Thin film formation method using chemical purging material

Abstract

To provide a method that can form a thin film having preferable step coverage, and to provide a method for forming a thin film that effectively removes an excessively absorbed reactant and dramatically improves step coverage of the thin film.SOLUTION: A method for forming a thin film using a chemical purge substance includes: a metal precursor supply step of supplying a metal precursor into a chamber in which a substrate is placed and adsorbing the metal precursor to the substrate; a step of purging the interior of the chamber; a thin film formation step of supplying a reactant into the chamber to react the reactant with the absorbed metal precursor and form a thin film; a chemical purge substance supply step of supplying the chemical purge substance into the chamber and removing part of the reactant; and a step of purging the interior of the chamber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for forming a thin film, and more particularly to a method for forming a thin film that can remove excess adsorbed reactants using a chemical purge material. [Background technology]

[0002] Currently, research into MIM (Metal / Insulator / Metal) capacitors using metal electrodes is being continuously conducted for capacitors in DRAM devices, and titanium nitride (TiN) is widely used as the electrode material.

[0003] In the field of semiconductor processing, deposition processes are important processes for depositing materials onto substrates. As the dimensions of electronic devices continue to shrink and device density increases, the aspect ratio of features becomes increasingly larger. Therefore, processes with good step coverage are becoming more and more important, and atomic layer deposition (ALD) in particular has attracted considerable interest.

[0004] Titanium nitride films must achieve excellent step coverage because they function as the upper and lower electrodes in capacitors. However, ammonia (NH3), a commonly used reactant in titanium nitride film deposition processes, is prone to over-adsorption due to intermolecular interactions such as hydrogen bonding and van der Waals forces, forming multiple layers that cannot be completely removed by physical purging.

[0005] Excessive adsorption of NH3 leads to excessive adsorption of subsequent precursors, making conformal thin film formation difficult and causing deterioration of step coverage, so a technology that can resolve this phenomenon is required. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a method for forming a thin film with good step coverage.

[0007] Another object of the present invention is to provide a method for forming a thin film that can effectively remove overabsorbed reactants and thereby significantly improve the step coverage of the thin film.

[0008] Other objects of the present invention will become more apparent from the following detailed description. [Means for solving the problem]

[0009] According to one embodiment of the present invention, a method for forming a thin film using a chemical purging material includes a metal precursor supplying step of supplying a metal precursor into a chamber in which a substrate is placed and causing the metal precursor to adsorb onto the substrate; a step of purging the interior of the chamber; a thin film forming step of supplying a reactant into the chamber and reacting with the adsorbed metal precursor to form a thin film; a chemical purging material supplying step of supplying the chemical purging material into the chamber and removing a portion of the reactant; and a step of purging the interior of the chamber.

[0010] The chemical purge material can be represented by the following <Chemical Formula 1>. [ka] In the above <Chemical Formula 1>, X is a chalcogen element (O, S, Se, Te, Po), and R1 and R2 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0011] The chemical purge material can be represented by the following <Chemical Formula 2>. [ka] In the above <Chemical Formula 2>, X is a chalcogen element (O, S, Se, Te, Po), n = 1 to 5, and R1 to R4 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0012] The chemical purge material can be represented by the following <Chemical Formula 3>. [ka] In the <Chemical Formula 3>, X is a chalcogen element (O, S, Se, Te, Po), and R1 to R4 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0013] The chemical purge material can be represented by the following <Chemical Formula 4>. [ka] In the <Chemical Formula 4>, X is a chalcogen element (O, S, Se, Te, Po), and R1 to R3 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0014] The chemical purge material can be represented by the following <Chemical Formula 5>. [ka] In the <Chemical Formula 5>, Y is a pnictogen element (N, P, As, Sb, Bi), and R1 to R3 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0015] The chemical purge material can be represented by the following <Chemical Formula 6>. [ka] In the <Chemical Formula 6>, Y is a pnictogen element (N, P, As, Sb, Bi), and R1 to R5 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0016] The metal precursor supplying step, the thin film forming step, and the chemical purge material supplying step may each be carried out at a temperature of 50 to 700°C.

[0017] The reactant can be at least one of ammonia (NH3), hydrazine (N2H4), nitrogen dioxide (NO2), and nitrogen (N2).

[0018] The metal precursor can be a compound containing at least one of tetravalent metals including Ti, pentavalent metals including Nb and Ta, hexavalent metals including Mo, and tetravalent metalloids including Si. [Effects of the Invention]

[0019] According to one embodiment of the present invention, the deposition thickness per cycle can be reduced using a chemical purge material, and the deposited thin film can have improved uniformity and step coverage.

[0020] Moreover, since excess adsorbed reactants are removed through chemical purging, the process time can be shortened compared to processes using physical purging. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a flowchart schematically illustrating a thin film forming method according to an embodiment of the present invention. [Figure 2] 1 is a graph that schematically illustrates a supply period according to an embodiment of the present invention. [Figure 3]1 is a graph showing GPC results of a titanium nitride film according to TiCl4 supply time (a), NH3 supply time (b), and NH3 purge time (c). [Figure 4] This is the result of confirming the step coverage by depositing a titanium nitride film on a patterned wafer (aspect ratio 20:1). [Figure 5] 1 is a graph showing GPC of a titanium nitride film as a function of the supply time of EMS, which is a chemical purge substance. [Figure 6] 1 is a graph showing GPC and resistivity of Comparative Examples / Examples, which were compared after thin films were prepared to the same thickness of 100 Å. [Figure 7] This is the result of confirming step coverage by depositing a titanium nitride film on a patterned wafer using EMS, a chemical purge material (aspect ratio 20:1). [Figure 8] 1 is a graph showing the results of H-NMR analysis performed to confirm the interaction between EMS, a chemical purge material, and reactants. [Figure 9] 1H-NMR analysis results before and after adduct formation. [Figure 10] The results are from the TGA analysis. DETAILED DESCRIPTION OF THE INVENTION

[0022] Preferred embodiments of the present invention will now be described in more detail with reference to the accompanying Figures 1 to 10. The embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. These embodiments are provided to explain the present invention in more detail to those skilled in the art to which the invention pertains. Therefore, the shape of each element shown in the drawings may be exaggerated to emphasize a clearer description.

[0023] Conventional precursor-only processes have the problem of poor step coverage due to uneven thin film formation, such as a thicker thin film on the top (or inlet side) and a thinner thin film on the bottom (or inner side) in trench structures with high aspect ratios (e.g., 40:1 or more).

[0024] 1 is a flow chart illustrating a thin film formation method according to an embodiment of the present invention, and FIG. 2 is a graph illustrating a supply cycle according to an embodiment of the present invention. A substrate is loaded into a process chamber, and the following ALD process conditions are adjusted. The ALD process conditions may include the temperature of the substrate or the process chamber, the chamber pressure, and the gas flow rate, and the temperature is 50 to 700°C.

[0025] The substrate is exposed to a metal precursor supplied to the interior of the chamber, and the metal precursor is adsorbed onto the surface of the substrate. The metal precursor can be a compound containing at least one of a tetravalent metal including Ti, a pentavalent metal including Nb and Ta, a hexavalent metal including Mo, and a tetravalent metalloid including Si.

[0026] Thereafter, a purge gas (for example, an inert gas such as Ar) is supplied into the chamber to remove and purify any unadsorbed metal precursors or by-products.

[0027] The substrate is then exposed to reactants supplied into the chamber to form a thin film on the surface of the substrate. The reactants react with the metal precursor layer to form a thin film. The reactants can be at least one of ammonia (NH), hydrazine (N2H4), nitrogen dioxide (NO2), and nitrogen (N2), and a metal nitride film can be formed through the reactants.

[0028] Thereafter, a purge gas (for example, an inert gas such as Ar) is supplied into the chamber to remove and purify unreacted materials or by-products.

[0029] The substrate is then exposed to a chemical purge material supplied into the chamber to remove excess adsorbed NH3, for example. The chemical purge material can be expressed as follows:

[0030] [ka] In the above <Chemical Formula 1>, X is a chalcogen element (O, S, Se, Te, Po), and R1 and R2 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0031] The chemical purge material can be expressed as the following <Chemical Formula 2>.

[0032] [ka] In the above <Chemical Formula 2>, X is a chalcogen element (O, S, Se, Te, Po), n = 1 to 5, and R1 to R4 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0033] The chemical purge material can be expressed as the following <Chemical Formula 3>.

[0034] [ka] In the <Chemical Formula 3>, X is a chalcogen element (O, S, Se, Te, Po), and R1 to R4 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0035] The chemical purge material can be expressed as the following <Chemical Formula 4>.

[0036] [ka] In the <Chemical Formula 4>, X is a chalcogen element (O, S, Se, Te, Po), and R1 to R3 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0037] The chemical purge material can be expressed as the following <Chemical Formula 5>.

[0038] [ka] In the above <Chemical Formula 5>, Y is a pnictogen element (N, P, As, Sb, Bi), and R1 to R3 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0039] The chemical purge material can be expressed as the following <Chemical Formula 6>.

[0040] [ka] In the <Chemical Formula 6>, Y is a pnictogen element (N, P, As, Sb, Bi), and R1 to R5 are each independently selected from hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogen element, and an alkyl halide.

[0041] Thereafter, a purge gas (for example, an inert gas such as Ar) is supplied into the chamber to remove or clean unreacted materials or by-products.

[0042] - Comparative Example Titanium nitride film was formed on silicon substrate by ALD process, and the ALD process temperature was 450℃, and NH3 gas was used as reactant.

[0043] The titanium nitride film formation process by the ALD process was as follows, and the following steps were carried out as one cycle. 1) Using Ar as a carrier gas, the titanium precursor TiCl4 (Titanium Tetrachloride) is supplied to a reaction chamber at room temperature, and the titanium precursor is adsorbed onto the substrate. 2) Ar gas is supplied into the reaction chamber to remove any unadsorbed titanium precursor or by-products. 3) NH3 gas is supplied to the reaction chamber to form a titanium nitride film. 4) Ar gas is supplied into the reaction chamber to remove unreacted substances or by-products.

[0044] Figure 3 shows the GPC of titanium nitride films as a function of TiCl4 supply time (a), NH3 supply time (b), and NH3 purging time (c). Even when the TiCl4 supply time was increased from 0.5 to 3, the GPC remained constant at 0.3 Å, indicating that the interaction between TiCl4 molecules was weak and multilayers were not formed.

[0045] As the NH supply time (b) increases from 1 to 5, the GPC shows a tendency to increase from 0.24 to 0.32 Å, which indicates that NH overadsorption occurs due to NH intermolecular interactions. Furthermore, the NH intermolecular interactions remain adsorbed even in the subsequent Ar purge step, which increases the amount of TiCl adsorbed and the GPC of the titanium nitride film.

[0046] As the NH3 purge time increases from 5 to 60, the GPC of the titanium nitride film tends to decrease. This indicates that increasing the Ar purge physically removes some of the excess NH3 molecules, thereby reducing the GPC.

[0047] Figure 4 shows the results of step coverage after depositing a titanium nitride film on a patterned wafer (aspect ratio 20:1). The top GPC was 0.28 Å and the bottom GPC was 0.22 Å, with a 27% increase in top GPC compared to bottom, resulting in a step coverage of 79%. This is due to the fact that NH3 over-adsorption occurs frequently at the top of the high aspect ratio pattern structure, while diffusion is relatively less at the bottom of the narrow hole structure, resulting in a decrease in NH3 over-adsorption and a difference in the amount of TiCl4 adsorbed due to over-adsorption to NH3.

[0048] 3 and 4, it can be seen that excessive NH3 adsorption increases the GPC of the titanium nitride film, thereby deteriorating the step coverage.

[0049] - Example Titanium nitride films were formed on silicon substrates using EMS (Ethyl methyl sulfide) as the chemical purge material. The titanium nitride films were formed using the ALD process, with the ALD process temperature at 450°C and NH3 gas as the reactant.

[0050] The titanium nitride film formation process by the ALD process is as follows, and the following steps were carried out as one cycle (see FIGS. 1 and 2). 1) Using Ar as a carrier gas, the titanium precursor TiCl4 (Titanium Tetrachloride) is supplied to the reaction chamber at room temperature, and the titanium precursor is adsorbed onto the substrate. 2) Ar gas is supplied into the reaction chamber to remove any unadsorbed titanium precursor or by-products. 3) NH3 gas is supplied to the reaction chamber to form a titanium nitride film. 4) Ar gas is supplied into the reaction chamber to remove unreacted materials or by-products. 5) A chemical purge substance is supplied into the reaction chamber to remove excess adsorbed NH3. 6) Ar gas is supplied into the reaction chamber to remove unreacted materials or by-products.

[0051] Figure 5 is a graph showing the GPC of titanium nitride films as a function of the supply time of EMS, a chemical purge material. As the EMS supply time increases, the GPC of titanium nitride films decreases. As the supply time increases from 1 to 5, the GPC ranges from 0.21 Å to 0.16 Å, respectively, and the GPC reduction rate is confirmed to be 28.6% to 43.5%.

[0052] This is thought to be due to the fact that the chemical purging material interacts with the reactants that are unevenly over-adsorbed on the surface, removing the over-adsorbed reactants in the form of chemical purging, thereby reducing the GPC of the titanium nitride film.

[0053] Figure 6 is a graph showing the GPC and resistivity of the comparative example and example, which were compared after preparing thin films with the same thickness of 100 Å. The GPC of the example was 0.22 Å, which showed a 21.4% reduction in GPC compared to the comparative example's GPC of 0.28 Å, and the resistivity was confirmed to be at the same level (see Figure 6).

[0054] This is because when a chemical purging material is used as in the example, the GPC of the titanium nitride film is reduced, and the chemical purging material is removed by forming an additional substance with the subsequent titanium precursor, and does not remain on the surface, so it is thought that the resistance is equal.

[0055] Figure 7 shows the step coverage results (aspect ratio 20:1) of a titanium nitride film deposited on a patterned wafer using EMS, a chemical purge material. Compared to the comparative example, the GPC at the top of the pattern decreased by 25%, from 0.28 Å to 0.21 Å, while the GPC at the bottom of the pattern decreased by 9%, from 0.22 Å to 0.20 Å, forming a uniform film with almost no significant difference in thickness between the top and bottom of the pattern.

[0056] By applying the chemical purge material, the step coverage increased dramatically from 79% to 95%, a 16% increase, resulting in the formation of titanium nitride films with excellent uniformity and step coverage.

[0057] From the results in Figure 7, it appears that when NH3 over-adsorption is removed, the titanium nitride film has a GPC of approximately 0.2 Å. Table 1 below shows data comparing the process times for physical and chemical purging methods for removing NH3 over-adsorption. When NH3 over-adsorption is removed using the physical purging method, the GPC can be reduced to 0.2 Å, but the process time per cycle takes 74 seconds. On the other hand, when NH3 over-adsorption is removed using the chemical purging method of the example, the GPC can be reduced to the 0.2 Å level, just like the physical purging method, and the process time per cycle can be more than doubled, from 74 seconds to 35 seconds.

[0058] In conclusion, to improve the step coverage of titanium nitride films, the excess adsorption of NH3 must be removed, and the chemical purging method appears to be much more advantageous in terms of UPH than the physical purging method.

[0059] [Table 1]

[0060] Figure 8 is a graph showing H-NMR analysis conducted to confirm the interaction between EMS, a chemical purge material, and reactants. NH4Cl, which has a similar structure to the reactant NH3 (gas phase), and the example were mixed in a 1:1 molar ratio, and then H-NMR analysis was conducted using dimethyl sulfoxide-d6 (DMSO-d6) as the NMR solvent.

[0061] NMR analysis of the NH4Cl and EMS mixed solution showed that after mixing with the chemical purging material, the NH4+ peak shifted by 0.11 from 7.38 to 7.27, confirming the interaction between NH4Cl and the chemical purging material. This phenomenon indirectly confirmed the interaction between the chemical purging material and the reactant NH3, and further suggested that the chemical purging material could remove excess NH3 adsorption through this interaction.

[0062] To confirm that the chemical purge material was removed without remaining on the surface due to the interaction between the reactant and the subsequent titanium precursor after adsorption and removal, the chemical purge material was mixed with the titanium precursor in a 1:1 molar ratio to form an adduct, which was then analyzed by H-NMR and TGA. Figure 9 shows the H-NMR analysis results before and after adduct formation, using benzene-d6 as the NMR solvent.

[0063] NMR analysis confirmed that the EMS peaks shifted chemically after the formation of adducts, which indicates the existence of interactions between the chemical purging material, titanium precursor, and adducts.

[0064] Figure 10 shows the results of the TGA analysis. The adduct formed from the chemical purging material and titanium precursor does not have an inflection point on the graph, and it appears to exist in the form of a stable adduct, volatilizing well at T1 / 2 of 91°C without leaving any residue. Furthermore, it is expected that the adduct will volatilize stably without remaining on the surface after thin film formation.

[0065] In conclusion, the non-uniformly excess NH3 adsorbed on the surface is removed by supplying a chemical purge material through an NH3-chemical purge material interaction, thereby preventing excessive deposition of the supplied metal precursor and improving the uniformity of the nitride film.

[0066] Furthermore, the chemical purge material remaining on the surface is removed in the form of a metal precursor and an additional material that are supplied in the next process, thereby preventing the chemical purge material from being included as an impurity in the nitride film.

[0067] The chemical purge material has the property of interacting with NH3 to form an adduct with the metal precursor, and the formed adduct does not remain on the thin film surface but is volatilized and removed.

[0068] Although the present invention has been described in detail above through examples, other embodiments are possible, and the technical spirit and scope of the following claims are not limited to the examples.

Claims

1. In a thin film formation method using a chemical purging material, a metal precursor supplying step of supplying a metal precursor into a chamber in which a substrate is placed and causing the metal precursor to adsorb onto the substrate; purging the interior of the chamber; a thin film formation step of supplying a reactant into the chamber to react with the adsorbed metal precursor to form a thin film; supplying the chemical purge material into the chamber to remove a portion of the reactant that has been non-uniformly over-adsorbed on the surface of the substrate through an interaction between the chemical purge material and the reactant; and and sequentially carrying out a step of purging the interior of the chamber. The chemical purging material is EMS (Ethyl methyl sulfide).

2. A method for forming a thin film using a chemical purging substance, a metal precursor supplying step of supplying a metal precursor into a chamber in which a substrate is placed and causing the metal precursor to adsorb onto the substrate; purging the interior of the chamber; a thin film formation step of supplying a reactant into the chamber to react with the adsorbed metal precursor to form a thin film; supplying the chemical purge material into the chamber to remove a portion of the reactant that has been non-uniformly over-adsorbed on the surface of the substrate through an interaction between the chemical purge material and the reactant; and and sequentially carrying out a step of purging the interior of the chamber. The chemical purging material is represented by the following Chemical Formula 1: In the above <Chemical Formula 1>, X is S, R1 is methyl, and R2 is propyl.

3. In a thin film formation method using a chemical purging material, a metal precursor supplying step of supplying a metal precursor into a chamber in which a substrate is placed and causing the metal precursor to adsorb onto the substrate; purging the interior of the chamber; a thin film formation step of supplying a reactant into the chamber to react with the adsorbed metal precursor to form a thin film; supplying the chemical purge material into the chamber to remove a portion of the reactant that has been non-uniformly over-adsorbed on the surface of the substrate through an interaction between the chemical purge material and the reactant; and and sequentially carrying out a step of purging the interior of the chamber. The chemical purging material is represented by the following Chemical Formula 2: In the above <Chemical Formula 2>, X is S, n is 3 to 4, and R1 to R4 are each independently selected from hydrogen, an alkyl group having 1 to 3 carbon atoms, a halogen element, and an alkyl halide.

4. 4. The method of forming a thin film using a chemical purging material according to claim 3, wherein in Formula 2, X is S, n=3, and R1 to R4 are each independently hydrogen.

5. In a thin film formation method using a chemical purging material, a metal precursor supplying step of supplying a metal precursor into a chamber in which a substrate is placed and causing the metal precursor to adsorb onto the substrate; purging the interior of the chamber; a thin film formation step of supplying a reactant into the chamber to react with the adsorbed metal precursor to form a thin film; supplying the chemical purge material into the chamber to remove a portion of the reactant that has been non-uniformly over-adsorbed on the surface of the substrate through an interaction between the chemical purge material and the reactant; and and sequentially carrying out a step of purging the interior of the chamber. The chemical purging material is represented by the following Chemical Formula 4. In the above <Chemical Formula 4>, X is S, and R1 to R3 are each independently selected from hydrogen, an alkyl group having 1 to 3 carbon atoms, a halogen element, and an alkyl halide.

6. 6. The method of forming a thin film using a chemical purging material according to claim 5, wherein in Formula 4, X is S and R1 to R3 are each hydrogen.

7. 6. The method for forming a thin film using a chemical purging material according to claim 1, 2, 3, or 5, wherein the metal precursor supplying step, the thin film forming step, and the chemical purging material supplying step are each performed at a temperature of 50 to 700°C.

8. The reactant is ammonia (NH 3 ), Hydrazine (Hydrazine, N 2 H 4 ), nitrogen dioxide (NO 2 ), and nitrogen (N 2 6. A method for forming a thin film using the chemical purging material according to claim 1, 2, 3 or 5, wherein the chemical purging material is at least one of the following:

9. 6. The method for forming a thin film using a chemical purge material according to claim 1, 2, 3, or 5, wherein the metal precursor is a compound containing at least one of a tetravalent metal including Ti, a pentavalent metal including Nb and Ta, a hexavalent metal including Mo, and a tetravalent metalloid including Si.

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