Chemical vapor deposition raw material including indium compound as main component and method for manufacturing indium containing thin film

Abstract

To provide a chemical vapor deposition raw material undecomposed for a long period of time at the room temperature to be stably stored and consisting of an indium compound, and a method for manufacturing an indium containing thin film using the chemical vapor deposition raw material.SOLUTION: A chemical vapor deposition raw material includes an indium compound expressed by the following general formula (1) as a main component (where in the general formula (1), R1 to R5 are independently a hydrogen atom or a 1-8C hydrocarbon group, where the number of R1 to R5 used as a hydrogen atom is 0 or more and three or less, and the total number of carbon atoms in R1 to R5 is eight or more).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a chemical vapor deposition material for forming an indium-containing thin film and a method for producing an indium-containing thin film using the chemical vapor deposition material. [Background technology]

[0002] Indium-containing oxide films are widely used industrially due to their electrical conductivity and high transmittance to visible light. For example, indium oxide (ITO) films containing tin as a dopant are used as electrodes in liquid crystal displays as low-resistance transparent conductive films. Indium, gallium, and zinc composite oxide (IGZO) films are also used in thin-film transistors for displays.

[0003] Films such as ITO and IGZO are formed by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Atomic layer deposition (ALD), a type of CVD, can deposit films with uniform thickness at the molecular level on the surface of flexible organic substrates.

[0004] Although many indium compound chemical vapor deposition sources are known to be solid at room temperature, liquid indium compound chemical vapor deposition sources are more suitable than solid indium compound chemical vapor deposition sources because they can be easily supplied to the device as vapors with a uniform concentration.

[0005] Several indium compounds having cyclopentadienyl-based ligands have been reported as raw materials for chemical vapor deposition of indium compounds, which are liquid materials. However, these compounds have stability problems, and various methods have been attempted to stabilize them.

[0006] Patent Document 1 discloses a compound having the general formula (1): In(C5R) as a chemical vapor deposition raw material that can be used in high-temperature film formation processes such as CVD, ALD, plasma enhanced chemical vapor deposition (PECVD), or plasma enhanced atomic layer deposition (PEALD). 1 X H (5-X) ) (wherein x is an integer of 1 to 5, R1 and each independently represent a hydrocarbon group having 5 to 8 carbon atoms.

[0007] In Patent Document 1, s-butylcyclopentadienylindium(I), s-pentylcyclopentadienylindium(I), i-pentylcyclopentadienylindium(I), and s-butylcyclopentadienylindium(I) are used as the indium compounds represented by the above general formula (1).

[0008] Regarding the stability of the indium compounds reported in Patent Document 1, for example, in Example 1, thermogravimetric analysis (TGA) showed that 99.4% evaporated by 200°C, leaving a residue of 0.6%, indicating that thermal decomposition did not occur. However, after one day of storage, precipitation due to decomposition was observed, indicating that the long-term stability was insufficient (Comparative Example 2 in this specification). Furthermore, when using as raw materials indium compounds containing S, Ge, or N, or indium compounds with a non-cyclopentadienyl-based ligand containing a large amount of C, as shown in Patent Document 1, there is a risk that these elements will remain in the formed film.

[0009] Patent Document 2 describes a chemical vapor deposition raw material that can be stored stably for a long period of time by mixing an indium compound represented by general formula (1): In(C5H4R) or general formula (2): In(C5(CH3)4R), such as tetramethyl-n-propylcyclopentadienyl indium(I), with a metal compound other than indium, such as gallium, zinc, or tin. However, obtaining the chemical vapor deposition raw material described in Patent Document 2 requires the complicated process of mixing unstable compounds before they decompose.

[0010] As described above, various methods have been investigated for stabilizing indium compound chemical vapor deposition raw materials, but no chemical vapor deposition raw material has yet been developed that remains stable for a sufficiently long period of time for industrial use without the need for complicated operations. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent No. 7240903 [Patent Document 2] Japanese Patent Publication No. 2022-89772 Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present invention is to provide a chemical vapor deposition raw material comprising an indium compound that can be stably stored at room temperature for long periods without decomposition, and a method for producing an indium-containing thin film using the chemical vapor deposition raw material.

[0013] The chemical vapor deposition material of the present invention is characterized by containing an indium compound represented by the following general formula (1) as a main component. [ka]

[0014] In general formula (1), R 1 ~R 5 are each independently a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 1 ~R 5 The number of is between 0 and 3, and R 1 ~R 5 The total number of carbon atoms in the group is 8 or more.

[0015] The method for producing an indium-containing thin film of the present invention is characterized in that an indium-containing thin film is produced by a CVD method using a chemical vapor deposition raw material containing an indium compound represented by the general formula (1) as a main component. [Effects of the Invention]

[0016] The chemical vapor deposition material containing the indium compound of the present invention as a main component is stable at room temperature for a long period of time, and therefore is easy to handle and can be stored stably for a long period of time. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be described in detail below. <Raw materials for chemical vapor deposition> The chemical vapor deposition material of the present invention contains, as a main component, an indium compound represented by general formula (1). The indium compound represented by general formula (1) is a monovalent compound. [ka]

[0018] In general formula (1), R 1 ~R 5 are each independently a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 1 ~R 5 The number of is between 0 and 3, and R 1 ~R 5 The total number of carbon atoms in is 8 or more.

[0019] Examples of hydrocarbon groups having 1 to 8 carbon atoms include alkyl groups having 1 to 8 carbon atoms. Examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, neopentyl, i-pentyl, s-pentyl, 3-pentyl, t-pentyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, n-heptyl, 2-methylhexyl, 3-methylhexyl, 3-ethylpentyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl, 3,3-dimethylpentyl, 2,2,3-trimethylpentyl, and 2,4,5-trimethylpentyl. trimethylbutyl, n-octyl, 1-methylheptyl, 2-methylheptyl, 3-methylheptyl, 4-methylheptyl, 2,2-dimethylhexyl, 2,3-dimethylhexyl, 2,4-dimethylhexyl, 2,5-dimethylhexyl, 3,3-dimethylhexyl, 3,4-dimethylhexyl, 3-ethylhexyl, 2,2,3-trimethylpentyl, 2,2,4-trimethylpentyl, 2,3,3-trimethylpentyl, 2,3,4-trimethylpentyl, 2-methyl-3-ethylpentyl, 3-methyl-3-ethylpentyl, and 2,2,3,3-tetramethylbutyl.

[0020] The hydrocarbon group having 1 to 8 carbon atoms may be, for example, the above-mentioned alkenyl group containing one double bond in the alkyl group, or an alkynyl group containing one triple bond in the alkyl group.

[0021] Furthermore, within the scope of the present invention, the hydrocarbon group having 1 to 8 carbon atoms, such as an alkyl group, an alkenyl group, or at least one hydrogen atom of the alkyl group, may be substituted with an atom of nitrogen, oxygen, sulfur, or a halogen atom.

[0022] In general formula (1), R 1 ~R 5The alkyl group that becomes the hydrocarbon group having 1 to 8 carbon atoms may have a linear structure or a branched structure. 1 ~R 5 The alkyl group forming the hydrocarbon group having 1 to 8 carbon atoms preferably has a branched structure. When a branched alkyl group with large steric hindrance is introduced into an indium compound, the reactivity of the indium compound decreases. Such an indium compound has a low melting point and is less susceptible to decomposition by air, heat, or light, and has chemically stable properties. As a result, the compound is easy to handle and can maintain a high purity state for a long period of time.

[0023] In general formula (1), R is a hydrogen atom. 1 ~R 5 The number of R is 0 to 3. 1 ~R 5 is not a hydrogen atom of a hydrocarbon group, but R 1 ~R 5 This refers to a hydrogen atom directly introduced into

[0024] In general formula (1), R 1 ~R 5 The total number of carbon atoms in R is 8 or more. However, if the total number of carbon atoms is too large, the vapor pressure decreases and the material becomes unsuitable as a deposition material, so the total number of carbon atoms is at most 15 or 16, preferably 12 or less, more preferably 10 or less, and particularly preferably 9. By keeping the total number of carbon atoms within the above range, R 1 ~R 5 The indium compound can be stabilized by the moderate steric hindrance of the hydrocarbon group.

[0025] In general formula (1), R 1 ~R 5 The hydrocarbon groups having 1 to 8 carbon atoms may be the same or different from one another, but are preferably the same from the viewpoint of availability of raw materials and ease of synthesis.

[0026] In general formula (1), R 1 ~R 5When the hydrocarbon groups having 1 to 8 carbon atoms are the same, examples of such hydrocarbon groups include an ethyl group, an i-propyl group, an s-butyl group, and a t-butyl group. Specific examples of indium compounds include those having R 1 ~R 5 The substituents have two hydrogen atoms and three i-propyl groups, such as tri-i-propylcyclopentadienylindium(I).

[0027] R 1 ~R 5 In the hydrocarbon group having 1 to 8 carbon atoms, the number of carbon atoms is preferably 1 to 4. Therefore, among the alkyl groups having 1 to 8 carbon atoms, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl and t-butyl are preferred, and ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl and t-butyl groups having 2 to 4 carbon atoms are more preferred.

[0028] Specific examples of the indium compound represented by general formula (1) include tetraethylcyclopentadienylindium(I), pentaethylcyclopentadienylindium(I), tri-i-propylcyclopentadienylindium(I), tetra-i-propylcyclopentadienylindium(I), di-s-butylcyclopentadienylindium(I), tri-s-butylcyclopentadienylindium(I), di-t-butylcyclopentadienylindium(I), and tri-t-butylcyclopentadienylindium(I).

[0029] Generally, a monovalent indium compound is disproportionated by light or heat at room temperature into a trivalent indium compound and metallic indium, as shown in the following general formula (2). [ka]

[0030] The decomposition of monovalent indium compounds into trivalent indium compounds accompanied by the generation of metallic indium due to such a disproportionation reaction means that it is difficult to store chemical vapor deposition raw materials consisting of indium compounds for long periods of time.

[0031] However, in the present invention, a plurality of hydrocarbon groups having 1 to 8 carbon atoms are attached to the cyclopentadienyl group of the indium compound, as shown in R 1 ~R 5 The total number of carbon atoms in the indium compound is increased to 8 or more, thereby increasing the steric hindrance of the ligands of the indium compound. This prevents the generation of trivalent indium compounds, and as a result, stabilizes the indium compound.

[0032] The chemical vapor deposition material of the present invention contains the indium compound represented by the general formula (1) as a main component, but the indium compound represented by the general formula (1) can also be used alone.

[0033] The chemical vapor deposition raw material of the present invention may contain a solvent. The solvent to be used is not particularly limited as long as it can be suitably used in a chemical vapor deposition liquid material vaporization and supply system. Among these, aprotic organic solvents that do not react with indium compounds are preferred, with tetrahydrofuran (THF), ethylcyclohexane, and toluene being more preferred. The concentration of the indium compound represented by general formula (1) in the solution is usually 0.01 wt% or more, and preferably 1 wt% or more.

[0034] <Method of manufacturing an indium-containing thin film> In the method for producing an indium-containing thin film of the present invention, an indium-containing thin film is produced by chemical vapor deposition (CVD) using a chemical vapor deposition raw material containing the above-mentioned indium compound as a main component.

[0035] Chemical vapor deposition (CVD) methods include, for example, thermal CVD, metalorganic chemical vapor deposition (MOCVD), low-pressure vapor deposition (LPCVD), PECVD, and ALD.

[0036] Here, as an example, a method for forming an indium-containing thin film by thermal CVD using tri-i-propylcyclopentadienyl indium(I) as a chemical vapor deposition raw material will be described.

[0037] The temperature of the substrate on which the thin film is formed is higher than the decomposition temperature of the raw material, typically 200 to 1000°C. The raw material container filled with the raw material for chemical vapor deposition is heated to vaporize it and then supplied to the reaction chamber. Vaporization is performed by a typical method for vaporizing organometallic compounds in chemical vapor deposition (CVD), for example, by heating and reducing the pressure inside the raw material container of the CVD apparatus.

[0038] In order to supply the chemical vapor deposition raw material to the substrate in the reaction chamber, the temperature of the piping from the raw material container to the reaction chamber and the reaction chamber is set to a temperature at which the raw material, tri-i-propylcyclopentadienyl indium(I), does not thermally decompose and remains in a gaseous state, i.e., higher than the temperature of the raw material container (the temperature at which the raw material is vaporized) and lower than the thermal decomposition temperature of the raw material. When the chemical vapor deposition raw material of the present invention is used, the heating temperature is approximately 23 to 200°C. Since a lower piping temperature is better, tri-i-propylcyclopentadienyl indium(I), which has sufficient vapor pressure at low temperatures, is suitable for chemical vapor deposition (CVD).

[0039] When mass production is carried out using the chemical vapor deposition (CVD) method, it can be carried out using the injection method, in which the liquid material is directly vaporized in the required amount while controlling the flow rate while it is still in a liquid state. However, when using the injection method for solid materials, the material must be made liquid by dissolving it in a solvent or by melting it by heating before being placed in the source container of the CVD device.

[0040] Indium-containing oxide films can be formed by thermal CVD by supplying a reactive gas containing oxygen along with a chemical vapor deposition source made of an indium compound. The reactive gas is not particularly limited as long as it contains oxygen, and examples include water, oxygen, and ozone. When water or oxygen is used as the reactive gas, a plasma source can also be used.

[0041] When an indium-containing nitride film is formed by thermal CVD, it can be formed by supplying a nitrogen-containing reactive gas together with a chemical vapor deposition raw material made of an indium compound. The reactive gas is not particularly limited as long as it contains nitrogen, and examples thereof include nitrogen and ammonia. When using these, a plasma source can also be used.

[0042] The chemical vapor deposition material of the present invention is also suitable for atomic layer deposition (ALD), a CVD method in which atomic layers are formed and stacked one by one. Atomic layer deposition (ALD) has the advantage of easy control of film quality. In order to extend the saturated adsorption time of the source gas and obtain a high-quality thin film, it is preferable to be able to perform film formation at high temperatures. Therefore, the chemical vapor deposition material containing the indium compound of the present invention as a main component has high thermal stability and is therefore suitable for film formation processes by atomic layer deposition (ALD) at high temperatures.

[0043] In atomic layer deposition (ALD), similar to thermal CVD, raw materials for chemical vapor deposition are prepared, and then a substrate is placed on a heater in a chamber. The following four steps are repeated until the desired thin film is obtained: 1) introducing a vapor phase indium compound to cause the indium compound to adsorb onto the substrate; 2) purging excess molecules from the chamber with an inert gas; 3) introducing a reactive gas to cause it to react with the indium compound on the substrate; and 4) purging excess reactive gas from the chamber with an inert gas.

[0044] When forming an indium-containing oxide film, the reactive gas is not particularly limited as long as it contains oxygen, and examples thereof include water, oxygen, ozone, etc. When water or oxygen is used as the reactive gas, a plasma source can also be used.

[0045] When forming an indium-containing nitride film, the reactive gas is not particularly limited as long as it contains nitrogen, and examples thereof include ammonia, nitrogen, etc. When using these, a plasma source can also be used. [Example]

[0046] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0047] [Example 1] Synthesis of tri-i-propylcyclopentadienylindium(I) A 500 mL four-neck flask was charged with 200 mL of hexane, 43 mL of n-butyllithium hexane solution (1.62 mol / L, 0.070 mol), and 15.16 g of tri-i-propylcyclopentadiene (0.079 mol), and the mixture was reacted at room temperature for 6 days. After that, the mixture was distilled off under reduced pressure at 120°C to obtain tri-i-propylcyclopentadienyllithium.

[0048] Next, 160 mL of toluene was added, followed by the addition of 9.56 g (0.064 mol) of indium chloride (InCl) at -78°C, and the mixture was stirred at room temperature for 1 day, followed by filtration. The resulting filtrate was evaporated under reduced pressure at 30°C to obtain a liquid.

[0049] The resulting liquid was distilled twice, once at 100°C, 0.3 torr, and once at 80°C, 0.3 torr, to give tri-i-propylcyclopentadienylindium(I) as a pale yellow liquid, 6.57 g (0.021 mol), a yield of 34%.

[0050] Regarding the obtained product 1 H NMR analysis confirmed that the product was a mixture of structural isomers of tri-i-propylcyclopentadienylindium(I).

[0051] 1 H NMR Measurement conditions (apparatus: AVANCE NEO 500 (500 MHz), Bruker BioSpin, solvent: benzene-d6, method: 1D) 5.77(1.7H,septet)ppm, 5.63(0.3H,singlet)ppm, 2.97(0.15H,septet)ppm,2.88(0.3H,septet)ppm,2.80(1.7H,septet)ppm,2.75(0.85H,septet)ppm,1.33(0.9H, doublet)ppm,1.22(5.1H,doublet)ppm,1.19-1.16(12H,multiplet)ppm

[0052] (Stability test) The purified tri-i-propylcyclopentadienylindium(I) was stored at room temperature for 3 months, and no precipitation was observed.

[0053] [Example 2] Synthesis of di-s-butylcyclopentadienylindium(I) A 1 L four-neck flask was charged with 370 mL of hexane, 62 mL of n-butyllithium cyclohexane solution (2.3 mol / L, 0.142 mol), and 22.21 g (0.125 mol) of di-s-butylcyclopentadiene, and the mixture was reacted at room temperature for 2 days. After that, the mixture was distilled off under reduced pressure at 120°C to obtain di-s-butylcyclopentadienyllithium.

[0054] Next, 300 mL of toluene was added, and then 18.81 g (0.125 mol) of indium chloride (InCl) was added at -78°C, and the mixture was stirred at room temperature for 1 day, and then filtered. The obtained filtrate was evaporated under reduced pressure at 30°C to obtain a liquid.

[0055] The resulting liquid was distilled twice at 100°C and 0.3 torr to give di-s-butylcyclopentadienylindium(I) as a pale yellow liquid in an amount of 2.61 g (0.009 mol) with a yield of 7.2%.

[0056] Regarding the obtained product 1 H NMR analysis confirmed that the product was a mixture of structural isomers of di-s-butylcyclopentadienylindium(I).

[0057] 1 H NMR Measurement conditions (apparatus: AVANCE NEO 500 (500 MHz), Bruker BioSpin, solvent: benzene-d6, method: 1D) 5.75-5.69(3H,multiplet)ppm,2.58-2.41(2H,multiplet)ppm,1.66-1.37(4H,multiplet)ppm,1.19-1.14(6H,multiplet)ppm,0.94-0.91(6H,multiplet)ppm

[0058] (Stability test) The purified di-s-butylcyclopentadienylindium(I) was stored at room temperature for 5 days or more, and no precipitation was observed.

[0059] [Example 3] Synthesis of tetraethylcyclopentadienylindium(I) A 1 L four-neck flask was charged with 440 mL of hexane, 67 mL of n-butyllithium cyclohexane solution (2.3 mol / L, 0.154 mol), and 30.04 g (0.168 mol) of tetraethylcyclopentadiene, and the mixture was reacted at room temperature for 1 day. After that, the reaction mixture was distilled off under reduced pressure at 80°C to obtain tetraethylcyclopentadienyllithium.

[0060] Next, 300 mL of toluene was added, and then 1.07 g (0.140 mol) of indium chloride (InCl) was added at -78 ° C., and the mixture was stirred at room temperature for 1 day, and then filtered. The obtained filtrate was evaporated under reduced pressure at 40 ° C. to obtain a liquid.

[0061] The resulting liquid was distilled twice at 100°C and 0.3 torr to obtain tetraethylcyclopentadienylindium(I) as a pale yellow liquid in an amount of 11.35 g (0.039 mol), a yield of 28%.

[0062] Regarding the obtained product 1 H NMR analysis confirmed that the product was tetraethylcyclopentadienylindium(I).

[0063] 1 H NMR Measurement conditions (apparatus: AVANCE NEO 500 (500 MHz), Bruker BioSpin, solvent: benzene-d6, method: 1D) 5.62(1H,singlet)ppm,2.49-2.36(8H,multiplet)ppm,1.16(6H,triplet)ppm,1.11(6H,triplet)ppm

[0064] (Stability test) The purified tetraethylcyclopentadienyl indium(I) was stored at room temperature for 5 days or more, and no precipitation was observed.

[0065] [Comparative Example 1] Stability test of ethylcyclopentadienylindium(I) After purifying ethylcyclopentadienyl indium(I), it was stored at room temperature for one day, and the generation of metallic In due to decomposition was observed.

[0066] [Comparative Example 2] Stability test of s-butylcyclopentadienyl indium(I) After s-butylcyclopentadienyl indium(I) was purified and stored at room temperature for one day, the generation of metallic In was observed due to decomposition.

[0067] [Comparative Example 3] Stability test of tetramethyl-n-propylcyclopentadienyl indium (I) After purifying tetramethyl-n-propylcyclopentadienyl indium(I), it was stored at room temperature for one day, and the generation of metallic In due to decomposition was observed.

[0068] [Comparative Example 4] Synthesis of 1-methylheptylcyclopentadienylindium(I) A 1 L four-neck flask was charged with 314 mL of hexane, 47 mL of n-butyllithium cyclohexane solution (2.3 mol / L, 0.108 mol), and 21.07 g of 1-methylheptylcyclopentadiene (0.118 mol), and the mixture was allowed to react at room temperature for 1 day. The resulting solution was diluted with 250 mL of toluene.

[0069] The diluted solution was added to a suspension of 15.01 g (0.100 mol) of indium(I) chloride (InCl) in 500 mL of toluene at -78°C, and the mixture was stirred at room temperature for 4 days. The resulting mixture was evaporated under reduced pressure at 40°C, and then 300 mL of hexane was added and filtered. The filtrate was evaporated under reduced pressure at 40°C to obtain a liquid.

[0070] The resulting liquid was distilled twice at 120°C and 0.3 torr to obtain 1-methylheptylcyclopentadienylindium(I) as a pale yellow liquid in an amount of 8.72 g (0.030 mol), a yield of 30%.

[0071] Regarding the obtained product 1 H NMR analysis confirmed that the compound was 1-methylheptylcyclopentadienylindium(I).

[0072] 1 H NMR Measurement conditions (apparatus: AVANCE NEO 500 (500 MHz), Bruker BioSpin, solvent: benzene-d6, method: 1D) 5.94-5.80(4H,multiplet)ppm,2.59(1H,sextet)ppm,1.63-1.23(10H,multiplet)ppm,1.19(3H,doublet)ppm,0.90(3H,triplet)ppm

[0073] (Stability test) After the purification, 1-methylheptylcyclopentadienyl indium(I) was stored at room temperature for one day, and the generation of metallic In due to decomposition was observed.

Claims

1. A chemical vapor deposition raw material containing, as a main component, an indium compound represented by the following general formula (1): 【Chemical 1】 (In general formula (1), R １ ~R ５ are each independently a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. １ ~R ５ The number of is 0 to 3, and R １ ~R ５ The total number of carbon atoms in

2. In the general formula (1), R １ ~R ５ 2. The chemical vapor deposition material according to claim 1, wherein the number of: is 0 or more and 2 or less.

3. A method for producing an indium-containing thin film, comprising producing an indium-containing thin film by chemical vapor deposition using a chemical vapor deposition raw material containing an indium compound represented by general formula (1) as a main component. 【Chemistry 2】 (In general formula (1), R １ ~R ５ are each independently a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. １ ~R ５ The number of is 0 to 3, and R １ ~R ５ The total number of carbon atoms in

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