JP2022037889A - Method for forming transition metal chalcogenide layered film, and apparatus therefor - Google Patents

Abstract

To provide a method for forming a transition metal chalcogenide layered film high in the controllability and stability of film deposition, capable of increasing an area and low in cost.SOLUTION: A method for forming a film comprises: oxidizing a transition metal block 32 to form a transition metal oxide layer on the surface; sublimating an oxide from the oxide layer to supply oxide gas and first inactive carrier gas to a substrate 38 through an exclusive pipe line 23; supplying chalcogen atom containing reactive gas and second inactive carrier gas to the substrate 38; heating the substrate 38 when supplying the oxide gas and the reactive gas to the substrate 38; and exhausting the oxide gas, the reactive gas, the first inactive carrier gas and the second inactive carrier gas.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for forming a transition metal chalcogenide layered film and an apparatus therefor.

In recent years, attention has been focused on semiconductor materials having a thickness at the molecular layer level called transition metal dichalcogenide layered films (hereinafter, also referred to as TMDC) such as MoS ₂ and WSe ₂ .

This material is a two-dimensional layered semiconductor with a finite bandgap. TMDC is a crystal in which the thickness of the unit cell is only three layers of atoms, and is essentially excellent in ultrathinness and flatness.
In addition, since it has a characteristic crystal structure without unsaturated bonds (dangling bonds) in the plane-to-plane (c-axis) direction of the two-dimensional crystal, there are various problems that conventional semiconductor materials have, such as lattice mismatch and surface recombination. Is expected to be significantly eased.
In addition, we are interested not only in the formation of single-layer films but also in the heterostructure between TMDCs via van der Waals (vdW) force, which is lightweight and has ultra-low power consumption, including MOSFET channels and tunnel transistors. Therefore, application to electronic devices with excellent mechanical flexibility is also being considered.
Furthermore, since it has been clarified that the monolayered TMDC has a direct transition type band structure and exhibits unique physical properties such as an extremely large exciton effect, it is extremely thin and has excellent light emission and light reception. In addition to devices, it is considered to be extremely promising as a material for optical functional devices.

As described above, TMDC has many features and possibilities that conventional semiconductors do not have, but there are many problems to be solved in its film formation technology, and it is excellent in controllability, stability, large area, and mass productivity. There is a problem that the forming method has not been established.

Research on the physical properties of TMDC and device application became active from around 2010, but in many early researches, the crystal surface of MoS ₂ produced as a natural mineral was peeled off with scotch tape and used. In 2012, as disclosed in Non-Patent Document 1, a monolayer film of MoS ₂ was synthesized using a gas component sublimated from a powder of molybdenum trioxide (MoO ₃ ) and sulfur (S). The method of doing so was reported for the first time. This method is also called the powder sublimation method (powder method), and many reports on MoS ₂ film formation still use the same or improved method.

For example, in the technique disclosed in Non-Patent Document 2, powdered MoO ₃ and S are used as raw materials for Mo and S, and each of them is placed in an optimum temperature range in a hot wall type quartz tube to be volatile. The gas component is sublimated and transported, and reacted on the substrate.
This method has the problem that the amount of raw material transported, including the start and end of sublimation, cannot be easily controlled, the amount of sublimation is reduced due to the decrease and depletion of powder raw materials, and MoO ₃ powder reacts with S in the boat. Then, there is a problem that it changes and sublimation is hindered. For this reason, it is necessary to replace the MoO ₃ powder every time in the film forming process, but it is still difficult to obtain reproducibility. In addition, the geometrical arrangement relationship between the MoO ₃ powder placed in a small boat and the substrate is also called the Point-to-face supply method, but this method makes the spatial concentration of the gas component uniform in the film formation region. There is a problem that it is difficult to realize the above, and in principle, it is not easy to make the film formation uniform and increase the area.

Non-Patent Document 3 is a kind of face-to-face method in which a metal foil of Mo is covered as a cover on a substrate region for film formation, and Mo oxide is sublimated from the surface of the Mo foil and supplied onto the substrate. A foil method using Mo (Mo foil method) is disclosed.
It has been reported that this method has an advantage that uniform film formation can be easily obtained as compared with the method using MoO ₃ powder because the Mo raw material is uniformly supplied on the substrate placed in the lower space of the Mo foil. There is. However, in this method, since the sulfur element S is supplied not only on the substrate but also on the surface of the Mo foil, MoS ₂ is unintentionally formed on the surface of the Mo foil, or a highly volatile component such as MoO ₃ is formed. It changes to a substance with a low oxidation number such as MoO ₂ , which has low volatility, and causes various problems such as a decrease in the production efficiency of Mo oxide gas and an unstable production.

As described above, in the method using the powdered _MoO3 raw material, it is difficult to stably supply the raw material gas and to form a uniform _MoS2 film. As one of the causes is the non-uniformity of the particle size distribution of the powder raw material, in Non-Patent Document 4, a small amount of MoO ₃ is vapor-deposited on the substrate in advance to make the particle size uniform, and this is opposed to the substrate. The method of using it as a raw material for Mo is disclosed.
Further, in order to increase the single crystal domain size of the single layer MoS ₂ , it is extremely important to significantly reduce the degree of supersaturation of MoO ₃ in the gas phase by using a very small volume of MoO ₃ . Non-Patent Document 5 discloses a method in which a solution in which MoO ₃ is dissolved on a substrate is dispersed and dried in advance by a spin coating method, and this is used as a sublimation source of MoO ₃ .
The methods disclosed in Non-Patent Documents 4 and 5 are techniques for positioning an intermediate composite method between the powder method and the Mo foil method described above.

However, even with these composite methods, it is not possible to form a _MoS2 continuous film completely covered on the substrate. It is considered that this is because the amount of MoO ₃ deposited in advance on the substrate is very small, so that all of the MoO 3 is sublimated within the film formation time, and the raw material is completely depleted.
Further, regarding the method of Non-Patent Document 4, it has been raised that there is a direct reaction between MoO ₃ for sublimation and the raw material S, and there is a problem of stable supply of the raw material gas.
Patent Documents 1 and 2 are disclosed as patents relating to the TMDC film forming method.
As described above, the conventional method has problems of quality and practical use such as stability and controllability of film formation, large area of film formation and cost. Although the prior art for the MoS ₂ film has been mainly described here, the above-mentioned problems are considered to be the same not only for the MoS ₂ film but also for the MoSe ₂ and the WS ₂ and WSe ₂ films, which are common problems for TMDC. It has become.

Japanese Unexamined Patent Publication No. 7-069782 Special Table 2019-522106 Gazette

Y. H. Lee et al. , Adv. Mater. , 24, 2320 (2012) H. Nguyen et al. , Mater. Let. , 168, 1 (2016) J. Zheng et al. , Adv. Mater. , 29,1604540 (2017) S. S. Withage. , ACS Omega, 3,18943 (2018) J. Lee et al. , Adv. Mater. , 29,1702206 (2017)

An object of the present invention is to provide a film forming method and a manufacturing apparatus for solving the problems of the prior art described in the background art. That is, to provide a film forming method and a manufacturing apparatus therefor, which have high stability and controllability of film formation of a transition metal dichalcogenide layered film such as MoS ₂ , can increase the film forming area, and are excellent in terms of cost. The challenge is to do.

The configuration of the present invention for solving the problem is shown below.
(Structure 1)
Oxidizing a block of a transition metal to form an oxide layer of the transition metal on the surface of the transition metal,
The oxide is sublimated from the oxide layer, and the gas of the oxide is supplied to the substrate together with the first inert carrier gas via a dedicated pipe.
To supply the substrate with a reactive gas containing a chalcogen atom together with the second inert carrier gas.
By heating the substrate when the oxide gas and the reactive gas are supplied to the substrate,
A method for forming a transition metal chalcogenide layered film, which comprises exhausting the oxide gas, the reactive gas, the first inert carrier gas and the second inert carrier gas.
(Structure 2)
The transition metals include titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), chromium (Cr), tungsten (W) and The method for forming a transition metal chalcogenide layered film according to Configuration 1, which is 1 selected from the group consisting of renium (Re).
(Structure 3)
The method for forming a transition metal chalcogenide layered film according to Configuration 1 or 2, further comprising forming the oxide layer into a hydrogenated oxide layer.
(Structure 4)
The method for forming a transition metal chalcogenide layered film according to composition 3, wherein the hydrogenation is performed by adding hydrogen gas at the time of performing the oxidation.
(Structure 5)
A block made of molybdenum is heated at a first temperature T1 while supplying a gas containing oxygen to form a molybdenum oxide layer on the surface of the block.
Molybdenum trioxide (MoO ₃ ) is sublimated from the molybdenum oxide layer, and the MoO ₃ gas is supplied to the substrate together with the first inert carrier gas via a dedicated pipe.
To supply the substrate with a reactive gas containing a chalcogen atom together with the second inert carrier gas.
When the MoO ₃ gas and the reactive gas are supplied to the substrate, the substrate is heated at the second temperature T2.
A method for forming a transition metal chalcogenide layered film, which comprises exhausting the MoO ₃ gas, the reactive gas, the first inert carrier gas and the second inert carrier gas.
(Structure 6)
The method for forming a chalcogenide layered film according to Configuration 5, wherein the first temperature T1 is 500 ° C. or higher and 1200 ° C. or lower.
(Structure 7)
The method for forming a transition metal chalcogenide layered film according to configuration 5 or 6, wherein the second temperature T2 is 300 ° C. or higher and 1200 ° C. or lower.
(Structure 8)
The dedicated pipe is heated from at least the place where the block is arranged to the region immediately before the substrate at a temperature at which the generated raw material gas component of MoO ₃ is prevented from being redeposited in the middle of the pipe. , The method for forming a transition metal chalcogenide layered film according to any one of configurations 5 to 7.
(Structure 9)
The method for forming a transition metal chalcogenide layered film according to any one of configurations 1 to 8, wherein the chalcogen atom is 1 selected from the group consisting of sulfur (S), selenium (Se) and tellurium (Te).
(Structure 10)
The first inert gas and the second inert gas are any one or more selected from the group consisting of nitrogen gas, argon gas, krypton gas, neon gas, helium gas and xenon gas, any of configurations 1 to 9. The method for forming a transition metal chalcogenide layered film according to 1.
(Structure 11)
The method for forming a transition metal chalcogenide layered film according to any one of configurations 1 to 9, wherein the first inert gas and the second inert gas are nitrogen gases.
(Structure 12)
The method for forming a transition metal chalcogenide layered film according to any one of configurations 1 to 11, wherein the substrate contains an alkali metal element as a composition.
(Structure 13)
The method for forming a transition metal chalcogenide layered film according to Constituent 12, wherein the alkali metal element is one or more selected from the group consisting of sodium (Na), lithium (Li) and potassium (K).
(Structure 14)
The method for forming a transition metal chalcogenide layered film according to any one of configurations 1 to 12, wherein the substrate is an alkaline aluminosilicate glass.
(Structure 15)
An oxide gas supply means for supplying an oxide gas to a substrate, a reactive gas supply means for supplying a reactive gas to the substrate, a reaction chamber portion for forming a transition metal cargogenide as a layered film on the substrate, and a reaction chamber portion. Equipped with exhaust means,
The oxide gas supply means includes a means for supplying a gas containing oxygen by controlling the flow rate, a means for supplying the first inert gas by controlling the flow rate, a block-shaped transition metal, and the transition metal. A first heating means for heating the substrate and a dedicated pipe for supplying an oxide gas sublimated from the transition metal onto the substrate.
The reactive gas supply means includes a means for supplying a reactive gas containing a chalcogen atom by controlling the flow rate, and a means for supplying the second inert gas by controlling the flow rate.
The reaction chamber is provided with a sample table and a second heating means for heating the substrate placed on the sample table, and is separated from the place where the transition metal is placed. ,
A device for forming a transition metal chalcogenide layered film, wherein the tube wall of the dedicated pipe is provided with a heat treatment means for keeping the temperature equal to or higher than the sublimation temperature of the oxide of the transition metal.
(Structure 16)
The apparatus for forming a transition metal chalcogenide layered film according to configuration 15, wherein the oxide gas supply means further includes means for supplying a gas containing hydrogen by controlling the flow rate.
(Structure 17)
A MoO ₃ gas supply means for supplying MoO ₃ gas to a substrate, a reactive gas supply means for supplying a reactive gas containing sulfur to the substrate, and a reaction chamber portion for forming MoS ₂ as a layered film on the substrate. And equipped with exhaust means,
The MoO ₃ gas supply means heats the gas containing oxygen by controlling the flow rate, the first inert gas by controlling the flow rate, the block made of molybdenum, and the block. A first heating means and a dedicated pipe for supplying the gas of MoO ₃ sublimated and generated from the block onto the substrate are provided.
The reactive gas supply means includes a means for supplying the reactive gas by controlling the flow rate and a means for supplying the second inert gas by controlling the flow rate.
The reaction chamber is provided with a sample table and a second heating means for heating the substrate placed on the sample table, and is separated from the place where the block is placed.
A device for forming a MoS _two -layered film, which is provided with a heat treatment means for maintaining a temperature equal to or higher than the sublimation temperature of MoO ₃ on the pipe wall of the dedicated pipe.
(Structure 18)
The reactive gas is sulfur (S), hydrogen sulfide (H ₂ S), dimethyl sulfur ((CH ₃ ) ₂ S), diethyl sulfur ((C ₂ H ₅ ) ₂ S), ditersial butyl sulfur ([(). CH ₃ ) ₃ C] ₂ S), diisopropyl sulfur ((i-C ₃ H ₇ ) ₂ S), one or more selected from the group consisting of the apparatus according to the configuration 17.
(Structure 19)
The apparatus according to any one of configurations 15 to 18, wherein the first heating means and the second heating means are one or more methods selected from the group consisting of resistance heating, induction heating, and lamp heating.
(Structure 20)
The first inert gas and the second inert gas are one or more selected from the group consisting of nitrogen gas, argon gas, krypton gas, neon gas, helium gas and xenon gas, any of configurations 15 to 19. The device according to 1.
(Structure 21)
The apparatus according to any one of configurations 15 to 19, wherein the first inert gas and the second inert gas are nitrogen gases.
(Structure 22)
The device according to any one of configurations 15 to 21, wherein the dedicated pipe is composed of 1 selected from the group consisting of quartz glass, glass, stainless steel and ceramics.
(Structure 23)
The apparatus according to configuration 22, wherein the ceramic is selected from the group consisting of alumina and SiC.
(Structure 24)
The device according to any one of configurations 15 to 23, wherein a shower head is provided in a portion of the dedicated pipe near the substrate.
(Structure 25)
The device according to any one of configurations 15 to 24, wherein the sample table is provided with a rotation mechanism.

According to the present invention, a film forming method and a manufacturing apparatus for forming a transition metal dichalcogenide, particularly MoS ₂ , which has high film forming stability and controllability, can increase the film forming area, and is excellent in terms of cost. Is provided.

It is explanatory drawing which shows the schematic structure of the apparatus. It is explanatory drawing which shows the schematic structure of the apparatus. It is explanatory drawing which shows the schematic structure of the apparatus. It is explanatory drawing which shows the structure of a gas supply system. It is a flowchart which shows the film formation method of this invention. It is a flowchart which shows the film formation method of this invention. It is explanatory drawing which shows the mechanism of MoO ₃ gas generation. It is sectional drawing of the prototype device. It is a block diagram centering on the gas piping system of the prototype device. It is an optical micrograph of the prepared MoS ₂ film. It is an optical micrograph of the prepared MoS ₂ film. It is an optical micrograph of the prepared MoS ₂ film. It is an optical micrograph of the prepared MoS ₂ film. It is an optical micrograph of the prepared MoS ₂ film. It is an optical micrograph of the prepared MoS ₂ film. It is the result of the film evaluation of the prepared MoS ₂ film, (a) is the result of Raman spectroscopic evaluation, and (b) is the result of the emission spectroscopic evaluation. It is an optical micrograph of the prepared MoS ₂ film. It is the result of the film evaluation of the prepared MoS ₂ film, (a) is the result of Raman spectroscopic evaluation, and (b) is the result of the emission spectroscopic evaluation. It is an SEM photograph of the prepared MoS ₂ film. It is a figure which evaluated the SEM photograph of the prepared _WS2 film and the film property by Raman and PL spectrum. It is an SEM photograph of the prepared MoS ₂ film.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(First Embodiment)
In the first embodiment, a film forming apparatus for a transition metal chalcogenide layered film and a film forming method using the apparatus will be described while exemplifying MoS ₂ .

<Device>
As shown in FIG. 1, the transition metal chalcogenide layered film forming apparatus of the present invention has an oxide gas supply means 6 for supplying an oxide gas onto a substrate and a reactive gas supply for supplying a reactive gas onto the substrate. The means 7 is provided with a reaction chamber portion 8 for forming a transition metal cargogenide as a layered film on a substrate (sample), and an exhaust means 9.

The oxide gas supply means 6 heats a means for supplying a gas containing oxygen by controlling the flow rate, a means for supplying the first inert gas by controlling the flow rate, a block-shaped transition metal, and the transition metal. The first heating means is provided, and the means is provided with a dedicated pipe for supplying the oxide gas sublimated and generated from the transition metal onto the substrate.
Specifically, as shown in FIG. 2, the oxide gas supply means of the transition metal chalcogenide layered film forming apparatus 10 of the present invention is open / closed / flow control as a means for controlling the flow rate of a gas containing oxygen. An oxide gas generation chamber 21 including a device 33, an opening / closing / flow rate control device 34 as a supply means for controlling the flow rate of the first inert gas, a block-shaped transition metal 32, and a stage 31 for mounting the block-shaped transition metal 32. , And a dedicated pipe 23 for supplying the oxide gas sublimated and generated from the transition metal onto the substrate. The open / close / flow rate control device 33 and the open / close / flow rate control device 34 may be one open / close / flow rate control device as shown in the open / close / flow rate control device 40 described later.

Here, as the transition metal, titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), chromium (Cr), tungsten ( One selected from the group consisting of W) and renium (Re) can be mentioned. When Mo is used, it is possible to form a MoS _two -layered film, which is highly expected to be applied. Further, as for Mo metal, there is an advantage that high-purity polycrystalline Mo metal is easily available and the cost is low.

A single crystal is preferable as the form of the transition metal to be used. There are many grain boundaries in polycrystals, but in that state, the progress of oxide formation, accumulation and sublimation differs between the single crystal and grain boundaries, and the reproducibility and stability of oxide formation and sublimation. Tends to decrease. For example, polycrystalline Mo has high-density grain boundaries, and the formation and accumulation of Mo oxides and the progress of sublimation differ between the single crystal and grain boundaries. Here, in general, the formation and accumulation of Mo oxide and the progress of sublimation tend to proceed predominantly at the grain boundaries. Therefore, from the viewpoint of improving the reproducibility and stability of MoO ₃ generation and sublimation and performing more strict control, it is preferable to use a single crystal Mo produced by, for example, an electron beam melting method.

As the first heating means for heating the transition metal, resistance heating, induction heating and lamp heating can be mentioned. For example, the stage 31 may be equipped with a heater. It should be noted that resistance heating is characterized by low cost and easy handling, and lamp heating and induction heating are characterized by excellent responsiveness.
The setting range of the temperature T1 by the first heating means is preferably 500 ° C. or higher and 1200 ° C. or lower. This temperature range allows the transition metal oxide gas to be efficiently produced with high stability, and as a result, the transition metal chalcogenide layered film that is uniform and has few defects can be stably formed.

As the first inert gas, one or more selected from the group consisting of nitrogen gas, argon gas, krypton gas, neon gas, helium gas and xenon gas can be mentioned. A layer of the transition metal oxide is formed on the block-shaped transition metal 32, and the nitrogen gas functions as a sufficient inert gas in relation to the temperature when the gas of the transition metal oxide is sublimated from the layer. Nitrogen gas is particularly suitable as the first inert gas because it is easily available and low in cost.

The dedicated pipe 23 needs to be configured to be maintained at a temperature equal to or higher than the sublimation temperature of the oxide of the transition metal used in the pipe wall. For example, as shown in FIG. 3, the heater 25 is located in or near the pipe wall. Be prepared. The heater 25 may be induction heating or lamp heating in addition to resistance heating. Further, as described in the examples, the dedicated pipe 23 is not provided with a heater dedicated to the dedicated pipe 23, and is installed in the furnace as part of the heat treatment of the sample 38 to keep the temperature above the sublimation temperature of the oxide of the transition metal. You may let it hang down.
If the transition metal oxide adheres to the pipe wall of the dedicated pipe, the controllability and stability of the supply of the transition metal oxide gas to the sample 38 deteriorates. The above configuration makes it possible to solve this problem.

As the material of the pipe wall of the dedicated pipe 23, 1 selected from the group consisting of quartz glass, glass, stainless steel and ceramics can be mentioned. Examples of the ceramics include those selected from the group consisting of alumina and SiC.
A shower head 36 is provided near the tip of the dedicated pipe 23 and the place where the sample 38 is placed so that the gas of the transition metal oxide is uniformly supplied into the plane of the sample 38. Is preferable.

The reactive gas supply means includes a means for supplying a reactive gas containing a chalcogen atom by controlling the flow rate and a means for supplying the second inert gas by controlling the flow rate, and supplies the reactive gas to the substrate. Provided with means to supply above.
Specifically, as shown in FIG. 2, the reactive gas supply means of the transition metal chalcogenide layered film forming apparatus 10 of the present invention is a means for supplying a reactive gas containing a chalcogen atom by controlling the flow rate and a second. It is provided with an opening / closing / flow rate control device 40 as a supply means for controlling the flow rate of the inert gas of No. 1 and a pipe 43 for supplying the reactive gas from the opening / closing / flow rate control device 40 to the vicinity of the sample 38. Here, the opening / closing / flow rate control device 40 is provided with a port (pipe) 41 for supplying the reactive gas and a port (pipe) 42 for supplying the second inert gas. Further, although the open / close / flow rate control device 40 is one device in FIG. 2, the open / close / flow rate control device for supplying the reactive gas and the open / close / flow rate control device for supplying the second inert gas are used. It may be a flow rate control device.

Examples of the chalcogen atom include 1 selected from the group consisting of sulfur (S), selenium (Se) and tellurium (Te).
The reactive gases containing chalcogen atoms include sulfur (S), hydrogen sulfide (H ₂ S), dimethyl sulfur ((CH ₃ ) ₂ S), diethyl sulfur ((C ₂ H ₅ ) ₂ S), and jittery. One or more selected from the group consisting of butyl sulfur ([(CH ₃ ) ₃ C] ₂ S) and diisopropyl sulfur ((i-C ₃ H ₇ ) ₂ S) can be mentioned. Among these, S and H 2S can be preferably used because _they are easily available and low in cost.

As the second inert gas, one or more selected from the group consisting of nitrogen gas, argon gas, krypton gas, neon gas, helium gas and xenon gas can be mentioned. Nitrogen gas is particularly suitable as the second inert gas because it is easily available and low in cost.

The reaction chamber (reaction chamber portion) 22 is a room provided with a sample 38 and a sample table 37 on which the sample 38 is placed, and gas flows in and out of the oxide gas generation chamber 21 on which the transition metal is placed and the dedicated pipe 23. It will be a separate room isolated from the viewpoint of. The reaction chamber (reaction chamber portion) 22 is provided with a second heating means for heating the sample 38. The second heating means may include resistance heating, induction heating and lamp heating, and may be used alone or in combination among these. The sample table 37 provided with a heater may be used as the second heating means. The setting range of the temperature T2 by the second heating means is preferably 300 ° C. or higher and 1200 ° C. or lower. This temperature range makes it possible to stably form a transition metal chalcogenide layered film that is efficiently uniform and has few defects.
It is preferable that the sample table 37 is provided with a rotation mechanism. By doing so, when the transition metal chalcogenide layered film is formed on the sample 38, the in-plane uniformity of the film formation can be improved by forming the film while rotating the sample 38.

The temperature control of the first heating means and the second heating means may be individually separated, or may be integrated into one to simplify the apparatus. That is, it may be 2 zones, 2 zones or more, or 1 zone. In the case of multi-zone control, for example, the temperature of the sample 32 and the temperature in the oxide gas generation chamber 21 can be controlled independently, and interference between mutual parameters can be suppressed, so that controllability is improved.

Further, in the first embodiment as the apparatus of the present invention, an apparatus classified into a shape called a horizontal reactor has been exemplified and described. However, this is not essential, and a vertical reactor in which the gas flow is in the vertical direction may be used.

The gas supply system 12 whose opening / closing and flow rate is controlled shown in FIG. 4 includes a first gas system including a pipe 51, a manual valve 52, a mass flow controller 53, and air valves 54 and 56, and a pipe 61, a manual valve 62, and a mass flow. The second gas system including the controller 63 and the air valves 64 and 66 is shown as an example. The gas from the first gas system and the gas from the second gas system are mixed, On / Off, and flow rate controlled and supplied by the pipe 55. Further, an exhaust pipe 57 for ensuring sufficient gas purity in the pipe is also provided, and the inside of the pipe can be exhausted by opening and closing the air valves 56 and 66. The gas supply system 12 shown here can be applied to the open / close / flow rate control devices 33, 34, 40, 44.

In the gas supply system 12, the gas flow rate on the supply side is controlled by the mass flow controllers 53 and 63. In the present invention, as shown in FIG. 2, the flow rates of the gas containing O ₂ and the first inert gas supplied to the oxide gas generation chamber 21 and the heat treatment temperature (T1) for the transition metal block 32 are controlled. By doing so, one feature is to control the flow rate of the oxide gas supplied to the sample 38.
If an attempt is made to control the flow rate and On / Off of the oxide gas generated in the oxide gas generation chamber 21 on the downstream side of the oxide gas generation chamber 21, On / Off and flow rate control at a high temperature are required, and the apparatus Problems such as increased cost, reduced control accuracy and instability, frequent failures, and difficulty in maintenance occur. The configuration of the present invention makes it possible to avoid such a problem.
Note that FIG. 3 shows an example in which two open / close / flow rate control devices 40 and 44 are connected to the reaction chamber 22. When a plurality of open / close / flow rate control devices are connected to the reaction chamber 22 in this way, not only the introduction of the reactive gas and the second inert gas but also the O ₂ mixed with the inert carrier gas for environmental control is performed. Gas can be supplied, and more advanced control becomes possible. The pipes 45, 46 and 47 are connected to the open / close / flow rate control device 44.

In the above, the case where the source of the oxide gas is a block-shaped transition metal is shown, but when the transition metal block 32 is a block-shaped metal molybdenum (Mo), the oxide gas sublimated becomes MoO ₃ . If this gas is guided to the reaction chamber 22 via the dedicated pipe 23, the reactive gas containing sulfur is guided to the reaction chamber 22 with the flow rate control in another system, and the sample 38 is heat-treated, MoS ₂ is added to the sample 38. A layered film can be formed.

The features of the apparatus of the present invention are shown below. Due to these characteristics, it is possible to provide a manufacturing apparatus which has high stability and controllability of film formation of a transition metal dichalcogenide layered film such as MoS ₂ , can increase the film formation area, and is excellent in terms of cost. It will be possible.

(1) The oxide gas generation chamber 21 on which the transition metal block 32 such as Mo is placed is separated so that other reactive gas such as S raw material gas does not unintentionally invade and react.
(2) Transition The oxide gas generation chamber 21 on which the metal block is placed is configured to be capable of supplying both an inert gas such as N ₂ and reactive O ₂ and transitions by valve operation. The gas in contact with the metal block 32 is switched.
(3) With the configuration of (2) above, a flow rate control device such as a mass flow controller is installed in each gas line, which makes it possible to control the flow rate and concentration of N ₂ and O ₂ gas. Moreover, since this flow rate control can be performed at room temperature, stability, controllability, and maintainability are high, costs can be suppressed, and the frequency of failure occurrence is low.
(4) The oxide gas generation chamber 21 on which the transition metal block is placed is independent of the region where the sample 38 is placed, and the generated oxide gas is guided to the region where the sample 38 is placed. It is configured to be able to.
(5) The oxide gas guided to the region where the sample 38 is placed has a structure in which the gas concentration can be made uniform in the place where the sample 38 is placed by processing the shape of the gas blowing portion such as a shower head method. It has become.
(6) The reactive gas such as the S raw material is mixed and reacted in the vicinity of the sample 38 with the oxide gas guided to the place where the sample 38 is placed as in (5). ..

<Method>
The method of the present invention will be described with reference to FIGS. 5 and 5 which are flowcharts.
In the method of the present invention, a block of the transition metal is oxidized to form an oxide layer of the transition metal on the surface of the transition metal (FIG. 5, step S1), and the oxide is sublimated from the oxide layer. The oxide gas is supplied to the substrate (sample) together with the first inert carrier gas via a dedicated pipe (step S2), and the reactive gas containing a chalcogen atom is supplied together with the second inert carrier gas. Supplying to the substrate (step S3) and heating the substrate when supplying the oxide gas and the reactive gas to the substrate to form a transition metal chalcogen layered film on the substrate (step S4). And, including the time of step S4, the oxide gas, the reactive gas, the first inert carrier gas and the second inert carrier gas are exhausted (step S5). Here, the process S2 and the process S3 may be performed at the same time, or the process S3 may be performed prior to the process S2.

Here, the transition metals are titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), chromium (Cr), and tungsten (W). ) And 1 selected from the group consisting of renium (Re).

When forming a MoS _two -layered film, which is highly desired as a transition metal chalcogenide layered film, a block made of molybdenum is heated at a first temperature T1 while supplying a gas containing oxygen, and molybdenum oxide is formed on the surface of the block. Forming a layer (FIG. 6, step S11) and sublimating molybdenum trioxide (MoO ₃ ) from the molybdenum oxide layer, the gas of MoO ₃ is used as a substrate together with the first inert carrier gas via a dedicated pipe. (Step S12), supplying a reactive gas containing a chalcogen atom to the substrate together with the second inert carrier gas (step S13), and supplying the MoO ₃ gas and the reactive gas to the substrate. Occasionally, the substrate is heated at the second temperature T2 (step S14), and the MoO ₃ gas, the reactive gas, the first inert carrier gas and the second inert carrier gas are exhausted including the step S14. (Step S15) is included to form a MoS _two -layered film. Here, the process S12 and the process S13 may be performed at the same time, or the process S13 may be performed prior to the process S12.

Here, the first temperature T1 is preferably 500 ° C. or higher and 1200 ° C. or lower. This temperature range allows the transition metal oxide gas to be efficiently produced with high stability, and as a result, the transition metal chalcogenide layered film that is uniform and has few defects can be stably formed.
The second temperature T2 is preferably 300 ° C. or higher and 1200 ° C. or lower. This temperature range makes it possible to stably form a transition metal chalcogenide layered film that is efficiently uniform and has few defects.

As mentioned in the equipment, the dedicated pipe is located in the area immediately before the substrate from the place where the metal block is placed, at least for the purpose of preventing the generated raw material gas components such as MoO ₃ from redepositing in the middle of the pipe. It is preferably heated to.

Examples of the chalcogen atom include 1 selected from the group consisting of sulfur (S), selenium (Se) and tellurium (Te).

The first inert gas and the second inert gas can be one or more selected from the group consisting of nitrogen gas, argon gas, krypton gas, neon gas, helium gas and xenon gas. Of these, nitrogen gas is particularly preferred because it is inexpensive and easily available.

The oxygen content of the gas containing oxygen is preferably 0.01% by volume or more and 100% by volume or less.
The ratio S ₂ / S ₀₂ of the sccm flow rate S ₂ of H ₂ S to the sccm flow rate S ₀₂ of the second inert gas is preferably 0.01% by volume or more and 100% by volume or less.
Under the above conditions, it becomes possible to stably form a transition metal chalcogenide layered film.

The substrate (sample substrate) forming the transition metal chalcogenide layered film preferably contains an alkali metal element as a composition.
Here, as the alkali metal element, one or more selected from the group consisting of sodium (Na), lithium (Li) and potassium (K) can be mentioned. When TMDC CVD such as MoS ₂ is carried out on a substrate containing an alkali metal, the deposition rate is improved due to the catalytic effect of the alkali metal, the production efficiency of film formation is increased, and the size of the single crystal domain is also increased to form a film. It also contributes to quality improvement.
Specific examples of this substrate include alkaline, aluminosilicate, and silicate glass. Alkaline / aluminosilicate glass is a material developed to promote the ion exchange reaction on the surface for reinforced cover glass such as smartphones. In addition to SiO ₂ and Al ₂ O ₃ , it is about 20% by weight. Contains the Na ₂ O component of.

Next, the mechanism of TMDC formation will be described by exemplifying MoS ₂ as the TMDC.
The important point of the present invention is that the metal molybdenum (Mo) is placed in the oxide gas generation chamber 21 provided independently, and the gas containing oxygen (O ₂ ) is supplied to the metal molybdenum (Mo) to obtain the raw material gas of Mo. Molybdenum oxide (mainly molybdenum trioxide (MoO ₃ )) is generated, and this Mo raw material gas is guided to a film forming region on which the sample (substrate) 38 is placed and used.
Generally, Mo, which is a transition metal element, is classified as a refractory metal, has a very high melting point of about 2600 ° C. or higher, and requires an extremely high temperature to evaporate the metal raw material itself.
On the other hand, the hexavalent oxide MoO ₃ obtained by oxidizing Mo has a relatively high vapor pressure, and sublimation proceeds rapidly at 500 ° C. or higher. In the present invention, the MoO ₃ formation reaction and sublimation that proceed simultaneously when a dilute O ₂ gas is supplied to the metal Mo surface are actively utilized.

Next, the present invention describes the formation of an oxide film (also called an oxide scale) and its sublimation reaction that proceed when O ₂ gas is supplied to the Mo metal surface.
FIG. 7 shows a picture of oxidation scale formation and sublimation that can be considered when O ₂ gas is supplied to Mo metal 1 in a heated environment. After the supplied O ₂ (4) is adsorbed on the Mo surface, it reacts with Mo to form an oxidation scale (2 or 3), but after the oxidation scale of a finite thickness is formed, O ₂ is formed. It diffuses to the interface between the Mo metal and the oxidation scale, where a new oxidation scale is formed. Then, MoO ₃ becomes gas and sublimates. Here, FIG. 7 (a) shows a case where a dilute O ₂ gas is supplied, and FIG. 7 (b) shows a case where a sufficient O ₂ gas is supplied, as will be described later.
Regarding the chemical composition of the oxide scale formed, most of the surface layer is MoO ₃ (3) with high vapor pressure (sublimation) under sufficient O ₂ partial pressure, but near the interface with Mo metal. There is MoO ₂ which has a low sublimation property and a very thin thickness. There are also suboxides such as MoO _x (2 <x <3) in the transition region from MoO ₃ to MoO ₂ . In FIG. 7, MoO ₂ and the suboxide are displayed as 2.

On the other hand, regarding the time evolution of the film thickness of the oxidation scale, it is reported that the film thickness increases linearly with time (t) at the initial stage of the start of oxidation and gradually changes to t ^1/2 (parabolic rule). It also depends on the temperature and O ₂ partial pressure. As described above, the formation process of the oxidation scale of Mo and its structure are complicated.

Of particular importance in the present invention is the competitive relationship between the rate of formation of the oxide scale and the rate of sublimation. This is because the growth rate or thickness of the subtracted oxidation scale is determined by the magnitude of the formation rate and the sublimation rate of the oxidation scale (2, 3). This competitive relationship is affected by the temperature and the amount of O ₂ supplied (partial pressure).

FIG. 7 shows two extreme situations that can be considered as a competitive relationship between the formation of the oxidation scale and sublimation.
FIG. 7A shows the case of “oxidation scale formation rate << sublimation rate” in which the sublimation rate is overwhelmingly higher than the oxidation scale formation rate. Such a situation is realized when the O ₂ supply is low, or the temperature is high and sublimation occurs extremely actively. Under ideal extreme conditions, the MoO ₃ component of the formed oxidation scale immediately becomes MoO ₃ (5) and sublimates and does not stay on the surface, and MoO _x and MoO ₂ which are constantly low in volatility. The picture looks like the thin film of is exposed. In this case, the amount of MoO ₃ sublimation per unit time, which is important for MoS ₂ CVD, is considered to be rate-determined by the supply flow rate of O ₂ . Therefore, if the supply amount of O ₂ is kept constant, the growth rate of MoS ₂ becomes constant, and the accumulation amount of MoS ₂ (integrated amount within the growth time) is proportional to the time.

On the other hand, FIG. 7B shows a situation in which the formation of the oxidation scale exceeds the reduction of the scale due to sublimation, and as a result, the thickness of the _MoO3 oxidation scale increases. That is, it is the case of "oxidation scale formation rate> sublimation rate". This is realized in a situation where the O ₂ supply amount is sufficient, the temperature is relatively low, and the sublimation rate is suppressed.
In such a situation, the surface of the Mo metal is always covered with MoO ₃ (3), and the thickness (ie, volume) of MoO ₃ (3) increases with time. When MoS ₂ is CVD in such a situation, the sublimation amount of MoO ₃ is not constant with respect to time even if the supply amount of O ₂ gas is made constant, and is proportional to the time with the thickness of MoO ₃ . It is thought that it will increase. Therefore, it is expected that the growth rate of MoS ₂ in CVD also increases linearly with time, and the total accumulated amount, which is an integral amount, increases quadratically with time. Further, under such a situation, even if the O ₂ supply is stopped by operating the valve, the generation continues until the Mo O ₃ ( ₃ ) accumulated on the Mo (1) surface is sublimated and disappears. If you stop growing, the response will be poor.
As described above, two states can occur in the CVD of MoS ₂ using the formation of an oxidation scale on the surface of metal Mo and the sublimation of MoO ₃ . Although the film formation of MoS ₂ can be realized under either situation, it is preferable to achieve the situation shown in FIG. 7 (a) from the viewpoint of controllability and responsiveness.
From the above, according to the first embodiment, the film formation stability and controllability of the transition metal dichalcogenide layered film such as MoS ₂ is high, the film formation area can be increased, and the cost is also excellent. It becomes possible to provide a membrane method.

The three methods described in the background technology, that is, (i) a method using a powder raw material as a metal oxide such as MoO ₃ (powder method), and (ii) a method using a metal foil such as Mo facing a sample (foil method). ), (Iii) The differences between the three methods of the composite method such as the combination of the above two methods and the method of the present invention are summarized below.

The difference from the powder method is that the method of the present invention does not require a powder raw material because the generation of metal oxides such as MoO ₃ is generated on the spot by supplying O ₂ gas to the block-shaped metal surface. This means that the raw material portion of the oxide does not directly react with a chalcogen element such as S, and the controllability is improved.
The difference from the foil method is that the shape and size of the metal raw material such as Mo can be selected without depending on the size and number of samples because it does not need to be a metal foil and is made into a block shape. There is no need to face the foil to the substrate, and there is a high degree of freedom to guide the metal oxide gas generated in the oxide gas generation chamber to the reaction chamber where the sample is placed by piping, nozzles, shower heads, etc., resulting in film formation. The structure should be easy to improve the uniformity, and the metal used should not be deteriorated and can be used repeatedly.
The difference from the composite method is that metal oxides such as MoO ₃ are generated in-situ by the reaction between the metal and O ₂ , so that depletion of the metal oxide can be avoided, and the sublimation amount of the metal oxide (particularly, low degree of hypersaturation). (Realization) can be controlled over a wide range by the O ₂ flow rate and can be freely changed during film formation, and the controllability is improved because the direct reaction with the chalcogen element such as S does not occur in the raw material portion of the metal oxide. ..

(Second embodiment)
In the second embodiment, a film forming apparatus for a transition metal chalcogenide layered film whose film forming efficiency is enhanced by adding hydrogen gas and a film forming method using the apparatus will be described.

The apparatus basically conforms to the first embodiment, but the difference from the first embodiment is that the oxide gas generation chamber is further provided with a hydrogen gas (H ₂ gas) supply system capable of accurately controlling the flow rate. That is. That is, in FIG. 2 or FIG. 3, in addition to the open / close / flow rate control devices 33 and 34, the same equipment as the open / close / flow rate control devices 33 and 34 for supplying hydrogen gas to the oxide gas generation chamber 21 is provided. Is.

When the transition metal chalcogenide layered film is produced from a metal oxide having a high sublimation temperature, the temperature T1 of the first heat treatment for producing the oxide gas becomes high in the method of the first embodiment, and the oxide gas is generated. It will not be easy to increase efficiency. For example, when the W metal block is oxidized and sublimated and WO ₃ gas is guided to the reaction chamber 22 to form a WS _two -layered film, WO ₃ is significantly less likely to sublimate than MoO ₃ , so the sublimation is difficult. High temperature treatment such as 800 ° C or higher is required.

In the second embodiment, hydrogen gas is added to the metal oxide formed on the transition metal block and the environment for producing the metal oxide. In this way, water (H ₂ O) is added to the metal oxide molecule. That is, a hydrogenated oxide layer is formed. In this way, the sublimation temperature is lowered, the equipment for giving the temperature T1 of the heat treatment can be simplified, the handling becomes easy, the controllability becomes easy, and the oxide gas generation efficiency becomes easy to improve.
For example, oxygen gas and hydrogen gas are supplied to the W metal block and the first heat treatment is performed to generate H ₂ WO ₄ on the surface of the W metal block and sublimate the substance. In this case, the sublimation temperature is lowered (the vapor pressure is relatively higher than that of WO ₃ ), and it becomes possible to form a WS _two -layered film at a temperature of 700 ° C.

Hereinafter, the present invention will be described in more detail by way of examples, but these examples are given here only for the purpose of assisting the understanding of the present invention, and the present invention is not limited thereto.

(Example 1)
In Example 1, a film forming apparatus for MoS ₂ was produced, MoS ₂ was formed on a substrate using the apparatus, and the film was evaluated.

<Device>
FIG. 8 shows the main configuration of the apparatus 13 prototyped in the first embodiment. Here, FIG. 8A is an overall overview, and the quartz tube portion 14 shown in FIG. 8B shows the configuration of the main portion in the quartz tube 71 with dimensions.
In the apparatus 13, a quartz tube 71 is arranged on a substrate 72 as a base via a support 73, and further, a MoS _two -layer film forming chamber portion (reaction chamber portion) 79 and Mo arranged in the quartz tube 71. The electric furnace 74 is arranged so as to cover the area including the reaction chamber (MoO ₃ gas generation chamber) 81. Further, a piping tube for A line 76 and B line 77 made of quartz is installed in the quartz tube 71, and a tube for C line 78 is attached to the quartz tube 71 for C line. The gas is supplied into the quartz tube 71.

Here, a susceptor 75 on which a sample on which a MoS _two -layer film is formed is placed is arranged in the MoS _two -layer film formation chamber 79, and is supplied from the Mo reaction chamber 81 from an upper nozzle 82 having a shower head. The MoO ₃ gas is supplied from the lower nozzle 83 connected to the B line 77, and the _H2S reactive gas is supplied. It should be noted that the atmosphere gas, the flow of gas, the promotion of exhaust gas, and the like can be controlled by the gas from the C line 78 connected to the quartz tube 71.

The tube wall of the Mo reaction chamber 81 is quartz, and a block of metallic molybdenum is arranged in the Mo reaction chamber 81. Oxygen gas (O ₂ gas) and nitrogen gas (N ₂ gas) as an inert carrier gas are supplied from the A line 76 connected to the upstream side, and MoO ₃ gas is supplied from the upper nozzle 82 connected to the downstream side. Is supplied to the MoS _two -layered film forming chamber 79. Here, the pipe from the Mo reaction chamber 81 to the upper nozzle 82 is in the state of a dedicated pipe, but the dedicated pipe is arranged inside the electric furnace 74, and when the electric furnace 74 is turned on, the pipe is used. Since the wall is heated, Mo and MoOx are hard to adhere to the pipe wall.
An exhaust system is connected to the end of the quartz tube 71 so that the exhaust 80 is exhausted. Here, an air-cooled small dry pump was used as the exhaust equipment. In addition, a detoxification device for dry adsorption of _H2S was installed downstream of the pump.

FIG. 9 shows a configuration diagram of the device 13 drawn centering on the gas supply system.
In the apparatus 13, the MoO ₃ gas in the Mo reaction chamber 81 connected to the A line 76 is operated by opening and closing the manual valve 62a and the air valve 64a installed in the diluted O ₂ gas supply line (A-2 line). It can be started and stopped. In addition, mass flow controllers (MFCs) 53a and 63a are installed in the A-1 line and the dilution _O2 line (A- ₂ ) dedicated to N2, respectively, and the flow ratio of these two MFCs allows the Mo reaction chamber to be installed. The structure is such that the effective O ₂ concentration can be changed precisely. Air valves 56a and 66a connected to the exhaust 57a are arranged in the A-1 line and the A-2 line, respectively, so that the cleanliness in the pipe can be sufficiently maintained by the exhaust operation. Further, an N ₂ line gas is connected to the A-1 line, and an O ₂ gas cylinder diluted to 1% using N ₂ is connected to the A-2 line. The device 13 is provided with a manual valve 85 so that the quartz tube 71 can be exhausted by opening the manual valve 85. Further, the device 13 is provided with a pressure indicator 84 so that the pressure in the quartz tube 71 can be monitored.

The sulfur (S) raw material was configured to supply _H2S gas from a gas line (B-1) of another system.
The gas supply system of the B line has the same configuration as the gas supply system of the A line. There, the reactive gas supplied from the cylinder of _H2S gas diluted to 1% via the manual valve 52b, MFC53b, and air valve 54b is supplied to the B-1 line, and the manual valve 62b, MFC63b, and air valve 64b are supplied. The _N2 gas of the line is supplied to the B-2 line via the line. Further, in order to increase the gas purity in the pipe, an air valve 56b is arranged on the B-1 line side and an air valve 64b is arranged on the B-2 line side so that exhaust can be taken from the tips of both air valves.

Here, it is possible to use powder S for the S raw material, but here, with this configuration that enables On / Off operation by a valve and more precise control of the supply amount using a mass flow controller (MFC). did. In order to avoid the problem of powder S depletion, organic metal compounds such as H ₂ S, (CH ₃ ) ₂ S and (C ₂ H ₅ ) ₂ S, which have been proven in the MOCVD method, can be supplied as a gas raw material. Is preferable.

For the C line, the _N2 gas of the line is supplied to the C-1 line via the manual valve 62c, MFC63c and air valve 64c, and diluted to 1% with _N2 gas via the manual valve 52c, MFC53c and air valve 54c. The diluted _O2 gas supplied from the O2 gas cylinder is supplied to the C- ₂ line.

The apparatus 13 is configured to satisfy the following technical items required for the formation of the transition metal chalcogenide layered film described in the first embodiment.
(1) The reaction chamber on which the metal Mo is placed is separated so that other reactive gases such as S raw material gas do not unintentionally invade and react.
(2) The reaction chamber in which the metal Mo is placed is configured to be capable of supplying both an inert gas such as N ₂ and reactive O ₂ and a gas that comes into contact with the Mo metal by valve operation. Can be switched.
(3) With the configuration of (2) above, flow control equipment such as a mass flow controller is installed in each gas line, which enables control of the flow rate and concentration of N ₂ and O ₂ gas.
(4) The reaction chamber on which the metal Mo is placed is independent of the substrate region, and the generated _MoO3 gas can be guided to the substrate region.
(5) The MoO ₃ gas guided to the substrate region has a structure that can make the gas concentration uniform in the substrate portion by processing the shape of the gas blowing portion such as the shower head method.
(6) The raw material gas of the S raw material is mixed and reacts with MoO ₃ guided to the substrate portion in the substrate portion region as in (5).

<Process>
As a metal Mo to be installed in the oxide gas (MoO ₃ gas) generation chamber (Mo reaction chamber) 81, a high-purity block (manufactured by Pansee) with a purity of 99.97% was prepared, and the block (manufactured by Pansee) was 20 mm × 6 mm × 2 mm. It was cut into strips. Then, after cleaning with an organic solvent and pure water, the oxide gas generation chamber 81 was charged.
For both O ₂ gas and H ₂ S, cylinders diluted to 1% with high-purity N ₂ were prepared. Typical film formation conditions are as follows.
-Quartz reaction chamber 71 internal pressure: 20 Torr
-Film film temperature: 700 ° C or 750 ° C
-A-line flow rate: 100 sccm (1% O ₂ / N ₂ 20 sccm + N ₂ 80 sccm, or N ₂ 100 sccm)
B-line flow rate: 50 sccm (1% H ₂ S / N _{2 10} sccm + N ₂ 40 sccm, or N ₂₅₀ sccm)
・ C line flow rate: 250 sccm (N ₂ )
・ Film formation time: 3 minutes or more and 15 minutes or less ・ Substrate: Alkaline, aluminosilicate glass (20 mm x 20 mm x 0.55 mm)

The substrate was ultrasonically cleaned with an organic solvent (acetone, IPS) and pure water, dried with an _N2 blow, placed on a susceptor 75 made of alumina, and introduced into a predetermined position of an electric furnace 74.
After that, the inside of the quartz tube is sufficiently evacuated to a degree of vacuum of about 2 Pa, and then exhausted so that the pressure inside the reactor becomes 20 Torr while flowing only the _N2 gas of a predetermined flow rate from the A line 76 to the C line 78. Adjusted the needle valve on the side. From this state of N ₂ flow, the temperature was raised to 700 ° C. at a temperature rising rate of 25 ° C./min, and the film was stabilized for 5 minutes after reaching 700 ° C.
After that, the H _2S mixed gas is passed through the B line 77 with the switching valve, and after waiting for 30 seconds, the O ₂ mixed gas is passed through the A line 76 with the switching valve to generate and sublimate the molybdenum oxide scale in the oxide gas generation chamber. Started.
Then, the time when O ₂ is started to flow on the A line 76 is defined as the film formation start time, and after the lapse of a predetermined film formation time, the generation of MoO ₃ is stopped by switching O ₂ to N ₂ with the switching valve. The film formation was completed.
Then, the electric furnace 74 was naturally cooled while the _H2S of the B line 77 was flowing, and the sample was taken out after reaching room temperature.

<Material evaluation>
10 to 13 show optical micrographs of MoS ₂ formed at 700 ° C. and 20 Torr with different film formation times of 3 minutes, 5 minutes, 10 minutes, and 15 minutes. Here, (a), (b) and (c) of each figure are upstream, central and downstream locations (locations on the left, center and right side of the region shown by 79 in FIG. 8 (b)). Show it.
It can be seen that the method of the present invention forms a triangular domain of MoS ₂ having a size recognizable by an optical microscope, but this fact is epoch-making in this field, and the quality is higher than that of the conventional method. It is TMDC.
In addition, as the film formation time increases, the size of the triangular domain increases from several μm (film formation time 3 minutes) to several tens of μm (film formation time 10 minutes, 15 minutes), and finally coalesces into a continuous film. Was formed. Here, as an example of a continuous film, a film formed at 700 ° C. and 20 Torr with a film formation time of 15 minutes is shown in FIG. 14 with an optical micrograph further downstream from (c) in the above figure.
It has also been confirmed that it can be realized with good reproducibility without replacing the Mo metal raw material.

Although time dependence was shown here, it was confirmed that it can also be controlled by the _O2 flow rate. There, when the linearity (proportionality) of the time response of the film formation process to O ₂ and the response rate are emphasized, as explained with reference to FIG. 7, the formation rate of the oxide scale is small and does not exceed the sublimation rate. It was important to keep the O ₂ flow rate within the range.

FIG. 16A is a measurement example of the Raman spectrum of MoS ₂ measured at the triangular domain portion (see FIG. 15) at the downstream location where the film was formed for 10 minutes. The modes of A ¹ _g and E 12 _g are clearly observed, and the wavenumber interval is 20 cm ^-1 , indicating that it is a single layer.
Further, FIG. 16B is a measurement result of the photoluminescence (PL) spectrum obtained from the same measuring unit at room temperature. From this figure, very strong emission was observed near 666 nm, suggesting that this MoS ₂ is a monolayer film having a direct transition type band structure.
18 (a) and 18 (b) are Raman and PL spectra measured in the continuous membrane portion (see FIG. 17) of the sample grown for 15 minutes, respectively. Also in this case, it is shown that the obtained film is a MoS ₂ monolayer film having extremely good crystallinity.
As described above, it has been experimentally shown that the present invention is useful as a method for forming a single-layer film of MoS ₂ having good crystallinity.

(Example 2)
In Example 2, the substrate dependence of MoS ₂ film formation was investigated using a MOCVD (Metal-Organic Chemical Vapor Deposition) type film forming apparatus.

The device used is a device for MOCVD using a decompression / horizontal reactor having a susceptor made of high-purity graphite. The wafer (sample) placed on the susceptor is configured to be able to be heat-treated at a desired temperature by heating the wafer (sample) from the back surface of the susceptor with a halogen lamp.

Oxychloride was used as the raw material precursor for the molybdenum element, and molybdenum dichloride (MoO ₂ Cl ₂ ) was used as the specific precursor. On the other hand, hydrogen sulfide ( _H2S ) gas diluted to a volume concentration of 10% with _N2 gas was used as the sulfur (S) raw material of the chalcogen element.
Here, MoO ₂ Cl ₂ is solid at room temperature, but gas can be generated by sublimation by heating. In Example 2, the enclosed container was kept warm in a constant temperature bath at about 20 ° C. to generate steam, and the raw material gas was transported using N ₂ gas as a carrier.

Example 2 is a carbonless film formation using the oxychloride and _H2S .
Therefore, although the MOCVD apparatus is used in the second embodiment, strictly speaking, it is not a MOCVD film formation. Again, it is a carbon-less (organic-less) film formation similar to that of Example 1.

The typical film formation conditions of the MoS ₂ film in Example 2 are shown below.
・ Growth temperature: 700 ℃
・ Pressure: 50 Torr
・ Growth time: 1 hour ・ Total flow rate in the reactor: N ₂ gas 2.5 slm
・ MoO ₂ Cl ₂ supply conditions: N ₂ gas 75 sccm, filling container 18.0 ° C, controlled by internal pressure 760 Torr ・ 10% H ₂ S flow rate: 10 sccm

As the substrate, aluminosilicate glass containing an alumina component (Al ₂ O ₃ ) in the glass and alkali such as Na and K, which have a high softening point from the viewpoint of avoiding deformation and melting of the substrate due to heat applied during film formation. Alkaline, aluminosilicate, and glass, which were expected to add the catalytic effect of the element, were selected and the film forming property was evaluated. A list of the glasses is shown in Tables 1 and 2 below. The composition was measured by fluorescent X-ray.
Here, A is Dragontrail ^TM (DT) (manufactured by AGC), B is Dragontrail Pro ^TM (manufactured by AGC), C is Dinorex ^TM (manufactured by NEG), D is Gorilla-3 ^TM (manufactured by Corning), and E is Eagle-. It is XG ^TM (manufactured by Corning). A to D are alkaline aluminosilicate glass, and E is non-alkali aluminosilicate glass.

Under the above film forming conditions, MoS ₂ was formed by changing the type of the glass substrate. The result of SEM observation of the sample surface is shown in FIG.
From FIG. 19, it can be seen that the domain size and density of MoS ₂ differ greatly depending on the type of glass. In particular, since the film formation of MoS ₂ was not observed in the non-alkali glass of E, it is presumed that the catalytic effect of alkali metal elements such as Na and K in the glass is working.
The largest single crystal domain was obtained when A or B glass was used. This reproducibility was extremely high.

Although the film formation of MoS ₂ using molybdenum dichloride (MoO ₂ Cl ₂ ) as a precursor is shown here, not only MoO ₂ Cl ₂ but also tungsten monoxide tetrachloride (WOCl ₄ ) is used. Similar results were obtained when a film of WS ₂ was formed.
As an example, FIG. 20 shows the results (electron micrograph, Raman spectrum, PL spectrum) of forming WS2 on the Dragontrail ^TM ₍ DT) (manufactured by AGC) glass of A by a MOCVD device. In the case of WS ₂ , a large single crystal domain was formed on the Dragontrail ^TM (DT) (made by AGC) glass of A, and the spectra of Raman and PL show good crystallinity. Here, when WOCl ₄ was used, the enclosed container was kept warm in a constant temperature bath at 40 to 45 ° C. to generate steam, and the raw material gas was transported using _N2 gas as a carrier.

Typical film formation conditions for the WS2 film _are shown below.
・ Growth temperature: 700 ℃
・ Pressure: 50 Torr
・ Growth time: 1 hour ・ Total flow rate in the reactor: N ₂ gas 2.5 slm
・ WOCl ₄ supply conditions: N ₂ gas 250 sccm, filling container 45.0 ° C, controlled by internal pressure 760 Torr ・ 10% H ₂ S flow rate: 5 sccm

As described above, in Example 2, the case where MoS ₂ is formed by using the MOCVD apparatus is shown, but in the first embodiment, Examples 1 and 2, both the inorganic film formation using the carbonless raw material gas is shown. By the method, the film forming characteristics for the glass substrate were also common to the first embodiment, Examples 1 and 2.

(Example 3)
In Example 3, the effect of adding a small amount of oxygen gas (O ₂ gas) in Example 2 was investigated using the apparatus described in Example 2.

The typical film formation conditions of the MoS ₂ film in Example 3 are shown below.
・ Growth temperature: 700 ℃
・ Pressure: 50 Torr
・ Growth time: 1 hour ・ Total flow rate in the reactor: N ₂ gas 2.5 slm
・ MoO ₂ Cl ₂ supply conditions: N ₂ gas 75 sccm, filling container 18.0 ° C, controlled by internal pressure 760 Torr ・ 10% H ₂ S flow rate: 10 sccm
・ 0.1% O ₂ flow rate: 100 sccm
Therefore, the conditions are the same as in Example 2 except that 0.1% O ₂ is added. Here, 0.1% O ₂ means O ₂ gas having a volume ratio of 0.1% with respect to N ₂ gas.
As the substrate, four types of alkali, aluminosilicate, and silicate glass of A to D shown in Example 2 were used for evaluation.

FIG. 21 shows the results of SEM observation of the surface of the MoS ₂ film-formed sample.
When glass A is used as the substrate, the single crystal domain is about 10 μm, which is overwhelmingly larger than when other glass substrates are used. It is several times larger than the glass substrate B and is an order of magnitude larger than the glass substrates C and D.
The effect of adding O ₂ can be seen by comparison with Example 2, but the single crystal domain has a significant difference only when the glass substrate A is used, and when another glass substrate is used, O ₂ is added. No difference in superiority was observed.
The glass substrate A was a substrate specifically effective for forming a single crystal MoS ₂ .
In the first embodiment and the first embodiment, O ₂ is automatically added at the time of film formation. Also in Example 1, when the glass substrate A was used, the effect was observed in the formation of MoS ₂ in a large single crystal domain.

As mentioned above, transition metal chalcogenide layered films (TMDCs) are highly expected as the main functional materials for ultra-thin and flexible light-emitting / light-receiving elements, optical functional devices, and ultra-low power consumption electronic devices. According to the present invention, a film forming method for forming a transition metal chalcogenide layered film, particularly MoS ₂ , which has high stability and controllability, can increase the film forming area, and is excellent in cost. Manufacturing equipment is provided.
Therefore, it is considered that the present invention contributes to the industry innovatively centering on the above-mentioned elements and devices.

1: Metallic molybdenum (Mo)
2: Oxidation scale (MoO _x layer (2 ≦ x <3))
3: Oxidation scale (MoO ₃ layer)
4: O ₂
5: MoO ₃
6: Oxide gas supply means 7: Reactive gas supply means 8: Reaction chamber 9: Exhaust means 10: Film formation device 11: Film formation device 12: Gas supply system 13: Device 14: Quartz tube section 21: Oxide Gas generation chamber 22: Reaction chamber 23: Dedicated piping 25: Heater 31: Stage (stage with heater)
32: Transition metal block 33: Open / close / flow rate control device 34: Open / close / flow rate control device 35: Exhaust piping 36: Nozzle 37: Sample stand (sample stand with heater)
38: Sample 40: Open / close / flow rate control device 41: Piping (port)
42: Piping (port)
43: Piping 44: Open / close / flow rate control device 45: Piping (port)
46: Piping (port)
47: Piping 51: Piping 52, 52a, 52b, 52c: Valve (manual valve)
53, 53a, 53b, 53c: Mass flow controller 54, 54a, 54b, 54c: Valve (air valve)
55: Piping 56, 56a, 56b: Valve (air valve)
57: Exhaust piping 61: Piping 62, 62a, 62b, 62c: Valve (manual valve)
63, 63a, 63b, 63c: Mass flow controller 64, 64a, 64b, 64c: Valve (air valve)
66, 66a, 66b: Valve (air valve)
71: Quartz tube 72: Hypokeimenon (base)
73: Support 74: Electric furnace 75: Sample stand (substrate susceptor)
76: A line 77: B line 78: C line 79: MoS ₂ -layer film forming chamber (reaction chamber)
80: Exhaust 81: Mo reaction chamber (MoO ₃ gas generation chamber)
82: Upper nozzle 83: Lower nozzle 84: Pressure indicator 85: Manual valve

Claims (25)

Oxidizing a block of a transition metal to form an oxide layer of the transition metal on the surface of the transition metal,
The oxide is sublimated from the oxide layer, and the gas of the oxide is supplied to the substrate together with the first inert carrier gas via a dedicated pipe.
To supply the substrate with a reactive gas containing a chalcogen atom together with the second inert carrier gas.
By heating the substrate when the oxide gas and the reactive gas are supplied to the substrate,
A method for forming a transition metal chalcogenide layered film, which comprises exhausting the oxide gas, the reactive gas, the first inert carrier gas and the second inert carrier gas. The transition metals include titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), chromium (Cr), tungsten (W) and The method for forming a transition metal chalcogenide layered film according to claim 1, which is 1 selected from the group consisting of renium (Re). The method for forming a transition metal chalcogenide layered film according to claim 1 or 2, further comprising making the oxide layer a hydrogenated oxide layer. The method for forming a transition metal chalcogenide layered film according to claim 3, wherein the hydrogenation is performed by adding hydrogen gas during the oxidation. A block made of molybdenum is heated at a first temperature T1 while supplying a gas containing oxygen to form a molybdenum oxide layer on the surface of the block.
Molybdenum trioxide (MoO ₃ ) is sublimated from the molybdenum oxide layer, and the MoO ₃ gas is supplied to the substrate together with the first inert carrier gas via a dedicated pipe.
To supply the substrate with a reactive gas containing a chalcogen atom together with the second inert carrier gas.
When the MoO ₃ gas and the reactive gas are supplied to the substrate, the substrate is heated at the second temperature T2.
A method for forming a transition metal chalcogenide layered film, which comprises exhausting the MoO ₃ gas, the reactive gas, the first inert carrier gas and the second inert carrier gas. The method for forming a chalcogenide layered film according to claim 5, wherein the first temperature T1 is 500 ° C. or higher and 1200 ° C. or lower. The method for forming a transition metal chalcogenide layered film according to claim 5 or 6, wherein the second temperature T2 is 300 ° C. or higher and 1200 ° C. or lower. The dedicated pipe is heated from at least the place where the block is arranged to the region immediately before the substrate at a temperature at which the generated raw material gas component of MoO ₃ is prevented from being redeposited in the middle of the pipe. The method for forming a transition metal chalcogenide layered film according to any one of claims 5 to 7. The method for forming a transition metal chalcogenide layered film according to any one of claims 1 to 8, wherein the chalcogen atom is 1 selected from the group consisting of sulfur (S), selenium (Se) and tellurium (Te). The first inert gas and the second inert gas are one or more selected from the group consisting of nitrogen gas, argon gas, krypton gas, neon gas, helium gas and xenon gas, according to claims 1 to 9. The method for forming a transition metal chalcogenide layered film according to any one of the above. The method for forming a transition metal chalcogenide layered film according to any one of claims 1 to 9, wherein the first inert gas and the second inert gas are nitrogen gases. The method for forming a transition metal chalcogenide layered film according to any one of claims 1 to 11, wherein the substrate contains an alkali metal element as a composition. The method for forming a transition metal chalcogenide layered film according to claim 12, wherein the alkali metal element is one or more selected from the group consisting of sodium (Na), lithium (Li) and potassium (K). The method for forming a transition metal chalcogenide layered film according to any one of claims 1 to 12, wherein the substrate is an alkaline aluminosilicate glass. An oxide gas supply means for supplying an oxide gas to a substrate, a reactive gas supply means for supplying a reactive gas to the substrate, a reaction chamber portion for forming a transition metal cargogenide as a layered film on the substrate, and a reaction chamber portion. Equipped with exhaust means,
The oxide gas supply means includes a means for supplying a gas containing oxygen by controlling the flow rate, a means for supplying the first inert gas by controlling the flow rate, a block-shaped transition metal, and the transition metal. A first heating means for heating the substrate and a dedicated pipe for supplying an oxide gas sublimated from the transition metal onto the substrate.
The reactive gas supply means includes a means for supplying a reactive gas containing a chalcogen atom by controlling the flow rate, and a means for supplying the second inert gas by controlling the flow rate.
The reaction chamber is provided with a sample table and a second heating means for heating the substrate placed on the sample table, and is separated from the place where the transition metal is placed. ,
A device for forming a transition metal chalcogenide layered film, wherein the tube wall of the dedicated pipe is provided with a heat treatment means for keeping the temperature equal to or higher than the sublimation temperature of the oxide of the transition metal. The apparatus for forming a transition metal chalcogenide layered film according to claim 15, wherein the oxide gas supply means further includes means for supplying a gas containing hydrogen by controlling the flow rate. A MoO ₃ gas supply means for supplying MoO ₃ gas to a substrate, a reactive gas supply means for supplying a reactive gas containing sulfur to the substrate, and a reaction chamber portion for forming MoS ₂ as a layered film on the substrate. And equipped with exhaust means,
The MoO ₃ gas supply means heats the gas containing oxygen by controlling the flow rate, the first inert gas by controlling the flow rate, the block made of molybdenum, and the block. A first heating means and a dedicated pipe for supplying the gas of MoO ₃ sublimated and generated from the block onto the substrate are provided.
The reactive gas supply means includes a means for supplying the reactive gas by controlling the flow rate and a means for supplying the second inert gas by controlling the flow rate.
The reaction chamber is provided with a sample table and a second heating means for heating the substrate placed on the sample table, and is separated from the place where the block is placed.
A device for forming a MoS _two -layered film, which is provided with a heat treatment means for maintaining a temperature equal to or higher than the sublimation temperature of MoO ₃ on the pipe wall of the dedicated pipe. The reactive gas is sulfur (S), hydrogen sulfide (H ₂ S), dimethyl sulfur ((CH ₃ ) ₂ S), diethyl sulfur ((C ₂ H ₅ ) ₂ S), ditersial butyl sulfur ([(). CH ₃ ) ₃ C] ₂ S), diisopropyl sulfur ((i-C ₃ H ₇ ) ₂ S), which is 1 or more selected from the group consisting of the apparatus according to claim 17. The apparatus according to any one of claims 15 to 18, wherein the first heating means and the second heating means are one or more methods selected from the group consisting of resistance heating, induction heating and lamp heating. The first inert gas and the second inert gas are one or more selected from the group consisting of nitrogen gas, argon gas, krypton gas, neon gas, helium gas and xenon gas, according to claims 15 to 19. The device according to any one. The apparatus according to any one of claims 15 to 19, wherein the first inert gas and the second inert gas are nitrogen gases. The device according to any one of claims 15 to 21, wherein the dedicated pipe is composed of 1 selected from the group consisting of quartz glass, glass, stainless steel and ceramics. 22. The apparatus according to claim 22, wherein the ceramic is selected from the group consisting of alumina and SiC. The device according to any one of claims 15 to 23, wherein a shower head is provided in the vicinity of the substrate of the dedicated pipe. The apparatus according to any one of claims 15 to 24, wherein the sample table is provided with a rotation mechanism.

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