Adsorption control method and film forming apparatus

Abstract

Provided is an adsorption control method for controlling adsorption of a raw material of a second layer to a first layer, the adsorption control method comprising the steps of: preparing a substrate having the first layer on a stage in a chamber; supplying a raw material of the second layer into the chamber and exposing a surface of the first layer in the raw material; and controlling adsorption of the raw material to the surface of the first layer by controlling charges provided to defects on the surface of the first layer.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an adsorption control method and a film formation apparatus. BACKGROUND

[0002] For example, Patent Document 1 describes a method in which, in the formation of a two-dimensional insulating material layer and a two-dimensional semiconductor material layer, after the formation of the two-dimensional insulating material layer, the surface is activated by ion doping, and a two-dimensional semiconductor material layer composed of a transition metal chalcogenide, black phosphorus, silicene, germanene, or graphene is formed by a CVD method or an ALD method.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Specification of Chinese Patent Application Publication No. 109962106 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present disclosure provides a technology capable of controlling adsorption of a raw material of a second layer to a first layer.

[0008] SOLUTION TO PROBLEM

[0009] According to one embodiment of the present disclosure, there is provided an adsorption control method for controlling adsorption of a raw material of a second layer to a first layer, the adsorption control method including the steps of: preparing a substrate having the first layer on a stage in a chamber; supplying a raw material of the second layer into the chamber and exposing a surface of the first layer to the raw material; and controlling adsorption of the raw material to the surface of the first layer by controlling electric charges provided to defects of the surface of the first layer.

[0010] EFFECT OF THE INVENTION

[0011] According to one aspect, it is possible to control adsorption of a raw material of a second layer to a first layer. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1A is a diagram showing an example of hexagonal boron nitride.

[0013] Figure 1B is a diagram showing an example of hexagonal boron nitride.

[0014] Figure 1C is a diagram showing an example of hexagonal boron nitride.

[0015] Figure 1D is a diagram showing an example of hexagonal boron nitride.

[0016] Figure 2 is a graph showing the results of simulation 1 of the adsorption energy involved in one embodiment.

[0017] Figure 3A is a graph showing the results of simulation 2 of the adsorption state of WF6involved in one embodiment.

[0018] Figure 3B is a graph showing the results of simulation 2 of the adsorption state of WF6involved in one embodiment.

[0019] Figure 3C is a graph showing the results of simulation 2 of the adsorption state of WF6involved in one embodiment.

[0020] Figure 4 is a graph showing the change in the adsorption energy based on the state of charge of V N .

[0021] Figure 5A is a graph showing the results of simulation 3 of the surface state of h-BN involved in one embodiment.

[0022] Figure 5B is a graph showing the results of simulation 3 of the surface state of h-BN involved in one embodiment.

[0023] Figure 5C is a graph showing the results of simulation 3 of the surface state of h-BN involved in one embodiment.

[0024] Figure 6 is a graph showing the correlation of the Fermi level with the formation energy of surface defects involved in one embodiment.

[0025] Figure 7A is a graph showing an example of the adjustment of the state of charge and its effects involved in one embodiment.

[0026] Figure 7B is a graph showing an example of the adjustment of the state of charge and its effects involved in one embodiment.

[0027] Figure 8 is a flowchart showing an example of the adsorption control method involved in one embodiment.

[0028] Figure 9A is a graph for explaining the adsorption control method involved in one embodiment.

[0029] Figure 9B is a graph for explaining the adsorption control method involved in one embodiment.

[0030] Figure 9C is a graph for explaining the adsorption control method involved in one embodiment.

[0031] Figure 10A is a view showing an example of a film formation apparatus according to an embodiment.

[0032] Figure 10B is a view showing an example of a film formation apparatus according to an embodiment.

[0033] Figure 10C is a view showing an example of a film formation apparatus according to an embodiment. DETAILED DESCRIPTION

[0034] Hereinafter, a mode for carrying out the present disclosure will be described with reference to the drawings. In each drawing, the same reference signs are attached to the same constituent parts, and sometimes repeated description is omitted.

[0035] [Example of Hexagonal Boron Nitride]

[0036] Evaporation of Transition Metal Dichalcogenides (hereinafter also referred to as "TMDC") on hexagonal Boron Nitride (hereinafter also referred to as "h-BN") is extremely important for applying two-dimensional substances to industry. h-BN and TMDC are examples of two-dimensional material layers. h-BN is an example of a two-dimensional insulating material layer. TMDC is an example of a two-dimensional semiconductor material layer, and MoS2, WS2, MoSe2, WSe2, and the like can be cited.

[0037] In Figure 1A , Figure 1B , Figure 1C and Figure 1D an example of an ideal, that is, a defect-free bilayer hexagonal Boron Nitride (bilayer h-BN) is shown. Figure 1A A surface (XY plane) of h-BN is shown. h-BN is a layered substance, Figure 1B A layered structure in the Z direction of bilayer h-BN is shown. The number of layers of h-BN is not limited to two layers, and has a layered structure in which hexagonal rings are alternately formed by boron (B) and nitrogen (N) through covalent bonds, the hexagonal rings are formed into a two-dimensional structure body by a large number of bonds, and the two-dimensional structure bodies are stacked to form a layered structure.

[0038] As with h-BN, TMDCs are layered materials having a two-dimensional (2D) structure. The band gap of TMDCs is 1 to 2 eV, and the carrier (electron) mobility is high, and thus, for example, used as a channel material of a transistor. In order to maintain the carrier mobility and subthreshold swing of TMDCs at an ideal level, it is necessary to employ an inactive two-dimensional h-BN as a protective layer of TMDCs. In addition, the band gap of h-BN is large, at 4 to 5 eV, and thus, electrons do not flow unless a larger energy than that of TMDCs is applied, and thus, functions as an insulating film for preventing leakage.

[0039] However, it is difficult to directly deposit TMDCs on h-BN or other two-dimensional materials to form a two-dimensional heterostructure. For example, WS2 is a strong candidate for a future FET channel having a relatively wide band gap and a relatively low subthreshold swing among all TMDCs. A precursor of WF6 and H2S is proposed as a precursor of an ALD process for forming WS2 by an ALD (Atomic Layer Deposition) method.

[0040] However, the usual precursors such as WF6 and H2S do not strongly interact with an ideal h-BN surface, and thus, it is difficult to use these materials in the film formation of WS2 on h-BN. In addition, the reactivity of the h-BN surface cannot be controlled in the ALD process. Thus, in the conventional ALD process, the domain size of WS2 cannot be controlled, and WS2 becomes a small domain of poor film quality. The "domain" is a similar meaning to the grain diameter, and if the grain diameter is large, the proportion of the grain boundary in which the nature of the WS2 film is poor decreases, and the film quality improves.

[0041] In contrast, the inventors found, using first-principle quantum simulation, that the adsorption of WF6 to an ideal h-BN is weak, but by forming a defect (lattice vacancy) in the h-BN, the adsorption of WF6 can be significantly enhanced.

[0042] Next, an adsorption control method in which the adsorption state of a precursor used in the film formation of TMDCs is controlled by adjusting the Fermi level of h-BN when TMDCs are formed on the surface of h-BN will be described. In the description of the adsorption control method according to the present embodiment, WS2 is exemplified as a TMDC deposited on the surface of h-BN, and WF6 and H2S are exemplified as precursors for forming WS2.

[0043] In Figure 1C and Figure 1D An example of a lattice vacancy (Vacancy, hole) formed in h-BN is shown. Figure 1C and Figure 1D The state of the surface (first layer) of h-BN is shown. In Figure 1CIn the first layer, the lattice site A1 that originally contained N becomes a nitrogen lattice vacancy (hereinafter also referred to as "V"). N Boron (B) present at lattice site A1 is the B of the second layer h-BN present at the lattice vacancy site A1.

[0044] exist Figure 1D In the first layer, the lattice site A2 that originally contained boron became a boron lattice vacancy (hereinafter also referred to as "V"). B The nitrogen (N) present at lattice site A2 is the N of the second layer h-BN present at the lattice vacancy site A2.

[0045] [Simulation 1]

[0046] In Simulation 1, the changes in the adsorption energy of WF6 and H2S onto the h-BN surface were simulated for both ideal h-BN and h-BN with defects. Figure 2 The results are shown in the figure.

[0047] Figure 2 The "Ideal" is an ideal h-BN, which produced no defects. "V" N "There are defects in h-BN where N is missing at lattice sites (N defects)." V B "There are defects where boron is missing at lattice sites (B defects)." Si N -H", "C" N -H", "C" N The N atom of h-BN is replaced by SiH, CH, and C, respectively. B -H", "C" B -H", "C" B "It has B defects where nearby nitrogen atoms are replaced by SiH, CH, and C, respectively." V N -H” in V N H and B exist nearby. N The N atom in "N" is replaced by B. B The B atom in "O" is replaced by N. N The N atom in the symbol is replaced by O (oxygen). N The N atom in "-H" is replaced by O (oxygen), and H (hydrogen) is bonded to O.

[0048] In Simulation 1, under ideal h-BN conditions and under various defective conditions of h-BN as described above, WF6 and H2S were adsorbed onto the surface of h-BN. Furthermore, the charge state at the defects of various h-BNs was set to 0, i.e., electrically neutral.

[0049] Figure 2The vertical axis represents the adsorption energy E_ad of WF6 and H2S adsorbed onto the surface of various h-BNs. E_ad is represented by the following equation (1).

[0050] E_ad=E_final-E_h-BN-E_molecule…(1)

[0051] In equation (1), E_final represents the adsorption energy of each WF6 and H2S molecule after it has been adsorbed onto the surface of h-BN and its structure optimized and stabilized. E_h-BN represents the adsorption energy of each WF6 or H2S molecule before it is adsorbed onto the surface of h-BN. E_molecule represents the adsorption energy of one WF6 or H2S molecule. Therefore, the adsorption energy E_ad represents the difference between the adsorption energy of each WF6 or H2S molecule adsorbed onto h-BN and its state before adsorption. The larger the absolute value of the adsorption energy E_ad, the stronger the adsorption.

[0052] In the ideal h-BN case represented by "Ideal", the adsorption of each WF6 and H2S molecule onto h-BN is a weak adsorption based on van der Waals forces. On the other hand, in the "V" case... N Under the condition of "C", the adsorption of WF6 to h-BN is enhanced. Additionally, under the condition of "C", B Under the condition of "O", the adsorption of WF6 to h-BN is enhanced. Additionally, under the condition of "O" N In the case of "", the adsorption of WF6 and H2S to h-BN is enhanced. The other adsorptions of h-BN mentioned above are weak adsorptions based on van der Waals forces.

[0053] Therefore, it can be concluded that when the charging state of the defect is set to 0, and "V" exists... N “C” B “O” N "The defective h-BN exhibits strong chemisorption between the defect and WF6."

[0054] Furthermore, it can be seen that when the charging state of the defect is set to 0, there is an "O" condition. N "The defective h-BN exhibits strong chemisorption between the defect and H2S."

[0055] [Simulation 2]

[0056] In Simulation 2, with the charging of the N defect set to 0, -1, and +1, the adsorption of WF6 on "V" was calculated. N The behavior of h-BN surface. Figure 3A , Figure 3B as well as Figure 3C The results of Simulation 2 are shown. Figure 3A This illustrates the "V" when the charge of the N-defect at the lattice vacancy is set to 0. N(Also denoted as "V" below) N 0 The adsorption of WF6 on h-BN. N has five outermost electrons. When the charge on the N defect is zero, it is electrically neutral, meaning no electrons enter or leave the N defect, and the number of outermost electrons remains five. Therefore, the number of outermost electrons is odd, thus generating electron spin. Under these conditions, strong chemisorption occurs between the N defect of h-BN and WF6.

[0057] Figure 3B This illustrates the "V" when the charge of the N-defect at the lattice vacancy is set to -1. N (Also referred to as "VN" below) -1 The adsorption of WF6 on h-BN. When the N defect is charged to -1, an electron enters the N defect. At this time, the number of outermost electrons is even, and h-BN is not magnetic, so no electron spin is generated. Under this condition, strong chemisorption occurs between the N defect of h-BN and WF6.

[0058] Figure 3C This illustrates the "V" when the charge of the N defect at the lattice vacancy is set to +1. N (Also denoted as "V" below) N +1 The adsorption of WF6 on h-BN is observed. When the N defect is charged to +1, an electron escapes from the defect. At this point, the number of outermost electrons is even, so no electron spin is generated. Under this condition, weak adsorption based on van der Waals forces occurs between the N defect of h-BN and WF6.

[0059] Figure 4 It shows that based on V N A graph showing the change in adsorption energy during the charging state. Figure 4 The horizontal axis represents V N State of charge V N -1 V N 0 V N +1 The vertical axis represents the adsorption energy E_ad at each charging state. In V N The charging state is V N -1 or V N 0 In the case of V, W and F in WF6 dissociate and adsorb, with low and stable adsorption energy, indicating that F readily adsorbs onto the substrate. N The charging state is V N +1 Under these conditions, the adsorption energy is high and unstable, indicating that F is difficult to adsorb onto the substrate.

[0060] [Simulation 3]

[0061] In Simulation 3, the density of states of the electrons on the surface of the h-BN having each of the charge states of "V N 0 ", "V N -1 ", and "V N +1 " was calculated. According to the results of Simulation 3, the mechanism of the difference in the adsorption state of WF6based on each of the charge states of the N defect was estimated. Figure 3A Figure 3B Figure 3C

[0062] Figure 5A Figure 5B Figure 5C The results of Simulation 3 are shown in FIGS. 12, Figure 5A Figure 5B Figure 5C The horizontal axis indicates the energy level, and the vertical axis indicates the density of states (DOS) of the electrons on the surface of the h-BN of "V N 0 ", "V N -1 ", and "V N +1 ". In Simulation 3, the temperature was set to absolute zero (0 Kelvin). As described above, in the case of "V N -1 ", "V N +1 ", the number of the electrons in the N defect is even, and no electron spin is generated. In the case of "V N 0 ", the number of the electrons in the N defect is odd, and the electrons generate spin, and are polarized to be positive (up spin) and negative (down spin).

[0063] Figure 5A The DOS of the surface of the h-BN in the case where "V N 0 " and the electron spin polarized to be positive and negative exist is shown in FIG. 12. The energy level of about -3 to 2 (eV) is the band gap (of the h-BN), and according to the Fermi-Dirac distribution, few carriers exist around the Fermi level. Further, the energy level smaller than -3 (eV) is the valence band (English), and the energy level larger than 2 (eV) is the acceptor band (English). The Fermi level can be defined at any position in the band gap. In FIG. 12, the Fermi level is defined as 0 (eV). Figure 5A - Figure 5C

[0064] ​​​​​​​​Figure 5A The upper half represents the DOS of the h-BN surface in the case of up-spin electrons, and the lower half represents the DOS of the h-BN surface in the case of down-spin electrons. Figure 5A In the results, for top-spin electrons, the DOS locally increases at the Fermi level (0 eV). For bottom-spin electrons, the DOS is 0 at the Fermi level (0 eV). This means that at "V N 0 "Furthermore, in h-BN with electron spin, only positively polarized electrons exist in isolated N defects."

[0065] exist Figure 5B In the middle, in "V" N -1 In h-BN, which has no electron spin, the energy levels from approximately -3 to +1 (eV) form a band gap. Figure 5B The results show that DOS increases locally at the Fermi level (0 eV). This indicates that at "V N -1 Electrons exist in the N-defects of h-BN.

[0066] exist Figure 5C In the middle, in "V" N +1 In h-BN, which has no electron spin, the energy levels above 0 eV constitute the band gap. Figure 5C In the results, the DOS is 0 at the Fermi level (0 eV). This means that "V N +1 The h-BN exhibits properties similar to those of the original ideal h-BN.

[0067] exist Figure 5A The "V" N 0 "And h-BN with electron spin and" Figure 5B The "V" N -1 "Furthermore, in h-BN without electron spin, the charge density of electrons in the space near the N defect becomes an electron distribution extending along the height direction from the XY plane of the h-BN surface."

[0068] When the wave function is set to Ψ, the probability of finding an electron in the space near the defect at a certain time t is equal to |Ψ(t)|. 2 Therefore, the charge density of an electron is proportional to the square root of its wave function, and the charge density of an electron can be indirectly represented by its wave function.

[0069] In “V” N 0 “V” N -1In the case of h-BN, based on the wavefunction of the electrons filling the space near the defect closest to the Fermi level, the electron orbits are Pz (or π orbitals), which increase in length along the Z direction (vertical direction) from the XY plane of the h-BN surface. Therefore, the charge density of electrons in the space near the defect becomes a distribution extending along the height direction from the plane of h-BN. In this case, the reactivity in the N defect increases, thus the adsorption force of WF6 is estimated to be stronger.

[0070] In “V” N +1 In the case of h-BN, based on the wavefunction of the electrons filling the space near the defect closest to the Fermi level, the electron orbits take the Pxy (or σ) orbitals, and the charge density of electrons in the space near the defect becomes a periodically distributed electron distribution on the XY plane of the h-BN surface. In this case, the h-BN surface becomes a state similar to the original ideal h-BN in terms of physical properties, and the adsorption of WF6 onto h-BN is based on weak adsorption by van der Waals forces.

[0071] [Correlation between Fermi level and formation energy of surface defects]

[0072] exist Figure 6 The text shows how to use "V" N The results were obtained by simulating the correlation between the Fermi level in h-BN and the formation energy of surface defects (N Vacancy). Figure 6 This is an example of a graph showing the correlation between the Fermi level and the formation energy of a defect in one embodiment. Figure 6 The horizontal axis represents the Fermi level E. f (Fermi level), with the vertical axis representing the formation energy of the defect. The lower the formation energy of the defect, the more stable the state of the defect.

[0073] from Figure 6 The results shown indicate that when the Fermi level E f During the transition, the most stable charge state in the N-vacancy changes. For example, at the Fermi level E... f In the range of 0 to slightly above 2.5 eV, the defect becomes most stable by making the N defect a +1 charge state. At the Fermi level E... f At voltages slightly above 2.5 eV to approximately 4 eV, the defect becomes most stable by reducing the charge state of the N defect to zero. This is achieved at the Fermi level E. f At a voltage of approximately 4 eV or higher, the N defect becomes the most stable state by making it a charge state of -1.

[0074] The charge state having the lowest formation energy of defects is a defect-stable state. Therefore, by adjusting the Fermi energy level E f to be "V N " h-BN, the N defect-stable charge state of "V N " h-BN is adjusted.

[0075] As a method of adjusting the Fermi energy level, the Fermi energy level can be adjusted by applying a direct current voltage from the outside for providing a charge to "V N " h-BN and / or doping an impurity into h-BN.

[0076] In the application of a direct current voltage from the outside for providing a charge to h-BN, by making the potential of h-BN positive or negative, it is possible to adjust whether the Fermi energy level is shifted to the high energy side or the low energy side using an electric field acting on h-BN. In the case where the Fermi energy level is 0 eV (no potential) to about 3 eV, Figure 6 "V N +1 " indicated by the dotted line of +1 is the lowest energy, and, in the case where the Fermi energy level is 3 eV to about 5 e on the right side, "V N 0 " indicated by the solid line of Neutral (0) is the lowest energy. And, in the case of 5 eV or more on the right side, "V N -1 " indicated by the dotted line of -1 is the lowest energy. In order to move the Fermi energy level to the right side, the surface of h-BN is made negative. In order to move the Fermi energy level to the left side, the surface of h-BN is made positive.

[0077] In the doping of an impurity into h-BN for providing a charge to h-BN, p-type doping and n-type doping can be performed, and, for p-type doping, for example, Mg, Be can be used. However, in order to provide a charge to h-BN, it is preferable to apply a direct current voltage from the outside, which has a higher degree of freedom of control than doping into h-BN.

[0078] As described above, in the adsorption control method according to the present embodiment, the electric field (voltage) acting on h-BN is controlled to move the Fermi energy level. Thereby, the charge state of defects of h-BN is adjusted, whereby the reactivity of WF6 is changed, and thus the adsorption of WF6 to h-BN is controlled.

[0079] Figure 7A and Figure 7B An example of adjustment of the charge state of N defects of h-BN and its effect according to one embodiment will be shown. For example, as Figure 7AAs shown, when the Fermi level is adjusted by applying a voltage to h-BN so that the charge on the N defect becomes +1, a state similar to ideal h-BN is achieved, and the adsorption force of WF6 onto h-BN weakens. Figure 7B As shown, if the Fermi level is adjusted by applying a voltage to h-BN so that the charge on the N defect becomes -1 or 0, the adsorption of WF6 near the N defect in h-BN becomes stronger. Furthermore, materials such as sapphire, SiO2, Si, and High-k can be used to replace h-BN.

[0080] [Adsorption Control Methods]

[0081] Next, refer to Figure 8 , Figure 9A , Figure 9B as well as Figure 9C This will illustrate an adsorption control method involved in one embodiment. Figure 8 This is a flowchart illustrating an example of an adsorption control method according to one embodiment. Figure 9A , Figure 9B as well as Figure 9C This is a diagram illustrating an adsorption control method according to one embodiment. (Regarding...) Figure 8 The adsorption control method shown is exemplified by the ALD method for forming WS2 films on h-BN. Adsorption control methods, for example, are described later. Figure 10A , Figure 10B as well as Figure 10C Controlled by control unit 3, by Figure 10A , Figure 10B as well as Figure 10C The film-forming device 1 is implemented.

[0082] When this adsorption control method is started, in step S1, a substrate having h-BN containing N defects is prepared on a stage within the chamber. Furthermore, as a means of controlling N defects formed in h-BN, it is possible to perform film formation in a nitrogen-deficient state during h-BN film formation, and the number of N defects can be controlled by the amount of nitrogen deficiency. However, since N defects are naturally generated during h-BN film formation, it is not necessarily necessary to control N defects during h-BN film formation.

[0083] Next, in step S2, while by sending... Figure 10A , Figure 10B as well as Figure 10C The electrode ( Figure 10A A negative DC voltage is applied to the electrode 40, etc., to adjust the Fermi level to become "V". N 0 (Charging of N defects is 0) or "V N -1 (The charge for N defects is -1), while a small amount of WF6 is supplied to the chamber. At this time, as...Figure 9A As shown, near the defects of the h-BN, the adsorption of WF6 becomes strong, and WF6 is adsorbed near the defects.

[0084] In step S2, WF6 is supplied for the first cycle. At this time, the charge state of the N defects is adjusted to 0, the reactivity near the defects is increased, the adsorption of WF6 is enhanced, but the amount of the supplied WF6 is controlled to be less than the amount of the supplied WF6 after the second cycle. Therefore, as shown, WF6 molecules are adsorbed to a part of the N defects, and most of the N defects are lattice vacancies. Further, in step S2 and step S5 described later, WF6 and Ar can be supplied. In this case, in the first cycle of step S2, the amount of WF6 can be made small by diluting WF6 with Ar as compared with the second cycle and after. Figure 9A

[0085] Next, in step S3 of the first cycle, H2S is supplied into the chamber in the same state as that of step S2 ("V N 0 " or "V N -1 " state). At this time, as shown, the adsorption of H2S to the N defects near the lattice vacancies in the state of charge 0 or the state of charge -1 not shown is weak. On the other hand, H2S reacts with the WF6 molecules adsorbed to the N defects, and a nucleus of W(SH)x is formed. In order to form the nucleus, in step S3, H2S is supplied in a sufficient amount. The nucleus used here means a nucleus that becomes a film growth center. A bias voltage is applied as needed. For example, a predetermined bias voltage is applied when the nucleus is formed. In film formation after the formation of the nucleus, the bias voltage need not be applied, and thus the application of the bias voltage can be appropriately stopped. Figure 9B

[0086] Next, in step S4, it is determined whether the set number of cycles is repeated. In the case where it is determined that the set number of cycles is not repeated, in step S5, WF6 is supplied into the chamber while adjusting the Fermi level to "V N +1 (+1) to the N defects, while WF6 is supplied into the chamber. Thereby, the adsorption of WF6 is weakened so that the adsorption of WF6 does not occur in a part other than the part where the nucleus of W(SH)x has been formed. Thereby, it is possible to grow in a two-dimensional lateral direction from the nucleus controlled to be small, and thus a large domain is formed. Thereby, as shown, it is possible to increase the particle diameter of the nucleus of W(SH)x. Next, in step S3 of the second cycle, H2S is supplied into the chamber in the same state as that of step S5 ("V N +1 " state) to further grow the nucleus of W(SH)x. Figure 9C

[0087] ​​​In a case where the number of cycles is set to three or more, step S5 and step S3 are also set as one cycle, and the process is repeated until the number of cycles is set. However, in step S5 after the third cycle, since the charge of the N defect has been adjusted to +1 in the second cycle, there is no need to further apply a voltage to adjust the Fermi level, and WF6 is supplied. In step S4, in a case where it is determined that the number of cycles is repeated, the present process is ended.

[0088] According to the adsorption control method according to the present embodiment, by adjusting the Fermi level while supplying WF6 into the chamber, it is possible to adjust the adsorption of WF6 to the h-BN surface. Further, by controlling the amount of supply of WF6, it is possible to control the formation density of the nucleus. The more the number of nuclei, the smaller the crystal domain, and the lower the film quality of WS2. Therefore, by reducing the number of nuclei to increase the crystal domain, grain boundaries are reduced. By thus controlling the crystal domain size of WS2, it is possible to form a high-quality WS2 film. In addition, by controlling the number of nuclei in the first cycle, there is no need to strictly control the number of defects of h-BN.

[0089] Further, in step S2, instead of adjusting the Fermi level so that the charge state of the defect is 0, the Fermi level can be adjusted so that the charge state of the defect is -1. However, in a case where the charge state of the defect is -1, a voltage greater than that in a case where the Fermi level is adjusted so that the charge state of the defect is 0 is required, and thus it is easier to control the Fermi level to be 0, and there is an advantage in terms of cost.

[0090] Further, in order to switch between WF6 and H2S, it is preferable to perform a purge process between the process of supplying WF6 in steps S2 and S5 and the process of supplying H2S in step S3. In the purge process, an inactive gas such as Ar gas can be supplied.

[0091] Regarding the adsorption control method according to the present embodiment, it is preferable to use the ALD method. However, after the nucleus is formed, regarding the film formation method of WS2, a method of CVD (Chemical Vapor Deposition), MOCVD (Metal Organic Chemical Vapor Deposition) can also be used.

[0092] In the present embodiment, the improvement in the film formation of WS2 on h-BN by WF6 and H2S is focused on, but the adsorption control method of the present embodiment can also be applied to other precursors (raw materials of transition metal dichalcogenide films) and other two-dimensional material layers.

[0093] For example, an adsorption control method for controlling adsorption of a raw material of a transition metal dichalcogenide film to a two-dimensional material layer includes the steps of: preparing a substrate having a two-dimensional material layer on a stage in a chamber; supplying a raw material of a transition metal dichalcogenide film into the chamber and exposing a surface of the two-dimensional material layer to the raw material; and controlling adsorption of the raw material to the surface of the two-dimensional material layer by controlling electric charge provided to a defect of the surface of the two-dimensional material layer.

[0094] The W precursor that becomes a raw material of WS2 is not limited to WF6, and can be a gas containing tungsten and halogen. As other examples of the W precursor, WCl5, WCl6, W(CO)6, and W2(NME2)6 can be listed.

[0095] The S precursor that becomes a raw material of WS2 is not limited to H2S, and can be a gas containing sulfur S. The gas containing sulfur S also includes gaseous sulfur.

[0096] In the case of applying the ALD method, in the adsorption control method, the raw material of the transition metal dichalcogenide film can have a first raw material (a gas containing tungsten and halogen) and a second raw material (a gas containing sulfur). The adsorption control method can include the steps of: step (A), supplying the first raw material into the chamber and exposing the surface of the two-dimensional material layer to the first raw material; step (B), supplying the second raw material into the chamber and exposing the surface of the two-dimensional material layer to the second raw material; step (C), repeating the steps (A) and (B) in the order of the steps (A) and (B) for a set number of cycles; and step (D), controlling adsorption of the first raw material to the two-dimensional material layer by controlling electric charge provided to a defect of the surface of the two-dimensional material layer when the step (A) is performed.

[0097] The above adsorption control method can also be applied to a case where a defect exists on a surface of a film (a first layer, a lower layer film) on which film formation of a non-two-dimensional material is to be performed, and adsorbability and reactivity of a raw material of a second layer (an upper layer film) to the first layer are changed by controlling electric charge to the defect.

[0098] [Film formation device]

[0099] Reference is made to Figure 10A , Figure 10B and Figure 10C to describe a film formation device for implementing the above-described adsorption control method. Figure 10A - Figure 10C is a view showing an example of a film formation device 1 according to an embodiment. The film formation device 1 is a device capable of generating plasma.

[0100] Figure 10A - Figure 10CThe film-forming apparatus 1 shown 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 processing gas into the chamber 2. The gas supply unit 12 supplies, for example, WF6 and H2S. The gas supply unit 12 includes a spray head 13. The spray head 13 is configured to introduce at least one processing gas from the gas supply unit 12 into a processing space. The spray head 13 has a gas supply port 13a, a gas diffusion chamber 13b, and a plurality of gas inlets 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the processing space from the plurality of gas inlets 13c.

[0101] The gas supply unit 12 may also include a gas source and a flow controller (not shown). In one embodiment, the gas supply unit 12 is configured to supply at least one processing gas from its respective gas source to the spray head 13 via its respective flow controller.

[0102] A stage 11 is disposed within a chamber 2 for mounting a substrate W, an example of which is a wafer. A spray head 13 is disposed above the stage 11. In one embodiment, the spray head 13 forms at least a portion of the top 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 outlet for discharging gas from the chamber 2. The chamber 2 is grounded. The spray head 13 and the stage 11 are electrically insulated from the housing of the chamber 2. The gas outlet is connected to an exhaust device (not shown). The exhaust device may include a pressure regulating valve and a vacuum pump. The pressure in the processing space within the chamber 2 is adjusted by the pressure regulating valve. The vacuum pump may also include a turbomolecular pump, a dry pump, or a combination thereof.

[0103] An RF (Radio Frequency) power supply 31 is connected to the spray head 13 via an impedance matching circuit (not shown) to supply RF power to the spray head 13. The spray head 13 also functions as an upper electrode. Plasma is thus formed from at least one processing gas supplied to the processing space. Therefore, the RF power supply 31 can function as at least part of a plasma generation unit configured to generate plasma from one or more processing gases in the chamber 2.

[0104] A bias power supply 32 is connected to the mounting stage 11 via an impedance matching circuit (not shown) to supply bias power to the mounting stage 11. The mounting stage 11 also functions as a lower electrode. By supplying bias power to the lower electrode, a bias potential can be generated on the substrate W, attracting the ionic components in the formed plasma to the substrate W.

[0105] DC (Direct Current) power supply 33 is connected to the electrodes, applying a DC voltage to the electrodes. Figure 10AIn this case, the DC power source 33 is connected to the electrode 40. The h-BN has a contact surface in contact with the electrode 40. By pressing the electrode 40 against the contact surface and applying a direct current voltage, a potential difference is generated between the h-BN and the stage 11, and an electric field in a prescribed direction is generated on the surface of the h-BN. Thus, the Fermi level can be adjusted based on the information shown in FIG. 8 relating the Fermi level to the formation energy of defects, and thus the charging state of defects of the h-BN can be directly adjusted. In addition, the electrode 40 can be in a frame shape, a probe shape, or another shape. Figure 6

[0106] In this case, the DC power source 33 is connected to the electrode 41. The electrode 41 is disposed near the surface of the substrate W between the stage 11 (lower electrode) and the shower head 13 (upper electrode). The DC power source 33 generates a potential difference between the electrode 41 and the h-BN by applying a direct current voltage to the electrode 41, and an electric field in a prescribed direction is generated on the surface of the h-BN. Thus, the Fermi level can be adjusted based on the information shown in FIG. 8 relating the Fermi level to the formation energy of defects, and thus the charging state of defects of the h-BN can be directly adjusted. In addition, the electrode 41 can also be in a mesh shape, for example. Figure 10B Figure 6

[0107] In this case, the DC power source 33 is connected to the shower head 13 (upper electrode). The DC power source 33 applies a direct current voltage to the shower surface (lower surface) of the shower head 13 as an electrode, and thus a potential difference is generated between the shower surface and the h-BN, and an electric field in a prescribed direction is generated on the surface of the h-BN. Thus, the Fermi level can be adjusted based on the information shown in FIG. 8 relating the Fermi level to the formation energy of defects, and thus the charging state of defects of the h-BN can be directly adjusted. Figure 10C Figure 6

[0108] ​​​​​The control section 3 processes computer executable instructions for causing the film formation apparatus 1 to perform various processes described in the present disclosure. The control section 3 can be configured to control each element of the film formation apparatus 1 to perform various processes described herein. In one embodiment, part or all of the control section 3 can be included in the film formation apparatus 1. The control section 3 can include a processing section, a storage section, and a communication interface. The control section 3 is implemented by, for example, a computer. The processing section can be configured to perform various control actions by reading out a program from the storage section and executing the read-out program. The program can be pre-stored in the storage section or acquired via a medium as needed. The acquired program is stored in the storage section, read out from the storage section by the processing section, and executed. The medium can be various storage media readable by a computer or a communication line connected to the communication interface. The processing section can be a CPU (Central Processing Unit). The storage section can include a RAM (Random Access Memory), a ROM (Read Only Memory), an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a combination thereof. The communication interface can communicate with the film formation apparatus via a communication line such as a LAN (Local Area Network). Figure 6 Information on the correlation between the Fermi level and the formation energy of the defect can be pre-stored in the storage section of the control section 3 or acquired from a communication line connected to the communication interface.

[0109] Using Figure 10A - Figure 10C The film formation apparatus 1 applies a desired direct current voltage to each of the electrodes 40, 41, the upper electrode, and forms WS2 on the h-BN by the ALD method using WF6 and H2S. Thereby, it is possible to control the domain size of WS2 while adjusting the charging state of the defect of h-BN and adjusting the adsorption state of the raw material of WS2 by adjusting the Fermi level, thereby forming high-quality WS2.

[0110] [Others]

[0111] For example, the h-BN surface can be provided with an electric charge by causing the h-BN surface to generate static electricity or charging the h-BN surface with UV light or the like, and adjusting the charging state of the defect of h-BN. That is, a substrate having h-BN charged in this way can be carried into the film formation apparatus 1, and WS2 can be formed on the h-BN by the ALD method using WF6 and H2S.

[0112] It is also possible to generate plasma in the film formation apparatus 1, and to supply charged particles in the plasma to the h-BN surface to adjust the charged state of the defects of the h-BN. That is, it is also possible to convey the substrate after the charged state of the defects of the h-BN has been adjusted in this way into the film formation apparatus 1, and to form WS2 on the h-BN using WF6 and H2S by the ALD method.

[0113] It is also possible that, after the charged state of the defects of the h-BN has been adjusted, the h-BN is subjected to an annealing process at a high temperature, and WF6 and H2S are supplied to the surface of the h-BN after the annealing process to form WS2. By annealing the h-BN after the charged state of the defects of the h-BN has been adjusted and before WS2 is formed, it is possible to move or diffuse the defects. By annealing the h-BN, atoms move, and it is thus possible to control the type and concentration of the defects.

[0114] The film formation of the h-BN and the film formation of the TMDC such as WS2 can also be performed in different film formation apparatuses. The annealing process can be performed using either of the film formation apparatus of the h-BN and the film formation apparatus of the TMDC. Furthermore, with regard to the film formation of the h-BN, it is also possible to perform the film formation without applying a bias power using an ICP (Inductively Coupled Plasma) apparatus.

[0115] It is also possible to perform a process of increasing the defects of the film surface of the h-BN. That is, it is also possible to increase the defects of the surface of the h-BN film after the h-BN film has been formed using a non-reactive gas or the like. However, defects already exist on the surface of the h-BN at the time of the film formation of the h-BN film in general, and thus there is no problem even if the process of increasing the defects is not performed.

[0116] [Effects]

[0117] The inventors have found that the adsorption of WF6 to ideal h-BN is weak, but by introducing defects such as N lattice vacancies ("V N " and N defects) into the h-BN, it is possible to significantly strengthen the adsorption of WF6 to the h-BN. Furthermore, the reactivity of WF6 with the N defects depends on the charge of the N defects. This means that, by an electric field, a gate, or additional doping, and / or by adjusting the Fermi level of the h-BN, it is possible to control the reactivity of WF6 with the defect surface of the h-BN. Such controllable surface reactivity can be applied to deposition (film formation) conditions to various 2D and / or 3D.

[0118] The TMDC is a layered material having a 2D structure like the h-BN, and has a band gap of 1 to 2 eV and a high carrier mobility, and thus can be used as, for example, a channel material of a transistor. According to film formation of the TMDC using the adsorption control method according to the present embodiment, the carrier mobility and the subthreshold swing can be improved.

[0119] In addition, the h-BN functions as a protective layer of the TMDC, and can prevent degradation of the mobility of the TMDC due to contamination caused by diffusion or the like from the substrate layer. In addition, the h-BN has a large band gap of 4 to 5 eV, and thus electrons do not flow unless a larger energy than that of the TMDC is applied, and thus can function as an insulating film for preventing leakage.

[0120] In addition, the h-BN can be used Figure 8 The adsorption control method according to the present embodiment can be used to increase the domain size of WS2 formed by the ALD method.

[0121] The reactivity of the surface of the electronically controllable two-dimensional material can also be applied to the fields of (1) to (3) below. However, the present embodiment is not limited thereto.

[0122] (1) Controllable size of the deposition area of the TMDC

[0123] (2) Controllable deposition rate of the TMDC

[0124] (3) Area selectivity of deposition to different surfaces (for example, h-BN, other 2D and / or 3D substrates)

[0125] It should be considered that the adsorption control method and the film formation apparatus according to the present embodiment are illustrative and not limiting in all aspects. The present embodiment can be modified and improved in various ways without departing from the scope of the appended claims and the spirit thereof. The matters described in the above-described embodiments can also take other structures within a range not departing from the scope, and can be combined within a range not departing from the scope.

[0126] According to the present adsorption control method, as Figure 2 indicated, not only the adsorption of WF6 but also the adsorption of H2S can be controlled.

[0127] The film formation apparatus disclosed in the present specification can be applied to any one 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.

[0128] The film formation apparatus disclosed in the present specification is not limited to an apparatus that processes a substrate using plasma, and can be an apparatus that processes a substrate without using plasma.

[0129] This international application claims priority based on Japanese Patent Application No. 2023-110691 filed on July 5, 2023, the entire contents of which are incorporated herein by reference.

[0130] Explanation of Reference Signs

[0131] 1: Film forming apparatus; 2: Chamber; 3: Control section; 11: Stage; 33: DC power supply; 40, 41: Electrode.

Claims

1. An adsorption control method for controlling the adsorption of raw material from a second layer to a first layer, the adsorption control method comprising the following steps: A substrate having the first layer is prepared on a stage inside the cavity; The material of the second layer is supplied into the chamber, and the surface of the first layer is exposed to the material. as well as The adsorption of the raw material onto the surface of the first layer is controlled by controlling the charge supplied to the defects on the surface of the first layer.

2. The adsorption control method according to claim 1, wherein, The first layer is a two-dimensional material layer, and the second layer is a transition metal dichalcogenide film.

3. The adsorption control method according to claim 2, wherein, The transition metal dichalcogenide film is formed by atomic layer deposition.

4. The adsorption control method according to claim 3, wherein, The raw materials for the transition metal dichalcogenide film include a first raw material and a second raw material. The adsorption control method includes the following steps: Step (A): Supply the first raw material into the chamber and expose the surface of the two-dimensional material layer to the first raw material; Step (B) involves supplying the second material into the chamber and exposing the surface of the two-dimensional material layer to the second material. Step (C) involves repeating the set number of loops in the order of steps (A) and (B); and Step (D) involves controlling the adsorption of the first raw material onto the two-dimensional material layer by controlling the charge supplied to the defects on the surface of the two-dimensional material layer during the execution of step (A).

5. The adsorption control method according to any one of claims 2 to 4, wherein, The step of controlling the charge provided to defects on the surface of the two-dimensional material layer includes applying a DC voltage to an electrode in contact with the 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.

6. The adsorption control method according to claim 5, wherein, The adsorption control method includes: storing information related to 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. Referring to the storage unit, the DC voltage applied to the electrode is controlled based on the relevant information, thereby controlling the charge supplied to defects on the surface of the two-dimensional material layer.

7. The adsorption control method according to any one of claims 2 to 4, wherein, The step of controlling the charge provided to defects on the surface of the two-dimensional material layer includes: preparing the substrate on the stage to which the surface of the two-dimensional material layer has been pre-charged, or providing the charge to the surface of the two-dimensional material layer on the substrate prepared on the stage from plasma generated in the chamber.

8. The adsorption control method according to any one of claims 2 to 4, wherein, After controlling the charge supplied to the defects on the surface of the two-dimensional material layer, the two-dimensional material layer is annealed, and the raw material is supplied to the surface of the annealed two-dimensional material layer, thereby controlling the adsorption of the raw material to the surface of the two-dimensional material layer.

9. The adsorption control method according to any one of claims 2 to 4, wherein, The raw material is a gas containing tungsten and halogens and / or a gas containing sulfur.

10. The adsorption control method according to claim 9, wherein, The gas containing tungsten and halogens is any one of WF6, WCl5, WCl6, W(CO)6, and W2(NME2)6. The sulfur-containing gas is H2S.

11. The adsorption control method according to claim 4, wherein, In the step of controlling the adsorption of the first raw material and the second raw material onto the two-dimensional material layer Control is performed such that, in the first cycle of the set number of cycles, the charge provided to the defects on the surface of the two-dimensional material layer is 0 or -1. Control is performed such that in the second cycle of the set number of cycles, the charge provided to the defects on the surface of the two-dimensional material layer is +1.

12. The adsorption control method according to any one of claims 2 to 4, wherein, The two-dimensional material layer is hexagonal boron nitride.

13. The adsorption control method according to claim 12, wherein, When the raw material is WF6, the surface defects of the hexagonal boron nitride are any one of the following states: nitrogen deficiency, boron deficiency replaced by carbon, and nitrogen deficiency replaced by oxygen.

14. The adsorption control method according to claim 12, wherein, When the raw material is H2S, the surface defects of the hexagonal boron nitride are those where nitrogen-deficient sites are replaced by oxygen.

15. The adsorption control method according to claim 4, wherein, In the first cycle of the set number of cycles, the flow rate of the first raw material supplied to the chamber is less than that in the second cycle of the set number of cycles and thereafter.

16. The adsorption control method according to claim 15, wherein, The nucleus formation density on the surface of hexagonal boron nitride is controlled based on the flow rate of the first raw material supplied to the chamber in the first cycle.

17. The adsorption control method according to claim 4, wherein, The first raw material is WF6, and the second raw material is H2S.

18. The adsorption control method according to any one of claims 2 to 4, wherein, The transition metal dichalcogenide film is a WS2 film or a WSe2 film.

19. A film-forming apparatus for controlled adsorption, the film-forming apparatus being used to form a transition metal dichalcogenide film on a first layer having a substrate, the film-forming apparatus comprising: chamber; A stage, disposed within the cavity, for placing the substrate; and Control Department in, The control unit controls the adsorption of the raw material of the transition metal dichalcogenide film onto the first layer by performing the following process: The substrate is prepared on a stage within the cavity; The raw material is supplied into the chamber, and the surface of the first layer is exposed to the raw material; as well as The adsorption of the raw material onto the surface of the first layer is controlled by controlling the charge supplied to the defects on the surface of the first layer.

20. The film-forming apparatus for controlled adsorption according to claim 19, wherein, The first layer is a two-dimensional material layer.

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