KR101800363B1 - METHOD OF MAMUFACTURING Transition Metal Dichalcogenide THIN FILM - Google Patents

Abstract

Disclosed is a method of manufacturing a transition metal dichalcogenide thin film capable of being mass produced with sputtering and electron beam treatment. According to the present invention, the method of manufacturing the transition metal dichalcogenide thin film deposits a crystalline or an amorphous transition metal dichalcogenide with less than ten layers with a sputtering process. Moreover, during the sputtering process or after the sputtering process, the amorphous transition metal dichalcogenide is crystallized with electron beam treatment.

Description

TECHNICAL FIELD [0001] The present invention relates to a thin film of a transition metal chalcogenide compound,

The present invention relates to a method for producing a transition metal chalcogenide (TMD) thin film such as molybdenum disulfide (MoS ₂ ), and more particularly, to a method for producing a transition metal chalcogenide (TMD) thin film using sputtering deposition and electron beam irradiation, To a method for producing a thin film.

Graphene is a representative two-dimensional material with excellent mechanical, thermal and electrical properties. However, due to the absence of energy bandgap, graphene has fundamental limitations in applications to electronic devices and optical devices.

Transition metal dichalcogenide (TMD) has recently been proposed as a two-dimensional material that can replace graphene. Transition metal chalcogen compounds are generally represented by the formula MX ₂ . Here, M is a transition metal element such as Mo, W, or Ti, and X is a chalcogen element such as S, Se, or Te.

These transition metal chalcogen compounds principally interact only with the constituent atoms in a two-dimensional manner. Therefore, the transport of carriers in the transition metal chalcogenide compounds exhibits a trajectory transporting behavior unlike conventional thin films or bulk, from which high mobility, high speed and low power characteristics can be realized.

MoS ₂ is a representative transition metal chalcogen compound material and has a sandwich structure in which molybdenum (Mo) is interposed between sulfur (S), as shown in Fig. MoS ₂ is layered through very strong covalent bonds between atoms. On the other hand, each layer has a two-dimensional layer structure having weak van der Waals bond.

Referring to FIG. 1, MoS ₂ can be classified into Hexagonal (2H) and Octahedral (1T) according to the direction of a triangle formed by Mo atoms and S atoms. Or a conductor (1T).

Most recently reported MoS ₂ devices, which exhibit high electron mobility and good photoelectric properties, are manufactured using flakes separated from a single crystal by a mechanical stripping method using a tape or the like. In order to make uniform large-area specimens Which is a process that can not be applied to industrial mass production.

Representative MoS ₂ production for industrial mass production method has been suggested a deposition method using a method of applying on a substrate to prepare a MoS ₂ of the ink type and the CVD (Chemical Vapor Deposition, CVD). The ink-based method uses lithium ions, which causes a problem of flammability and scarcity, and also low uniformity of MoS ₂ formed. The CVD method requires a high temperature of 700 DEG C or more and is not easy to form a uniform film.

In addition to these methods, transition metal chalcogen compounds, including MoS ₂ , are prepared by heating and evaporating transition metal oxide (e.g., MoO ₃ ) powder and sulfur powder to a high temperature so that the vapor contacts the adjacent substrate to deposit the sulfide , A method of supplying sulfur vapor to a transition metal film such as Mo and sulphating by heating, and a method of dip coating a substrate with (NH ₄ ) ₂ MoS ₄ solution and then heating it under a sulfur vapor to produce a sulfide film And so on. However, all of these methods require a high temperature of 700 DEG C or more, and it is difficult to form a uniform film such as a region where a single crystal grows on a substrate and a region that does not grow properly.

In addition, the mobility of the MoS ₂ thin films obtained by the above-described method is about 1/100 of the mobility of the MoS ₂ thin films obtained by the peeling method.

Therefore, there are the following manufacturing technology requirements for mass production of MoS ₂ . First, MoS ₂ should be uniformly produced on a large area substrate. Second, MoS ₂ for device fabrication must be able to be manufactured in-situ. Third, MoS ₂ fabrication processes should be possible at low temperatures to enable fabrication on glass, thin metal foils, and even polymer substrates.

As a background related to the present invention, there is disclosed a method of synthesizing a self-controlled molybdenum disulfide single layer using an electroplating process disclosed in Korean Patent Laid-Open Publication No. 10-2015-0078876 (published on Jul. 2015.08.08), and a self- There is a transistor using a single layer of molybdenum.

It is an object of the present invention to provide a method for producing a mass production of a transition metal chalcogenide compound thin film.

According to an aspect of the present invention, there is provided a method of fabricating a thin film of a transition metal chalcogenide compound, comprising: depositing 10 or less transition metal chalcogenide compounds on a substrate using a sputtering process; And irradiating an electron beam onto the transition metal chalcogenide compound deposited during the sputtering process to crystallize the transition metal chalcogenide compound.

In this case, the chalcogen element may be contained in the source used for the electron beam irradiation, the chalcogen element may be contained as a gas or a vapor in the chamber in which the sputtering process is performed, or the chalcogen element may be contained in the chamber of the transition metal chalcogenide compound target The atomic ratio of the chalcogen element may be higher than the stoichiometric ratio of the transition metal chalcogen compound.

 According to another aspect of the present invention, there is provided a method of fabricating a thin film of a transition metal chalcogenide compound, comprising: depositing 10 or less transition metal chalcogenide compounds on a substrate using a sputtering process; And irradiating an electron beam to the deposited amorphous transition metal chalcogenide after the sputtering process to crystallize the amorphous transition metal chalcogenide compound.

In the above embodiments, the transition metal contained in the transition metal chalcogenide compound is selected from Mo, W, Hf, Re, Ta and Ti, and the chalcogen element contained in the transition metal chalcogenide compound is S, Se And Te.

In the above embodiments, the transition metal chalcogenide compound thin film may have a thickness of 10 nm or less.

In the above embodiments, the sputtering process and the electron beam irradiation may be performed at a substrate temperature of 300 ° C or lower.

In the embodiments where the electron beam irradiation is performed during the sputtering process, the sputtering process is performed at an RF power of 5 to 40 W and a process pressure of 1 mTorr or less, and the electron beam irradiation is performed at an RF power of 50 to 300 W and a DC power of 50 to 3000 V .

In the embodiments in which the electron beam irradiation is performed after the sputtering process, the sputtering process is performed at an RF power of 5 to 20 W and a process pressure of 20 mTorr or less, and the electron beam irradiation is performed at an RF power of 50 to 300 W, And the time may be 0.5 to 20 minutes.

According to the method for producing a thin film of a transition metal chalcogenide compound according to the present invention, it is based on a sputtering process which is the most widely used mass production process in an industrial field. Among the conventional methods for preparing the transition metal chalcogenide compound thin film, the peeling method is difficult in large area and the CVD method is a process accompanied by high temperature, but its application is limited. However, by sputtering and electron beam irradiation, The tabernacle is possible. Of course, there have been attempts to fabricate MoS ₂ thin films by sputtering. However, there have been attempts to deposit Mo thin films and to carry out sulfurization using sulfur vapor at a high temperature of 600 ° C or higher, Which is not suitable for application and mass production. However, in the case of the present invention, both the sputtering process and the electron beam process can proceed at a low temperature, which is suitable for mass production.

Ultra-thin two-dimensional semiconductors within a single layer or several layers are distinguished from conventional thick or bulk semiconductors in principle because they only interact with the constituent atoms in a two dimensional manner, And it is possible to realize high mobility, high speed and low power characteristics from this.

Furthermore, since the thickness of the transition metal chalcogenide thin film is within a range of several nanometers, when the material exhibiting the indirect transient characteristics in a thin and transparent state and particularly in a thin film having a bulk or ordinary thickness is produced within a single layer or several layers, Transition characteristics can be shown.

1 shows a MoS ₂ structure having a two-dimensional layer structure.
2 is a schematic diagram of an electron beam assisted sputtering process.
FIG. 3 shows the atomic arrangement change of the MoS ₂ layer when electron beam post-treatment is used.
Figure 4 shows the MoS ₂ sample Raman results at a substrate temperature of 80 캜, 150 W RF power simultaneously.
Figure 5 is a 300 W 1000V electron beam post-treatment WS ₂ sample Raman result.
Fig. 6 shows the results of Raman analysis of a 300W 1000V 1min electron beam post-treatment MoS ₂ sample.
FIG. 7 shows the results of Raman map analysis of a MoS ₂ sample in a deposited state and a 300 W 1000 V 1 min electron beam post-treatment MoS ₂ sample.
Figure 8 is a TEM plan-view of a 300 W 1000 V 1 min electron beam post-treated MoS ₂ sample.
9 shows the XPS analysis result of 300W 1000V 1min electron beam post-treatment MoS ₂ sample.
FIG. 10 shows the results of substrate temperature measurement with electron beam irradiation time.
11 shows the result of TEM analysis of 300W 1000V 1min electron beam post-treatment MoS ₂ sample.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent with reference to the embodiments and drawings described in detail below. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims.

Hereinafter, a method for producing a thin film of a transition metal chalcogenide compound according to the present invention will be described in detail with reference to the accompanying drawings.

Transition metal chalcogen compounds such as MoS ₂ and WS ₂ have attracted attention as two-dimensional materials capable of replacing graphene, as described above, and are generally represented by the formula of MX ₂ . Here, M is a transition metal element selected from Mo, W, Hf, Re, Ta and Ti, and X is a chalcogen element such as S, Se and Te. These transition metal chalcogen compounds principally interact only with the constituent atoms in a two-dimensional manner. Therefore, the transport of carriers in the transition metal chalcogenide compounds exhibits a trajectory transporting behavior unlike conventional thin films or bulk, from which high mobility, high speed and low power characteristics can be realized.

It is necessary to form a thin and uniform thin film of several nanometers in the nature of a chalcogen compound having a two-dimensional structure. On the other hand, a crystalline thin film can be directly formed in the sputtering process, but in this case, uniformity of the thin film is a problem. In the present invention, an amorphous thin film favorable in terms of uniformity is first deposited by a sputtering process.

In order to obtain an amorphous thin film with minimized pores or defects in the sputtering process, the RF power is minimized and the distance between the sputter gun and the substrate is maintained at a certain distance or more to keep the deposition rate to a minimum, Can be maximized.

In the present invention, crystallization is carried out simultaneously with or after the sputtering process by electron beam irradiation. Such electron beam irradiation causes atom rearrangement to form a two-dimensional structure such as MoS ₂ and WS ₂ . When the electron beam irradiation is performed after the sputtering process, the process temperature of the electron beam irradiation process is 300 DEG C or lower, preferably 200 DEG C or lower, or even lower. The process time of the electron beam irradiation process is 1 minute or less, which is an efficient process.

 Particularly, in the present invention, it is preferable that the transition metal chalcogenide compound thin film is formed to 10 layers or less so that the above-described two-dimensional semiconductor characteristics are exhibited. As a result, the transition metal chalcogen compound can be formed to a thickness of 10 nm or less.

At this time, the transition metal chalcogenide compound can be formed by various methods such as CVD and sputtering, but a sputtering method capable of vapor deposition at a low temperature of 300 DEG C or less is most preferable. In this case, the electron beam treatment can also be performed at 300 DEG C or lower, so that the formation of the thin film of the transition metal chalcogenide compound can be performed as a whole at a low temperature of 300 DEG C or lower.

In addition, in the case of low-temperature sputtering, crystallization is required through atom rearrangement of the deposited transition metal chalcogenide compound, and the high temperature heat treatment method is mainly used for crystallization. However, in the case of the high temperature heat treatment method, the manufacturing cost is increased according to the long process time and the high temperature. In the present invention, the crystallization of the transition metal chalcogenide compound is performed by electron beam treatment which can be performed at low temperature and the process time is short. This electron beam treatment can be performed simultaneously with sputtering or after sputtering. This electron beam treatment will be described later.

2 is a schematic view of an electron beam assisted sputtering apparatus.

Referring to FIG. 2, the electron beam assisted sputtering apparatus includes a transition metal chalcogenide target (TMD Target) 210 for sputtering and an electron beam source 220 for electron beam irradiation. 2 (a) shows an example in which electron beam irradiation is performed during sputtering, and FIG. 2 (b) shows an example in which electron beam irradiation is performed after sputtering. The transition metal chalcogenide compound target and the electron beam source are preferably disposed in one chamber, but may be disposed in different chambers as needed.

The electron beam treatment may be performed during the sputtering process for forming the thin film of the transition metal chalcogenide compound. When the sputtering process and the electron beam deposition are performed simultaneously, the atomic ratio of the transition metal: chalcogen element of the transition metal chalcogenide compound layer formed may be smaller than 1: 2. In order to compensate for the lack of such a chalcogen element, it is necessary to either contain a chalcogen element as a gas or a vapor in the chamber in which the sputtering process is performed, or to change the atomic ratio of the chalcogen element of the transition metal chalcogenide target used in the sputtering process May be higher than the stoichiometric ratio of the metal chalcogen compound. As another example, a chalcogen element may be included in the source for electron beam processing.

Further, the electron beam treatment may be performed after the sputtering process for forming the thin film of the transition metal chalcogenide compound. FIG. 3 shows the atomic arrangement change of the MoS ₂ layer when the electron beam post-treatment is used. Referring to FIG. 3, it can be seen that the MoS ₂ layer near the amorphous state is changed to crystalline through electron beam irradiation by sputtering.

The crystalline or amorphous transition metal chalcogenide compound thin film may be formed by the sputtering process, and it is more preferable that the chalcogenide compound thin film is formed of amorphous in terms of uniformity.

Meanwhile, when electron beam irradiation is performed during sputtering, the sputtering process is preferably performed at an RF power of 5 to 40 W and a process pressure of 1 mTorr or less, and the electron beam irradiation is performed at an RF power of 50 to 300 W and a DC power of 50 to 3000 V . When the electron beam is irradiated at the same time, the plasma for sputtering can be maintained even at a low pressure, so that the energy of the sputtered atoms can be maintained by maintaining the process pressure of 1 mTorr or less, which facilitates the crystallization of the transition metal chalcogenide compound.

On the other hand, when electron beam irradiation is performed after sputtering, the sputtering process is performed at an RF power of 5 to 20 W and a process pressure of 20 mTorr or less, and the electron beam irradiation is performed at an RF power of 50 to 300 W, a DC power of 50 to 3000 V, Min. ≪ / RTI > When the RF power is lowered by sputtering, the deposition rate is reduced. When the process pressure is increased, the amorphous transition metal chalcogenide compound thin film is more easily formed, thereby obtaining a thin film having uniform surface roughness. In the crystallization process through post-treatment, transition to crystalline is easier in the case of an amorphous thin film which is thermodynamically more unstable. Under the above conditions, deposition of less than 10 transition metal chalcogenide compounds can be easily performed, and crystallization by atomic rearrangement can be performed well by electron beam irradiation.

According to the method for preparing a thin film of a transition metal chalcogenide compound according to the present invention, a thin film of a transition metal chalcogenide compound is formed by an electron beam treatment crystallization process based on a sputtering process that can be performed at a low temperature. In the case of the present invention, this is advantageous in mass production.

Ultra-thin two-dimensional semiconductors within a single layer or several layers are distinguished from conventional thick or bulk semiconductors in principle because they only interact with the constituent atoms in a two dimensional manner, And it is possible to realize high mobility, high speed and low power characteristics from this.

Further, since the thickness of the thin film of the transition metal chalcogenide compound to be produced is within a range of several nm, the material exhibiting the indirect transition characteristic in a thin and flexible state, especially in a bulk state or a thin film state, The transition characteristics can be expressed directly.

Hereinafter, various measurements were performed while changing the material of the transition metal chalcogenide compound, the method of simultaneous irradiation with sputtering or the irradiation after sputtering, and the electron beam irradiation energy. More specifically, in the case of electron beam simultaneous irradiation sputtering, sputtering was performed at a power of 10 to 40 W, a process pressure of 1 mTorr or less, and a substrate temperature of 25 to 300 ° C. and RF power of 150 to 300 W, DC power of 500 to 1500 V, Electron beam irradiation was performed at 5 min. On the other hand, in the case of electron beam post-treatment sputtering, sputtering conditions of a power of 10 to 20 W, a process pressure of 1 to 10 mTorr and a substrate temperature of 25 DEG C, and an electron beam condition of RF power of 150 to 300 W, DC power of 500 to 2000 V and irradiation time of 0.5 to 20 min .

Figure 4 shows the MoS ₂ sample Raman results at a substrate temperature of 80 캜, 150 W RF power simultaneously. In this case, a sputtering and electron beam simultaneous irradiation deposition process was applied.

Referring to FIG. 4, it was confirmed by Raman analysis that the ratio of Mo: S in the MoS ₂ thin film was not easily maintained in the 1: 2 ratio due to the low degree of vacuum in the electron beam concurrent irradiation deposition process .

In this experiment, the above problem can be solved by adding sulfur (S) to the electron beam source.

Figure 5 is a 300 W 1000V electron beam post-treatment WS ₂ sample Raman result.

The asymmetric WS ₂ thin film (as-dep) was synthesized by sputtering and the electron beam post-treatment was applied to confirm the crystalline two-dimensional WS ₂ synthesis. The crystallinity improvement was analyzed by Raman analysis according to the post-treatment time (1, 5 min) I could confirm.

Fig. 6 shows the results of Raman analysis of a 300W 1000V 1min electron beam post-treatment MoS ₂ sample.

In addition, the amorphous MoS ₂ thin film (as-dep) was synthesized by sputtering, and the crystallinity improvement with electron beam post-treatment time (1, 5, 10 min) was confirmed by Raman spectra.

FIG. 7 shows the results of Raman map analysis of a MoS ₂ sample in a deposited state and a 300 W 1000 V 1 min electron beam post-treatment MoS ₂ sample.

Referring to FIG. 7, the synthesis of MoS ₂ in a wide region can be confirmed by Raman map.

Figure 8 is a TEM plan-view of a 300 W 1000 V 1 min electron beam post-treated MoS ₂ sample. The figure on the right shows the diffraction pattern of the area A in the middle figure. As the diffraction patterns appeared as symmetrical hexagons, it was confirmed that MoS ₂ was formed with hexagonal crystal structure. 9 shows the XPS analysis result of 300W 1000V 1min electron beam post-treatment MoS ₂ sample.

Referring to FIGS. 8 and 9, the improvement of crystallinity through electron beam post-treatment was verified by XPS analysis, and it was confirmed that Mo: S had a ratio of 1: 2.

FIG. 10 shows the results of substrate temperature measurement with electron beam irradiation time.

As a result of the temperature measurement according to the electron beam irradiation time, 300 ° C was reached when irradiated for 7 minutes at 300W 1000V, and less than 250 ° C for 15 minutes irradiated at 150W 1000V.

11 shows the TEM analysis result of 300W 1000V 1min electron beam post-treatment MoS ₂ sample. Referring to FIG. 11, the cross-section of the synthesized MoS ₂ was subjected to TEM analysis. As a result, it was confirmed that 6 to 7 layers were formed at a thickness of 4 nm.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is to be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (9)

Depositing 10 or less layers of a transition metal chalcogenide compound on a substrate using a sputtering process; And
And irradiating an electron beam onto the transition metal chalcogenide compound deposited during the sputtering process to crystallize the transition metal chalcogenide compound,
Wherein the transition metal contained in the transition metal chalcogenide compound is selected from Mo, W, Hf, Re, Ta and Ti, the chalcogen element contained in the transition metal chalcogenide is selected from S, Se and Te, The transition metal chalcogen compound is deposited to a thickness of less than 10 nm,
Wherein the electron beam irradiation is performed under conditions including a DC power of 50 to 3000 V.
The method according to claim 1,
The chalcogen element may be contained in the source used for the electron beam irradiation, the chalcogen element may be contained as a gas or vapor in a chamber in which the sputtering process is performed, or the chalcogen element of the transition metal chalcogenide target used in the sputtering process Wherein the atomic ratio of the transition metal chalcogen compound is higher than the stoichiometric ratio of the transition metal chalcogen compound.
Depositing 10 or less layers of a transition metal chalcogenide compound on a substrate using a sputtering process; And
Irradiating the deposited transition metal chalcogenide compound with an electron beam to crystallize after the sputtering process,
Wherein the transition metal contained in the transition metal chalcogenide compound is selected from Mo, W, Hf, Re, Ta and Ti, the chalcogen element contained in the transition metal chalcogenide is selected from S, Se and Te, The transition metal chalcogen compound is deposited to a thickness of less than 10 nm,
Wherein the electron beam irradiation is performed under conditions including a DC power of 50 to 3000 V.
delete delete 4. The method according to any one of claims 1 to 3,
Wherein the amorphous transition metal chalcogen compound is deposited by the sputtering process.
4. The method according to any one of claims 1 to 3,
Wherein the sputtering process and the electron beam irradiation are performed at a substrate temperature of 300 DEG C or less.
3. The method according to claim 1 or 2,
The sputtering process is performed at an RF power of 5 to 40 W and a process pressure of 1 mTorr or lower,
Wherein the electron beam irradiation is performed at an RF power of 50 to 300 W and a DC power of 50 to 3000 V.
The method of claim 3,
The sputtering process is performed at an RF power of 5 to 20 W and a process pressure of 20 mTorr or less,
Wherein the electron beam irradiation is performed at an RF power of 50 to 300 W, a DC power of 50 to 3000 V, and an irradiation time of 0.5 to 20 minutes.

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