Patent Publication Number: US-2022238692-A1

Title: Method of patterning two-dimensional material layer on substrate, and method of fabricating semiconductor device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0010355, filed on Jan. 25, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The present inventive concepts relate to methods of patterning a two-dimensional (2D) material layer on a substrate and methods of manufacturing a semiconductor device. 
     2. Description of the Related Art 
     As the degree of integration of semiconductor devices increases, the size of semiconductor devices included in semiconductor apparatuses becomes smaller. In order to increase an operating speed of semiconductor devices, attempts have been made to reduce not only contact resistance between semiconductor devices, but also contact resistance between members or layers that constitute semiconductor devices (e.g., transistors). As part of this, a 2D material is employed. A 2D material has a high electron mobility compared to a three-dimensional (3D) material used in the related art. For example, a transistor employing a 2D material as a channel shows a high operating speed compared to a transistor using a 3D material as a channel. 
     In order to form a 2D material layer in a particular (or, alternatively, predetermined) region on a substrate, a photolithography process and a reactive ion etching (RIE) process are used. 
     SUMMARY 
     Provided are patterning methods capable of forming a 2D material layer of a uniform quality. 
     Provided are patterning methods efficient and capable of reducing contamination of a 2D material layer. 
     Provided are methods of manufacturing a semiconductor device capable of increasing a manufacturing yield. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of some example embodiments of the inventive concepts. 
     According to some example embodiments, a method of patterning a two-dimensional (2D) material layer may include selectively forming a first material layer on a surface of a substrate to form a first region in which the first material layer covers the surface of the substrate and to further form a second region in which the surface of the substrate is exposed from the first material layer, the first material layer having a strong adhesive force with a 2D material, forming a 2D material layer in both the first region and the second region, and removing the 2D material layer from the second region based on using a physical removal method and not removing the 2D material layer from the first region, such that the 2D material layer remains exclusively in the first region. 
     The first material layer may include a metal layer. The metal layer may include at least one of copper, nickel, gold, or platinum. 
     The first material layer may include a metal oxide layer. The metal oxide layer may include at least one of TiO 2  or HFO 2 . 
     The first material layer may include a self-assembled monolayer. The self-assembled monolayer may include at least one of a —NH 2  functional group or a —SH 2  functional group. 
     The 2D material layer may include at least one of graphene, black phosphorous, or transition-metal dichalcogenide. 
     The forming of both the first region and the second region may include forming, on the surface of the substrate in the second region, a second material layer having a weak adhesive force with respect to the 2D material. The second material layer may include at least one of Si, SiO 2 , or Al 2 O 3 . The second material layer may include a self-assembled monolayer including at least one of a —CF 3  functional group or a —CH 3  functional group. 
     The physical removal method may include one of sonication or mechanical detachment. 
     According to some example embodiments, a method of manufacturing a semiconductor device may include selectively forming a first material layer on a surface of a substrate to form a first region in which the first material layer covers the surface of the substrate and to further form a second region in which the surface of the substrate is exposed from the first material layer, the first material layer having a strong adhesive force with a two-dimensional (2D) material, forming a 2D material layer having a layered structure of a 2D material in both the first region and the second region, forming a channel layer based on removing the 2D material layer from the second region based on using a physical removal method and not removing the 2D material layer from the first region, such that the 2D material layer remains exclusively in the first region, forming a first electrode and a second electrode, wherein the first electrode and the second electrode are each in direct contact with the channel layer and are isolated from direct contact with each other, and forming a third electrode extending in parallel with the channel layer. 
     The two-dimensional material layer may include at least one of graphene, black phosphorous, or transition-metal dichalcogenide. The first material layer may be one of a metal layer including at least one of copper, nickel, gold, or platinum, a metal oxide layer including at least one of TiO 2  or HfO 2 , or a self-assembled monolayer including at least one of a —NH 2  functional group or a —SH 2  functional group. 
     The forming of both the first region and the second region may include forming, on the surface of the substrate in the second region, a second material layer having a weak adhesive force with respect to the 2D material. The 2D material layer may include at least one of graphene, black phosphorous, or transition-metal dichalcogenide. The second material layer may include at least one of Si, SiO 2 , or Al 2 O 3 . The second material layer may include a self-assembled monolayer including at least one of a —CF 3  functional group or a —CH 3  functional group. 
     The physical removal method may include one of sonication or mechanical detachment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of some example embodiments of the inventive concepts will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIGS. 1A, 1B, and 1C  are diagrams showing a method of patterning a 2D material layer according to some example embodiments; 
         FIGS. 2A, 2B, and 2C  are diagrams showing a method of patterning a 2D material layer according to some example embodiments; 
         FIGS. 3A, 3B, and 3C  are diagrams showing a method of manufacturing a semiconductor device according to some example embodiments; and 
         FIGS. 4A, 4B, and 4C  are diagrams showing a method of manufacturing a semiconductor device according to some example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, some example embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it may be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. It will further be understood that when an element is referred to as being “on” another element, it may be above or beneath or adjacent (e.g., horizontally adjacent) to the other element. 
     It will be understood that elements and/or properties thereof (e.g., structures, surfaces, directions, or the like), which may be referred to as being “perpendicular,” “parallel,” “coplanar,” or the like with regard to other elements and/or properties thereof (e.g., structures, surfaces, directions, or the like) may be “perpendicular,” “parallel,” “coplanar,” or the like or may be “substantially perpendicular,” “substantially parallel,” “substantially coplanar,” respectively, with regard to the other elements and/or properties thereof. 
     Elements and/or properties thereof (e.g., structures, surfaces, directions, or the like) that are “substantially perpendicular” with regard to other elements and/or properties thereof will be understood to be “perpendicular” with regard to the other elements and/or properties thereof within manufacturing tolerances and/or material tolerances and/or have a deviation in magnitude and/or angle from “perpendicular,” or the like with regard to the other elements and/or properties thereof that is equal to or less than 10% (e.g., a. tolerance of ±10%). 
     Elements and/or properties thereof (e.g., structures, surfaces, directions, or the like) that are “substantially parallel” with regard to other elements and/or properties thereof will be understood to be “parallel” with regard to the other elements and/or properties thereof within manufacturing tolerances and/or material tolerances and/or have a deviation in magnitude and/or angle from “parallel,” or the like with regard to the other elements and/or properties thereof that is equal to or less than 10% (e.g., a. tolerance of ±10%). 
     Elements and/or properties thereof (e.g., structures, surfaces, directions, or the like) that are “substantially coplanar” with regard to other elements and/or properties thereof will be understood to be “coplanar” with regard to the other elements and/or properties thereof within manufacturing tolerances and/or material tolerances and/or have a deviation in magnitude and/or angle from “coplanar,” or the like with regard to the other elements and/or properties thereof that is equal to or less than 10% (e.g., a. tolerance of ±10%)). 
     It will be understood that elements and/or properties thereof may be recited herein as being “the same” or “equal” as other elements, and it will be further understood that elements and/or properties thereof recited herein as being “identical” to, “the same” as, or “equal” to other elements may be “identical” to, “the same” as, or “equal” to or “substantially identical” to, “substantially the same” as or “substantially equal” to the other elements and/or properties thereof. Elements and/or properties thereof that are “substantially identical” to, “substantially the same” as or “substantially equal” to other elements and/or properties thereof will be understood to include elements and/or properties thereof that are identical to, the same as, or equal to the other elements and/or properties thereof within manufacturing tolerances and/or material tolerances. Elements and/or properties thereof that are identical or substantially identical to and/or the same or substantially the same as other elements and/or properties thereof may be structurally the same or substantially the same, functionally the same or substantially the same, and/or compositionally the same or substantially the same. 
     It will be understood that elements and/or properties thereof described herein as being “substantially” the same and/or identical encompasses elements and/or properties thereof that have a relative difference in magnitude that is equal to or less than 10%. Further, regardless of whether elements and/or properties thereof are modified as “substantially,” it will be understood that these elements and/or properties thereof should be construed as including a manufacturing or operational tolerance (e.g., ±10%) around the stated elements and/or properties thereof. 
     When the terms “about” or “substantially” are used in this specification in connection with a numerical value, it is intended that the associated numerical value include a tolerance of ±10% around the stated numerical value. When ranges are specified, the range includes all values therebetween such as increments of 0.1%. 
     Hereinafter, patterning methods of a 2D material layer and manufacturing methods of a semiconductor device will be described in detail with reference to the accompanying drawings. The widths and thicknesses of layers and regions shown in the accompanying drawings may be exaggerated for convenience of explanation and clarity of the specification. Like reference numerals refer to like elements throughout detailed descriptions. 
       FIGS. 1A to 1C  are diagrams showing a method of patterning a two-dimensional (2D) material layer according to some example embodiments. Referring to  FIGS. 1A to 1C , a method of patterning a 2D material layer, according to some example embodiments includes forming a first region  31  on which a first material layer  21  having strong adhesion to a 2D material is formed on a surface  11  of a substrate  10  and a second region  32  on which the first material layer  21  is not formed; forming a 2D material layer  40  in the first region  31  and the second region  32 ; and removing a 2D material layer  42  in the second region  32  based on using a physical removal method (non-photolithography process) and remaining a 2D material layer  41  in the first region  31 . 
     First, referring to  FIG. 1A , the substrate  10  is prepared. The substrate  10  may be a semiconductor substrate, an insulating substrate, and a semiconductor substrate with an insulating layer formed on a surface  11  of the substrate  10 , and is not limited thereto. The semiconductor substrate may include, for example, Si, GE, SiGe or a Group III-V semiconductor material, and the like. For example, the substrate  10  may be a silicon substrate on which a silicon oxide is formed. 
     The first material layer  21  is formed in the first region  31  of the substrate  10 . The second region  32  is a region of the surface  11  of the substrate  10  on which the first material layer  21  is not formed. Restated, the preparation of the substrate  10  as shown in  FIG. 1A  may include selectively forming the first material layer  21  on the surface  11  of the substrate  10  to establish (e.g., form, define, etc.) the first region  31  as a region in which the first material layer  21  covers the surface  11  of the substrate  10  and to further establish (e.g., form, define, etc.) the second region  32  as a region in which the surface  11  of the substrate  10  is exposed from (e.g., not covered by) the first material layer  21 . The first material layer  21  has adhesiveness with respect to the 2D material (e.g., a strong adhesive force with the 2D material). For example, the adhesion between the first material layer  21  and the 2D material is greater than the adhesion between the 2D material and the surface  11  of the substrate  10 . 
     In some example embodiments, the first material layer  21  may include a metal layer. The metal layer may be formed by depositing a metal onto the surface  11  (e.g., insulating surface) of the substrate  10 . A metal having adhesive force with respect to the 2D material greater than the adhesive force between the 2D material and the surface  11  (e.g., insulating surface) of the substrate  10  is used as the metal. For example, the metal may include at least one of copper (Cu), nickel (Ni), gold (Au), or platinum (Pt). The first material layer  21  may be a single metal thin film and may be a thin film including two or more metals, and may be a multilayer metal thin film including different metals from each other. 
     In some example embodiments, the first material layer  21  may include a metal oxide having an insulating property. A metal oxide having adhesive force with respect to a 2D material greater than the adhesive force between the 2D material and the surface  11  (e.g., insulating surface) of the substrate  10  may be used as the metal oxide. The metal oxide may be a high-k dielectric material having a high dielectric constant. For example, the metal oxide may include at least one of TiO 2  or HfO 2 . The first material layer  21  may be a layer including a single metal oxide, may be a layer including two or more metal oxides, and/or may be a multilayer structure including different metal oxides from each other. Accordingly, the first material layer may include a metal oxide layer that may include any of the metal oxides described herein (e.g., at least one of TiO 2  or HfO 2 ). The method of forming the first material layer  21  is not particularly limited. For example, the first material layer  21  may be formed based on using a sputtering method, an atomic layer deposition (ALD) method, etc. 
     In some example embodiments, the first material layer  21  may include a self-assembled monolayer (SAM). The SAM refers to an organic monolayer that is spontaneously formed on a surface of a solid. The SAM includes a head group, a hydrocarbon chain, and a terminal group. The head group is chemically adsorbed on a surface of a solid to form monolayers. The hydrocarbon chain allows the monolayers to be aligned by the Van der Waals interaction. The terminal group includes functional groups. The functional groups are part of the SAM that enables application of the SAM, and in some example embodiments, an SAM having functional groups having adhesive force with respect to a 2D material is employed. For example, a self-assembled monolayer having (e.g., including) at least one of a —NH 2  functional group or a —SH 2  functional group may be employed as an insulating material layer. Restated, the self-assembled monolayer of the first material layer  21  may have (e.g., may include) at least one of a —NH 2  functional group or a —SH 2  functional group. If only an ionic bond exists between the surface  11  of the substrate  10  and the first material layer  21 , it is difficult to form a strong molecular film. However, in the case of the self-assembled monolayer, because a chemical bond is formed between the surface  11  of the substrate  10  and the molecules of the head group constituting the monolayer, a very strong molecular film, that is, the first material layer  21 , may be formed. Also, the functional group of the monolayer and the 2D material may be combined with strong adhesive force. Accordingly, as a result, the self-assembled monolayer is strongly bonded to the surface  11  of the substrate  10  and the 2D material layer, and thus, the adhesive force of the 2D material layer may be enhanced. 
     Next, referring to  FIG. 1B , a 2D material layer  40  is formed in both the first region  31  and the second region  32 . The 2D material layer  40  may be formed on (e.g., directly and/or indirectly on) an entire surface  11  of the substrate  10  including the first region  31  and the second region  32 . In  FIG. 1B , the 2D material layer  40  is shown to be separated from (e.g., isolated from direct contact with) the surface  11  of the substrate  10  in the second region  32  (e.g., the first material layer  21  is directly or indirectly between the 2D material layer  40  and the substrate  10  in the first region  31  but not in the second region  32 ), but the 2D material layer  40  may be formed on the surface  11  of the substrate  10 . Also, the thickness of a 2D material layer  41  of the first region  31  and the thickness of a 2D material layer  42  of the second region  32  may be the same. The thickness of the 2D material layer  41  of the first region  31  and the thickness of the 2D material layer  42  of the second region  32  may be different from each other. For example, the thickness of the 2D material layer  41  of the first region  31  may be greater than that of the 2D material layer  42  of the second region  32 . As shown in  FIG. 1B , in some example embodiments, the 2D material layer  42  of the second region  32  may be isolated from direct contact with the surface  11  of the substrate  10  by a space  99 . In some example embodiments, space  99  is partially or completely filled with a material (e.g., second material layer  22  as described herein) that may be different from both the material of the first material layer  21  and the material of the 2D material layer  40 , such that the 2D material layer  42  of the second region  32  may be isolated from direct contact with the surface  11  of the substrate  10  by the second material layer  22 . In some example embodiments, space  99  may be absent and the 2D material layer  42  of the second region  32  may be in direct contact with the surface  11  of the substrate  10  in the second region  32 . 
     The 2D material refers to a semiconductor material having a 2D crystal structure. The 2D material layer may have a layered structure of the 2D material. The 2D material may have a layered structure of a monolayer or a multilayer. Each layer constituting the 2D material may have a thickness of an atomic level. The 2D material of the 2D material layer  40  may include, for example, at least one of graphene, black phosphorous, or transition-metal dichalcogenide (TMD). Restated, the 2D material layer  40  (and thus the 2D material layers  41  and  42 ) may include at least one of graphene, black phosphorous, or transition-metal dichalcogenide (TMD). Graphene is a material having a hexagonal honeycomb structure formed by two-dimensionally bonding of carbon atoms, and has the advantages of high electrical mobility, high thermal properties, chemical stability, and having a large surface area compared to silicon (Si). The black phosphorous is a substance in which black phosphorous atoms are two-dimensionally bonded. 
     The TMD may include, for example, one transition-metal of Mo, W, Nb, V, Ta, Ti, Zr, Hf, Tc, and Re and one chalcogen element of S, Se, and Te. The TMD may be expressed as, for example, MX 2 , wherein M represents a transition-metal and X represents a chalcogen element. For example, M may be Mo, W, Nb, V, Ta, Ti, Zr, Hf, Tc, Re, and the like, and X may be S, Se, Te, and the like. Accordingly, for example, TMD may include MoS 2 , MoSe 2 , MoTe 2 , WS 2 , WSe 2 , WTe 2 , ZrS 2 , ZrSe 2 , HfS 2 , HfSe 2 , NbSe 2 , ReSe 2 , and the like. Alternatively, the TMD may not be expressed as MX 2 . In this case, for example, the TMD may include CuS which is a compound of Cu which is a transition-metal and S which is a chalcogen element. On the other hand, the TMD may be a chalcogenide material including a non-transition-metal. The non-transition-metal may include, for example, Ga, in, Sn, Ge, Pb, and the like. In this case, the TMD may include a compound of a nontransition-metal, such as Ga, In, Sn, Ge, and Pb and a chalcogen element, such as S, Se, and Te. For example, the TMD may include SnSe 2 , GaS, GaSe, GaTe, GeSe, In 2 Se 3 , InSnS 2 , and the like. 
     As described above, the TMD may include one of metal elements, such as Mo, W, Nb, V, Ta, Ti, Zr, Hf, Tc, Re, Cu, Ga, In, Sn, Ge, and/or Pb and one of chalcogen element, such as S, Se, and/or Te. However, the materials mentioned above are merely examples, and other materials may also be used as a TMD material. 
     The 2D material may be doped with a p-type dopant or an n-type dopant to control the mobility of the 2D material. Here, the p-type dopant and n-type dopant may be, for example, a p-type dopant and an n-type dopant used for graphene or CNTs. The p-type dopant or the n-type dopant may be doped based on using an ion implantation method, a chemical doping method, or a substitutional doping method. The substitutional doping refers to that a heterogeneous metal of the TMD is substituted with some dopants. The TMD doped in this form includes, for example, Nb-doped MoS 2 , Re-doped MoS 2 , V-doped MoS 2 , etc. 
     The 2D material layer  40  may further include an intercalation material inserted into an interlayer of a 2D material, and here, the intercalation material may include, for example, lithium (Li) or potassium (K), etc. For example, the intercalation material may include Li atoms, include K atoms, or include both Li atoms and K atoms. The carrier mobility (for example, electron mobility) in a thickness direction of the 2D material layer  40  may be increased by the intercalation material, and as a result, the performance and operation characteristics of the semiconductor device may be improved. A semiconductor device having a vertical-type structure using a 2D material may exhibit a relatively high current density even at a low input voltage compared to a horizontal type semiconductor device, and thus, may be used as a low power semiconductor device. Also, because a 2D material may have a small thickness and, in a vertical-type semiconductor device, a short channel of several tens of nm or less may be readily implemented, the manufacturing process of the semiconductor device is easy, and a high-density integrated circuit may be implemented due to the small device size. 
     The 2D material layer  40  may be formed by, for example, a growth method, a transfer method, or the like. As an example, the process of forming the 2D material layer  40  based on using a transfer method will be briefly described. 
     First, a 2D material layer is grown on a growth substrate. The growth may be performed, for example, based on using an organometallic chemical vapor deposition (MOCVD), an atomic layer deposition (ALD), etc. As needed, a process of doping the 2D material layer with a p-type dopant or an n-type dopant may be performed. Here, the p-type dopant and n-type dopant may be, for example, a p-type dopant and an n-type dopant used for graphene or carbon nanotubes (CNTs). The p-type dopant or the n-type dopant may be doped based on using an ion implantation method, a chemical doping method, or a substitutional doping method, etc. A source of the p-type dopant may include an ionic liquid, such as NO 2 BF 4 , NOBF 4 , NO 2 SbF 6 , etc. an acidic compound, such as HCl, H 2 PO 4 , CH 3 COOH, H 2 SO 4 , HNO 3 , etc. and an organic compound, such as dichlorodicyanoquinone (DDQ), oxone, dimristoylphosphatidylinositol (DMPI), trifluoromethaneimide (DMPI), etc. Alternatively, the source of the p-type dopant may include HPtCl 4 , AuCl 3 , HAuCl 4 , silver trifluoromethaesulfonate (AgOTf), AgNO 3 , H 2 PdCl 6 , Pd(OAc) 2 , Cu(CN) 2 , etc. A source of the n-type dopant may include, for example, a reduction product of a substituted or unsubstituted nicotinamide; a reduction product of a compound which is chemically bound to a substituted or unsubstituted nicotinamide; and a compound including at least two pyridinium derivatives in which a nitrogen atom of at least one of the pyridinium derivative is reduced. For example, the source of the n-type dopant may include nicotinamide mononucleotide-H (NMNH), nicotinamide adenine dinucleotide-H (NADH), nicotinamide adenine dinucleotide phosphate-H (NADP), or viologen. Alternatively, the source of the n-type dopant may include a polymer, such as polyethylenimine (PEI), etc. Alternatively, the n-type dopant may include an alkali metal, such as K and Li. The p-type dopant materials and the n-type dopant materials mentioned above are examples, and other various other substances may be used as a dopant. 
     Then, a carrier polymer layer is formed on an upper surface of the 2D material layer, and the carrier polymer layer and the 2D material layer are separated from the growth substrate. The carrier polymer layer and the 2D material layer are attached to the first region  31  and the second region  32  of the substrate  10  and the carrier polymer layer is removed. 
     As a result, as shown in  FIG. 1B , the 2D material layer  40  may be formed on both the first region  31  and the second region  32 . In the first region  31 , a 2D material layer  41  is formed on the first material layer  21 . The first material layer  21  has a strong adhesive force with the 2D material layer  41 . Thus, in a process of removing the carrier polymer layer, the 2D material layer  41  may be maintained (e.g., may remain) on the first material layer  21  without peeling-off from the first material layer  21 . Therefore, the 2D material layer  41  of stable quality may be formed. 
     Next, referring to  FIG. 1C , a 2D material layer  42  of the second region  32  is removed (e.g., selectively removed) based on using a physical removal method, and the 2D material layer  41  of the first region  31  is not removed such that the 2D material layer  41  of the first region  31  is left (e.g., remains exclusively on the surface  11  of the substrate  10  in the first region  31  and thus is not on the surface  11  of the substrate  10  at all in the second region  32 ). The physical removal method may include a non-photolithography process, for example, sonication, mechanical detachment, etc. For example, the physical removal method may comprise one of sonication or mechanical detachment. For example, the sonication may be performed in acetone. 
     As described above, a surface of the first material layer  21  is strongly adhered to the 2D material layer  41  in the first region  31 . The adhesive force between the first material layer  21  and the 2D material layer  41  is greater than the adhesive force between the substrate  10  and the 2D material layer  42  in the second region  32 . Accordingly, in the physical removal method, the 2D material layer  41  in the first region  31  is not separated from the first material layer  21  and thus at least partially remains in the first region  31 , and the 2D material layer  42  in the second region  32  is peeled-off and removed from the substrate  10 . Thus, as shown in  FIG. 1C , the 2D material layer  40  may be selectively removed from the second region  32  based on using a physical removal method, such that the 2D material layer  40  remains (e.g., exclusively remains) in the first region  31 . Restated, the selective removal of the 2D material layer may include removing the 2D material layer  42  from the second region  32  but not removing the 2D material layer  41  from the first region  31  so that the 2D material layer  41  remains exclusively in the first region  31  on the substrate  10  (e.g., directly on the first material layer  21 ). Accordingly, as shown in  FIG. 1C , a patterned 2D material layer  41  in a form in which the first material layer  21  and the 2D material layer  41  are sequentially stacked on the first region  31  of the substrate  10  may be obtained. 
     According to an existing process in which a 2D material layer  40  is formed on an entire surface  11  of the substrate  10  and the 2D material layer  42  is patterned based on using a photolithography process, the process may take a long time, and contamination of the 2D material layer  42  may be caused by residual photoresist. Also, a toxic substance, for example, SF6, etc. may be used in a reactive ion etching process. 
     In the patterning method according to some example embodiments, the 2D material layer is patterned based on using an adhesive force difference between the adhesive force between the 2D material layer  40  and the first material layer  21  and the adhesive force between the 2D material layer  40  and the substrate  10 , and thus, the patterning process may take less time than the photolithography process, and contamination of the 2D material layer  41  after patterning may be reduced or prevented. Also, because the 2D material layer  42  of the second region  32  is removed based on a physical removal method, not based on a reactive ion etching process, the process of using a toxic material may be reduced or eliminated. Further, because the 2D material layer  41  of the first region  31  is strongly adhered to the first material layer  21 , a 2D material layer of a uniform quality may be formed, and the process yield may be improved. 
       FIGS. 2A to 2C  are diagrams showing a method of patterning a 2D material layer according to some example embodiments. Referring to  FIGS. 2A to 2C , the method of patterning a 2D material layer according to some example embodiments is different from the patterning method shown in  FIGS. 1A to 1C  in that the patterning method according to some example embodiments includes forming a second material layer  22  having a weak adhesive force with respect to a 2D material on (e.g., directly or indirectly on) the surface  11  of the substrate  10  in the second region  32 . Hereinafter, the differences will be mainly described, and redundant descriptions will be omitted. 
     First, referring to  FIG. 2A , a first material layer  21  is formed on the surface  11  of the substrate  10  in the first region  31  of the surface  11  of the substrate  10  and a second material layer  22  is formed on the surface  11  of the substrate  10  in the second region  32  of the surface  11  of the substrate  10 . Adhesive force between the second material layer  22  and the 2D material is less than the adhesive force between the 2D material and the first material layer  21 . The adhesive force between the second material layer  22  and the 2D material of the 2D material layer  40  may be less than the adhesive force between the 2D material of the 2D material layer  40  and the surface  11  of the substrate  10 . The second material layer  22  includes a material having a small adhesive force with the 2D material (e.g., a weak adhesive force with respect to the 2D material of the 2D material layer  40 ). 
     In some example embodiments, the second material layer  22  may include at least one of Si, SiO 2 , or Al 2 O 3 . The second material layer  22  may be a layer including one of Si, SiO 2  or Al 2 O 3 , and may be a layer including two or more of Si, SiO 2  and/or Al 2 O 3 . The second material layer  22  may have a multilayer structure including different materials in Si, SiO 2  and/or Al 2 O 3 . 
     In some example embodiments, the second material layer  22  may include a self-assembled monolayer (SAM) having a functional group having a weak bonding force with a 2D material. For example, the second material layer  22  may include a SAM having (e.g., including) at least one of a —CF 3  functional group or a —CH 3  functional group. 
     Next, as shown in  FIG. 2B , a 2D material layer  40  is formed on the substrate  10 . The 2D material layer  40  may be formed based on using a growth method, a transfer method, etc. as described above. The 2D material layer  40  includes a 2D material layer  41  on the first material layer  21  and a 2D material layer  42  on the second material layer  22 . 
     Next, as shown in  FIG. 2C , the 2D material layer  42  on the second material layer  22  is removed (e.g., selectively removed) based on using a physical removal method and the 2D material layer  41  on the first material layer  21  is left (e.g., remains in the first region  31 ). As described above, the 2D material layer  41  is strongly adhered to the first material layer  21 . On the other hand, the adhesive force between the 2D material layer  42  and the second material layer  22  is relatively weak. Accordingly, in the physical removal operation, the 2D material layer  41  of the first region  31  is not separated from the first material layer  21 , and the 2D material layer  42  of the second region  32  is peeled-off and removed from the second material layer  22 . Accordingly, as shown in  FIG. 2C , a patterned 2D material layer  41  in a form in which the first material layer  21  and the 2D material layer  41  are sequentially stacked on the first region  31  of the substrate  10  may be obtained. The second material layer  22  may be left (e.g., may remain on the surface  11  of the substrate  10  in the second region  32 ) and may be removed as needed. 
     The method of patterning the 2D material layer described above may be applied to a method of manufacturing semiconductor devices, for example, field effect transistors in various forms. 
       FIGS. 3A to 3C  are diagrams showing a method of manufacturing a semiconductor device according to some example embodiments. 
     First, referring to  FIG. 3A , a channel layer  50  having a layered structure of a 2D material is formed on the substrate  10 . The channel layer  50  may be formed by the method shown in  FIGS. 1A to 1C  or by the method shown in  FIGS. 2A to 2C  (e.g., selectively removing the 2D material layer  42  from the second region  32  based on using a physical removal method, such that the 2D material layer  41  remains in the first region  31 ). For example, the patterned 2D material layer  41  in which the first material layer  21  and the 2D material layer  41  are sequentially stacked on the substrate  10  is formed by the method shown in  FIGS. 1A to 1C  or by the method shown in  FIGS. 2A to 2C . The 2D material layer  41  will be the channel layer  50 . According to the method shown in  FIGS. 2A to 2C , the second material layer  22  may remain on the substrate  10  as shown in the dashed line in  FIG. 3A . The substrate  10  may be an insulating substrate or a semiconductor substrate in which an insulating layer is formed on the surface  11  of the substrate  10 , but is not limited thereto. The semiconductor substrate may include, for example, Si, Ge, SiGe or a Group III-V semiconductor material, and the like. For example, the substrate  10  may include a silicon substrate including a silicon oxide. 
     Next, as shown in  FIG. 3B , a first electrode  61  and a second electrode  62  are formed. The first electrode  61  and the second electrode  62  may each contact (e.g., may each be in direct contact with, may each independently directly contact, etc.) the channel layer  50  and separate from each other (e.g., are isolated from direct contact with each other). The first electrode  61  and the second electrode  62  are a source electrode and a drain electrode, respectively. As an example, the first electrode  61  and the second electrode  62  may be formed on the channel layer  50 . In some example embodiments, the first electrode  61  and the second electrode  62  may include a metal material having high electrical conductivity. For example, the first electrode  61  and the second electrode  62  may include a metal, such as magnesium (Mg), aluminum (Al), scandium (Sc), titanium (Ti), vanadium (V), chrome (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), zirconium (Zr), niobium (Nb), molybdenum (Mo), lead (Pb), silver (Ag), cadmium (Cd), indium (In), tin (Sn), lanthanum (La), hafnium (Hf), tantalum (Ta), tungsten (W), iridium (Ir), platinum (Pt), gold (Au), bismuth (Bi), etc. or an alloy of these metals. 
     Next, referring to  FIG. 3C , a third electrode  70  facing the channel layer  50  (e.g., extending in parallel with the channel layer  50 ) is formed with the insulating layer  71  therebetween. The third electrode  70  may be a gate electrode. In some example embodiments, the third electrode  70  is formed on the channel layer  50 . First, the insulating layer  71  is formed on the channel layer  50 . The insulating layer  71  is a gate insulating film that blocks a leakage current between the channel layer  50  and the third electrode  70 . The insulating layer  71  also insulates between the third electrode  70  and the first electrode  61  and between the third electrode  70  and the second electrode  62 . Next, the third electrode  70  is formed on the insulating layer  71 . 
     The insulating layer  71  may include a high-k dielectric material having a high dielectric constant. The insulating layer  71  may include, for example, aluminum oxide, hafnium oxide, zirconium hafnium oxide, lanthanum oxide, etc. However, it is not limited thereto. The third electrode  70  may include a metal material or a conductive oxide. Here, the metal material may include, for example, at least one selected from the group consisting of Au, Ti, Ti, TiN, TaN, W, Mo, Wn, Pt and Ni. The conductive oxide may include, for example, indium tin oxide (ITO), indium zinc oxide (IZO), etc. The third electrode  70  may include the same material as the first electrode  61  and the second electrode  62 . 
     According to the method of manufacturing the semiconductor device described above, the first material layer  21  is strongly adhered to the 2D material layer  41  formed on a surface of the first material layer  21 . Because the adhesive force between the first material layer  21  and the 2D material layer  41  is large, the peeling-off of the 2D material layer  41  in a process of transferring the 2D material layer  41  may be prevented. The adhesive force between the first material layer  21  and the 2D material layer  41  is greater than the adhesive force between the substrate  10  and the 2D material layer  42  in the second region  32  or the adhesive force between the second material layer  22  and the 2D material layer  42  in the second region  32 . In the physical removal process, the 2D material layer  41  of the first region  31  is not separated from the first material layer  21 , and the 2D material layer  42  of the second region  32  is peeled-off and removed from the substrate  10 . Accordingly, the uniform quality channel layer  50  in a form in which the first material layer  21  and the 2D material layer  41  are sequentially stacked on the first region  31  of the substrate  10  may be obtained, and the process yield of the semiconductor device may be improved. 
     Further, the process time is less than the photolithography process of the related art, and the contamination of the channel layer  50  after patterning may be reduced or prevented. Also, because a physical removal method is used, not a reactive ion etching process, the process of using a toxic material may be reduced or eliminated. 
     According to the channel layer  50  including a 2D material, the performance and operation characteristics of the semiconductor device may be improved. A semiconductor device having a vertical-type structure using a 2D material may exhibit a relatively high current density even at a low input voltage compared to a horizontal type semiconductor device, and thus, may be used as a low power semiconductor device. Also, because a 2D material may have a small thickness and, in a vertical-type semiconductor device, a short channel of several tens of nm or less may be readily implemented, a manufacturing process of the semiconductor device is easy, and a high-density integrated circuit may be implemented due to the small device size. 
       FIGS. 4A to 4C  are diagrams showing a method of manufacturing a semiconductor device according to some example embodiments. 
     First, referring to  FIG. 4A , a substrate  10  having a third electrode  70  (e.g., gate electrode) is prepared. The substrate  10  may be an insulating substrate or a semiconductor substrate in which an insulating layer is formed on the surface  11  (which may be an insulating surface) of the substrate  10 , but is not limited thereto. The semiconductor substrate may include, for example, Si, Ge, SiGe or a Group III-V semiconductor material, and the like. For example, the substrate  10  may include a silicon substrate including a silicon oxide. The third electrode  70  may be formed to be inwardly sunken from a rear surface  12  which is opposite to the surface  11  of the substrate  10  and exposed through the rear surface  12 . The third electrode  70  may be formed on the rear surface  12  of the substrate  10 . 
     Next, as shown in  FIG. 4B , a channel layer  50  is formed. The channel layer  50  is formed to face the third electrode  70 . The channel layer  50  may be formed based on using the method shown in  FIGS. 1A to 1C  or the method shown in  FIGS. 2A to 2C . In this case, a region of the substrate  10  facing the third electrode  70  in a thickness direction may be the first region  31  where the channel layer  50  is to be formed. A patterned 2D material layer  41  in which the first material layer  21  and the 2D material layer  41  are sequentially stacked is formed on the substrate  10  based on using the method shown in  FIGS. 1A to 1C  or the method shown in  FIGS. 2A to 2C . The 2D material layer  41  becomes the channel layer  50 . According to the method shown in  FIGS. 2A to 2C , as shown by the dashed line in  FIG. 4B , the second material layer  22  may remain on the substrate  10 . The surface  11  (e.g., insulating surface) of the substrate  10  may function as a gate insulating film that suppresses a leakage current by insulating the channel layer  50  from the third electrode  70 . 
     Next, as shown in  FIG. 4C , the first electrode  61  and the second electrode  62  are formed. The first electrode  61  and the second electrode  62  may contact the channel layer  50  and may be separated from each other. The first electrode  61  and the second electrode  62  are a source electrode and a drain electrode, respectively. As an example, the first electrode  61  and the second electrode  62  may be formed on the channel layer  50 . 
     Because a material that is strongly adhered to a 2D material is used, a uniform quality 2D material layer may be formed in a particular (or, alternatively, predetermined) region on a substrate. 
     Because a photolithography process is not applied in a process of patterning the 2D material layer, the patterning process is efficient and contamination of the 2D material layer may be reduced. 
     In a process of manufacturing a semiconductor device, the peeling-off of the 2D material layer may be reduced or prevented, and thus, the manufacturing yield of the semiconductor device may be improved. 
     A semiconductor device having high performance and operation characteristics with high carrier mobility may be manufactured. 
     While some example embodiments have been described in detail, the scope of the inventive concepts is not defined by the detailed descriptions but by the appended claims. 
     It should be understood that example embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each example embodiment should typically be considered as available for other similar features or aspects in other example embodiments. While some example embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.