Method for producing bismuth metal thin film and raw material for forming thin film

Abstract

Provided is a method for producing a bismuth metal thin film, said method comprising forming a bismuth metal thin film using a bismuth compound represented by general formula (1) and a reactive gas selected from the group consisting of diol gases, triol gases, carboxylic acid gases, and reducing gases. In general formula (1), R1, R2, and R3 each independently represent a hydrogen atom, a halogen atom, a C1-5 alkyl group, a C6-20 aryl group, a group represented by -NR4R5, or a group represented by -SiR6R7R8, R4 and R5 in the group represented by -NR4R5 each independently represent a C1-5 alkyl group or a group represented by -SiR6R7R8, and R6, R7, and R8 in the group represented by -SiR6R7R8 each independently represent a C1-5 alkyl group.

Description

Method for manufacturing bismuth metal thin films and raw materials for forming thin films

[0001] This disclosure relates to a method for producing a bismuth metal thin film and to raw materials for forming a thin film.

[0002] Thin films containing bismuth are used in various semiconductor devices due to their excellent electrical properties, and atomic layer deposition (ALD) is a known method for manufacturing such thin films. For example, Patent Document 1 discloses the use of a bismuth-containing thin film in a three-layer phase-change memory unit. Patent Document 2 discloses bismuth-containing thin films such as bismuth strontium tantalate thin films and bismuth lanthanum titanate thin films as thin films of multi-element alloys. Patent Document 3 discloses a method for manufacturing a bismuth-containing oxide thin film using an organic bismuth compound. Patent Document 4 exemplifies compounds such as Bi[N(SiMe3)2]3 and Bi[N(Me)(SiMe3)]3 as metal metalloid amides. Patent Document 5 discloses a method for manufacturing a germanium-bismuth-tellurium alloy film.

[0003] Japanese Patent Publication No. 2013-236079, Japanese Patent Publication No. 2006-225381, Japanese Patent Publication No. 2005-135914, International Publication No. 2002 / 027063, Japanese Patent Publication No. 2016-84544

[0004] However, bismuth has the drawback of having good reactivity with dissimilar metal compounds but low reactivity with similar metal compounds. No method was known for producing metal thin films in which the metal is pure bismuth (hereinafter sometimes referred to as "bismuth metal thin films"). Patent documents 1 to 4 do not disclose a method for producing bismuth metal thin films. Patent document 5 discloses forming a Bi-H bond by reacting substituents of a bismuth compound as a precursor with an alcohol, but it has been difficult to obtain a bismuth metal thin film with excellent coating properties using bismuth compounds and alcohols.

[0005] Therefore, the object of this disclosure is to provide a method for manufacturing a bismuth metal thin film that can form a bismuth metal thin film with excellent coverage.

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by a combination of a specific bismuth compound and a specific reactive gas, and have completed the present disclosure.

[0007] That is, the present disclosure provides a method for manufacturing a bismuth metal thin film, including a precursor layer forming step of forming a precursor layer using a raw material for thin film formation containing a bismuth compound represented by the following general formula (1), and a bismuth metal thin film forming step of bringing the precursor layer into contact with a reactive gas to form a bismuth metal thin film, wherein the reactive gas is selected from the group consisting of diol gas, triol gas, carboxylic acid gas, and reducing gas.

[0008]

[0009] (In general formula (1), R 5 , 7 , 6 , 8 , 4 , R 2 and R 3 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 20 carbon atoms, a group represented by -NR 4 R 5 or a group represented by -SiR 6 R 7 R 8 ; in the group represented by -NR 4 R <00000IO>, R 4 and R 5 each independently represents an alkyl group having 1 to 5 carbon atoms or a group represented by -SiR 6 R 7 R 8 ; in the group represented by -SiR 6 R 7 R 8 , R 6 , R 7 and R 8 each independently represents an alkyl group having 1 to 5 carbon atoms.)

[0010] Furthermore, this disclosure provides a thin-film forming raw material containing a bismuth compound represented by the above general formula (1), which forms a bismuth metal thin film by reaction with a reactive gas selected from the group consisting of diol gas, triol gas, carboxylic acid gas, and reducing gas.

[0011] According to this disclosure, a bismuth metal thin film with excellent coverage can be easily formed.

[0012] Figure 1 is a schematic diagram showing an example of an ALD apparatus used in a method for manufacturing a bismuth metal thin film, which is one embodiment of the present disclosure. Figure 2 is a schematic diagram showing another example of an ALD apparatus used in a method for manufacturing a bismuth metal thin film, which is one embodiment of the present disclosure. Figure 3 is a schematic diagram showing another example of an ALD apparatus used in a method for manufacturing a bismuth metal thin film, which is one embodiment of the present disclosure. Figure 4 is a schematic diagram showing another example of an ALD apparatus used in a method for manufacturing a bismuth metal thin film, which is one embodiment of the present disclosure.

[0013] The method for manufacturing a bismuth metal thin film and the raw materials for forming the thin film according to this disclosure will be described below.

[0014] A. Raw materials for forming thin films First, the raw materials for forming thin films of this disclosure will be described. The raw materials for forming thin films of this disclosure include a bismuth compound represented by the above general formula (1) as a precursor.

[0015] A1. Bismuth compounds represented by general formula (1) In the above general formula (1), R 1 , R 2 and R 3 Each of these independently consists of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 20 carbon atoms, and -NR 4 R 5 A group represented by -SiR 6 R 7 R 8 It represents the group represented by -NR 4 R 5 R in the base represented by 4 and R 5 Each of these is independently an alkyl group or -SiR having 1 to 5 carbon atoms. 6 R 7 R 8It represents a group represented by -SiR 6 R 7 R 8 R in the base represented by 6 , R 7 and R 8 Each of these independently represents an alkyl group having between 1 and 5 carbon atoms.

[0016] In the above general formula (1), R 1 , R 2 and R 3 Examples of halogen atoms represented by this formula include fluorine, chlorine, bromine, and iodine atoms.

[0017] In the above general formula (1), R 1 , R 2 and R 3 Examples of alkyl groups with 1 to 5 carbon atoms represented by include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group (n-amyl group), isopentyl group (isoamyl group), sec-pentyl group (sec-amyl group), tert-pentyl group (tert-amyl group), neopentyl group, and the like.

[0018] In the above general formula (1), R 1 , R 2 and R 3 Examples of aryl groups with 6 to 20 carbon atoms represented by this formula include phenylene, naphthalene-1-yl, naphthalene-2-yl, and biphenyl groups.

[0019] In the above general formula (1), R 1 , R 2 and R 3 -NR 4 R 5 In R 4 and R 5 The alkyl group having 1 to 5 carbon atoms represented by the above general formula (1) is R 1 Examples of alkyl groups with 1 to 5 carbon atoms, as represented by the same group as the example alkyl group, include the same group.

[0020] In the above general formula (1), R 1 , R2 and R 3 Represented by -SiR 6 R 7 R 8 In R 6 , R 7 and R 8 The alkyl group having 1 to 5 carbon atoms represented by the above general formula (1) is R 1 Examples of alkyl groups with 1 to 5 carbon atoms, as represented by the same group as the example alkyl group, include the same group.

[0021] Preferred specific examples of the bismuth compound represented by the above general formula (1) include, for example, the bismuth compounds No. 1 to No. 21 listed below. However, this disclosure is not limited to these bismuth compounds. In the following chemical formulas, "Me" represents a methyl group, "Et" represents an ethyl group, "nPr" represents an n-propyl group, and "iPr" represents an isopropyl group.

[0022]

[0023]

[0024]

[0025]

[0026]

[0027] In this disclosure, from the viewpoint of easily forming a high-purity bismuth metal thin film with excellent coverage, uniform film thickness, and low residual carbon, R in the above general formula (1) 1 , R 2 and R 3 However, halogen atoms, alkyl groups with 1 to 5 carbon atoms, -NR 4 R 5 A group represented by -SiR 6 R 7 R 8 Preferably, the group is represented by an alkyl group having 1 to 5 carbon atoms, -NR 4 R 5 A group represented by -SiR 6 R 7 R 8It is more preferable that it is a group represented by, -NR 4 R 5 or a group represented by -SiR 6 R 7 R 8 It is still more preferable that it is a group represented by, -SiR 6 R 7 R 8 It is particularly preferable that it is a group represented by.

[0028] In the present disclosure, from the viewpoint of easily forming a high-purity bismuth metal thin film having excellent coating properties, a uniform film thickness, and little residual carbon, R 1 R 2 and R 3 at least one of is preferably a group represented by -SiR 6 R 7 R 8 It is more preferable that at least two of R 1 R 2 and R 3 are groups represented by -SiR 6 R 7 R 8 It is still more preferable that all three of R 1 R 2 and R 3 are groups represented by -SiR<000​​​​​​​​​​​​​​​​A2. Other Components In this disclosure, the thin film forming raw material may contain the bismuth compound represented by the general formula (1) as a precursor, and its composition will vary depending on the type of thin film to be formed. For example, other components may be included in the thin film forming raw material as needed. Examples of these other components include other precursors, nucleophiles, etc.

[0031] (1) Other Precursors The other precursors can be compounds different from the bismuth compound represented by the general formula (1) above. From the viewpoint of forming a metal thin film in which the metal is elemental bismuth, it is preferable that the metal atoms constituting the other precursors are the same bismuth atoms as those in the bismuth compound represented by the general formula (1) above.

[0032] The above-mentioned raw material for thin film formation may include other commonly known precursors. Examples of these other precursors include reaction products of one or more compounds selected from compounds used as organic ligands, such as alcohol compounds, glycol compounds, β-diketone compounds, cyclopentadiene compounds, and organic amine compounds, with a bismuth atom.

[0033] Alcohol compounds used as organic ligands for the above-mentioned precursors include, for example, alkyl alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, pentyl alcohol, isopentyl alcohol, and tert-pentyl alcohol; 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-methoxy-1-methylethanol, 2-methoxy-1,1-dimethylethanol, 2-ethoxy-1,1-dimethylethanol, and 2-isopropoxy-1,1-dimethylethanol. Examples include ether alcohols such as 2-butoxy-1,1-dimethylethanol, 2-(2-methoxyethoxy)-1,1-dimethylethanol, 2-propoxy-1,1-diethylethanol, 2-sec-butoxy-1,1-diethylethanol, and 3-methoxy-1,1-dimethylpropanol; and dialkylamino alcohols such as dimethylaminoethanol, ethylmethylaminoethanol, diethylaminoethanol, dimethylamino-2-pentanol, ethylmethylamino-2-pentanol, dimethylamino-2-methyl-2-pentanol, ethylmethylamino-2-methyl-2-pentanol, and diethylamino-2-methyl-2-pentanol.

[0034] Examples of glycol compounds that can be used as organic ligands for the other precursors mentioned above include 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 2,4-hexanediol, 2,2-dimethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,3-butanediol, 2,4-butanediol, 2,2-diethyl-1,3-butanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,4-pentanediol, 2-methyl-1,3-propanediol, 2-methyl-2,4-pentanediol, 2,4-hexanediol, and 2,4-dimethyl-2,4-pentanediol.

[0035] Examples of β-diketone compounds used as organic ligands for the above-mentioned precursors include acetylacetone, hexane-2,4-dione, 5-methylhexane-2,4-dione, heptane-2,4-dione, 2-methylheptane-3,5-dione, 5-methylheptane-2,4-dione, 6-methylheptane-2,4-dione, 2,2-dimethylheptane-3,5-dione, 2,6-dimethylheptane-3,5-dione, 2,2,6-trimethylheptane-3,5-dione, 2,2,6,6-tetramethylheptane-3,5-dione, octane-2,4-dione, 2,2,6-trimethyloctane-3,5-dione, 2,6-dimethyloctane-3,5-dione, 2,9-dimethylnonane-4,6-dione, 2-methyl- Examples include alkyl-substituted β-diketones such as 6-ethyldecane-3,5-dione and 2,2-dimethyl-6-ethyldecane-3,5-dione; fluorine-substituted alkyl β-diketones such as 1,1,1-trifluoropentane-2,4-dione, 1,1,1-trifluoro-5,5-dimethylhexane-2,4-dione, 1,1,1,5,5,5-hexafluoropentane-2,4-dione, and 1,3-diperfluorohexylpropane-1,3-dione; and ether-substituted β-diketones such as 1,1,5,5-tetramethyl-1-methoxyhexane-2,4-dione, 2,2,6,6-tetramethyl-1-methoxyheptane-3,5-dione, and 2,2,6,6-tetramethyl-1-(2-methoxyethoxy)heptane-3,5-dione.

[0036] Examples of cyclopentadiene compounds used as organic ligands for the above-mentioned precursors include cyclopentadiene, methylcyclopentadiene, ethylcyclopentadiene, propylcyclopentadiene, isopropylcyclopentadiene, butylcyclopentadiene, sec-butylcyclopentadiene, isobutylcyclopentadiene, tert-butylcyclopentadiene, dimethylcyclopentadiene, tetramethylcyclopentadiene, and pentamethylcyclopentadiene.

[0037] Examples of organic amine compounds used as organic ligands for the above-mentioned precursors include methylamine, ethylamine, propylamine, isopropylamine, butylamine, sec-butylamine, tert-butylamine, isobutylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, ethylmethylamine, propylmethylamine, and isopropylmethylamine.

[0038] The other precursors mentioned above are known in the art, and their manufacturing methods are also known. As an example of a manufacturing method, when an alcohol compound is used as an organic ligand, the precursor can be produced by reacting an inorganic salt of a bismuth atom or its hydrate with an alkali metal alkoxide of the alcohol compound. Examples of inorganic salts of bismuth atoms include bismuth halides and nitrates. Examples of alkali metal alkoxides include sodium alkoxide, lithium alkoxide, and potassium alkoxide.

[0039] When the above-mentioned raw material for forming the thin film contains the above-mentioned other precursor, it is preferable that the above-mentioned other precursor is a compound whose thermal decomposition and / or oxidative decomposition behavior is similar to that of the bismuth compound represented by the above-mentioned general formula (1), in order to facilitate the formation of a high-purity bismuth metal thin film with excellent coating properties, uniform film thickness, and low residual carbon.

[0040] When the thin film forming raw material is a mixture of the bismuth compound represented by the general formula (1) and the other precursor, it is preferable that the other precursor is a compound that exhibits similar thermal decomposition and / or oxidative decomposition behavior to the bismuth compound represented by the general formula (1), and does not undergo alteration due to chemical reactions after mixing with the bismuth compound represented by the general formula (1).

[0041] When the above-mentioned raw material for forming thin films contains the above-mentioned other precursors, from the viewpoint of easily forming a high-purity bismuth metal thin film with excellent coverage, uniform film thickness, and low residual carbon content, the content of the above-mentioned other precursors is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, per 100 parts by mass of the raw material for forming thin films. From the viewpoint of forming a high-purity bismuth metal thin film with even better coverage, more uniform film thickness, and lower residual carbon content, it is preferable that the above-mentioned raw material for forming thin films does not contain the above-mentioned other precursors.

[0042] (2) Nucleophile In this disclosure, the thin film forming raw material may include a nucleophile in order to promote the reaction between the bismuth compound represented by the general formula (1) or the other precursor and the reactive gas.

[0043] Examples of the nucleophile mentioned above include polyamines such as ethylenediamine, N,N'-tetramethylethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, 1,1,4,7,7-pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetramine, triethoxytriethyleneamine, cyclic polyamines such as cyclam and cyclene, pyridine, pyrrolidine, piperidine, Examples include heterocyclic compounds such as morpholine, N-methylpyrrolidine, N-methylpiperidine, N-methylmorpholine, tetrahydrofuran, tetrahydropyran, 1,4-dioxane, oxazole, thiazole, and oxathiolane; β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, and 2-methoxyethyl acetoacetate; and β-diketones such as acetylacetone, 2,4-hexanedione, 2,4-heptanedione, 3,5-heptanedione, and dipivaloylmethane.

[0044] When the thin film forming raw material contains the nucleophile, the content of the nucleophile is preferably in the range of 0.1 moles to 10 moles, and more preferably in the range of 1 mole to 4 moles, per mole of the total amount of precursor, from the viewpoint of facilitating the reaction between the bismuth compound represented by the general formula (1) and the other precursor and the reactive gas described later.

[0045] Here, the total amount of precursors refers to the total amount of precursors contained in the thin-film forming raw material, and represents the sum of the bismuth compound represented by the general formula (1) and the other precursors. If the thin-film forming raw material does not contain the other precursors, the total amount of precursors refers to the amount of the bismuth compound represented by the general formula (1).

[0046] (3) Impurities The raw materials for forming the thin film should, with the exception of the above-mentioned constituent components, i.e., the bismuth compound represented by the above general formula (1), the other precursors, and the nucleophile, contain as few impurities as possible, such as metal elements, halogens, and organic compounds.

[0047] The above-mentioned impurity metal elements include metal elements different from the bismuth metal that constitutes the bismuth compound represented by the above general formula (1). The content of each impurity metal element in the above-mentioned raw material for thin film formation is preferably 100 ppm or less, more preferably 10 ppm or less, and even more preferably 1 ppm or less, in terms of elemental content.

[0048] The content of impurity halogens in the above-mentioned raw materials for thin film formation is preferably 100 ppm or less, more preferably 10 ppm or less, and even more preferably 1 ppm or less.

[0049] The above-mentioned impurity organic content can be an organic content different from the bismuth compound represented by the above general formula (1) and the organic content constituting the other precursors. The above-mentioned organic content is a compound excluding carbon monoxide and carbon dioxide, and includes organic compounds excluding the bismuth compound represented by the above general formula (1) and the other precursors. The total amount of the impurity organic content in the above-mentioned raw material for thin film formation is preferably 500 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less.

[0050] Furthermore, since moisture can cause particle generation in the raw materials for thin film formation and during thin film formation, it is preferable to remove moisture from the bismuth compound represented by general formula (1), the other precursors, and the nucleophile before use in order to reduce their respective moisture content. The moisture content of the bismuth compound represented by general formula (1), the other precursors, and the nucleophile is preferably 10 ppm or less, and more preferably 1 ppm or less.

[0051] Furthermore, the raw materials for forming the thin film are preferably made to contain as few particles as possible in order to reduce or prevent particle contamination of the formed thin film. Specifically, in particle measurement using a light scattering type liquid particle detector in the liquid phase, it is preferable that the number of particles larger than 0.3 μm is 100 or less per 1 ml of liquid phase, and it is more preferable that the number of particles larger than 0.2 μm is 100 or less per 1 ml of liquid phase.

[0052] The physical properties of the bismuth compound represented by the above general formula (1) are also suitable for CVD, so the above-mentioned raw material for thin film formation is useful as a raw material for chemical vapor deposition. The bismuth compound represented by the above general formula (1) has a wide ALD window, and is therefore particularly useful as a raw material for thin film formation in atomic layer deposition.

[0053] The above-mentioned raw material for forming thin films can form bismuth metal thin films with excellent electrical and optical properties, and these bismuth metal thin films are useful in various semiconductor devices, for example, as electrodes or contact layers.

[0054] B. Method for Manufacturing a Bismuth Metal Thin Film Next, the method for manufacturing a bismuth metal thin film according to the present disclosure will be described. The present disclosure provides a method for manufacturing a bismuth metal thin film using a bismuth compound represented by the above general formula (1) and a specific reactive gas.

[0055] The apparatus used in the method for manufacturing bismuth metal thin films according to this disclosure can be a well-known ALD apparatus. Specific examples of apparatus include apparatus capable of bubbling and supplying a precursor, as shown in Figures 1 and 3, and apparatus having a vaporization chamber 102, as shown in Figures 2 and 4. Also, apparatus capable of performing plasma treatment on the deposition chamber 100, as shown in Figures 3 and 4, can be used. Note that the apparatus is not limited to single-wafer apparatuses equipped with deposition chambers 100 as shown in Figures 1 to 4; apparatuses capable of processing multiple sheets simultaneously using a batch furnace can also be used. These can also be used as CVD apparatuses.

[0056] The present disclosure's method for producing a bismuth metal thin film by the ALD method includes, for example, a precursor layer formation step in which a raw material gas obtained by vaporizing a thin film formation raw material containing a bismuth compound represented by the above general formula (1) is introduced into a film formation chamber, and the bismuth compound contained in the raw material gas is deposited on a substrate to form a precursor layer, and a bismuth metal thin film formation step in which a reactive gas is introduced into the film formation chamber, and the precursor layer and the reactive gas are brought into contact to form a bismuth metal thin film.

[0057] The following describes each step of the method for producing a bismuth metal thin film by the ALD method of this disclosure with reference to Figures 1 to 4. B1. Precursor layer formation step In this step, a raw material gas obtained by vaporizing a thin film formation raw material M containing the bismuth compound represented by the general formula (1) above is introduced into the film formation chamber 100, and the bismuth compound contained in the raw material gas is deposited on the surface of the substrate S to form a precursor layer.

[0058] (1) Substrate The substrate S is not particularly limited as long as it can support the precursor layer. The substrate S may be any known substrate, for example, an organic compound or an inorganic compound. Examples of materials for the substrate S include silicon; ceramics such as silicon nitride, titanium nitride, tantalum nitride, titanium oxide, molybdenum oxide, zirconium oxide, hafnium oxide, and lanthanum oxide; glass; and metals such as metallic cobalt, metallic molybdenum, molybdenum sulfide, molybdenum selenide, tungsten sulfide, tungsten selenide, and metallic ruthenium. Examples of substrate shapes include plate-like, spherical, fibrous, flake-like, flat or disc-like, cylindrical, prismatic, tubular, spiral, spherical, ring-like, and three-dimensional structures such as trench structures. In this disclosure, from the viewpoint of facilitating the formation of a continuous bismuth metal thin film, it is preferable that the substrate S is made of ceramics or metal, or has a surface coated with ceramics or a surface coated with metal.

[0059] The thickness of the substrate S is not particularly limited in this disclosure, but from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with excellent coverage, uniform film thickness, and low residual carbon content, it is preferably 1 Å to 1 μm, and more preferably 1 Å to 50 nm. The surface of the substrate S includes not only the surface of the substrate S such as silicon, but also the surface of the bismuth metal thin film formed by the cycle of the bismuth metal thin film manufacturing method described later.

[0060] (2) Introduction of raw material gas In the method for producing a bismuth metal thin film according to the present disclosure, the raw material gas is obtained by vaporizing a thin film forming raw material M containing a bismuth compound represented by the above general formula (1). A method for obtaining the raw material gas is, for example, a method of heating and / or reducing the pressure of the thin film forming raw material M.

[0061] Methods for heating the thin film forming raw material M include, for example, heating the thin film forming raw material M in the raw material container 101 of the ALD apparatus shown in Figure 1 or Figure 3 using a heater 103 or the like, or heating the thin film forming raw material M in the vaporization chamber 102 of the ALD apparatus shown in Figure 2 or Figure 4. The temperature range for heating the thin film forming raw material M is preferably 300°C or lower, more preferably 20°C to 250°C, and even more preferably 30°C to 200°C, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with excellent coating properties, uniform film thickness, and low residual carbon.

[0062] Methods for reducing the pressure of the thin film forming raw material M include, for example, reducing the pressure inside the raw material container 101 of the ALD apparatus shown in Figure 1 or Figure 3 to vaporize the thin film forming raw material M, or reducing the pressure inside the vaporization chamber 102 of the ALD apparatus shown in Figure 2 or Figure 4 to vaporize the thin film forming raw material M. From the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a fast film formation rate, uniform film thickness, and low residual carbon, the above-mentioned reduced pressure (vacuum) conditions are preferably in the range of 1 Pa to 10,000 Pa, more preferably in the range of 10 Pa to 5,000 Pa, and even more preferably in the range of 20 Pa to 1,000 Pa.

[0063] Methods for introducing the above-mentioned raw material gas into the film deposition chamber 100 include gas transport methods and liquid transport methods. As an example of the gas transport method, as shown in Figures 1 and 3, the thin-film forming raw material M is heated and / or vaporized in the raw material container 101 to produce the raw material gas, and if necessary, the raw material gas is introduced into the film deposition chamber 100 together with a carrier gas 201 such as argon, nitrogen, or helium. As an example of the liquid transport method, as shown in Figures 2 and 4, the thin-film forming raw material M is transported in liquid or solution form to the vaporization chamber 102, the thin-film forming raw material M is heated and / or depressurized in the vaporization chamber 102 to produce the raw material gas, and if necessary, the raw material gas is introduced into the film deposition chamber 100 together with a carrier gas 201 such as argon, nitrogen, or helium. The flow rate of each gas is adjusted by a mass flow controller (MFC) 104. Furthermore, if the thin film formation raw material M contains the other precursors mentioned above, the raw material gas can be introduced into the film formation chamber 100, for example, using a single-source method.

[0064] (3) Formation of Precursor Layer In the precursor layer formation step described above, as stated above, a bismuth compound in the raw material gas introduced into the film formation chamber 100 is deposited on the surface of a substrate S that has been previously placed in the film formation chamber 100 to form a precursor layer. In this disclosure, "deposit" refers to a concept that includes the chemical adsorption of the bismuth compound on the surface of the substrate S, and "bismuth compound" refers to a precursor containing bismuth atoms in the thin film formation raw material M described above.

[0065] In this process, it is preferable to heat the raw material gas by heating the inside of the film deposition chamber 100 and / or the substrate S. From the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a fast deposition rate, uniform film thickness, and low residual carbon, it is preferable to heat the raw material gas in the range of 25°C to 300°C, more preferably in the range of 50°C to 280°C, even more preferably in the range of 100°C to 270°C, and particularly preferably in the range of 150°C to 250°C.

[0066] In this process, the heating of the raw material gas is preferably carried out in a non-oxygen atmosphere, and more preferably in an inert gas atmosphere such as nitrogen or argon, from the viewpoint of easily forming a high-purity bismuth metal thin film with excellent coating properties, uniform film thickness, and low residual carbon. Furthermore, the heating may be carried out under any of the following conditions: under pressure, under reduced pressure, at normal pressure, or at atmospheric pressure, but in this process, it is preferable to carry it out under reduced pressure (20 Pa to 1,000 Pa). This is because it is possible to form a high-purity bismuth metal thin film with a fast film formation rate, uniform film thickness, and low residual carbon.

[0067] B2. Bismuth Metal Thin Film Formation Process In this process, a reactive gas is introduced into the film formation chamber 100, and the precursor layer and the reactive gas are brought into contact to form a bismuth metal thin film.

[0068] (1) Formation of Bismuth Metal Thin Film In this step, a reactive gas 202 is introduced into the film deposition chamber 100, and a bismuth metal thin film is formed by the reactive gas coming into contact with the precursor layer and reacting. The method for introducing the reactive gas 202 into the film deposition chamber 100 in this step can be the same as the method for introducing the raw material gas into the film deposition chamber 100 as described above. However, the heating of the reactive gas and the pressure inside the film deposition chamber can be carried out under the same conditions as the heating of the raw material gas in the section "B1 (3) Formation of Precursor Layer" described above.

[0069] (2) Introduction of Reactive Gas In the method for producing a bismuth metal thin film according to the present disclosure, the reactive gas 202 includes at least one selected from the group consisting of diol gas, triol gas, carboxylic acid gas, and reducing gas. Diol gas, triol gas, or carboxylic acid gas is obtained by vaporizing a diol, triol, or carboxylic acid by heating and / or reducing the pressure as needed. The reactive gas 202 can be introduced into the film deposition chamber 100 together with a carrier gas 201 such as argon, nitrogen, or helium as needed.

[0070] (a) Diol The above diol is a dihydric alcohol, and examples of low molecular weight diols include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-isobutanediol, 1,5-pentanediol, and 1,6-hexanediol. These diols may be used alone or in combination of two or more. From the viewpoint of easily forming a high-purity bismuth metal thin film with excellent coating properties, uniform film thickness, and low residual carbon, the above diol is preferably a liquid at room temperature, more preferably ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol, and even more preferably ethylene glycol and propylene glycol.

[0071] (b) Triol The above triol is a trivalent alcohol, for example, glycerol (glycerin).

[0072] (c) Carboxylic acids Examples of the carboxylic acids include aliphatic carboxylic acids having 1 to 12 carbon atoms, such as formic acid, acetic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, 2-methylsuccinic acid, 3-methylpentanedioic acid, 2-methyladipic acid, 3-methyladipic acid, 2-methyloctanedioic acid, and 3,8-dimethyldecanediic acid; aromatic carboxylic acids such as terephthalic acid, isophthalic acid, and orthophthalic acid. These carboxylic acids may be used alone or in combination of two or more.

[0073] (d) Reducing gases The reducing gases include, for example, carbon monoxide, nitrogen (N2), ammonia, hydrogen (H2), monosilane, hydrazine, monomethylhydrazine, borane-dimethylamine complex, borane-trimethylamine complex, 1-butene, 2-butene, 2-methylpropene, 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-butene, 1-hexene, 2-hexene, 3-hexene, 2-methyl-1-pentene, 2-methyl-2-pentene, 4-methyl-2-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 3-methyl-2-pentene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2,3-dimethyl-2-butene, 3,3-dimethyl-1-butene, buta-1,3-diene, penta-1,3 Chain-like unsaturated hydrocarbons such as -diene, penta-1,4-diene, 2-methylbuta-1,3-diene, hexa-1,3-diene, hexa-2,4-diene, 2-methylpenta-1,3-diene, 3-methylpenta-1,3-diene, 4-methylpenta-1,3-diene, 2-ethylbuta-1,3-diene, 3-methylpenta-1,4-diene, 2,3-dimethylbuta-1,3-diene; cyclo Examples of reducing gases include hexa-1,3-diene, cyclohexa-1,4-diene, 1-methylcyclohexa-1,3-diene, 2-methylcyclohexa-1,3-diene, 5-methylcyclohexa-1,3-diene, 3-methylcyclohexa-1,4-diene, α-phellandrene, β-phellandrene, α-terpinene, β-terpinene, γ-terpinene, limonene, and other cyclic unsaturated hydrocarbons. These reducing gases may be used individually or in combination of two or more. Among these, ammonia gas and hydrogen are preferred as reducing gases because they are easier to handle and have fewer restrictions due to the specifications of the ALD equipment.

[0074] In the method for manufacturing a bismuth metal thin film according to this disclosure, the reactive gas can be plasma-generated. For example, the reactive gas can be plasma-generated using a direct current (DC) current, an alternating current (RF) current, microwaves, etc. Specifically, as shown in Figures 3 and 4, an RF matching system 106 connected to a high-frequency (RF) power supply 107 can be installed in the deposition chamber 100, and the reactive gas 202 can be plasma-generated within the deposition chamber 100.

[0075] In this process, in addition to the reactive gas 202, other gases can be introduced into the film deposition chamber 100. Examples of these other gases include organic amine compounds such as monoalkylamines, dialkylamines, trialkylamines, and alkylenediamines; nitriding gases obtained by vaporizing hydrazine, etc.; sulfurizing gases such as sulfur, hydrogen sulfide, dimethyl sulfide, diethyl sulfide, diisopropyl sulfide, and other dialkyl sulfides; and inert gases such as argon and nitrogen. Two or more of these other gases may be used in mixture form. In the method for producing a bismuth metal thin film according to this disclosure, from the viewpoint of easily forming a high-purity bismuth metal thin film with a fast deposition rate, uniform film thickness, and low residual carbon content, the content of the other gases is preferably 50% by volume or less, more preferably 10% by volume or less, and even more preferably 5% by volume or less, of the total of the reactive gas 202 and the other gases.

[0076] In this process, from the viewpoint of easily forming a high-purity bismuth metal thin film with excellent coating properties, uniform film thickness, and low residual carbon, it is preferable that the reactive gas 202 consists only of a selection from the group consisting of diol gases and reducing gases, more preferably of a selection from the group consisting of ethylene glycol gas, propylene glycol gas, diethylene glycol gas, dipropylene glycol gas, ammonia gas, and hydrogen, even more preferably of a selection from the group consisting of ethylene glycol gas, propylene glycol gas, diethylene glycol gas, and dipropylene glycol gas, and particularly preferably of a selection from the group consisting of ethylene glycol gas and propylene glycol gas.

[0077] The method for introducing the reactive gas 202 into the film deposition chamber 100 in this process can be the same as the method for introducing the raw material gas into the film deposition chamber 100 as described above. However, when introducing a plasma-like reactive gas 202, for example, one method is to introduce the reactive gas 202 into the film deposition chamber 100 as shown in Figure 3 or Figure 4, and then apply a voltage to create a plasma.

[0078] B3. Other steps The method for manufacturing a bismuth metal thin film according to the present disclosure may include other steps such as a first exhaust step, a second exhaust step, a plasma treatment step, an annealing step, a reflow step, etc.

[0079] (1) First exhaust process This process is performed after the precursor layer formation process to exhaust 203 unreacted raw material gas that did not participate in the formation of the precursor layer from the film formation chamber 100. In this process, it is ideal for the unreacted raw material gas to be completely exhausted from the film formation chamber 100, but it is not necessarily required to exhaust it completely. Examples of exhaust methods include introducing an inert gas such as helium, nitrogen, or argon as a purge gas 204 into the film formation chamber 100 and purging the system, exhausting the system by reducing the pressure while controlling the degree of pressure reduction with a vacuum pump 105 and an automatic pressure controller 108, and a combination of these methods. The exhausted raw material gas is liquefied in a cooling trap 109. When reducing the pressure in the system, the degree of pressure reduction is preferably in the range of 0.01 Pa to 300 Pa, more preferably in the range of 0.05 Pa to 200 Pa, and even more preferably in the range of 0.1 Pa to 150 Pa. This is because the exhaust of the raw material gas becomes sufficient, making it easier to form a bismuth metal thin film with excellent continuity.

[0080] (2) Second exhaust process This process is performed after the bismuth metal thin film formation process to exhaust 203 the reactive gases that did not participate in the formation of the bismuth metal thin film and the by-product gases generated by the reaction between the precursor layer and the reactive gases from inside the film formation chamber 100. In this process, it is ideal that the unreacted reactive gases and by-product gases are completely exhausted from inside the film formation chamber 100, but it is not necessarily required to exhaust them completely. The exhaust method and degree of reduced pressure can be carried out under the same conditions as in the first exhaust process.

[0081] (3) Plasma Treatment Step The method for manufacturing a bismuth metal thin film according to the present disclosure may include a plasma treatment step in which a voltage is applied to the raw material gas and / or the reactive gas to create plasma in order to promote the formation of the precursor layer and the bismuth metal thin film. In this step, as shown in Figures 3 and 4, an RF matching system 106 connected to a high-frequency (RF) power supply 107 is installed in the film deposition chamber 100, and the raw material gas and / or the reactive gas can be created as plasma in the film deposition chamber 100. In this step, if the power applied when the voltage is too high, the substrate S supporting the precursor layer or the bismuth metal thin film will be severely damaged. Therefore, the power applied when the voltage is to be applied is preferably in the range of 10W to 1,500W, more preferably in the range of 30W to 1,000W, and even more preferably in the range of 50W to 600W.

[0082] (4) Annealing process The annealing process described above may be a process in which the bismuth metal thin film is annealed after the bismuth metal thin film has been purified, in order to improve the electrical properties of the bismuth metal thin film. In the annealing process described above, the bismuth metal thin film may be annealed in an inert atmosphere or a reducing atmosphere. In this process, from the viewpoint of making it easy to form a high-purity bismuth metal thin film with a fast film formation rate, uniform film thickness, and low residual carbon, the temperature in the annealing process described above is preferably in the range of 100°C to 270°C, more preferably in the range of 150°C to 260°C, and even more preferably in the range of 200°C to 250°C.

[0083] (5) Reflow process The reflow process described above may be a process of heating the bismuth metal thin film after it has been formed in order to fill in any steps in the bismuth metal thin film. The temperature in the reflow process is preferably in the range of 200°C to 600°C, more preferably in the range of 230°C to 550°C, and even more preferably in the range of 250°C to 500°C, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a fast film formation rate, uniform film thickness, and low residual carbon.

[0084] B4. Film Formation Cycle The method for manufacturing a bismuth metal thin film according to this disclosure involves repeating a cycle in which the precursor layer formation step, the first exhaust step, the bismuth metal thin film formation step, and the second exhaust step are performed in this order multiple times until a bismuth metal thin film of the required thickness is obtained, thereby producing a bismuth metal thin film with a desired thickness. In other words, the thickness of the formed bismuth metal thin film can be controlled by the number of cycles. For example, the above cycle may be performed only once to form one layer of bismuth metal thin film, or it may be performed two or more times to produce a bismuth metal thin film of the desired thickness.

[0085] B5. Methods for manufacturing thin films other than the ALD method In this embodiment, a method for manufacturing a bismuth metal thin film by the ALD method has been described, but the method for manufacturing a bismuth metal thin film according to this disclosure is not limited to the above, and a bismuth metal thin film may be manufactured by, for example, the CVD method.

[0086] The bismuth metal thin film formed by the method for producing a bismuth metal thin film according to this disclosure contains 90 parts by mass or more of bismuth atoms in 100 parts by mass of the bismuth metal thin film. In this disclosure, it is preferable that the content of bismuth atoms in 100 parts by mass of the bismuth metal thin film be 96 parts by mass or more, more preferably 97 parts by mass or more, even more preferably 98 parts by mass or more, and particularly preferably 99 parts by mass or more. This is because the bismuth metal thin film exhibits excellent electrical properties and can be used in various semiconductor devices.

[0087] Examples of the above-mentioned semiconductor devices include field-effect transistors (FETs), nanosheet transistors, nanowire transistors, and complementary field-effect (FET) transistors. In this disclosure, it is preferable that the above-mentioned semiconductor device is an FET having a transition metal dichalcogenide such as MoS2, MoSe2, WS2, or WSe2 in its semiconductor layer. The thin film formation raw material of this disclosure is preferably used to form a contact or metal thin film on the upper or lower part of the transition metal dichalcogenide semiconductor layer. This is because the bismuth metal thin film formed by the manufacturing method of the bismuth metal thin film of this disclosure has excellent electrical properties. Furthermore, the above-mentioned semiconductor device may also include other layers (for example, an insulating layer, a conductive layer, a semiconductor layer, a buffer layer, or other intermediate layers). This is because it can be used in the semiconductor device.

[0088] The present disclosure will be further described below with reference to examples. However, the present disclosure is not limited by the following examples.

[0089] [Example 1] Production of bismuth metal thin film by ALD method using ethylene glycol gas as the reactive gas. The bismuth compound represented by the above general formula (1) is the bismuth compound represented by No. 14 (R in general formula (1)). 1 , R 2 and R 3 Using -Si(Me)3 as the raw material for thin film formation, a bismuth metal thin film was formed on a Si substrate, TiN substrate, or Ru substrate as the substrate by the ALD method under the following conditions using the ALD apparatus shown in Figure 1.

[0090] (Conditions) Manufacturing method: ALD method Reaction temperature (substrate temperature): 150°C Reactive gas: Ethylene glycol gas (ethylene glycol vaporized at 80°C)

[0091] (Process) The following series of processes (1) to (4) constituted one cycle, and this was repeated 100 times. (1) The vapor of the raw material for thin film formation (raw material gas: bismuth compound represented by general formula (1)), obtained by vaporizing the raw material under the conditions of raw material container temperature: 80°C and raw material container internal pressure: 26 Pa, was introduced into the film formation chamber, and the bismuth compound represented by general formula (1) in the raw material gas was deposited on the surface of the substrate for 0.5 seconds at a system pressure of 26 Pa to form a precursor layer (precursor layer formation process). (2) The raw material gas that did not deposit was exhausted from the system by argon purging for 20 seconds (first exhaust process). (3) The reactive gas was introduced into the film formation chamber, and the precursor layer and the reactive gas were reacted for 0.1 seconds at a system pressure of 26 Pa (bismuth metal thin film formation process). (4) The unreacted reactive gas and by-product gases were exhausted from the system by argon purging for 20 seconds (second exhaust process).

[0092] [Example 2] Except for changing the reaction temperature (substrate temperature) to 100°C, the same procedure as in Example 1 was followed to form a bismuth metal thin film on a Si substrate, TiN substrate, or Ru substrate.

[0093] [Example 3] Except for changing the reaction temperature (substrate temperature) to 200°C, the same procedure as in Example 1 was followed to form a bismuth metal thin film on a Si substrate, TiN substrate, or Ru substrate.

[0094] [Example 4] Except for changing the reaction temperature (substrate temperature) to 250°C, the same procedure as in Example 1 was followed to form a bismuth metal thin film on a Si substrate, TiN substrate, or Ru substrate.

[0095] [Comparative Example 1] Production of bismuth metal thin film by ALD method using ethanol gas as the reactive gas. The procedure was carried out in the same manner as in Example 1, except that the reactive gas was changed to ethanol gas (ethanol vaporized at room temperature). However, the formation of a bismuth metal thin film on a Si substrate, TiN substrate, or Ru substrate could not be confirmed.

[0096] (Evaluation) The bismuth metal thin films formed in Examples 1 to 4 and Comparative Example 1 were evaluated as follows. The results are shown in Table 1 below.

[0097] (Evaluation) (1) Coverage The coverage of the obtained bismuth metal thin film was observed using FE-SEM. Coverage was evaluated as "Yes" if it was confirmed that the bismuth metal thin film was formed on the substrate, and as "No" if it could not be confirmed. (2) Continuity The surface condition of the obtained bismuth metal thin film was observed using FE-SEM. Continuity was evaluated as "Yes" if the surface of the bismuth metal thin film was uniform and smooth, and as "No" if there was peeling or voids in part of the bismuth metal thin film, or if the bismuth metal thin film could not be formed. (3) Film Thickness The film thickness of the obtained bismuth metal thin film was measured by X-ray reflectivity.

[0098]

[0099] Comparative Example 1 showed that when ethanol gas was used as the reactive gas, the formation of bismuth metal thin films on Si, TiN, and Ru substrates could not be confirmed. In contrast, the bismuth metal thin films obtained in Examples 1 to 4 were confirmed to be thin films of pure bismuth by analysis using XPS and XRD. Furthermore, surface observation of the bismuth metal thin films obtained in Examples 1 to 4 using FE-SEM confirmed the formation of bismuth metal thin films on Si, TiN, and Ru substrates. In particular, the continuity of the bismuth metal thin films formed on TiN and Ru substrates was remarkably excellent. It is considered possible to produce bismuth metal thin films with excellent continuity on other metal substrates, nitride films, binary substrates, etc.

[0100] 100 Film deposition chamber 101 Raw material container 102 Vaporization chamber 103 Heater 104 Mass flow controller (MFC) 105 Vacuum pump 106 RF matching system 107 Radio frequency (RF) power supply 108 Automatic pressure controller 109 Cooling trap 201 Carrier gas 202 Reactive gas 203 Exhaust 204 Purge gas M Raw material for thin film formation S Substrate

Claims

1. A method for manufacturing a bismuth metal thin film, comprising a precursor layer forming step of forming a precursor layer using a raw material for thin film formation containing a bismuth compound represented by the following general formula (1), and a bismuth metal thin film forming step of bringing the precursor layer into contact with a reactive gas to form a bismuth metal thin film, wherein the reactive gas is selected from the group consisting of a diol gas, a triol gas, a carboxylic acid gas, and a reducing gas. (In general formula (1), R 1 , R 2 and R 3 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 20 carbon atoms, a group represented by -NR 4 R 5 or a group represented by -SiR 6 R 7 R 8 , and in the group represented by -NR 4 R 5 , R 4 and R 5 each independently represent an alkyl group having 1 to 5 carbon atoms or a group represented by -SiR 6 R 7 R 8 , and in the group represented by -SiR 6 R 7 R 8 , R 6 , R 7 and R 8 each independently represent an alkyl group having 1 to 5 carbon atoms.) 2. The method for producing a bismuth metal thin film according to claim 1, wherein the precursor layer formation step includes introducing a raw material gas obtained by vaporizing the thin film forming raw material into a film formation chamber and depositing the bismuth compound in the raw material gas onto a substrate to form the precursor layer, and the bismuth metal thin film formation step includes introducing the reactive gas into the film formation chamber and bringing the precursor layer into contact with the reactive gas to form the bismuth metal thin film.

3. A method for producing a bismuth metal thin film according to claim 2, further comprising a first exhaust step of exhausting the raw material gas from the film formation chamber and a second exhaust step of exhausting the reactive gas from the film formation chamber, wherein the bismuth metal thin film is formed by repeating a cycle of performing the precursor layer formation step, the first exhaust step, the bismuth metal thin film formation step and the second exhaust step in this order multiple times.

4. The method for manufacturing a bismuth metal thin film according to claim 2, wherein the substrate is a ceramic or a metal, or has a surface coated with ceramics or a surface coated with metal.

5. A thin-film forming raw material comprising a bismuth compound represented by the following general formula (1), which forms a bismuth metal thin film by reaction with a reactive gas selected from the group consisting of diol gas, triol gas, carboxylic acid gas, and reducing gas. (In general formula (1), R 1 , R 2 and R 3 Each of these independently consists of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 20 carbon atoms, and -NR 4 R 5 A group represented by -SiR 6 R 7 R 8 It represents the group represented by -NR 4 R 5 R in the base represented by 4 and R 5 Each of these is independently an alkyl group or -SiR having 1 to 5 carbon atoms. 6 R 7 R 8 It represents a group represented by -SiR 6 R 7 R 8 R in the base represented by 6 , R 7 and R 8 Each of these independently represents an alkyl group having between 1 and 5 carbon atoms.

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