrates between the substrate 13 and the first atomic film 21, causing the substrate 13 to dissolve near the interface between the substrate 13 and the first atomic film 21, and the first atomic film 21 to peel off from the substrate 13. If the substrate 13 is sapphire, sodium hydroxide or potassium hydroxide can be used as the etchant. If the substrate 13 is a silicon substrate with a thermal oxide film, hydrofluoric acid can be used as the etchant. After that, the laminate containing the support substrate 14 and the first atomic film 21 is washed with water.

[0025] Next, the side of the laminate containing the support substrate 14 and the first atomic film 21 that faces the first atomic film 21 is brought into close contact with the surface of the first substrate 11 that constitutes the hetero-laminated device 1 (Figure 5D). To bring the first atomic film 21 and the first substrate 11 into close contact, it is effective to remove moisture contained in the interface by heating. The heating temperature is, for example, about 25 to 300°C.

[0026] Next, the support substrate 14 is dissolved with a solvent (Figure 5E). If the material of the support substrate 14 is a resist, acetone can be used as the solvent. By going through the above steps, the transfer of the first atomic film 21 to the first substrate 11 is completed.

[0027] After forming a first atomic film 21 on a first substrate 11, a first mask 41 for patterning the first atomic film 21 is formed on the surface of the first atomic film 21 (Figure 3B). The material of the first mask 41 may be a commercially available resist. The resist is applied by spin coating and patterned into a desired shape using lithography techniques. The material of the first mask 41 is not limited to a resist, but may be other materials that are easy to pattern and remove (e.g., polymers, metals, semiconductors, etc.).

[0028] Next, the portion of the first atomic film 21 exposed from the first mask 41 is removed (Figure 3C). Partial removal of the first atomic film 21 can be performed, for example, by dry etching using oxygen plasma. After the partial removal of the first atomic film 21 is complete, the first mask 41 is removed. This completes the patterning of the first atomic film 21. If the material of the first mask 41 is a resist, the first mask 41 can be removed using a solvent such as acetone.

[0029] Next, a second mask 42 is formed on the first substrate 11 for patterning the second atomic film 22 by lift-off (Figure 3D). The second mask 42 has openings 42A that expose a portion of the first atomic film 21 and a portion of the surface of the first substrate 11. The material of the second mask 42 may be a commercially available resist. The resist is applied by spin coating and patterned into a desired shape using lithography techniques. The material of the second mask 42 is not limited to a resist, but may be other materials that are easy to pattern and remove (e.g., polymers, metals, semiconductors, etc.).

[0030] Next, a second atomic film 22 is formed on the second substrate 12 (Figure 3E). The second atomic film 22 may be formed directly on the second substrate 12 by a synthesis method such as CVD, similar to the first atomic film 21, or the second atomic film 22 formed on a substrate other than the second substrate 12 may be transferred onto the second substrate 12. These methods are the same as those used to form the first atomic film 21, so a detailed explanation is omitted.

[0031] Next, the side of the laminate containing the second substrate 12 and the second atomic film 22 facing the second atomic film 22 is brought into close contact with the surface of the laminate containing the first substrate 11 and the first atomic film 21. That is, the portions of the first atomic film 21 and the first substrate 11 exposed from the second mask 42 are brought into close contact with the second atomic film 22 (Figure 3F). After that, the laminate containing the first substrate 11, the first atomic film 21, the second atomic film 22, and the second substrate 12 is heated. The heating temperature is, for example, 80 to 200°C. If the material of the second mask 42 and the second substrate 12 is a thermosetting resist, it is preferable that the heating temperature is lower than the curing temperature of the resist. Heating strengthens the adhesion between the second atomic film 22 and the first atomic film 21 and the first substrate 11.

[0032] Next, by dissolving the second mask 42, the portion of the second atomic film 22 other than the portion in close contact with the first atomic film 21 and the first substrate 11 is removed along with the second mask 42. That is, the second atomic film 22 is patterned by lift-off (Figure 3G). If the material of the second mask 42 is a resist, acetone can be used as the solvent. If the material of the second substrate 12 is the same as the material of the second mask 42, the second substrate 12 can be removed along with the second mask 42.

[0033] Next, the first electrode 31 and the second electrode 32 are formed (Figure 3H). The first electrode 31 and the second electrode 32 are formed by sequentially performing resist patterning, metal film deposition, and lift-off. The first electrode 31 is connected to the first atomic film 21 at its edge, and the second electrode 32 is connected to the second atomic film 22 at its edge. By going through these steps, the heteromultilayer device 1 is completed.

[0034] Preliminary experiments were conducted to demonstrate the process shown in Figures 3D to 3G (i.e., atomic film transfer and patterning by lift-off). A resist (TSMR®, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was formed on the surface of a silicon substrate with a thermal oxide film. The resist was exposed and developed to pattern the resist. A single layer of graphene was formed on a support substrate made of PMMA (polymethyl methacrylate). The single layer of graphene was synthesized by CVD. The graphene was placed in close contact with the substrate on which the patterned resist had formed, and heated at 80°C. Subsequently, the resist was dissolved with acetone, and a portion of the graphene was removed along with the resist. This formed a graphene pattern on the substrate. Figure 6 is a microscopic image showing the graphene pattern formed on the substrate by the above method. As shown in Figure 6, graphene 200 having a pattern corresponding to the resist pattern was successfully formed on the substrate 100.

[0035] As described above, a method for manufacturing a heterostacked device 1 according to an embodiment of the disclosed technology includes the steps of: forming a first atomic film 21 made of a layered material on a first substrate 11; patterning the first atomic film 21; forming a mask on the first atomic film 21 that partially exposes the first atomic film 21 and the first substrate; forming a second atomic film 22 made of a layered material on a second substrate 12; bringing the exposed portions of the first atomic film 21 and the first substrate 11 into close contact with the second atomic film 22; and removing a portion of the second atomic film 22 together with the mask.

[0036] According to the manufacturing method of this embodiment, the first atomic film 21 and the second atomic film 22 are formed by synthesis methods such as CVD, so a hetero-stacked device can be manufactured without using flake-like atomic films exfoliated from the bulk crystal. Therefore, according to the manufacturing method of this embodiment, it is possible to efficiently manufacture a hetero-stacked device of a desired size.

[0037] Here, Figures 7A to 7E are cross-sectional views showing an example of a method for manufacturing a heterost multilayer device according to a comparative example. A first atomic film 21 is formed on a first substrate 11. Then, the first atomic film 21 is patterned (Figure 6A). These steps are the same as those for the manufacturing method according to the embodiments of the disclosed technology described above. Next, a second atomic film 22 is formed on the first substrate 11 so as to cover the entire first atomic film 21 (Figure 7B). The second atomic film 22 is formed by CVD or transfer. Next, a mask 43 for patterning the first atomic film 21 and the second atomic film 22 is formed on the second atomic film 22 (Figure 7C). Next, the first atomic film 21 and the second atomic film 22 are patterned by partially etching them through the mask 43 (Figure 7D). Next, the mask 43 is removed (Figure 7E).

[0038] According to the manufacturing method of the comparative example, the first atomic film 21 and the second atomic film 22 are patterned using a common mask 43, resulting in a structure where the edges of these atomic films are aligned. This structure makes it difficult to form an electrode that is connected only to the first atomic film 21.

[0039] On the other hand, according to the manufacturing method of the embodiment of the disclosed technology, the patterning of the second atomic film 22 is performed independently of the first atomic film 21, making it possible to form a structure in which electrodes are individually connected to the first atomic film 21 and the second atomic film 22.

[0040] The following additional information is disclosed regarding the embodiments described above. (Note 1) A step of forming a first atomic film made of a layered material on a first substrate, The process of patterning the first atomic film, A step of forming a mask on the first atomic film that partially exposes the first atomic film and the first substrate, A step of forming a second atomic film on a second substrate, the second atomic film being made of a layered material different from the first atomic film, A step of bringing the exposed portion of the first atomic film and the first substrate into close contact with the second atomic film, A step of removing a portion of the second atomic film together with the mask, A method for manufacturing a heterost stacked device.

[0041] (Note 2) The first atomic film and the second atomic film are atomic films obtained by synthesis using chemical vapor deposition, respectively. The manufacturing method described in Appendix 1.

[0042] (Note 3) A step of forming a first electrode connected to the first atomic film, A step of forming a second electrode connected to the aforementioned second atomic film, The manufacturing method described in Appendix 1 or Appendix 2, further comprising the above.

[0043] (Note 4) The first atomic film and the second atomic film are graphene or layered chalcogenides. The manufacturing method described in any one of the appendices 1 to 3.

[0044] (Note 5) The mask is a thermosetting resist, In the step of bringing the exposed portion of the first atomic film and the first substrate into close contact with the second atomic film, the laminate including the first substrate, the first atomic film and the second atomic film is heated at a temperature lower than the curing temperature of the resist. The manufacturing method described in any one of the appendices 1 to 4.

[0045] (Note 6) The first atomic film is formed on the first substrate by depositing the constituent elements of the first atomic film onto the first substrate. The manufacturing method described in any one of the appendices 1 to 5.

[0046] (Note 7) The first atomic film is formed on the first substrate by transferring the first atomic film, which is formed on a third substrate different from the first substrate, onto the first substrate. The manufacturing method described in any one of the appendices 1 to 5.

[0047] (Note 8) The first and second atomic films are transition metal dichalcogenides, group 13 chalcogenides, group 14 chalcogenides, or bismuth chalcogenides. A manufacturing method described in any one of the appendices 1 through 7. [Explanation of Symbols]

[0048] 11. First substrate 12 Second substrate 21 First atomic film 22 The second atomic film 31 First electrode 32 Second electrode 41, 42, 43 Masks

Claims

1. A step of forming a first atomic film made of a layered material on a first substrate, The process involves patterning the first atomic film, A step of forming a mask on the first atomic film that partially exposes the first atomic film and the first substrate, A step of forming a second atomic film on a second substrate, the second atomic film being made of a layered material different from the first atomic film, A step of bringing the first atomic film and the exposed portion of the first substrate into close contact with the second atomic film, A step of removing a portion of the second atomic film together with the mask, A method for manufacturing a heterost stacked device.

2. The first atomic film and the second atomic film are atomic films obtained by synthesis using chemical vapor deposition. The manufacturing method according to claim 1.

3. A step of forming a first electrode connected to the first atomic film, A step of forming a second electrode connected to the second atomic film, The manufacturing method according to claim 1, further comprising:

4. The first atomic film and the second atomic film are graphene or layered chalcogenides. The manufacturing method according to claim 1.

5. The mask is a thermosetting resist, In the step of bringing the exposed portion of the first atomic film and the first substrate into close contact with the second atomic film, the laminate including the first substrate, the first atomic film and the second atomic film is heated at a temperature lower than the curing temperature of the resist. The manufacturing method according to claim 1.

6. The first atomic film is formed on the first substrate by depositing the constituent elements of the first atomic film onto the first substrate. The manufacturing method according to claim 1.

7. The first atomic film is formed on the first substrate by transferring the first atomic film, which is formed on a third substrate different from the first substrate, onto the first substrate. The manufacturing method according to claim 1.

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