JP2024009495A - Method for manufacturing chalcogenide layered material and method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide chalcogenide layered materials with few atomic defects.

SOLUTION: A manufacturing method has a first step of forming a metal chalcogenide film with a compound of metal and chalcogen on a substrate, a second step of forming a chalcogen film with chalcogen on the metal chalcogenide film, a third step of placing graphene or hexagonal boron nitride on the chalcogen film, and a fourth step of heating the chalcogen film and the metal chalcogenide film after the third step.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for manufacturing a chalcogenide-based layered material and a method for manufacturing a semiconductor device.

A layered material is a material in which atomic layers each having a plurality of atoms strongly bonded to each other by covalent bonds or the like are weakly bonded to each other by van der Waals forces or the like. The atomic layer itself is also called a layered material. For example, graphite is a layered material in which atomic layers of carbon (ie, graphene) are weakly bonded to each other. Graphene itself is also a layered material.

Chalcogenide-based layered materials are layered materials that have attracted attention in recent years (see, for example, Patent Documents 1 to 4). A chalcogenide-based layered material is a compound of a metal and a chalcogen. For this reason, chalcogenide-based layered materials are also called metal chalcogenides (see, for example, Patent Document 2).

Among the many metal chalcogenides that exist, substances that have attracted particular attention are MoS ₂ and WSe ₂ . MoS ₂ and WSe ₂ with a few layers or less are flexible semiconductors. Therefore, MoS ₂ and WSe ₂ are expected to be applied to flexible devices and semiconductor devices (see, for example, Patent Documents 1 to 4).

Metal chalcogenides other than MoS ₂ and WSe ₂ (eg, WTe ₂ ) also exhibit physical properties different from those of bulk crystals when the number of layers is less than a few. For this reason, metal chalcogenides other than MoS ₂ and WSe ₂ (particularly WTe ₂ ) are also attracting attention.

US Patent Application Publication No. 2021/0375619 US Patent Application Publication No. 2020/0347494 JP2020-84323A JP 2018-100194 Publication

The main methods for synthesizing metal chalcogenides are chemical vapor deposition (hereinafter abbreviated as CVD) and thermal sulfidation. Metal chalcogenides synthesized by these methods are exposed to high temperatures during their synthesis. Therefore, metal chalcogenides synthesized by these methods have a large deficiency (ie, lack) of chalcogen atoms. This is because the vapor pressure of chalcogen is higher than that of metals. Such chalcogen atom deficiencies lead to unintended carrier generation and low mobility in metal chalcogenides.

When there is a shortage of chalcogen atoms, chalcogen atom vacancies are generated. These vacancies combine with moisture or oxygen in the atmosphere, causing undesirable chemical changes (eg, formation of an oxide film, etc.) in the metal chalcogenide. Therefore, defects in chalcogen atoms (hereinafter referred to as atomic defects) make metal chalcogenides chemically unstable.

Therefore, it is an object of the present invention to solve such problems.

In order to solve the above problem, in one embodiment, a manufacturing method includes a first step of forming a metal chalcogenide film having a compound of metal and chalcogen on a substrate, and a step of forming a metal chalcogenide film on the metal chalcogenide film. a second step of forming a chalcogen film having another chalcogen different from chalcogen and at least one of the chalcogen; a third step of disposing graphene or hexagonal boron nitride on the chalcogen film; Thereafter, a fourth step of heating the chalcogen film and the metal chalcogenide film is included.

In one aspect, according to the present invention, a chalcogenide-based layered material with few atomic defects can be provided.

FIG. 1 is a diagram showing an example of the manufacturing method according to the first embodiment. FIG. 2 is a process cross-sectional view of the manufacturing method shown in FIG. FIG. 3 is a process cross-sectional view of the manufacturing method shown in FIG. FIG. 4 is a process cross-sectional view of the manufacturing method shown in FIG. FIG. 5 is an example of a side view of a single layer MoS ₂ deposited by CVD. FIG. 6 is a plan view of a single layer MoS ₂ deposited by CVD. FIG. 7 is a diagram showing another method for compensating for the deficiency of S atoms. FIG. 8 is a diagram for explaining the reason why the S atoms 112 cannot pass through the graphene 122. FIG. 9 is a cross-sectional view of the copper foil after heating. FIG. 10 is a diagram showing an example of forming a metal chalcogenide film by the CVD method. FIG. 11 is a diagram showing an example of formation of a metal chalcogenide film by a thermal sulfurization method. FIG. 12 is a process cross-sectional view showing an example of the process of transferring graphene 22 to the S film 20. FIG. 13 is a process cross-sectional view showing an example of the process of transferring graphene 22 to the S film 20. FIG. 14 is a diagram illustrating an example of the manufacturing method according to the second embodiment. FIG. 15 is a process cross-sectional view of the manufacturing method shown in FIG. 14. FIG. 16 is a process cross-sectional view of the manufacturing method shown in FIG. 14.

Embodiments of the present invention will be described below with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof. Even if the drawings are different, parts having the same structure will be designated by the same reference numerals, and their explanation will be omitted.

(Embodiment 1)
Embodiment 1 relates to a method for producing a chalcogenide-based layered material (ie, metal chalcogenide). FIG. 1 is a diagram showing an example of the manufacturing method according to the first embodiment. 2 to 4 are process cross-sectional views of the manufacturing method shown in FIG. 1.

The manufacturing method illustrated in FIGS. 1 to 4 is a method for manufacturing molybdenum disulfide (ie, MoS ₂ ). However, the manufacturing method illustrated in FIGS. 1 to 4 can also be applied to manufacturing other chalcogenide-based layered materials (eg, WSe ₂ and WTe ₂ ) by appropriately changing the precursors and the like.

(1) Manufacturing method (1-1) Formation of metal chalcogenide film (first step S1 shown in FIG. 1)
First, a MoS ₂ film 18 is deposited on a substrate 16 (see FIG. 2(a)) by CVD.

The substrate 16 is, for example, a silicon substrate with a thermal oxide film. The number of layers of the MoS ₂ film 18 to be deposited is, for example, from a single layer to several layers. The number of layers of the MoS ₂ film 18 may be more than a single layer to several layers.

Details of the CVD method are described in "(5) Method for forming metal chalcogenide film" below. In the following explanation, forming a film by the CVD method will be referred to as CVD.

A compound word containing a word representing material X and "membrane" in this order (eg, MoS ₂ film) means a film having material "Membrane" means a thin substance that covers the surface of something. Therefore, the above compound word means a thin object that has substance X and covers the surface of something. Therefore, the MoS ₂ film 18 (see FIG. 2(a)) is a thin film (here, an atomic layer) containing MoS ₂ and covering the surface of the substrate 16.

FIG. 5 is an example of a side view of a single layer MoS ₂ (ie, one layer of MoS ₂ ) deposited by CVD. FIG. 6 is a plan view of this single layer MoS ₂ .

As illustrated in _FIG . and a plurality of Mo atoms 8 arranged on top. The monolayer MoS ₂ further has a plurality of S atoms 12 arranged on the third surface 10 located above the second surface 6.

When viewed from directly above, the single-layer MoS ₂ has two types of atoms located alternately at the vertices of a regular hexagon (not shown) arranged without gaps, as shown in FIG. These two types of atoms are Mo atoms 8 and S atoms 12. Mo is a metal element. S is a chalcogen element.

Chalcogen (eg, sulfur S) is an element with a higher vapor pressure than metals (eg, Mo). During CVD, the deposited film is exposed to high temperatures. Therefore, the MoS ₂ film synthesized by CVD has a large deficiency (that is, a shortage) of S atoms. In such a MoS ₂ film, there are many vacancies 14 of S atoms.

Even if a MoS ₂ film is formed by a method other than the CVD method, defects in S atoms occur. The same applies to metal chalcogenide films other than the MoS ₂ film. Additionally, metal chalcogenide crystals produced in nature also have chalcogen atom defects.

Note that chalcogen that can be a constituent element of metal chalcogenide is sulfur (S), selenium (Se), or tellurium (Te). Therefore, unless otherwise specified, "chalcogen" means any one of sulfur (S), selenium (Se), and tellurium (Te).

(1-2) Formation of chalcogen film (second step S2 shown in FIG. 1)
Next, a sulfur film 20 (hereinafter referred to as an S film) is formed on the MoS ₂ film 18 (see FIG. 2(b)) formed in the first step S1. The S film 20 is formed, for example, by vacuum deposition. The thickness of the S film 20 to be formed is, for example, 1 nm to 1000 nm. The S film 20 is preferably made of simple sulfur.

(1-3) Covering the chalcogen film with graphene (third step S3 shown in Figure 1)
Graphene 22 is placed on the S film 20 (see FIG. 2(c)) formed in the second step S2. As a result, the S film 20 is covered with graphene 22. Graphene 22 may be either a single layer or a multilayer.

Specifically, first, graphene 22 is formed on a substrate different from substrate 16. Thereafter, this graphene 22 is transferred to the S film 20. The graphene transfer method is shown in "(6) Graphene transfer method".

(1-4) Heating the metal chalcogenide film and chalcogen film (fourth step S4 shown in FIG. 1)
After the third step S3, the S film 20 and the MoS ₂ film 18 covered with the graphene 22 are heated (see FIG. 3(a)).

The S atoms in the S film, which have obtained thermal energy through this heating, move to the MoS ₂ film 18 and combine with the Mo atoms 108 surrounding the S atom vacancies 14 (see FIG. 6). In other words, the atomic vacancies in the MoS ₂ film 18 are compensated for by the S atoms in the S film 20.

At this time, since the graphene 22 formed in the third step S3 suppresses the diffusion of S atoms into the atmosphere, the atomic defects present in the MoS ₂ film 18 formed in the first step S1 are removed from the S film 20. It is effectively compensated by S atoms (see "(2) Comparative Example"). Note that the above-mentioned "atmosphere" means the gas surrounding the substrate 16.

Specifically, the fourth step is a step of heating the substrate 16 on which the MoS ₂ film 18, the S film 20, and the graphene 22 are laminated in this order in an inert atmosphere maintained at atmospheric pressure, for example. (See Figure 3(a)). The substrate 16 is heated, for example, by an electric furnace (not shown) having a heater 24. The heating temperature is, for example, 200°C to 1000°C. The heating time is, for example, 1 minute to 24 hours.

(1-5) Removal of graphene (fifth step S5 shown in Figure 1)
After the fourth step S4, the graphene 22 is removed by, for example, oxygen plasma treatment (see FIG. 3(b)). The time for performing this plasma treatment is the time for all graphene 22 to be removed. The time for performing the plasma treatment is, for example, 10 seconds to 60 minutes.

(1-6) Removal of chalcogen film (sixth step S6 shown in Figure 1)
After the fifth step S5, the S film 20 (see FIG. 3(b)) is removed in the evacuated space 26 (see FIG. 4(a)).

Specifically, the substrate 16 with the S film 20 (see FIG. 3(b)) exposed is heated inside the vacuum apparatus (that is, the evacuated space 26). The substrate 16 is heated, for example, by a heater 124 provided inside the vacuum device.

Then, S (that is, sulfur) having a high vapor pressure evaporates, and the MoS ₂ film 18 is exposed (see FIG. 4(a)). The heating temperature is, for example, 100°C to 600°C. The heating time is, for example, 10 seconds to 60 minutes.

As will be described later, it is possible to compensate for chalcogen atom deficiencies in the MoS ₂ film 18 by using a chalcogen film different from the S film (see "(4) Variations of chalcogen film"). If a separate chalcogen film is used, the substrate 16 is heated at a temperature suitable for evaporation of the separate chalcogen film.

(1-7) Covering the metal chalcogenide film with an insulating film (seventh step S7 shown in FIG. 1)
After the sixth step S6, an insulating film 28 (see FIG. 4(b)) is formed on the MoS ₂ film 18 in the evacuated space 26. As a result, the MoS ₂ film 18 is covered with the insulating film 28. The space 26 continues to be evacuated from the beginning of the sixth step S6 in which the S film 20 is removed to the end of the seventh step S7 in which the MoS ₂ film 18 is covered with the insulating film 28.

Specifically, the insulating film 28 is deposited on the MoS ₂ film 18 inside the evacuated vacuum device (ie, the evacuated space 26). Finally, the atmosphere is introduced into the vacuum apparatus, and then the substrate 16 on which the insulating film 28 is deposited is taken out from the vacuum apparatus.

The insulating film 28 is, for example, a SiO ₂ film. The insulating film 28 may be another insulator (for example, an Al ₂ O ₃ film or a HfO ₂ film). The thickness of the insulating film 28 is, for example, 0.5 nm to 100 nm.

Since the sixth and seventh steps are vacuum integrated processes, the MoS ₂ film 18 whose atomic vacancies have been compensated for in the fourth step S4 can be covered with the insulating film 28 without being exposed to the atmosphere. Therefore, according to the sixth and seventh steps, deterioration (for example, oxidation) of the MoS ₂ film 18 due to the atmosphere can be suppressed.

The fifth to seventh steps may be omitted. Even if the fifth to seventh steps are omitted, the first to fourth steps are executed, so the atomic vacancies in the MoS ₂ film 18 formed in the first step S1 are replaced by chalcogen atoms replenished from the chalcogen film. effectively compensated.

(2) Comparative Example In the example described with reference to FIGS. 1 to 4, the MoS ₂ film 18 (see FIG. 3(a)), the S film 20, and the graphene 22 are layered in this order on the substrate 16. By heating, deficiencies in S atoms present in the MoS ₂ film 18 are compensated for.

However, it is also possible to compensate for the deficiency of S atoms by other methods. FIG. 7 is a diagram showing an example of another method (hereinafter referred to as a comparative example) for compensating for the deficiency of S atoms. In this comparative example, the substrate 16 on which the MoS ₂ film 18 is formed is sealed together with solid sulfur 120 in one container 30 (for example, a quartz ampoule). Next, the MoS ₂ film 18 and the sulfur 120 are heated together with the container 30 using, for example, a heater 224.

Then, sulfur vapor (hereinafter referred to as S vapor) is generated from the heated sulfur 120. When this S vapor comes into contact with the MoS ₂ film 18, the S atoms in the S vapor combine with the Mo atoms surrounding the vacancies 14 (that is, the vacancies of S atoms) in the MoS ₂ film 18. In other words, atomic vacancies in the MoS ₂ film 18 are compensated for by S atoms from the S vapor.

On the other hand, some of the S atoms in the MoS ₂ film escape from the MoS ₂ film 18 and diffuse into the atmosphere. As a result, new defects of S atoms occur in the MoS ₂ film 18. Therefore, in the comparative example shown in FIG. 7, it is difficult to sufficiently reduce the defects of S atoms as a whole. The same situation applies to metal chalcogenide films other than MoS ₂ films.

On the other hand, according to the example described with reference to FIGS. 1 to 4, the amount of S atoms diffused into the atmosphere from the heated MoS ₂ film 18 (see FIG. 3(a)) can be reduced compared to the comparative example. This is because the S atoms hardly pass through the graphene 22, so that the diffusion of the S atoms into the atmosphere surrounding the MoS ₂ film 18 is suppressed.

FIG. 8 is a diagram illustrating the reason why S atoms 112 hardly pass through graphene 122. Graphene is a single layer with multiple carbon atoms regularly arranged on one surface.

The interatomic distance d of carbon atoms in graphene is 0.142 nm. This distance is approximately the same as the radius R (=0.105 nm) of the S atom 112. Therefore, as shown in FIG. 8, the S atoms 112 hardly pass through the graphene 122. This is even more true for sulfur molecules larger than 112 S atoms. The situation is the same for other chalcogens (namely Se and Te).

The inventor confirmed through the following experiment that even oxygen, whose atomic radius is smaller than chalcogen, hardly passes through graphene. First, graphene was formed to partially cover the copper foil using the CVD method. Thereafter, this copper foil was heated in the air and the surface was observed. The heating temperature is 200°C.

FIG. 9 is a cross-sectional view of the copper foil 32 after heating. The portion of this copper foil 32 covered with graphene 122 had the same copper color as before heating. On the other hand, a portion 34 not covered with graphene 122 (hereinafter referred to as an exposed portion) was discolored.

These facts indicate that the exposed portion 34 was oxidized, but the portion covered with graphene 122 was not. This shows that oxygen can hardly pass through the graphene 122.

Hexagonal boron nitride is a layered material with approximately the same interatomic distance as graphene. Therefore, instead of the graphene 22 (see FIG. 3(a)), the S film 20 may be covered with a single layer to several layers of hexagonal boron nitride.

By the way, in the example described with reference to FIGS. 1 to 4, the atomic vacancies in the MoS ₂ film 18 are compensated for by the S atoms of the S film 20 (see FIG. 3(a)). The amount of sulfur contained in the S film 20 is extremely small compared to the amount of sulfur 120 (see FIG. 7) used in the comparative example. Therefore, according to the examples described with reference to FIGS. 1 to 4, the deficiency of S atoms can be compensated for with a much smaller amount of sulfur than in the comparative example.

Similarly, when chalcogen atoms are compensated for by a chalcogen film other than the S film (see "(4) Chalcogen film variations"), the atomic deficiencies can be compensated for by a small amount of chalcogen.

(3) Variation of metal chalcogenide film In the manufacturing method illustrated in FIGS. 1 to 4, the MoS ₂ film 18 is formed in the first step S1 (see FIG. 1). However, in the first step S1, a metal chalcogenide film other than the MoS ₂ film 18 may be formed. The metal chalcogenide film formed in the first step S1 may be either a single layer or a multilayer.

For example, the metal chalcogenide film formed in the first step S1 may be a metal chalcogenide film having any one of a transition metal dichalcogenide, a group 13 chalcogenide, a group 14 chalcogenide, and a bismuth chalcogenide.

Transition metal dichalcogenide means a compound of a transition metal (ie, Mo, Nb, W, Ta, Ti, Zr, Hf, V, etc.) and a chalcogen (ie, S, Se, Te). Group 13 chalcogenide means a compound of a Group 13 element (ie, Ga, In, Tl) and chalcogen. Group 14 chalcogenide means a compound of a Group 14 element (ie, Ge, Sn, Pb) and chalcogen. Bismuth chalcogenide means a compound of bismuth and chalcogen.

(4) Variation of Chalcogen Film In the manufacturing method illustrated in FIGS. 1 to 4, the S film 20 (see FIG. 2(b)) is formed in the second step S2 (see FIG. 1). However, in the second step S2, a chalcogen film other than the S film may be formed. The main chalcogen films that can be formed in the second step S2 can be classified into the first to third types described below.

-The first type of chalcogen film-
By the way, a metal chalcogenide film is an object that includes metal chalcogenide and covers the surface of a certain object (for example, a substrate). In the following description, chalcogen (eg, S) among the constituent elements (eg, Mo and S) of the above-mentioned "metal chalcogenide" (eg, MoS ₂ ) will be referred to as a chalcogen constituent element.

The first type of chalcogen film is a simple substance of the chalcogen constituent element that the metal chalcogenide film formed in the first step S1 has. In the manufacturing method illustrated in FIGS. 1 to 4, a MoS ₂ film is formed in the first step S1. Therefore, the first type of chalcogen film in the manufacturing method illustrated in FIGS. 1 to 4 is composed of S alone.

When WSe ₂ is formed in the first step S1, the first type of chalcogen film is Se alone. When WTe ₂ is formed in the first step S1, the first type of chalcogen film is a simple substance of Te.

The first type of chalcogen film compensates for atomic vacancies in the metal chalcogenide film by chalcogen constituent elements of the metal chalcogenide film. Therefore, according to the first type of chalcogen film, atomic vacancies in the metal chalcogenide film can be compensated for without increasing the impurity concentration.

-Second type of chalcogen membrane-
The second type of chalcogen film is a simple substance of another chalcogen (e.g., Se) different from the chalcogen constituent element (e.g., S) contained in the metal chalcogenide film (e.g., MoS ₂ film 18) formed in the first step S1. be.

In the manufacturing method illustrated in FIGS. 1 to 4, a MoS ₂ film is formed in the first step S1. Therefore, the second type of chalcogen film is a simple substance of Se or a simple substance of Te.

The second type of chalcogen film not only makes it possible to compensate for atomic vacancies in a metal chalcogenide film (for example, MoS ₂ film), but also makes it possible to dope the metal chalcogenide film. The dopant in this case is "another chalcogen" (eg, Se) different from the chalcogen constituent element (eg, S) of the metal chalcogenide film.

-Third type of chalcogen film-
The third type of chalcogen film is a mixture containing both a simple substance of the chalcogen constituent element included in the metal chalcogenide film formed in the first step S1 and a simple substance of "another chalcogen" different from this chalcogen constituent element.

In the manufacturing method illustrated in FIGS. 1 to 4, a MoS ₂ film is formed in the first step S1. Therefore, the third type of chalcogen film is, for example, a mixture of a simple substance of S and a simple substance of Se.

The third type of chalcogen film can not only compensate for atomic defects in a metal chalcogenide film (eg, MoS ₂ film), but also allow doping into this metal chalcogenide film (eg, MoS ₂ film). Again, the dopant is the above-mentioned "another chalcogen" (eg, Se).

Furthermore, by controlling the proportion of "another chalcogen" mixed in the third type chalcogen film, the density of the dopant introduced into the metal chalcogenide can be controlled.

The first to third types of chalcogen films contain up to two types of chalcogen, but the chalcogen film formed in the second step is a substance containing all three types of chalcogen (i.e., S, Se, Te). It's okay to have one.

(5) Method for Forming Metal Chalcogenide Film In the first step S1 (see FIG. 1) of the manufacturing method illustrated in FIGS. 1 to 4, a metal chalcogenide film is formed using the CVD method. However, in the first step S1, the metal chalcogenide film may be formed by a method other than the CVD method (for example, a thermal sulfurization method). Here, the CVD method and the thermal sulfurization method will be explained.

(5-1) CVD method FIG. 10 is a diagram showing an example of forming a metal chalcogenide film by the CVD method. In the example shown in FIG. 10, a MoS ₂ film is formed. The CVD method shown in FIG. 10 is performed under atmospheric pressure.

First, a substrate 16, MoO ₃ 40 (molybdenum trioxide), and S42 (e.g., sulfur powder) are placed in this order inside a reaction tube 38 having three zones surrounded by separate heaters 36a, 36b, 36c. Deploy. The substrate 16 is placed in a first zone surrounded by the first heater 36a. MoO ₃ 40 is placed in a second zone surrounded by the second heater 36b. S42 is arranged in the third zone surrounded by the third heater 36c. Note that FIG. 10 shows the MoS ₂ film 18 being formed.

The weight of MoO ₃ 40 placed in the second zone is, for example, 1 mg to 100 mg. The weight of S42 placed in the third zone is, for example, 10 mg to 1000 mg.

In this state, Ar gas 44 is introduced into the reaction tube 38 from one end closest to S42 among both ends of the reaction tube 38. The flow rate of Ar gas is, for example, 100 sccm to 1000 sccm. Ar gas 44 is a carrier gas.

Next, the substrate 16 is heated to 500° C. to 1000° C. by the first heater 36a. Further, the MoO ₃ 40 is heated to 300° C. to 600° C. by the second heater 36b. Furthermore, S42 is heated to 100° C. to 200° C. by the third heater 36c. Then, MoO ₃ vapor is generated from MoO ₃ 40, and S vapor is generated from S42.

This MoO ₃ vapor and S vapor react in the gas phase, and a MoS ₂ film 18 is deposited on the substrate 16 . That is, a MoS ₂ film 18 is formed on the substrate 16 .

The CVD method described with reference to FIG. 10 is an example, and various modifications are possible. For example, in the example shown in FIG. 10, the carrier gas is Ar gas 44. However, the carrier gas may be an inert gas other than Ar gas 44. These carrier gases may also contain hydrogen.

In the example shown in FIG. 10, the metal chalcogenide film (eg, MoS ₂ film 18) is formed under atmospheric pressure. However, the metal chalcogenide film may also be formed under reduced pressure (eg, in a vacuum).

The precursor of the metal chalcogenide film (for example, MoS ₂ film) may be either a single substance or a compound. The above-mentioned "compound" may be any of oxides, chlorides, fluorides, hydrides, and organic compounds. However, the above-mentioned "single substance" and the above-mentioned "compound" are substances containing constituent elements of the metal chalcogenide film.

In the example shown in FIG. 10, the precursors are multiple substances. However, the precursor of the metal chalcogenide film may be a single substance containing all the constituent elements of the metal chalcogenide film.

MoS ₃ is an example of such a precursor. When MoS ₃ is heated in an inert gas containing H ₂ S, MoS ₃ changes to MoS ₂ and is deposited on the substrate. When MoS ₄ , Mo ₂ S ₃ , Mo ₂ S ₅ , and Mo ₃ S ₄ are also heated in an inert gas containing H ₂ S, they change to MoS ₂ and precipitate on the substrate. These compounds are also single precursors containing all the constituent elements of the metal chalcogenide film.

The form of the precursor may be solid, liquid, or gas. The solid precursor may be either crystalline or amorphous. When the precursor is solid or liquid, the precursor is vaporized by heat treatment or the like. The vaporized precursor transports the constituent elements of the metal chalcogenide film to the substrate. The amount of evaporation of the precursor depends on the heating temperature of the precursor, the pressure of the atmosphere, the amount of the precursor loaded into the reaction tube, and the vapor pressure of the precursor.

These parameters regarding the precursor (i.e., heating temperature, etc.) are set so that the thickness and area of the metal chalcogenide film formed on the substrate (e.g., the substrate 16 shown in FIG. 10) reach respective target values. Ru. Further, the heating temperature of the substrate on which the metal chalcogenide film is formed is also set so that the thickness, area, and quality of the metal chalcogenide film formed on the substrate reach their respective target values.

A variety of substrates can be used as substrate 16 for forming the metal chalcogenide film. For example, a silicon substrate with a thermal oxide film, a sapphire substrate, a magnesium oxide substrate, etc. can be used.

The arrangement of the substrate and the precursor in the container for synthesizing the metal chalcogenide film (for example, the reaction tube 38 shown in FIG. 10) is not limited to the example shown in FIG. Appropriate arrangement of the substrate etc. varies depending on the synthesis conditions of the metal chalcogenide film, the structure of the reactor, etc.

According to a reactor in which the temperatures of a plurality of zones are controlled separately (hereinafter referred to as a multi-temperature reactor), two precursors can be heated to different temperatures. The apparatus shown in FIG. 10 (ie, the apparatus having a reaction tube 38 and three heaters 36a, 36b, 36c) is an example of such a reactor.

According to the multi-temperature reactor, since the heating temperature of each of the plurality of precursors can be controlled separately, the amount of evaporation of each of the plurality of precursors can be independently controlled. Therefore, according to the multi-temperature reactor, the stoichiometric composition ratio of the metal chalcogenide film formed on the substrate can be controlled.

(5-2) Thermal sulfurization method FIG. 11 is a diagram showing an example of formation of a metal chalcogenide film by the thermal sulfurization method. In the example shown in FIG. 11, a MoS ₂ film is formed. The thermal sulfurization method shown in FIG. 11 is performed under atmospheric pressure.

First, a substrate 116 whose surface is covered with a Mo film 46 (preferably a pure molybdenum film) and an S142 ( For example, sulfur powder) are placed in this order. The substrate 116 is placed in a first zone surrounded by the first heater 36a. S142 is arranged in the third zone surrounded by the third heater 36c. Note that FIG. 11 shows the MoS ₂ film 118 being formed.

The thickness of the Mo film 46 covering the surface of the substrate 116 is, for example, 0.5 nm to 1000 nm. The weight of S142 placed in the third zone is, for example, 1 mg to 1000 mg.

In this state, Ar gas 44 is introduced into the reaction tube 38 from one end of the reaction tube 38 that is closest to S142. The flow rate of Ar gas is, for example, 10 sccm to 1000 sccm.

Next, the substrate 116 is heated to 500° C. to 1000° C. by the first heater 36a. Further, S142 is heated to 100° C. to 300° C. by the third heater 36c. Then, S vapor is generated from S142. This S vapor reacts with the Mo film 46 covering the substrate 116, and a MoS ₂ film 118 is deposited on the substrate 116. That is, a MoS ₂ film 118 is formed on the substrate 116. The time for heating the substrate 116 and S142 is, for example, 1 second to 10 hours. This time is set so that the thickness and area of the MoS ₂ film 118 formed on the substrate 116 reach their respective target values.

The Mo film 46 covering the surface of the substrate 116 may be a compound of Mo (eg, MoO ₃ , MoCl ₅ , etc.) instead of Mo alone. The Mo film 46 is deposited on the substrate 116 by, for example, a vacuum evaporation method or a sputtering method. The substrate temperature when depositing the Mo film 46 is, for example, room temperature to 500°C. The target value of the film thickness of the Mo film 46 is a film thickness at which a metal chalcogenide film of a desired thickness is formed on the substrate 116.

The thermal sulfurization method described with reference to FIG. 11 is an example, and various modifications are possible. For example, in the example shown in FIG. 11, the formation of the metal chalcogenide film (eg, MoS ₂ film 118) is performed under atmospheric pressure. However, the formation of metal chalcogenides may also be carried out under reduced pressure or under increased pressure.

In the example described with reference to FIG. 11, the source of chalcogen is a solid (eg, sulfur powder). However, the source of chalcogen does not have to be solid. For example, the source of chalcogen may be a gas (eg, hydrogen sulfide).

If the source of chalcogen is a solid, the chalcogen is transported to the substrate 116 by evaporating the solid. The amount of chalcogen that evaporates from the source depends on the heating temperature of the source, the pressure of the atmosphere, the amount of source loaded into the reactor, and the vapor pressure of the source.

Therefore, these parameters regarding the source are such that the thickness and area of the metal chalcogenide film (e.g., MoS ₂ film 118) formed on the substrate (e.g., the substrate 116 shown in FIG. 11) reaches the respective target values. It is set as follows. Similarly, the heating temperature of the substrate is also set so that the thickness, area, and quality of the metal chalcogenide film formed on the substrate reach their respective target values.

A variety of substrates can be used as the substrate 116 on which the metal chalcogenide film is formed. For example, a silicon substrate with a thermal oxide film, a sapphire substrate, a magnesium oxide substrate, etc. can be used.

The arrangement of the substrate 116 and the chalcogen supply source (for example, S142) in the container (for example, reaction tube 38) for synthesizing a metal chalcogenide film is not limited to the example shown in FIG. 11. The optimum arrangement of the substrate etc. is determined by the synthesis conditions of the metal chalcogenide film (for example, the MoS ₂ film 118), the structure of the reactor, etc.

(6) Graphene transfer method Graphene transfer means transferring graphene formed on a catalyst by, for example, a CVD method onto a substrate different from the catalyst. 12 and 13 are process cross-sectional views showing an example of the process of transferring graphene 22 to the S film 20 (see FIG. 2(c)). When graphene 22 is transferred to S film 20 by the method shown in FIGS. 12 and 13, a high coverage rate (for example, 99%) can be achieved.

First, a substrate 48 on which a catalyst 50 (see FIG. 12(a)) and graphene 22 are stacked in this order is prepared. Instead of such a substrate 48, a free-standing catalyst foil on which graphene is formed may be prepared. The catalyst 50 is, for example, one of Fe, Ni, and Cu. Graphene 22 is an atomic film formed on catalyst 50 by, for example, CVD.

Next, a support film 52 (see FIG. 12(b)) having a thickness of 0.1 μm to 100 μm, for example, is formed on the graphene 22. Specifically, first, a resist is applied onto the graphene 22 by spin coating or the like. A polymer may be applied instead of a resist. The applied resist (or polymer) is then heated. The heating temperature is, for example, room temperature to 200°C.

Then, the applied resist (or polymer) solidifies and becomes the support film 52. The support film 52 may be formed by a method other than the above (eg, vacuum deposition).

Next, the graphene 22 supported by the support film 52 is peeled off from the catalyst 50 (see FIG. 12(c)). Specifically, the substrate 48 on which the catalyst 50, graphene 22, and support film 52 are stacked in this order is immersed in an etching solution for the catalyst 50. Then, the catalyst 50 is removed by side etching. The etching solution is, for example, an aqueous solution of iron(III) chloride (ie, FeCl ₃ ).

Through the processing up to this point, graphene 22 supported by the support film 52 (hereinafter referred to as graphene with support film 222) is formed. Thereafter, the etching solution adhering to the supporting film-attached graphene 222 is removed by washing with water.

Next, the graphene 222 with a supporting film and the S film 20 are overlapped so that the graphene 222 with a supporting film and the S film 20 are in contact with each other (see FIG. 13(a)). In this state, the substrate 16 is heated to bring the support film-attached graphene 222 and the S film 20 into close contact (that is, to make them tightly adhere). The heating temperature is, for example, room temperature to 300°C.

Finally, the support film 52 is removed by dissolving it with, for example, an organic solvent (for example, acetone) (see FIG. 13(b)). Through the above steps, the transfer of the graphene 22 to the S film 20 is completed.

In the manufacturing method according to the first embodiment, a metal chalcogenide film (e.g., MoS ₂ film 18) having a compound (e.g., MoS ₂ ) of metal (e.g., Mo) and chalcogen (e.g., S) is formed on a substrate. The method includes a first step S1 (see FIG. 2(a)).

The manufacturing method according to the first embodiment further includes a second step S2 (see FIG. 2(b)) of forming a chalcogen film (eg, S film 20) on the metal chalcogenide film. Such a chalcogen film has at least one of another chalcogen (eg, Se or Te) different from the above chalcogen (eg, S) and the above chalcogen (eg, S).

The manufacturing method according to the first embodiment further includes a third step S3 (see FIG. 2(c)) of disposing graphene 22 or hexagonal boron nitride on the chalcogen film (for example, S film 20).

The manufacturing method according to the first embodiment further includes, after the third step S3, a fourth step S4 of heating the chalcogen film (for example, the S film 20) and the metal chalcogenide film (for example, the MoS ₂ film 18). (see FIG. 3(a)). The above-mentioned "chalcogen" is sulfur, selenium, or tellurium. Furthermore, the above-mentioned "another chalcogen" is also one of sulfur, selenium, and tellurium.

In the fourth step S4, deficiencies in chalcogen atoms (eg, S atoms) in the metal chalcogenide film (eg, MoS ₂ film 18) are compensated for. On the other hand, some of the chalcogen atoms in the metal chalcogenide film escape from the metal chalcogenide film and diffuse into the atmosphere.

When chalcogen atoms escape from the metal chalcogenide film, vacancies of chalcogen atoms are left behind. That is, new atomic defects are generated in the metal chalcogenide film.

However, since chalcogen atoms hardly pass through the graphene (or hexagonal boron nitride) on the chalcogen film, almost no new atomic defects are generated in the metal chalcogenide film. Therefore, according to the first embodiment, a metal chalcogenide film (that is, a chalcogenide-based layered material) with few atomic defects can be manufactured.

The manufacturing method of Embodiment 1 preferably further includes fifth to seventh steps. The fifth step S5 is a step of removing graphene 22 (or hexagonal boron nitride) after the fourth step S4. The sixth step S6 is a step of removing the chalcogen film (for example, the S film 20) in the evacuated space 26 (for example, inside the vacuum device) after the fifth step S5. The seventh step S7 is a step of forming an insulating film 28 on the metal chalcogenide film (for example, the MoS ₂ film 18) in the space 26 evacuated after the sixth step S6. However, the space 26 continues to be exhausted from the beginning of the sixth step S6 to the end of the seventh step S7.

According to the fifth to seventh steps, the metal chalcogenide film (for example, the MoS ₂ film 18) whose atomic vacancies have been compensated for in the first to fourth steps can be covered with the insulating film 28 without being exposed to the atmosphere. Therefore, according to the fifth to seventh steps, the metal chalcogenide film (for example, the MoS ₂ film 18) whose atomic vacancies have been compensated for in the first to fourth steps is prevented from being degraded (for example, oxidized) by the atmosphere. can.

(Embodiment 2)
Embodiment 2 relates to a method of manufacturing a semiconductor device having a metal chalcogenide film and a plurality of electrodes. FIG. 14 is a diagram illustrating an example of the manufacturing method according to the second embodiment. 15 and 16 are process cross-sectional views of the manufacturing method shown in FIG. 14.

In an example shown in FIGS. 14 to 16, a semiconductor device having a MoS ₂ film and a plurality of electrodes is manufactured. However, the examples shown in FIGS. 14 to 16 may be applied to semiconductor devices having metal chalcogenide films other than MoS ₂ films.

(1) Formation of metal chalcogenide film ~ Covering the metal chalcogenide film with an insulating film (first step S1 to seventh step S7 shown in FIG. 1 or 14)
First, in accordance with the first to seventh steps (see FIGS. 1 to 4) described in Embodiment 1, a MoS ₂ film 18 (see FIG. 4(b)) in which atomic vacancies have been compensated and a coating film ₁₈ is formed. An insulating film 28 is formed on the substrate 16.

(2) Electrode formation step (eighth step S8 shown in FIG. 14)
After the seventh step S7, the plurality of electrodes are formed.

Specifically, first, the atmosphere is introduced into the space 26 (see FIG. 4(b)) in which the substrate 16 is placed, and the substrate 16 is taken out from this space 26. Thereafter, a band-shaped photoresist film 54 is formed on the insulating film 28 (see FIG. 15(a)) using a lithography technique. FIG. 15 is a cross-sectional view across this photoresist film 54.

The insulating film 28 and the MoS ₂ film 18 are etched through the photoresist film 54. This etching is performed, for example, by dry etching. By this etching, the insulating film 28 is formed into a band-shaped insulating film 128 (see FIG. 15(b)), and the MoS ₂ film 18 is further formed into a band-shaped MoS ₂ film 218.

Next, a photoresist film 154 is formed which has a first opening 56a (see FIG. 15(c)) that exposes the center of the strip-shaped insulating film 128, and second and third openings 56b and 56c that are in contact with the side surfaces of the insulating film 128. is formed by lithography technology.

A metal film 58 (see FIG. 16(a)) is deposited on the substrate 16 via this photoresist film 154. The deposition of the metal film 58 is controlled so that the metal film 58 is not excessively thicker than the strip-shaped MoS ₂ film 218. The thickness of the metal film 58 is, for example, 10 nm to 100 nm. The metal film 58 is, for example, a Ti/Au film or a Pd film.

After forming the metal film 58, the photoresist film 154 is removed. Then, the portion of the metal film 58 that covers the photoresist film 154 is removed. As a result, the top gate electrode TG is formed on the strip-shaped insulating film 128 (see FIG. 16(b)). Further, a source electrode S in contact with one side surface of the strip-shaped MoS ₂ film 218 and a drain electrode D in contact with the other side surface of the strip-shaped MoS ₂ film 218 are formed. That is, a top gate electrode TG, a source electrode S, and a drain electrode D are formed by lift-off.

Through the above steps, a top gate transistor 62 having an active layer 60 having the MoS ₂ film 218, a top gate electrode TG, a source electrode S, and a drain electrode D is completed.

The manufacturing method illustrated in FIGS. 14 to 16 is a method for manufacturing a top-gate transistor. However, the manufacturing method illustrated in FIGS. 14 to 16 can also be applied to manufacturing semiconductor elements other than top-gate transistors (eg, thermoelectric conversion elements) by changing the electrodes formed in the eighth step S8, for example.

As described above, in the manufacturing method according to the second embodiment, a plurality of electrodes (for example, top gate electrode TG, source electrode S, and an electrode forming step of forming a drain electrode D).

The manufacturing method according to the second embodiment includes the first to fourth steps described in the first embodiment. Therefore, according to the manufacturing method according to the second embodiment, it is possible to manufacture a semiconductor device having an active layer 60 with fewer chalcogen atoms. The active layer 60 is a metal chalcogenide film with atomic vacancies compensated for.

Like the manufacturing method according to Embodiment 1, the manufacturing method according to the second embodiment preferably includes the fifth to seventh steps. Further, one of the plurality of electrodes (for example, top gate electrode TG) is formed on the insulating film 128.

According to the fifth to seventh steps, deterioration of the active layer 60 due to the atmosphere can be suppressed (see Embodiment 1). However, the fifth to seventh steps may be omitted as in the first embodiment.

Although the embodiments of the present invention have been described above, the first and second embodiments are illustrative and not restrictive. For example, the third step S3 illustrated in Embodiments 1 and 2 is a step of transferring graphene (or hexagonal boron nitride) to a chalcogenide film. However, the third step may be a step of growing graphene (or hexagonal boron nitride) directly on the chalcogenide film.

Furthermore, the metal chalcogenide films (eg, MoS ₂ films) exemplified in Embodiments 1 and 2 do not contain any substance different from metal chalcogenide. However, the metal chalcogenide film in Embodiments 1 and 2 may contain a substance different from metal chalcogenide.

For example, the metal chalcogenide film in Embodiments 1 and 2 may be a composite film containing a metal (eg, Mo) and a metal chalcogenide (eg, MoS ₂ ) in this order. Such a composite film may be formed, for example, when forming a metal chalcogenide film by a thermal sulfurization method.

When forming a metal chalcogenide film by a thermal sulfurization method, if the metal film (for example, Mo film 46) formed on the substrate 116 (see FIG. 11) is too thick, unreacted parts may form between the metal chalcogenide and the substrate 116. of metal (eg, Mo) is left behind. As a result, a metal chalcogenide film including metal chalcogenide (eg, MoS ₂ ) and metal in this order is formed on the substrate 116.

Regarding the first and second embodiments described above, the following additional notes are further disclosed.

(Additional note 1)
A first step of forming a metal chalcogenide film having a compound of metal and chalcogen on the substrate;
a second step of forming a chalcogen film having at least one of the chalcogen and another chalcogen different from the chalcogen on the metal chalcogenide film;
a third step of arranging graphene or hexagonal boron nitride on the chalcogen film;
A method for manufacturing a chalcogenide-based layered material, comprising a fourth step of heating the chalcogen film and the metal chalcogenide film after the third step.

(Additional note 2)
The method for producing a chalcogenide-based layered material according to Supplementary Note 1, wherein the chalcogen and the other chalcogen are each one of sulfur, selenium, and tellurium.

(Additional note 3)
The method for producing a chalcogenide-based layered material according to Supplementary Note 1, wherein the chalcogen film is a simple substance of the chalcogen.

(Additional note 4)
The method for producing a chalcogenide-based layered material according to Supplementary Note 1, wherein the chalcogen film is a simple substance of the other chalcogen.

(Appendix 5)
The method for producing a chalcogenide-based layered material according to Supplementary Note 1, wherein the chalcogen film contains both the simple substance of the chalcogen and the simple substance of the other chalcogen.

(Appendix 6)
a fifth step of removing the graphene or the hexagonal boron nitride after the fourth step;
a sixth step of removing the chalcogen film in the evacuated space after the fifth step;
After the sixth step, further comprising a seventh step of forming an insulating film on the metal chalcogenide film in the space,
The method for producing a chalcogenide-based layered material according to any one of Supplementary Notes 1 to 5, wherein the space is continuously evacuated from the beginning of the sixth step to the end of the seventh step.

(Appendix 7)
The method for producing a chalcogenide-based layered material according to appendix 6, wherein the sixth step is a step of heating the chalcogen film in the space.

(Appendix 8)
The method for producing a chalcogenide-based layered material according to any one of Supplementary Notes 1 to 7, wherein the third step is a step of transferring the graphene or the hexagonal boron nitride to the chalcogen film.

(Appendix 9)
A method for manufacturing a semiconductor device having a metal chalcogenide film having a compound of metal and chalcogen, and a plurality of electrodes, the method comprising:
a first step of forming the metal chalcogenide film on a substrate;
a second step of forming a chalcogen film having at least one of the chalcogen and another chalcogen different from the chalcogen on the metal chalcogenide film;
a third step of arranging graphene or hexagonal boron nitride on the chalcogen film;
a fourth step of heating the chalcogen film and the metal chalcogenide film after the third step;
A method for manufacturing a semiconductor device, comprising, after the fourth step, an electrode forming step of forming the plurality of electrodes.

(Appendix 10)
the chalcogen and the other chalcogen are each one of sulfur, selenium, and tellurium;
A method for manufacturing a semiconductor device according to Supplementary Note 9.

(Appendix 11)
a fifth step of removing the graphene or the hexagonal boron nitride after the fourth step;
a sixth step of removing the chalcogen film in the evacuated space after the fifth step;
After the sixth step, further comprising a seventh step of forming an insulating film on the metal chalcogenide film in the space,
The space continues to be evacuated from the beginning of the sixth step to the end of the seventh step,
11. The method of manufacturing a semiconductor device according to appendix 9 or 10, wherein one of the plurality of electrodes is formed on the insulating film.

16: Substrate 18: MoS ₂ film 20: S film 22: Graphene 26: Space 28: Insulating film

Claims (9)

A first step of forming a metal chalcogenide film having a compound of metal and chalcogen on the substrate;
a second step of forming a chalcogen film having at least one of the chalcogen and another chalcogen different from the chalcogen on the metal chalcogenide film;
a third step of arranging graphene or hexagonal boron nitride on the chalcogen film;
A method for manufacturing a chalcogenide-based layered material, comprising a fourth step of heating the chalcogen film and the metal chalcogenide film after the third step. The method for producing a chalcogenide-based layered material according to claim 1, wherein the chalcogen and the other chalcogen are each one of sulfur, selenium, and tellurium. The method for producing a chalcogenide-based layered material according to claim 1, wherein the chalcogen film is a simple substance of the chalcogen. The method for producing a chalcogenide-based layered material according to claim 1, wherein the chalcogen film is a simple substance of the other chalcogen. The method for producing a chalcogenide-based layered material according to claim 1, wherein the chalcogen film contains both the chalcogen alone and the other chalcogen alone. a fifth step of removing the graphene or the hexagonal boron nitride after the fourth step;
a sixth step of removing the chalcogen film in the evacuated space after the fifth step;
After the sixth step, further comprising a seventh step of forming an insulating film on the metal chalcogenide film in the space,
The method for producing a chalcogenide-based layered material according to any one of claims 1 to 5, wherein the space is continuously evacuated from the beginning of the sixth step to the end of the seventh step. A method for manufacturing a semiconductor device having a metal chalcogenide film having a compound of metal and chalcogen, and a plurality of electrodes, the method comprising:
a first step of forming the metal chalcogenide film on a substrate;
a second step of forming a chalcogen film having at least one of the chalcogen and another chalcogen different from the chalcogen on the metal chalcogenide film;
a third step of arranging graphene or hexagonal boron nitride on the chalcogen film;
a fourth step of heating the chalcogen film and the metal chalcogenide film after the third step;
A method for manufacturing a semiconductor device, comprising, after the fourth step, an electrode forming step of forming the plurality of electrodes. 8. The method for manufacturing a semiconductor device according to claim 7, wherein the chalcogen and the other chalcogen are each one of sulfur, selenium, and tellurium. a fifth step of removing the graphene or the hexagonal boron nitride after the fourth step;
a sixth step of removing the chalcogen film in the evacuated space after the fifth step;
After the sixth step, further comprising a seventh step of forming an insulating film on the metal chalcogenide film in the space,
The space continues to be evacuated from the beginning of the sixth step to the end of the seventh step,
9. The method of manufacturing a semiconductor device according to claim 7, wherein one of the plurality of electrodes is formed on the insulating film.

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