Adsorption control method and film deposition apparatus

Abstract

To control the adsorption of the raw material of a second layer to a first layer.SOLUTION: A method for controlling the adsorption of the raw material of a second layer on a first layer comprises: preparing a substrate including the first layer on a stage in a chamber; supplying the raw material of the second layer into the chamber to expose the raw material to the surface of the first layer; and controlling the adsorption of the raw material on the surface of the first layer by controlling electric charges provided to defects on the surface of the first layer.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to an adsorption control method and a film forming apparatus. [Background technology]

[0002] For example, Patent Document 1 describes a method for forming a two-dimensional insulating material layer and a two-dimensional semiconductor material layer, in which after forming a two-dimensional insulating material layer, the surface is activated by ion doping, and a two-dimensional semiconductor material layer made of a transition metal chalcogenide, black phosphorus, silylene, germanium alkene, or graphene is formed by a CVD method or an ALD method. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] China Patent Application Publication No. 109962106 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can control the adsorption of a raw material in a second layer into a first layer. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, there is provided a method for controlling adsorption of a raw material for a second layer onto a first layer, the method including: preparing a substrate having the first layer on a stage in a chamber; supplying raw material for the second layer into the chamber and exposing the raw material to a surface of the first layer; and controlling adsorption of the raw material onto the surface of the first layer by controlling an electric charge applied to defects on the surface of the first layer. Effect of the Invention

[0006] According to one aspect, the adsorption of the raw material of the second layer to the first layer can be controlled. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 shows an example of hexagonal boron nitride. [Diagram 2] FIG. 13 is a diagram showing the results of a first simulation of adsorption energy according to an embodiment. [Diagram 3] FIG. 13 is a diagram showing the results of a second simulation of the adsorption state of WF6 according to an embodiment. [Figure 4] FIG. 13 shows the change in adsorption energy depending on the charge state of VN. [Diagram 5] FIG. 13 is a diagram showing the results of a third simulation of the surface state of h-BN according to an embodiment. [Figure 6] 1 is a graph showing the correlation between the Fermi level and the formation energy of surface defects according to an embodiment. [Figure 7] 11A and 11B are diagrams illustrating an example of charge state adjustment and its effect according to an embodiment. [Figure 8] 4 is a flowchart showing an example of an adsorption control method according to an embodiment. [Figure 9] 5A to 5C are diagrams for explaining an adsorption control method according to an embodiment. [Figure 10] FIG. 1 is a diagram showing an example of a film forming apparatus according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicated descriptions may be omitted.

[0009] [An example of hexagonal boron nitride] The deposition of transition metal dichalcogenides (TMDCs) onto hexagonal boron nitride (h-BN) is crucial for industrial applications of 2D materials. h-BN and TMDCs are examples of 2D material layers. h-BN is an example of a 2D insulating material layer. TMDCs are an example of a 2D semiconductor material layer, such as MoS2, WS2, MoSe2, and WSe2.

[0010] Figure 1 shows an example of pure, i.e. defect-free, bilayer hexagonal boron nitride (bilayer h-BN). Figure 1(a) shows the surface (XY plane) of h-BN. h-BN is a layered material, and Figure 1(b) shows the layered structure of bilayer h-BN in the Z direction. The number of layers in h-BN is not limited to two, and it has a layered structure in which two-dimensional structures are stacked in which many six-membered rings formed by alternating covalent bonds between boron (B) and nitrogen (N) are bonded together.

[0011] Like h-BN, TMDCs are layered materials with a two-dimensional (2D) structure. TMDCs have a band gap of 1-2 eV and high carrier (electron) mobility, so they are used, for example, as channel materials for transistors. In order to maintain the carrier mobility and subthreshold swing of TMDCs at ideal levels, inert two-dimensional h-BN is required as a protective layer for TMDCs. In addition, h-BN has a large band gap of 4-5 eV, so electrons do not flow unless more energy than TMDC is applied, so it functions as an insulating film to prevent leakage.

[0012] However, it is challenging to directly deposit TMDCs on h-BN or other 2D materials to create 2D heterostructures. For example, WS2 is a promising candidate for future FET channels, with a relatively wide bandgap and low subthreshold swing among all TMDCs. WF6 and H2S precursors have been proposed as precursors for the ALD process to deposit WS2.

[0013] However, common precursors such as WF6 and H2S do not strongly interact with the pure h-BN surface, making it difficult to use these sources to deposit WS2 on h-BN. Furthermore, the reactivity of the h-BN surface cannot be controlled during the ALD process. Therefore, in conventional ALD processes, the domain size of WS2 is uncontrollable, resulting in small domains of WS2 with inferior film quality. The word "domain" is analogous to the grain size, and a larger grain size reduces the ratio of grain boundaries, which are inferior to the inherent properties of the WS2 film, and improves the film quality.

[0014] In response to this, the inventors used first-principles quantum simulations to find that while the adsorption of WF6 to pure h-BN is weak, the adsorption of WF6 can be significantly enhanced by forming defects (vacancies) in h-BN.

[0015] In the following, an adsorption control method is described that can control the adsorption state of the precursor used for forming the TMDC film by adjusting the FeMil level of h-BN when forming the TMDC film on the h-BN surface. In the description of the adsorption control method according to this embodiment, WS2 is taken as an example of the TMDC deposited on the surface of h-BN, and WF6 and H2S are taken as precursors for forming the WS2 film.

[0016] An example of a vacancy formed in h-BN is shown in Figures 1(c) and (d). Figures 1(c) and (d) show the state of the surface (first layer) of h-BN. In Figure 1(c), the lattice point A1, where N was originally present in the first layer, has become a nitrogen vacancy (hereafter referred to as "V N The boron (B) at the lattice point A1 is the B of the second layer of h-BN that exists at the vacant lattice point A1.

[0017] In Figure 1(d), the lattice point A2 in the first layer, where B is originally present, is a boron vacancy (hereafter, V B The nitrogen (N) at the lattice point A2 is the N of the second layer of h-BN at the vacant lattice point A2.

[0018] [Simulation 1] In Simulation 1, we simulated the change in the adsorption energy of WF6 and H2S on the h-BN surface for pure h-BN and for defective h-BN. The results are shown in Figure 2.

[0019] The "Ideal" in Figure 2 is pure h-BN with no defects. N " has a defect (N defect) where N is missing at the lattice point of h-BN. "V B " has a defect (B defect) where B is missing at the lattice point. "Si N -H", "C N -H", "C N " is a type of h-BN in which the N atoms are replaced by SiH, CH, and C, respectively. "Si B -H", "C B -H", "C B " has a B defect in which the nearby nitrogen is replaced by SiH, CH, or C, respectively. "V N -H" is V N If there is H near B N " has the N atom replaced by B. "N B " is a compound in which the B atom is replaced by N. "O N " has an N atom replaced with O (oxygen). N "-H" means that the N atom has been replaced with O (oxygen) and H (hydrogen) is bonded to the O.

[0020] In Simulation 1, WF6 and H2S are adsorbed on the surface of h-BN in the cases of pure h-BN and the cases of h-BN with various defects as described above. In addition, the charge state of the various h-BN defects is set to 0, i.e., electrically neutral.

[0021] The vertical axis of Fig. 2 shows the adsorption energy E_ad of WF6 and H2S on the surface of various h-BN. E_ad is expressed by the following formula (1). E_ad=E_final-E_h-BN-E_molecule···(1) In formula (1), E_final indicates the adsorption energy when each molecule of WF6 and H2S is adsorbed on the surface of h-BN, structurally optimized, and stable. E_h-BN indicates the adsorption energy when each molecule of WF6 or H2S is not adsorbed on the surface of h-BN. E_molecule indicates the adsorption energy of one molecule of WF6 or H2S. Therefore, the adsorption energy E_ad indicates the difference in adsorption energy between the state in which each molecule of WF6 or H2S is adsorbed on h-BN and the state before adsorption. The larger the absolute value of the adsorption energy E_ad, the stronger the adsorption.

[0022] In the case of pure h-BN shown as "Ideal", the adsorption of both WF6 and H2S molecules to h-BN is weak due to van der Waals forces. N In the case of "C", the adsorption of WF6 to h-BN is strengthened. B In the case of "O", the adsorption of WF6 to h-BN is strengthened. N In the case of ", the adsorption of WF6 and H2S to h-BN is strong. The adsorption of other above-mentioned h-BN is weak adsorption due to van der Waals forces.

[0023] This means that when the charge state of the defect is set to 0, "V N ", "C B ", "O N It is found that in h-BN containing the defect ", strong chemical adsorption occurs between the defect and WF6.

[0024] In addition, when the charge state of the defect is set to 0, N It is found that in h-BN containing the defect ", strong chemical adsorption occurs between the defect and H2S.

[0025] [Simulation 2] In simulation 2, when the charge of the N defect is set to 0, -1, and +1, "V N The behavior of WF6 adsorption on the h-BN surface of "V" is calculated. Figure 3 shows the results of simulation 2. Figure 3(a) shows the behavior of WF6 adsorption on the h-BN surface of "V" when the charge of the N defect at the vacancy is set to 0. N ” (hereinafter referred to as “VN 0 "). The number of electrons in the outermost shell of N is 5, and when the charge on the N defect is 0, it is electrically neutral, that is, no electrons enter or leave the N defect, and the number of electrons in the outermost shell remains at 5. Because the number of electrons in the outermost shell is odd, an electron spin is generated. Under these conditions, strong chemical adsorption occurs between the N defect in h-BN and WF6.

[0026] Figure 3(b) shows the V N ” (hereinafter referred to as “V N -1 "). When the charge on the N defect is -1, one electron enters the N defect. In this case, the number of electrons in the outermost shell is even, and h-BN is not magnetic, so no electron spin is generated. Under these conditions, strong chemical adsorption occurs between the N defect in h-BN and WF6.

[0027] Figure 3(c) shows the V N ” (hereinafter referred to as “V N +1 "). When the charge on the N defect is +1, one electron leaves the defect. In this case, since the number of electrons in the outermost shell is even, no electron spin is generated. Under these conditions, weak adsorption occurs between the N defect in h-BN and WF6 due to van der Waals forces.

[0028] Figure 4 shows the V N The horizontal axis of FIG. 4 shows the change in adsorption energy depending on the charge state of V. N Charge state V N -1 , V N 0 , V N +1 The vertical axis shows the adsorption energy E_ad at each charge state. V N The charge state of V N -1 Or V N 0In the case of , W and F of WF6 are dissociated and adsorbed, and the adsorption energy is low, which indicates that F is easily and stably adsorbed to the underlayer. N The charge state of V N +1 In the case of , the adsorption energy is high and unstable, indicating that F is difficult to adsorb to the underlayer.

[0029] [Simulation 3] In Simulation 3, "V N 0 ", "V N -1 ", "V N +1 The electron density of states on the surface of h-BN with N defects in each charge state is calculated. From the results of Simulation 3, the mechanism of the difference in the adsorption state of WF6 due to the charge state of the N defects shown in Figure 3 is inferred.

[0030] FIG. 5 shows the results of Simulation 3. The horizontal axis of FIG. 5 shows the energy level, and the vertical axis shows the "V N 0 ", "V N -1 ", "V N +1 The electron density of states (DOS) on the surface of h-BN in the V N -1 ", "V N +1 In the case of "V", the number of electrons in the N defect is even and no electron spin occurs. N 0 In the case of ", the number of electrons in the N defect is odd, and the electrons have a spin, which causes them to be polarized to positive (up spin) and negative (down spin).

[0031] Figure 5(a) shows the V N 0" shows the DOS of the h-BN surface with positively and negatively polarized electron spins. The energy level of approximately -3 to 2 eV is the band gap (of h-BN), and according to the Fermi-Dirac distribution, there are few carriers except near the Fermi level. Note that the energy level smaller than -3 eV is the valence band, and the energy level larger than 2 eV is the conduction band (acceptor band). The Fermi level in the band gap can be defined anywhere in the band gap. In Figures 5 (a) to (c), the Fermi level is defined as 0 eV.

[0032] The upper half of Figure 5(a) shows the DOS of the h-BN surface for up-spin electrons, and the lower half for down-spin electrons. In the results in Figure 5(a), the DOS is locally increased at the Fermi level (0 eV) for up-spin electrons. For down-spin electrons, the DOS is 0 at the Fermi level (0 eV). This is the "V N 0 " shows that in h-BN with electron spin, isolated N defects have only positively polarized electrons.

[0033] In Figure 5(b), "V N -1 In h-BN, which has no electron spin, the energy level of about -3 to +1 (eV) is the band gap. In the result shown in Figure 5(b), the DOS is locally increased at the Fermi level (0 eV). This is because N -1 " indicates the presence of an electron in the N defect of h-BN.

[0034] In Figure 5(c), "V N +1 In h-BN with no electron spin, the energy level above 0 eV is the band gap. In the result shown in Figure 5(c), the DOS is 0 at the Fermi level (0 eV). This is the "V N +1 This means that the h-BN exhibits properties similar to those of the original pure h-BN.

[0035] In Figure 5(a), "V N 0 ", h-BN with electron spin, and "V N -1 In h-BN without electron spin, the electron charge density in the space near the N defect becomes an electron distribution that extends in the height direction from the XY plane of the h-BN surface.

[0036] If the wave function is Ψ, the probability that an electron is found in the space near the defect at a certain time t is |Ψ(t)| 2 Therefore, the charge density of an electron is proportional to the square root of the electron's wave function, and the charge density of an electron can be indirectly expressed from the electron's wave function.

[0037] "V N 0 ", "V N -1 In the case of h-BN, the wave function of the electrons filling the space near the defect closest to the Fermi level indicates that the electron orbit is a Pz (or π orbital), which elongates in the Z direction (vertical direction) from the XY plane of the h-BN surface. Therefore, the charge density of the electrons in the space near the defect is distributed in the height direction from the plane of the h-BN. In this case, it is presumed that the reactivity at the N defect is high, which causes the adsorption force of WF6 to become stronger.

[0038] "V N +1 In the case of h-BN, the electron orbital is Pxy (or σ orbital) based on the wave function of the electrons filling the space near the defect closest to the Fermi level, and the charge density of the electrons in the space near the defect is a distribution of electrons periodically scattered on the XY plane of the h-BN surface. In this case, the h-BN surface becomes similar to the physical properties of the original pure h-BN, and WF6 is weakly adsorbed to the h-BN by van der Waals forces.

[0039] [Correlation between Fermi level and formation energy of surface defects] "V NFIG. 6 shows the results of simulating the correlation between the Fermi level and the formation energy of surface defects (N vacancy) in h-BN of ". FIG. 6 is an example of a graph showing the correlation between the Fermi level and the formation energy of defects according to one embodiment. The horizontal axis of FIG. 6 is the Fermi level E f The vertical axis indicates the Fermi Level, and the vertical axis indicates the formation energy of the defect. The lower the formation energy of the defect, the more stable the defect is.

[0040] From the results shown in Figure 6, the Fermi level E f When the charge state is moved, the most stable charge state at the N vacancy changes. For example, the Fermi level E f However, between 0 and 2.5 eV, the defect is most stable when the N defect is in a +1 charge state. f At a Fermi level E of just over 2.5 eV to approximately 4 eV, the N defect is placed in a zero charge state, making the defect the most stable state. f Above about 4 eV, the most stable state for the N defect is achieved by placing it in the −1 charge state.

[0041] The charge state with the lowest defect formation energy is the most stable state of the defect. Therefore, the Fermi level E f By adjusting the "V N " We directly adjust h-BN so that the N defects in h-BN are in a stable charge state.

[0042] One method for adjusting the Fermi level is "V N The Fermi level can be adjusted by applying an external DC voltage to charge the h-BN and / or by doping impurities into the h-BN.

[0043] When applying an external DC voltage to give charge to h-BN, the Fermi level can be adjusted to shift to higher or lower energy depending on whether the electric field applied to the h-BN is positive or negative. The Fermi level is between 0 eV (no potential) and 3 eV, and is shown by the dashed line +1 in Figure 6 as "V N +1 " is the lowest energy, and at around 3 eV to 5 e on the right side, "V N 0 " is the lowest energy. At 5 eV or more on the right, the "V N -1 " has the lowest energy. To shift the Fermi level to the right, the h-BN surface is placed at a negative potential. To shift the Fermi level to the left, the h-BN surface is placed at a positive potential.

[0044] In doping impurities into h-BN to give a charge to the h-BN, p-type doping and n-type doping are possible, and Mg or Be may be used for p-type doping. However, in order to give a charge to the h-BN, applying a DC voltage from the outside is preferable because it provides a higher degree of control than doping into the h-BN.

[0045] As described above, in the method for controlling adsorption according to the present embodiment, the electric field (voltage) applied to h-BN is controlled to move the FeMil level, thereby adjusting the charge state of defects in h-BN, thereby changing the reactivity of WF6 and controlling the adsorption of WF6 to h-BN.

[0046] FIG. 7 shows an example of the adjustment of the charge state of N defects in h-BN according to an embodiment and the effect thereof. For example, as shown in FIG. 7(a), when the Fermi level is adjusted so that the charge on the N defects becomes +1 by applying a voltage to h-BN, the state becomes similar to that of pure h-BN, and the adsorption force of WF6 to h-BN becomes weak. As shown in FIG. 7(b), when the Fermi level is adjusted so that the charge on the N defects becomes -1 or 0 by applying a voltage to h-BN, the adsorption of WF6 becomes strong near the N defects of h-BN. Note that instead of h-BN, materials such as sapphire, SiO2, Si, and high-k can be applied.

[0047] [Adsorption control method] Next, an adsorption control method according to an embodiment will be described with reference to Figs. 8 and 9. Fig. 8 is a flowchart showing an example of the adsorption control method according to an embodiment. Fig. 9 is a diagram for explaining the adsorption control method according to an embodiment. The adsorption control method shown in Fig. 8 takes the formation of a WS2 film on h-BN by the ALD method as an example. The adsorption control method is controlled by, for example, a control unit 3 shown in Fig. 10, which will be described later, and is performed by a film formation apparatus 1 shown in Fig. 10.

[0048] When the present adsorption control method is started, in step S1, a substrate having h-BN containing N defects is prepared on a stage in a chamber. In order to control the N defects formed in h-BN, the film may be formed in a state in which there is a shortage of nitrogen, and the number of N defects can be controlled by the amount of nitrogen deficiency. However, since N defects naturally occur in h-BN during film formation, it is not necessarily necessary to control N defects during h-BN film formation.

[0049] Next, in step S2, a negative DC voltage is applied to the electrodes in FIG. 10 (such as electrode 40 in FIG. 10(a)) to obtain “V N 0 " (N defect charge is 0) or "V N -1While adjusting the Fermi level so that the charge on the N defect is -1, a small amount of WF6 is supplied into the chamber. At this time, as shown in Figure 9(a), the adsorption of WF6 becomes stronger near the defects in the h-BN, and WF6 is adsorbed near the defects.

[0050] In step S2, WF6 is supplied in the first cycle. At that time, the charge state of the N defects is adjusted to 0, the reactivity around the defects is increased, and the adsorption of WF6 is strengthened, but the supply amount of WF6 is controlled to be less than that in the second cycle and thereafter. Therefore, as shown in FIG. 9(a), WF6 molecules are adsorbed to some of the N defects, and most of the N defects become vacant lattice points. Note that WF6 and Ar may be supplied in step S2 and step S5 described later. In this case, the first cycle of step S2 may be diluted with Ar to make the amount of WF6 smaller than that in the second cycle and thereafter of step S5.

[0051] Next, in step S3 of the first cycle, the same state as in step S2 ("V N 0 " or "V N -1 H2S is supplied into the chamber in a charge state of 0 ("charge state"). At this time, as shown in FIG. 9(b), the adsorption of H2S to the vicinity of N defects of vacancies in a charge state of 0 or a charge state of -1 (not shown) is weak. On the other hand, H2S reacts with WF6 molecules adsorbed to the N defects to form nuclei of W(SH)x. In order to form nuclei, a sufficient amount of H2S is supplied in step S3. The nuclei used here refer to nuclei that are the centers of film growth. A bias voltage is applied as necessary. For example, a predetermined bias voltage is applied when forming nuclei. It is not necessary during film formation after nuclei formation, so the application of the bias voltage can be stopped as appropriate.

[0052] Next, in step S4, it is determined whether the set number of cycles has been repeated. If it is determined that the set number of cycles has not been repeated, in step S5, a positive DC voltage is applied to the electrodes to set "V N +1WF6 is supplied into the chamber while adjusting the Fermi level so that the charge on the N defect is +1. This weakens the adsorption of WF6, and prevents it from occurring in areas other than where W(SH)x nuclei have already formed. This allows a small number of controlled nuclei to grow two-dimensionally in the lateral direction and form large domains. This allows the grain size of the W(SH)x nuclei to grow, as shown in Figure 9(c). Next, in step S3 of the second cycle, the same state as in step S5 ("V N +1 In this state, H2S is supplied into the chamber to further grow the W(SH)x nuclei.

[0053] If the set number of cycles is 3 or more, step S5 and step S3 are counted as one cycle and are repeated until the set number of cycles is reached. However, in step S5 from the third cycle onwards, since the charge to the N defect has already been adjusted to +1 in the second cycle, there is no need to apply a voltage to further adjust the FeMil level, and WF6 is supplied. If it is determined in step S4 that the set number of cycles has been repeated, this process is terminated.

[0054] According to the adsorption control method of this embodiment, the adsorption of WF6 on the h-BN surface can be adjusted by supplying WF6 into the chamber while adjusting the Fermi level. In addition, the density of nuclei formed can be controlled by controlling the supply amount of WF6. The more the number of nuclei, the smaller the domains become, and the lower the quality of the WS2 film. Therefore, by reducing the number of nuclei, the domains are enlarged and the domain boundaries are reduced. By controlling the domain size of WS2 in this way, a good quality WS2 film can be formed. In addition, by controlling the number of nuclei in the first cycle, it is not necessary to strictly control the number of defects in h-BN.

[0055] In step S2, the Fermi level may be adjusted so that the charge state of the defect is −1 instead of 0. However, when the charge state of the defect is set to −1, a larger voltage is required than when adjusting the Fermi level so that the charge state of the defect is set to 0. Therefore, setting the charge state of the defect to 0 is easier to control and is also advantageous in terms of cost.

[0056] In order to switch between WF and H2S, it is preferable to perform a purge step between the steps S2 and S5 of supplying WF6 and the step S3 of supplying H2S. In the purge step, an inert gas such as Ar gas may be supplied.

[0057] The adsorption control method according to the present embodiment preferably uses the ALD method, but after the nuclei are formed, the WS2 film may be formed by chemical vapor deposition (CVD) or metal organic chemical vapor deposition (MOCVD).

[0058] While this embodiment focuses on improvements in the deposition of WS2 films on h-BN using WF6 and H2S, the adsorption control method of this embodiment can also be applied to other precursors (raw materials for transition metal dichalcogenide films) and other two-dimensional material layers.

[0059] For example, a method for controlling adsorption of a precursor of a transition metal dichalcogenide film onto a two-dimensional material layer, the adsorption control method including: preparing a substrate having the two-dimensional material layer on a stage within a chamber; supplying a precursor of the transition metal dichalcogenide film into the chamber and exposing the precursor to a surface of the two-dimensional material layer; and controlling an electric charge imparted to defects on the surface of the two-dimensional material layer to control adsorption of the precursor to the surface of the two-dimensional material layer.

[0060] The W precursor used as the raw material for WS2 is not limited to WF6, but may be a gas containing tungsten and a halogen. Other examples of W precursors include WCl5, WCl6, W(CO)6, and W2(NME2)6.

[0061] The S precursor that is the raw material for WS2 is not limited to H2S, but may be any gas containing sulfur S. The gas containing sulfur S also includes gaseous sulfur.

[0062] In the case of applying the ALD method, in the adsorption control method, the source of the transition metal dichalcogenide film may have a first source (a gas containing tungsten and a halogen) and a second source (a gas containing sulfur). The adsorption control method may include: (A) supplying a first source into a chamber and exposing the first source to a surface of the two-dimensional material layer; (B) supplying a second source into the chamber and exposing the second source to the surface of the two-dimensional material layer; (C) repeating (A) and (B) in that order for a set number of cycles; and (D) controlling the adsorption of the first source to the two-dimensional material layer when performing (A) by controlling the charge given to defects on the surface of the two-dimensional material layer.

[0063] The above adsorption control method can also be applied to cases where defects exist on the surface of the film (first layer, lower layer) to be formed of a material other than two-dimensional material, and the defects control the charge, thereby changing the adsorption and reactivity of the raw material of the second layer (upper layer) to the first layer.

[0064] [Film forming equipment] A film formation apparatus for carrying out the above-described adsorption control method will be described with reference to Fig. 10. Figs. 10(a) to (c) are diagrams showing an example of a film formation apparatus 1 according to an embodiment. The film formation apparatus 1 is an apparatus capable of generating plasma.

[0065] The film forming apparatus 1 shown in FIGS. 10(a) to (c) includes a chamber 2, a control unit 3, a stage 11, and a gas supply unit 12. The gas supply unit 12 is configured to introduce at least one process gas into the chamber 2. The gas supply unit 12 supplies, for example, WF6 and H2S. The gas supply unit 12 includes a shower head 13. The shower head 13 is configured to introduce at least one process gas from the gas supply unit 12 into a processing space. The shower head 13 has a gas supply port 13a, a gas diffusion chamber 13b, and multiple gas inlets 13c. The process gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the processing space from the multiple gas inlets 13c.

[0066] The gas supply 12 may include gas sources and flow controllers, not shown. In one embodiment, the gas supply 12 is configured to supply at least one process gas from a corresponding gas source through a corresponding flow controller to the showerhead 13.

[0067] The stage 11 is disposed in the chamber 2, and a substrate W, for example a wafer, is placed thereon. The shower head 13 is disposed above the stage 11. In one embodiment, the shower head 13 constitutes at least a part of the ceiling of the chamber 2. The chamber 2 has at least one gas supply port for supplying at least one processing gas into the chamber 2, and at least one gas exhaust port for exhausting gas from the chamber 2. The chamber 2 is grounded. The shower head 13 and the stage 11 are electrically insulated from the housing of the chamber 2. The gas exhaust port is connected to an exhaust device (not shown). The exhaust device may include a pressure regulating valve and a vacuum pump. The pressure of the processing space in the chamber 2 is adjusted by the pressure regulating valve. The vacuum pump may include a turbo molecular pump, a dry pump, or a combination thereof.

[0068] The RF (Radio Frequency) power supply 31 is connected to the showerhead 13 via an impedance matching circuit (not shown) and supplies RF power to the showerhead 13. The showerhead 13 also functions as an upper electrode. This allows plasma to be generated from at least one processing gas supplied to the processing space. Thus, the RF power supply 31 can function as at least a part of a plasma generating unit configured to generate plasma from one or more processing gases in the chamber 2.

[0069] The bias power supply 32 is connected to the stage 11 via an impedance matching circuit (not shown) and supplies bias power to the stage 11. The stage 11 also functions as a lower electrode. By supplying bias power to the lower electrode, a bias potential is generated on the substrate W, and ion components in the formed plasma can be attracted to the substrate W.

[0070] A DC (Direct Current) power supply 33 is connected to the electrodes and applies a DC voltage to the electrodes. In FIG. 10(a), the DC power supply 33 is connected to an electrode 40. The h-BN has a contact surface with the electrode 40, and by pressing the electrode 40 against the contact surface and applying a DC voltage, a potential difference is generated between the h-BN and the stage 11, and an electric field in a predetermined direction is generated on the surface of the h-BN. This makes it possible to adjust the Fermi level based on the correlation information between the Fermi level and the formation energy of defects shown in FIG. 6, and to directly adjust the charge state of defects in the h-BN. The electrode 40 may be in a frame shape, a probe shape, or another shape.

[0071] In FIG. 10(b), the DC power supply 33 is connected to an electrode 41. The electrode 41 is disposed between the stage 11 (lower electrode) and the shower head 13 (upper electrode) near the surface of the substrate W. The DC power supply 33 applies a direct current voltage to the electrode 41, thereby generating a potential difference between the electrode 41 and the h-BN, and generating an electric field in a predetermined direction on the surface of the h-BN. This makes it possible to adjust the Fermi level based on the correlation information between the Fermi level and the defect formation energy shown in FIG. 6, and to directly adjust the charge state of defects in the h-BN. The electrode 41 may be, for example, mesh-shaped.

[0072] In Fig. 10(c), the DC power supply 33 is connected to the shower head 13 (upper electrode). When the DC power supply 33 applies a DC voltage to the shower surface (lower surface) of the shower head 13 as an electrode, a potential difference is generated between the shower surface and h-BN, and an electric field in a predetermined direction is generated on the surface of the h-BN. This makes it possible to adjust the Fermi level based on the correlation information between the Fermi level and the formation energy of defects shown in Fig. 6, and to directly adjust the charge state of defects in the h-BN.

[0073] The control unit 3 processes computer-executable instructions that cause the film forming apparatus 1 to perform various steps described in the present disclosure. The control unit 3 may be configured to control each element of the film forming apparatus 1 to perform various steps described herein. In one embodiment, a part or all of the control unit 3 may be included in the film forming apparatus 1. The control unit 3 may include a processing unit, a storage unit, and a communication interface. The control unit 3 is realized, for example, by a computer. The processing unit may be configured to perform various control operations by reading a program from the storage unit and executing the read program. This program may be stored in the storage unit in advance, or may be acquired via a medium when necessary. The acquired program is stored in the storage unit and is read from the storage unit by the processing unit and executed. The medium may be various storage media readable by a computer, or may be a communication line connected to the communication interface. The processing unit may be a CPU (Central Processing Unit). The storage unit may include a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), an SSD (Solid State Drive), or a combination thereof. The communication interface may communicate with the film forming apparatus via a communication line such as a LAN (Local Area Network). The correlation information between the Fermi level and the defect formation energy in FIG. 6 may be stored in advance in the storage unit of the control unit 3, or may be obtained from a communication line connected to the communication interface.

[0074] 10(a)-(c), a WS2 film is formed on h-BN using WF6 and H2S by the ALD method while applying desired DC voltages to the electrodes 40, 41 and the upper electrode. This adjusts the Fermi level to adjust the charge state of the defects in h-BN, and while adjusting the adsorption state of the WS2 raw material, it is possible to control the domain size of WS2 and form a high-quality WS2 film.

[0075] [others] For example, a charge may be supplied to the h-BN surface by generating static electricity or charging with UV light, etc., to adjust the charge state of defects in the h-BN. That is, a substrate having h-BN charged in this manner may be transported into the film-forming apparatus 1, and a WS2 film may be formed on the h-BN by the ALD method using WF6 and H2S.

[0076] A plasma may be generated in the deposition apparatus 1, and charged particles in the plasma may be supplied to the surface of the h-BN to adjust the charge state of defects in the h-BN. In other words, the substrate in which the charge state of the h-BN defects has been adjusted in this manner may be transferred into the deposition apparatus 1, and a WS2 film may be formed on the h-BN by the ALD method using WF6 and H2S.

[0077] After adjusting the charge state of the defects in h-BN, the h-BN may be annealed at high temperature, and WF6 and H2S may be supplied to the surface of the annealed h-BN to form a WS2 film. After adjusting the charge state of the defects in h-BN, the h-BN may be annealed before forming a WS2 film, which allows the defects to move or diffuse. By annealing h-BN, atoms move, allowing the type and concentration of defects to be controlled.

[0078] The deposition of h-BN and the deposition of TMDC such as WS2 may be performed in different deposition equipment. The annealing process can be performed in either the deposition equipment for h-BN or the deposition equipment for TMDC. The deposition of h-BN may be performed using an ICP (Inductively Coupled Plasma) device without applying bias power.

[0079] A process may be carried out to increase the number of defects on the surface of the h-BN film. In other words, after the formation of the h-BN film, an inert gas or the like may be used to increase the number of defects on the surface of the h-BN film. However, since defects already exist on the surface of the h-BN film when the normal h-BN film is formed, there is no problem even if a process to increase the number of defects is not carried out.

[0080] [effect] The inventors found that the adsorption of WF6 on pure h-BN was weak, but that the presence of N vacancies ("V N We found that the adsorption of WF6 on h-BN can be significantly enhanced by introducing defects such as N defects (N defects). Furthermore, the reactivity of WF6 with N defects depends on the charge of the N defects. This means that the reactivity of WF6 with the h-BN defect surface can be controlled by electric fields, gates, or extra doping, and / or by tuning the Fermi level of h-BN. Such controllable surface reactivity can be applied in various 2D and / or 3D deposition scenarios.

[0081] TMDC is a layered material having a 2D structure similar to h-BN, and since TMDC has a band gap of 1 to 2 eV and high carrier mobility, it can be used, for example, as a channel material for transistors. By forming a TMDC film using the adsorption control method according to this embodiment, carrier mobility and subthreshold swing can be improved.

[0082] In addition, h-BN functions as a protective layer for the TMDC, and can prevent the mobility of the TMDC from being deteriorated by contamination due to diffusion from the underlayer, etc. In addition, since h-BN has a large band gap of 4 to 5 eV, electrons do not flow unless energy greater than that of the TMDC is applied, so it can function as an insulating film to prevent leakage.

[0083] In addition, the domain size of WS2 formed by the ALD method can be enlarged by using the adsorption control method shown in FIG.

[0084] The surface reactivity of electronically controllable two-dimensional materials can be applied to the following fields (1) to (3), but is not limited thereto.

[0085] (1) Controllable size of TMDC deposition area (2) Controllable deposition rate of TMDCs (3) Controllable area selectivity of deposition onto different surfaces (e.g., h-BN and other 2D and / or 3D substrates)

[0086] The adsorption control method and the film forming apparatus according to the presently disclosed embodiments should be considered as illustrative and not restrictive in all respects. The embodiments can be modified and improved in various ways without departing from the spirit and scope of the appended claims. The matters described in the above embodiments can be configured in other ways without any contradiction, and can be combined without any contradiction.

[0087] According to this adsorption control method, as shown in FIG. 2, it is possible to control not only the adsorption of WF6 but also the adsorption of H2S.

[0088] The film forming apparatus disclosed in this specification can be applied to any of a single wafer apparatus that processes substrates one by one, a batch apparatus that processes a plurality of substrates at once, and a semi-batch apparatus.

[0089] The film forming apparatus disclosed in this specification is not limited to an apparatus that processes a substrate using plasma, and may be an apparatus that processes a substrate without using plasma. [Explanation of symbols]

[0090] 1 Film deposition equipment 2 Chamber 3. Control Unit 11 Stage 33 DC power supply 40, 41 electrode

Claims

1. 1. A method for controlling adsorption of a feedstock of a second layer into a first layer, comprising the steps of: providing a substrate having the first layer on a stage within a chamber; supplying a source material for the second layer into the chamber and exposing the source material to a surface of the first layer; controlling the charge given to defects on the surface of the first layer to thereby control adsorption of the source material onto the surface of the first layer; The adsorption control method includes:

2. the first layer being a two-dimensional material layer and the second layer being a transition metal dichalcogenide film; The method of claim 1 .

3. forming the transition metal dichalcogenide film by an ALD method; The method for controlling suction according to claim 2.

4. the source material of the transition metal dichalcogenide film includes a first source material and a second source material; (A) providing the first source material into the chamber and exposing the first source material to a surface of the two-dimensional material layer; (B) providing the second source material into the chamber and exposing the second source material to a surface of the two-dimensional material layer; (C) repeating the steps (A) and (B) in this order for a set number of cycles; (D) when carrying out (A), controlling adsorption of the first source material to the two-dimensional material layer by controlling charges given to defects on the surface of the two-dimensional material layer; The method for controlling adsorption according to claim 3.

5. Controlling the charge applied to defects on the surface of the two-dimensional material layer includes: applying a DC voltage to an electrode in contact with a contact surface of the two-dimensional material layer, an upper electrode facing the stage, or an electrode disposed between the stage and the upper electrode; The method for controlling adsorption according to any one of claims 2 to 4.

6. storing correlation information between the Fermi level of the two-dimensional material layer and the formation energy of defects on the surface of the two-dimensional material layer in a storage unit; Controlling the charge applied to defects on the surface of the two-dimensional material layer includes: by referring to the storage unit and controlling the DC voltage applied to the electrodes based on the correlation information. The method for controlling adsorption according to claim 5.

7. Controlling the charge applied to defects on the surface of the two-dimensional material layer includes: preparing the substrate on the stage, the surface of the two-dimensional material layer being previously charged, or providing a charge from plasma generated in the chamber to the surface of the two-dimensional material layer of the substrate prepared on the stage; The method for controlling adsorption according to any one of claims 2 to 4.

8. Controlling the adsorption of the source material onto the surface of the layer of two-dimensional material comprises: After controlling the charge applied to the defects on the surface of the two-dimensional material layer, the two-dimensional material layer is annealed, and the source material is supplied to the surface of the annealed two-dimensional material layer. The method for controlling adsorption according to any one of claims 2 to 4.

9. The raw material is a gas containing tungsten and a halogen and / or a gas containing sulfur. The method for controlling adsorption according to any one of claims 2 to 4.

10. The gas containing tungsten and a halogen is WF ６ , W.C.L. ５ , W.C.L. ６ , W(CO) ６ Or W ２ (N.M.E. ２ ) ６ Either The sulfur-containing gas is H ２ S. The method for controlling adsorption according to claim 9.

11. Controlling the adsorption of the first source material and the second source material into the two-dimensional material layer comprises: Controlling the charge applied to the defects on the surface of the two-dimensional material layer in a first cycle of the set number of cycles to be 0 or −1; Controlling the charge imparted to the defects on the surface of the two-dimensional material layer in a second cycle of the set number of cycles so that the charge is +1; The method for controlling adsorption according to claim 4.

12. the two-dimensional material layer is hexagonal boron nitride; The method for controlling adsorption according to any one of claims 2 to 4.

13. The raw material is WF ６ In the case of (a), the surface defects of the hexagonal boron nitride are either a state in which nitrogen is missing, a state in which the positions where boron is missing are replaced with carbon, or a state in which the positions where nitrogen is missing are replaced with oxygen. The method for controlling adsorption according to claim 12.

14. The raw material is H ２ In the case of S, the defects on the surface of the hexagonal boron nitride are in a state where the nitrogen missing positions are replaced with oxygen. The method for controlling adsorption according to claim 12.

15. a flow rate of the first source material supplied into the chamber in a first cycle of the set number of cycles is less than a flow rate of the first source material supplied into the chamber in a second cycle of the set number of cycles and thereafter; The method for controlling adsorption according to claim 4.

16. controlling a nucleation density on a surface of hexagonal boron nitride based on a flow rate of the first source material supplied into the chamber in the first cycle; The method for controlling adsorption according to claim 15.

17. The first raw material is WF ６ and the second source is H ２ S. The method for controlling adsorption according to claim 4.

18. The transition metal dichalcogenide film is WS ２ Membrane or WSe ２ It is a membrane, The method for controlling adsorption according to any one of claims 2 to 4.

19. A chamber; a stage disposed within the chamber and configured to support a substrate; A control unit; A film forming apparatus for forming a transition metal dichalcogenide film on a first layer of the substrate, comprising: The control unit is providing the substrate on a stage within a chamber; supplying a source of the transition metal dichalcogenide film into the chamber and exposing the source to a surface of the first layer; controlling the charge given to defects on the surface of the first layer to thereby control adsorption of the source material onto the surface of the first layer; The film forming apparatus controls adsorption of the source material onto the first layer by performing the above-mentioned step.

20. the first layer being a two-dimensional material layer; A film forming apparatus for controlling adsorption according to claim 19.

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