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

Abstract

The present invention relates to: a method for producing a thin film, the method involving forming a bismuth metal thin film using a bismuth compound represented by general formula (1), and at least one selected from among Bi(SiMe3)3 and a reducing gas; and a raw material for forming a thin film. (In general formula (1), R1 represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms, and R2, R3 and R4 each independently represent an alkyl group having 1 to 3 carbon atoms).

Description

Thin film manufacturing method and raw material for forming thin film

[0001] The present invention relates to a method for producing a thin film and a raw material for forming a thin film.

[0002] Thin films containing Group 5 elements such as bismuth are used in various semiconductor devices, and atomic layer deposition is a well-known method for manufacturing such thin films. For example, Patent Document 1 discloses the use of a single-layer bismuth thin film as one layer of a three-layer phase-change memory unit. Patent Document 2 also discloses bismuth-containing thin films, such as bismuth strontium tantalate thin films and bismuth lanthanum titanate thin films, as multi-element alloy thin films. Patent Document 3 discloses a method for manufacturing a bismuth-containing oxide thin film using an organic bismuth compound. Patent Document 4 lists compounds such as Bi[N(SiMe)2]3 and Bi[N(Me)(SiMe3)]3 as metal metalloid amides.

[0003] Japanese Patent Application Laid-Open No. 2013-236079 Japanese Patent Application Laid-Open No. 2006-225381 Japanese Patent Application Laid-Open No. 2005-135914 International Publication WO2002 / 027063

[0004] However, it has been difficult to form a high-purity bismuth metal thin film with little residual carbon using conventional methods. Patent Document 1 discloses a method for manufacturing a thin film of a metal silicate, metal phosphate, or oxide, but does not disclose a method for manufacturing a bismuth metal thin film. Patent Documents 2, 3, and 4 do not disclose a method for manufacturing a bismuth metal thin film containing only bismuth as the metal. Note that bismuth has the problem that, although it reacts well with compounds of different metals, it has low reactivity with compounds of the same metal. Therefore, no method for manufacturing a thin film has been known that can form a high-purity bismuth metal thin film with a high film deposition rate, a uniform film thickness, and little residual carbon.

[0005] Therefore, an object of the present invention is to provide a method for producing a thin film, which is capable of forming a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, and a thin film-forming raw material to be used in the thin film production method.

[0006] As a result of intensive research into solving the above problems, the present inventors have found that the above problems can be solved by a method for producing a thin film that uses a specific compound as a thin film-forming raw material, and have thus completed the present invention.

[0007] That is, the present disclosure provides a method for producing a thin film, which comprises forming a bismuth metal thin film using a bismuth compound represented by the following general formula (1) and at least one selected from Bi(SiMe3)3 and a reducing gas, where Me in "Bi(SiMe3)3" represents a methyl group.

[0008]

[0009] R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms; R 2 , R 3 and R 4 each independently represents an alkyl group having 1 to 3 carbon atoms.

[0010] The present disclosure provides a set of thin film-forming raw materials including a first thin film-forming raw material containing a bismuth compound represented by the following general formula (1) and a second thin film-forming raw material containing Bi(SiMe3)3:

[0011]

[0012] In general formula (1), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms; R 2 , R 3 and R 4 each independently represents an alkyl group having 1 to 3 carbon atoms.

[0013] The present disclosure provides a thin film manufacturing method capable of forming a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, and a thin film-forming raw material used in this manufacturing method.

[0014] Fig. 1 is a schematic diagram showing an example of an ALD apparatus used in the method for producing a thin film according to the present invention. Fig. 2 is a schematic diagram showing another example of an ALD apparatus used in the method for producing a thin film according to the present invention. Fig. 3 is a schematic diagram showing yet another example of an ALD apparatus used in the method for producing a thin film according to the present invention. Fig. 4 is a schematic diagram showing yet another example of an ALD apparatus used in the method for producing a thin film according to the present invention.

[0015] The method for producing a thin film according to the present disclosure will be described below. First, the thin film-forming raw materials used in the method for producing a thin film according to the present disclosure will be described.

[0016] A. Thin film forming raw materials The thin film forming raw materials used are a set of thin film forming raw materials including a first thin film forming raw material containing a bismuth compound represented by the general formula (1) as a precursor and a second thin film forming raw material containing Bi(SiMe3)3 as a precursor. The components constituting the first thin film forming raw material and the second thin film forming raw material will be described below.

[0017] A1. First Thin Film Forming Material In the present disclosure, the first thin film forming material contains a bismuth compound represented by the above general formula (1) as a precursor. In the above general formula (1), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms; R 2 , R 3 and R 4 each independently represents an alkyl group having 1 to 3 carbon atoms.

[0018] R in the above general formula (1) 1 Examples of the hydrocarbon group having 1 to 5 carbon atoms represented by the formula (I) include an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, and an alkynyl group having 2 to 5 carbon atoms.

[0019] Examples of the alkyl group having 1 to 5 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group (an n-amyl group), an isopentyl group (an isoamyl group), a sec-pentyl group (an sec-amyl group), a tert-pentyl group (an tert-amyl group), and a neopentyl group.

[0020] The alkenyl group having 2 to 5 carbon atoms represents a group in which two hydrogen atoms have been removed from the alkyl group described above, and examples thereof include a vinyl group, a propenyl group, a butenyl group, and a pentenyl group.

[0021] The alkynyl group having 2 to 5 carbon atoms represents a group in which two hydrogen atoms have been removed from a carbon atom having an unsaturated bond in the alkenyl group, and examples thereof include an ethynyl group, a propynyl group, a butynyl group, and a pentynyl group.

[0022] R in the above general formula (1) 2 , R 3 and R 4 The alkyl group having 1 to 3 carbon atoms represented by the formula: 1 Examples of the alkyl group having 1 to 5 carbon atoms include groups having a predetermined number of carbon atoms.

[0023] In the present disclosure, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, R 1 is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom, a methyl group or an n-propyl group, and even more preferably a methyl group or an n-propyl group.

[0024] In the present disclosure, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, R 2 , R 3 and R 4 is more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

[0025] Preferred specific examples of the bismuth compound represented by the above general formula (1) include compounds No. 1 to No. 75 below. However, the present invention is not limited to these compounds. In the following chemical formulae, "Me" represents a methyl group, "Et" represents an ethyl group, "nPr" represents an n-propyl group, "iPr" represents an isopropyl group, "nBu" represents an n-butyl group, "iBu" represents an isobutyl group, "sBu" represents a sec-butyl group, "tBu" represents a tert-butyl group, "n-Amyl" represents an n-amyl group, "i-Amyl" represents an isoamyl group, "s-Amyl" represents a sec-amyl group, "t-Amyl" represents a tert-amyl group, and "Np" represents a neopentyl group.

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045] In the present disclosure, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, it is preferable that the first thin film-forming raw material contain compounds No. 1, No. 21, No. 25, and No. 29, more preferably compounds No. 21, No. 25, or No. 29, and even more preferably compounds No. 21 and No. 29.

[0046] In the present disclosure, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film that has a high film formation rate, a uniform film thickness, and little residual carbon, the molecular weight of the bismuth compound represented by the general formula (1) is preferably 400 or more and 1,000 or less, more preferably 450 or more and 750 or less, even more preferably 480 or more and 650 or less, and most preferably 500 or more and 600 or less.

[0047] A2. Second Thin Film Forming Raw Material In the present disclosure, the second thin film forming raw material contains Bi(SiMe3)3 as a precursor.

[0048] A3. Other Components The first thin film-forming raw material and the second thin film-forming raw material may each contain a bismuth compound represented by the general formula (1) or Bi(SiMe3)3, and their compositions vary depending on the type of thin film desired. For example, other components may be included in the thin film-forming raw material as needed. Examples of the other components include other precursors and nucleophilic reagents, which will be described later.

[0049] (1) Other Precursor The other precursor may be a compound different from the bismuth compound represented by the general formula (1) and Bi(SiMe3)3. From the viewpoint of forming a single bismuth metal thin film, it is preferable that the metal atom constituting the other precursor is the same bismuth atom as the bismuth compound represented by the general formula (1) and Bi(SiMe3)3.

[0050] The first and second thin film-forming materials may each contain a well-known precursor as the other precursor, such as a compound of bismuth atoms and 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.

[0051] Examples of alcohol compounds that can be used as organic ligands for the other precursors include 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. 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.

[0052] Examples of glycol compounds used as organic ligands for the other precursors 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.

[0053] Examples of the β-diketone compound used as the organic ligand of the other precursor 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, and 2-methyl-6 alkyl-substituted β-diketones such as 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.

[0054] Examples of the cyclopentadiene compound used as the organic ligand of the other precursor include cyclopentadiene, methylcyclopentadiene, ethylcyclopentadiene, propylcyclopentadiene, isopropylcyclopentadiene, butylcyclopentadiene, sec-butylcyclopentadiene, isobutylcyclopentadiene, tert-butylcyclopentadiene, dimethylcyclopentadiene, tetramethylcyclopentadiene, and pentamethylcyclopentadiene.

[0055] Examples of the organic amine compound used as the organic ligand of the other precursor include methylamine, ethylamine, propylamine, isopropylamine, butylamine, sec-butylamine, tert-butylamine, isobutylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, ethylmethylamine, propylmethylamine, and isopropylmethylamine.

[0056] The other precursors are known in the art, and their manufacturing methods are also known. For example, when an alcohol compound is used as the organic ligand, the other precursor can be manufactured by reacting an inorganic salt of bismuth or a hydrate thereof with an alkali metal alkoxide of the alcohol compound. Examples of inorganic salts of bismuth include halides and nitrates of bismuth. Examples of alkali metal alkoxides include sodium alkoxides, lithium alkoxides, and potassium alkoxides.

[0057] In the method for producing a thin film according to the present disclosure, when the other precursors are used as raw materials for forming a thin film, it is preferable that the other precursors are bismuth compounds represented by the general formula (1) above or compounds whose thermal decomposition and / or oxidative decomposition behavior is similar to that of Bi(SiMe3)3, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon.

[0058] In the method for producing a thin film according to the present disclosure, when a mixture of the bismuth compound represented by the general formula (1) or Bi(SiMe3)3 and the other precursor is used as the thin film forming raw material, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, it is preferable that the other precursor exhibits similar thermal decomposition and / or oxidative decomposition behavior to the bismuth compound represented by the general formula (1) or Bi(SiMe3)3 and is also a compound that does not undergo deterioration due to chemical reaction or the like after being mixed with the bismuth compound represented by the general formula (1) or Bi(SiMe3)3.

[0059] In the method for producing a thin film according to the present disclosure, when the thin film-forming raw material contains the other precursors, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, the content of the 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, still more preferably 5 parts by mass or less, and most preferably 0 parts by mass, i.e., the thin film-forming raw material does not contain any other precursors.

[0060] (2) Nucleophilic Reagent In the method for producing a thin film according to the present disclosure, a nucleophilic reagent may be contained in each of the first and second thin film-forming raw materials in order to promote the reaction of the bismuth compound represented by the general formula (1), Bi(SiMe) or the other precursor with a reducing gas.

[0061] Examples of the nucleophilic reagent include ethylene glycol ethers such as glyme, diglyme, triglyme, and tetraglyme; crown ethers such as 18-crown-6, dicyclohexyl-18-crown-6, 24-crown-8, dicyclohexyl-24-crown-8, and dibenzo-24-crown-8; ethylenediamine, N,N'-tetramethylethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, 1,1,4,7,7-pentamethyldiethylenetriamine, and 1,1,4,7,10,10-hexamethyltriethylenetetramine. , polyamines such as triethoxytriethyleneamine, cyclic polyamines such as cyclam and cyclen, heterocyclic compounds such as pyridine, pyrrolidine, piperidine, 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.

[0062] When the first and second thin-film-forming raw materials contain the nucleophilic reagent, the content of the nucleophilic reagent is preferably in the range of 0.1 mol or more and 10 mol or less, and more preferably in the range of 1 mol or more and 4 mol or less, relative to 1 mol of the total amount of precursors, from the viewpoint of facilitating control of the reaction between the bismuth compound represented by general formula (1), Bi(SiMe3)3, or the other precursor and a reducing gas, which will be described later.

[0063] Here, the total amount of precursors refers to the total amount of precursors contained in the first and second thin film-forming materials, and refers to the total amount of the bismuth compound represented by general formula (1), Bi(SiMe3)3, and the other precursors. When the first and second thin film-forming materials do not contain the other precursors, the total amount of precursors refers to the amount of the bismuth compound represented by general formula (1) and the bismuth compound represented by Bi(SiMe3).

[0064] (3) Impurities It is desirable that the thin film-forming raw material contains as few impurities as possible, such as impurity metal elements, impurity halogens, impurity organic components, etc., except for the above-mentioned components, i.e., the bismuth compound represented by the general formula (1), Bi(SiMe3)3, the other precursors, and the nucleophilic reagent, which constitute the thin film-forming raw material.

[0065] The impurity metal element content includes metal elements different from the bismuth compound represented by the general formula (1) and the bismuth metal of Bi(SiMe3)3. The content of the impurity metal element in the first thin film-forming material or the second thin film-forming material 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.

[0066] The content of impurity halogens in the first and second thin film-forming materials is preferably 100 ppm or less, more preferably 10 ppm or less, and even more preferably 1 ppm or less.

[0067] The impurity organic component may be an organic component different from the bismuth compound represented by the general formula (1), Bi(SiMe3)3, and the organic components constituting the other precursors. The organic component is a compound containing carbon and oxygen, excluding carbon monoxide and carbon dioxide, and may be an organic compound excluding the bismuth compound represented by the general formula (1), Bi(SiMe3)3, and the other precursors. The total content of the impurity organic component in each of the first and second thin-film-forming materials is preferably 500 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less.

[0068] Furthermore, since moisture can cause particle generation in the first and second thin film-forming materials and during thin film formation, it is preferable to remove moisture from the bismuth compound represented by general formula (1), Bi(SiMe3)3, the other precursors, and the nucleophilic reagent before use in order to reduce the moisture content of each. The moisture content of each of the bismuth compound represented by general formula (1), Bi(SiMe3)3, the other precursors, and the nucleophilic reagent is preferably 10 ppm or less, and more preferably 1 ppm or less.

[0069] Furthermore, the first and second thin film-forming materials are preferably made to contain as few particles as possible in order to reduce or prevent particle contamination of the thin film to be formed. Specifically, in particle measurement in the liquid phase using a light scattering liquid-borne particle detector, the number of particles larger than 0.3 μm is preferably 100 or less per 1 ml of liquid phase, and the number of particles larger than 0.2 μm is more preferably 100 or less per 1 ml of liquid phase.

[0070] The physical properties of the bismuth compound represented by the general formula (1) or Bi(SiMe3)3 are also suitable for CVD, making the thin film-forming raw material useful as a chemical vapor deposition raw material. Among these, the bismuth compound represented by the general formula (1) has a wide ALD window, making the first thin film-forming raw material particularly suitable for ALD. Therefore, the first thin film-forming raw material is particularly useful as a thin film-forming raw material for ALD.

[0071] The first and second sets of thin film-forming raw materials of the present disclosure can form bismuth metal thin films with excellent electrical and optical properties, and these thin films are useful in various semiconductor devices, for example, as electrodes or contact layers. The set of thin film-forming raw materials of the present disclosure is particularly useful as thin film-forming raw materials for forming bismuth metal thin films.

[0072] B. Thin Film Manufacturing Method Next, a thin film manufacturing method according to the present disclosure will be described. The present disclosure provides a thin film manufacturing method that forms a bismuth metal thin film using a bismuth compound represented by the above general formula (1) and Bi(SiMe3)3 or a reducing gas. As a thin film manufacturing method according to the present disclosure, it is particularly preferable to manufacture a thin film by the ALD method.

[0073] The apparatus used in the thin film manufacturing method of the present disclosure may be a well-known ALD apparatus. Specific examples of the apparatus include an apparatus capable of supplying a precursor by bubbling as shown in FIGS. 1 and 3, and an apparatus having a vaporization chamber 102 as shown in FIGS. 2 and 4. Another example is an apparatus capable of performing plasma processing on a film formation chamber 100 as shown in FIGS. 3 and 4. The apparatus is not limited to the single-wafer apparatus equipped with the film formation chamber 100 as shown in FIGS. 1 to 4, but an apparatus capable of simultaneously processing multiple wafers using a batch furnace may also be used. These may also be used as CVD apparatus.

[0074] The method for producing a thin film using the ALD method of the present disclosure includes, for example, a step of introducing a first source gas obtained by vaporizing a first thin film-forming source containing a bismuth compound represented by the general formula (1) into a film-forming chamber and depositing the bismuth compound represented by the general formula (1) in the first source gas on the surface of a substrate to form a precursor thin film, and a step of introducing a second source gas or a reducing gas obtained by vaporizing a second thin film-forming source containing Bi(SiMe) into the film-forming chamber and reacting the precursor thin film with the second source gas or the reducing gas to form a bismuth metal thin film. Furthermore, when the second thin film-forming source is used in the bismuth metal thin film-forming step, the method may optionally include a step of introducing a reducing gas into the film-forming chamber after the bismuth metal thin film-forming step and reacting the bismuth metal thin film with the reducing gas to highly purify the bismuth metal thin film.

[0075] Each step of the thin film manufacturing method using the ALD method of the present disclosure will be described below with reference to Figures 1 to 4. B1. Precursor thin film formation step In this step, a first source gas obtained by vaporizing a first thin film formation source M1 containing a bismuth compound represented by general formula (1) is introduced into the film formation chamber 100, and the bismuth compound in the first source gas is deposited on the surface of the substrate S to form a precursor thin film.

[0076] (1) Substrate The substrate S is not particularly limited as long as it can support the precursor thin film. The substrate S may be any known substrate, and may be, 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, and tungsten selenide. Examples of the shape of the substrate include plate-like, spherical, fibrous, scale-like, flat, disc-like, and other plate-like shapes; fibrous, cylindrical, prismatic, cylindrical, spiral, spherical, ring-like, and three-dimensional structures such as trench structures.

[0077] The thickness of the substrate S is not particularly limited in the present disclosure, but from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, it is preferably, for example, 1 Å or more and 1 μm or less, and more preferably 1 Å or more and 50 nm or less. Note that 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 thin film manufacturing method described below.

[0078] (2) Introduction of First Source Gas In the thin film manufacturing method of the present disclosure, the first source gas is obtained by vaporizing a first thin film-forming raw material M1 containing a bismuth compound represented by the general formula (1). Examples of a method for obtaining the first source gas include a method of heating and / or reducing the pressure of the first thin film-forming raw material M1 containing a bismuth compound represented by the general formula (1).

[0079] Examples of methods for heating the first thin film forming raw material M1 include a method of heating the thin film forming raw material by a heater 103 or the like in a raw material container 101 in the ALD apparatus shown in Figure 1 or 3, and a method of heating the thin film forming raw material in a vaporization chamber 102 in the ALD apparatus shown in Figure 2 or 4. The temperature range for heating the first thin film forming raw material M1 is, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, preferably 300°C or less, more preferably 20°C to 250°C, and even more preferably 30°C to 200°C.

[0080] Examples of methods for reducing the pressure of the first thin film forming raw material M1 include a method of reducing the pressure of the thin film forming raw material in the raw material container 101 of the ALD apparatus shown in Figure 1 or 3, or a method of reducing the pressure of the thin film forming raw material in the vaporization chamber 102 of the ALD apparatus shown in Figure 2 or 4. The reduced pressure (degree of vacuum) conditions are, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, 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.

[0081] Methods for introducing the first source gas into the film formation chamber 100 include a gas transport method and a liquid transport method. As shown in FIGS. 1 and 3 , the gas transport method involves heating and / or vaporizing the first thin film forming source material M1 in a source container 101 to form a first source gas, and then introducing the first source gas into the film formation chamber 100, if necessary, together with a carrier gas 201 such as argon, nitrogen, or helium. As shown in FIGS. 2 and 4 , the liquid transport method involves transporting the first thin film forming source material M1 in a liquid or solution state to a vaporization chamber 102, heating and / or reducing the pressure of the first thin film forming source material M1 in the vaporization chamber 102 to form a first source gas, and then introducing the first source gas into the film formation chamber 100, if necessary, together with a carrier gas 201 such as argon, nitrogen, or helium. The flow rates of each gas are adjusted by a mass flow controller (MFC) 104. When the first thin film forming source material M1 contains the other precursor, the first source gas can be introduced into the film forming chamber 100 using, for example, a single source method.

[0082] (3) Formation of Precursor Thin Film In the precursor thin film formation step, as described above, a precursor thin film is formed by depositing a bismuth compound in the first source gas introduced into the film formation chamber 100 on the surface of the substrate S previously placed in the film formation chamber 100. In this disclosure, the term "deposited" refers to a concept including chemical adsorption of a compound on the surface of the substrate S, and the term "bismuth compound" refers to a precursor containing bismuth atoms in the first thin film forming raw material M1 or the second thin film forming raw material M2.

[0083] In this step, it is preferable to heat either the inside of the film formation chamber 100 or the substrate S. From the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, the first source gas is heated, for example, preferably within a range of 25°C or higher and 270°C or lower, more preferably within a range of 25°C or higher and 250°C or lower, and even more preferably within a range of 25°C or higher and 230°C or lower.

[0084] In this step, the heating of the first source gas is preferably carried out in an oxygen-free atmosphere, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film having a high film formation rate, a uniform film thickness, and little residual carbon, and is particularly preferably carried out in an atmosphere of an inert gas such as nitrogen gas or argon gas, and is more preferably carried out in an inert gas atmosphere. Furthermore, the heating reaction may be carried out under any of conditions of increased pressure, reduced pressure, normal pressure, and atmospheric pressure, but in this step, it is preferable to carry out the reaction under reduced pressure (20 Pa or more and 1,000 Pa or less). This is because a high-purity bismuth metal thin film having a high film formation rate, a uniform film thickness, and little residual carbon can be formed.

[0085] B2. Bismuth metal thin film formation step In this step, a second source gas or reducing gas 202 obtained by vaporizing a second thin film formation source material M2 containing Bi(SiMe3)3 is introduced into the film formation chamber 100, and the precursor thin film is reacted with the bismuth compound or reducing gas 202 in the second source gas to form a bismuth metal thin film.

[0086] (1-1) Introduction of Second Source Gas In the thin film manufacturing method of the present disclosure, the second source gas is obtained by vaporizing a second thin film-forming source material M2 containing Bi(SiMe3)3. The method for obtaining the second source gas can be the same as that described in "B1. (2) Introduction of First Source Gas" except that the bismuth compound represented by the general formula (1) is replaced with Bi(SiMe3)3, and therefore a detailed description thereof will be omitted here. However, Bi(SiMe3)3 may react and decompose when it comes into contact with the bismuth compound represented by the general formula (1) above. Therefore, in the ALD apparatus shown in FIGS. 1 to 4, for example, it is preferable to separate the supply lines for the thin film forming raw materials from the source container 101 to the film forming chamber 100 so that Bi(SiMe3)3 and the bismuth compound represented by the general formula (1) above are not simultaneously supplied to the film forming chamber 100, thereby preventing direct contact between the first thin film forming raw material M1 containing the bismuth compound represented by the general formula (1) above and the second thin film forming raw material M2 containing Bi(SiMe3)3.

[0087] (1-2) Formation of Bismuth Metal Thin Film In this step, as described above, the bismuth metal thin film is formed by reacting the precursor thin film with the second source gas introduced into the film formation chamber 100. The heating of the second source gas and the pressure inside the film formation chamber 100 during heating can be performed under the same conditions as those for heating the first source gas in the above-mentioned section "B1(3) Formation of Precursor Thin Film."

[0088] In this step, the second source gas is heated to promote the reaction between the bismuth compound represented by general formula (1) in the precursor thin film and Bi(SiMe3)3 contained in the second source gas, thereby forming a bismuth metal thin film on the substrate S. For example, when Bi[N(Me)(SiMe3)]3 (Compound No. 21) is used as the bismuth compound represented by general formula (1) above, and Bi(SiMe3)3 is used, the following chemical reaction occurs in the bismuth metal thin film formation step, resulting in the formation of a bismuth metal thin film on the substrate S.

[0089]

[0090] In this embodiment, an example has been described in which the first source gas is first introduced into the film formation chamber 100, a precursor thin film is formed, and then the second source gas is introduced. However, a process may also be performed in which the second source gas obtained by vaporizing the second thin film formation source M2 is first introduced into the film formation chamber 100, Bi(SiMe3)3 is deposited on the surface of the substrate S to form a precursor thin film, and then the first source gas obtained by vaporizing the first thin film formation source M1 containing the bismuth compound represented by general formula (1) is introduced into the film formation chamber 100, and the precursor thin film and the first source gas are reacted to form a bismuth metal thin film.

[0091] (2-1) Introduction of Reducing Gas In the thin film manufacturing method of the present disclosure, a bismuth metal thin film may be formed using a reducing gas 202 instead of the second source gas obtained by vaporizing the second thin film-forming raw material M2. In the thin film manufacturing method of the present disclosure, the type of reducing gas 202 is not limited, but from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, it is preferable that the reducing gas 202 contains at least one gas selected from the group consisting of H2, NH3, H2 plasma, and NH3 plasma. The reducing gas 202 can be introduced into the film formation chamber 100 together with a carrier gas 201 such as argon, nitrogen, or helium, as necessary.

[0092] (a) H2 The H2 preferably contains impurities of 10 ppm or less, more preferably 1 ppm or less, and even more preferably 100 ppb or less, because this allows for the formation of a high-purity bismuth metal thin film with a high film deposition rate, a uniform film thickness, and little residual carbon.

[0093] (b) NH3 The NH3 preferably contains 10 ppm or less of the above impurities, more preferably 1 ppm or less, and even more preferably 100 ppb or less, because this allows for the formation of a high-purity bismuth metal thin film with a high film deposition rate, a uniform film thickness, and little residual carbon.

[0094] (c) H Plasma H plasma refers to a plasma containing H radicals. H plasma can be produced by converting H into plasma using, for example, a direct current (DC) current, an alternating current (RF) current, microwaves, or the like. Specifically, as shown in Figures 3 and 4, an RF matching system 106 connected to a radio frequency (RF) power supply 105 is installed in a film formation chamber 100, and H plasma can be generated within the film formation chamber 100.

[0095] (d) NH3 Plasma NH3 plasma refers to NH3 having radicals. NH3 plasma can be produced by directly reacting H2 and N2 using, for example, direct current (DC) current, alternating current (RF) current, microwaves, or the like. Specifically, as shown in Figures 3 and 4, an RF matching system 106 connected to a radio frequency (RF) power supply 105 is installed in a film formation chamber 100, and NH3 plasma can be generated within the film formation chamber 100.

[0096] In this process, other gases may be contained in addition to the reducing gas 202. Examples of the other gases include organic amine compounds such as monoalkylamines, dialkylamines, trialkylamines, and alkylenediamines; nitriding gases obtained by vaporizing hydrazine; sulfuric acid gases such as sulfur, hydrogen sulfide, and dialkyl sulfides such as dimethyl sulfide, diethyl sulfide, and diisopropyl sulfide; and inert gases such as argon and nitrogen. Two or more of the other gases may be mixed and used. In the thin film manufacturing method of the present disclosure, from the viewpoint of easily forming a high-purity bismuth metal thin film with a high film deposition rate, a uniform film thickness, and little residual carbon, the content of the other gases in the reducing gas 202 is preferably 50% by volume or less, more preferably 10% by volume or less, and even more preferably 5% by volume or less.

[0097] In this step, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, it is preferable that the reducing gas 202 contains only a gas selected from the group consisting of H, NH, H plasma, and NH plasma, and it is more preferable to use only a gas selected from the group consisting of H and NH, and it is even more preferable to use only H from the viewpoint of high reactivity and suppression of damage to the underlying layer.

[0098] In this step, the reducing gas 202 can be introduced into the film formation chamber 100 in the same manner as the first or second source gas described above. However, when H plasma or NH plasma is introduced, for example, a method in which H and NH are introduced into the film formation chamber 100 shown in FIG. 3 or 4 and then a voltage is applied to generate plasma is used.

[0099] (2-2) Formation of Bismuth Metal Thin Film In the bismuth metal thin film formation step, as described above, the bismuth metal thin film may be formed by reacting the precursor thin film with a reducing gas introduced into the film formation chamber 100. The heating of the reducing gas here and the pressure inside the film formation chamber 100 during heating can be carried out under the same conditions as those for heating the first source gas in the above-mentioned section "B1(3) Formation of Precursor Thin Film."

[0100] In this step, a first source gas is introduced into the film formation chamber 100, and a precursor thin film, which is formed by depositing a bismuth compound in the first source gas on the surface of the substrate S, is reacted with the reducing gas to form a bismuth metal thin film. However, from the viewpoint of facilitating the formation of a high-purity metal thin film with a uniform thickness and little residual carbon, it is preferable that in this step the precursor thin film formed using the first source gas is reacted with the second source gas, or the precursor thin film formed using the second source gas is reacted with the first source gas.

[0101] B3. Bismuth Metal Thin Film Purification Process In this process, a reducing gas 202 is introduced into the deposition chamber 100 and reacted with the bismuth metal thin film to purify the bismuth metal thin film. The reducing gas 202 not only reacts with the precursor thin film formed using the first source gas to form the bismuth metal thin film, but can also be used to further purify the proportion of bismuth atoms in the metal thin film by reacting with the bismuth metal thin film. Note that the purification process here refers to a process of bringing the content of bismuth atoms contained in 100 parts by mass of the bismuth metal thin film obtained in the previous process closer to 100 parts by mass. The reducing gas 202 used in this process can be the same as the reducing gas 202 used in the bismuth metal thin film formation process, so a description of it will be omitted here.

[0102] In this step, the reducing gas 202 can be introduced into the film formation chamber 100 in the same manner as the first or second source gas described above. However, when H plasma or NH plasma is introduced, for example, a method in which H and NH are introduced into the film formation chamber 100 shown in FIG. 3 or 4 and then a voltage is applied to generate plasma is used.

[0103] In this step, the reaction between the bismuth metal thin film and the reducing gas 202 is carried out by heating the metal thin film and / or the reducing gas. From the viewpoint of facilitating efficient production of a high-purity metal thin film, the heating in this step is preferably carried out at the same temperature as in the precursor formation step and the bismuth metal thin film formation step.

[0104] From the viewpoint of facilitating the formation of a high-purity metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, this step is preferably carried out after the step of forming a bismuth metal thin film by reacting a precursor thin film formed using a first source gas with a second source gas, or after the step of forming a bismuth metal thin film by reacting a precursor thin film formed using a second source gas with the first source gas.

[0105] B4. Other Steps The method for producing a thin film according to the present disclosure may include other steps such as exhaust steps 1 to 3, a plasma treatment step, an annealing treatment step, and a reflow step.

[0106] (1) Exhaust Step 1 This step is a step of exhausting (203) unreacted first precursor gas that was not involved in the formation of the precursor thin film from the film formation chamber 100 after the precursor thin film formation step. In this step, it is ideal to completely exhaust the unreacted first precursor gas from the film formation chamber 100, but complete exhaust is not necessarily required. Examples of exhaust methods include purging the film formation chamber 100 with an inert gas (purge gas 204) such as helium, nitrogen, or argon; exhausting the system by reducing the pressure while controlling the degree of vacuum using a vacuum pump 107 and an automatic pressure controller 108; and a combination of these methods. The exhausted first precursor gas is liquefied in a cooling trap 109. The degree of vacuum when reducing the pressure in the system is preferably in the range of 0.01 Pa to 300 Pa, more preferably 0.05 Pa to 200 Pa, and particularly preferably 0.1 Pa to 150 Pa. This is because the first source gas is sufficiently exhausted, the film formation rate is fast, and a high-purity bismuth metal thin film with a uniform film thickness and little residual carbon can be formed.

[0107] (2) Exhaust Step 2 This step is a step of exhausting (203) from the deposition chamber 100 any unreacted second source gas that was not involved in the formation of the bismuth metal thin film and any by-product gas produced by the reaction of the precursor thin film with the second source gas, after the bismuth metal thin film formation step. In this step, it is ideal that the unreacted second source gas and by-product gas are completely exhausted from the deposition chamber 100, but complete exhaust is not always necessary. The exhaust method and pressure reduction can be performed under the same conditions as in Exhaust Step 1.

[0108] (3) Exhaust Step 3 This step is a step in which, after the bismuth metal thin film purification step, unreacted reducing gas and by-product gases generated during the reduction of the metal thin film are exhausted from the film formation chamber 100. In this step, it is ideal that the unreacted reducing gas 202 and by-product gases are completely exhausted from the film formation chamber 100, but complete exhaust is not necessarily required. The exhaust method and degree of pressure reduction can be the same as those in Exhaust Step 1.

[0109] (4) Plasma Treatment Step The thin film manufacturing method of the present disclosure may include a plasma treatment step of applying a voltage to the first or second source gas to convert it into plasma, in order to promote the formation of the precursor thin film or the metal thin film. In this step, as shown in Figures 3 and 4, an RF matching system 106 connected to a radio frequency (RF) power supply 105 is installed in the film formation chamber 100, and the first or second source gas can be converted into plasma within the film formation chamber 100. In this step, if the power when applying the voltage is too high, damage to the substrate S supporting the precursor thin film or the bismuth metal thin film will be significant. Therefore, the power when applying the voltage is preferably in the range of 10 W to 1,500 W, more preferably 30 W to 1,000 W, and preferably 50 W to 600 W.

[0110] (5) Annealing Step The annealing step can be a step of annealing the bismuth metal thin film after purifying the bismuth metal thin film in order to improve the electrical properties of the bismuth thin film. In the annealing step, the bismuth metal thin film can be annealed in an inert atmosphere or a reducing atmosphere. In this step, from the viewpoint of facilitating the formation of a high-purity bismuth metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, the temperature in the annealing step 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.

[0111] (6) Reflow Process The reflow process can 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. From the viewpoint of facilitating the formation of a high-purity metal thin film with a high film formation rate, a uniform film thickness, and little residual carbon, 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 particularly preferably in the range of 250°C to 500°C.

[0112] B5. Film Formation Cycle In the thin film manufacturing method of the present disclosure, a precursor thin film formation step, an evacuation step 1, a bismuth metal thin film formation step, an evacuation step 2, a purification step, and an evacuation step 3 are sequentially performed. This series of operations constitutes one cycle of forming a thin film. This cycle is repeated until a thin film of the required thickness is obtained, thereby producing a thin film of the bismuth metal layer having a desired thickness. In other words, the thickness of the thin film formed can be controlled by the number of cycles. For example, the above cycle may be performed only once to form a single bismuth metal thin film, or may be performed two or more times to produce a bismuth metal thin film of the desired thickness. The thickness of the thin film obtained per cycle is preferably in the range of 0.1 Å to 1.0 nm, more preferably in the range of 0.3 Å to 0.5 nm, and particularly preferably in the range of 0.5 Å to 0.1 nm. This is because a bismuth metal thin film of uniform thickness can be easily obtained.

[0113] B6. Thin Film Manufacturing Method Other Than ALD Method In this embodiment, a method for manufacturing a bismuth metal thin film by ALD has been described, but the method for manufacturing a thin film of the present disclosure is not limited to the above, and a bismuth metal thin film may also be manufactured by a CVD method, for example. When the thin film manufacturing method of the present disclosure manufactures a bismuth metal thin film using a CVD method, the first source gas and the second source gas may be introduced into the film formation chamber 100 simultaneously.

[0114] The bismuth metal thin film produced by the thin film production method of the present disclosure contains 90 parts by mass or more of bismuth atoms per 100 parts by mass of the thin film. In the present disclosure, the content of bismuth atoms per 100 parts by mass of the thin film is preferably 96 parts by mass or more, more preferably 97 parts by mass or more, even more preferably 98 parts by mass or more, and even more 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.

[0115] Examples of the semiconductor device include a field effect transistor (FET), a nanosheet transistor, a nanowire transistor, and a complementary field effect transistor (FET). In the present disclosure, the semiconductor device is preferably a FET having a transition metal dichalcogenide such as MoS2, MoSe2, WS2, or WSe2 in the semiconductor layer. The thin film forming material of the present disclosure is preferably formed as a contact or metal thin film on the top or bottom of the transition metal dichalcogenide semiconductor layer. This is because the bismuth metal thin film produced by the thin film production method of the present disclosure has excellent electrical properties. The semiconductor device may also include other layers (e.g., an insulator layer, a conductor layer, a semiconductor layer, a buffer layer, or other intermediate layers).

[0116] Example 1 Using the above-mentioned No. 21 as the first thin-film forming source M1 and Bi(SiMe3)3 as the second thin-film forming source M2, a bismuth metal thin film was produced on a silicon substrate (substrate S) under the following conditions using the ALD apparatus shown in FIG. 1. The composition of the resulting thin film was analyzed using X-ray diffraction and X-ray photoelectron spectroscopy. The thin film was found to be a bismuth metal thin film, with a residual carbon content of less than 1 atom% and a residual oxygen content of less than 1 atom%. Furthermore, when the film thickness was measured using X-ray reflectivity or spectroscopic ellipsometry, the thin film formed on the substrate was a smooth film with a thickness of 500 Å, and the film thickness obtained per cycle was 0.5 Å. Generally, a film thickness of 0.5 Å or more per cycle can be considered to indicate a fast film formation rate. The X-ray reflectivity method was performed using an apparatus manufactured by Rigaku Corporation, and the spectroscopic ellipsometry was performed using a method manufactured by J.A. A Woollam device was used.

[0117] (Conditions) Reaction temperature (substrate temperature): 200°C (Steps 1 to 6) Reducing gas: H2 Substrate: Silicon substrate

[0118] (Steps) A series of steps consisting of the following steps 1 to 6 constitute one cycle, and 1,000 cycles were repeated. Step 1: Vapor of first thin film forming raw material M1 (first raw material gas) vaporized under conditions of a source container 101 heating temperature of 80°C and an internal source container 101 pressure of 100 Pa was introduced into the film formation chamber 100, and the bismuth compound in the first raw material gas was adsorbed on the surface of the substrate S for 15 seconds at a system pressure of 100 Pa to form a precursor thin film. Step 2: Unadsorbed first raw material gas was purged from the system by argon purging for 10 seconds. Step 3: Vapor of second thin film forming raw material (second raw material gas) vaporized under conditions of a source container 101 heating temperature of 100°C and an internal source container 101 pressure of 100 Pa was introduced into the film formation chamber 100, and the precursor thin film formed in step 1 was reacted with the second raw material gas for 15 seconds at a system pressure of 100 Pa to form a bismuth metal thin film. Step 4: Unreacted second source gas and by-product gas are discharged from the system by argon purging for 10 seconds. Step 5: Reducing gas is introduced into the film formation chamber 100 and reacted with the bismuth metal thin film formed in step 3 for 15 seconds at a system pressure of 100 Pa to highly purify the bismuth metal thin film. Step 6: Unreacted reducing gas and by-product gas are discharged from the system by argon purging for 10 seconds.

[0119] Example 2 In Example 1, the above-mentioned No. 29 was used as the first thin-film-forming source M1, and NH3 was used as the reducing gas instead of the second source gas. Using the ALD apparatus shown in FIG. 1 , a thin film was produced on a silicon substrate (substrate S) under the following conditions. The composition of the resulting thin film was analyzed using X-ray diffraction and X-ray photoelectron spectroscopy. The thin film was found to be a bismuth metal thin film, with a residual carbon content of less than 1 atom % and a residual oxygen content of less than 1 atom %. Furthermore, the film thickness was measured using X-ray reflectivity or spectroscopic ellipsometry. The thin film formed on the substrate was a smooth film with a thickness of 600 Å, and the film thickness obtained per cycle was 0.6 Å.

[0120] (Conditions) Reaction temperature (substrate temperature): 200°C (Steps 1 to 4) Reducing gas: NH3 Substrate: Silicon substrate

[0121] (Steps) A series of steps consisting of the following steps 1 to 4 constitute one cycle, and 1,000 cycles were repeated. Step 1: Vaporized first thin film-forming source material M1 (first source gas) was introduced into the film-forming chamber 100 under conditions of a source container heating temperature of 90°C and a source container internal pressure of 100 Pa. The bismuth compound in the first source gas was adsorbed onto the surface of the substrate S for 15 seconds at a system pressure of 100 Pa to form a precursor thin film. Step 2: Unadsorbed first source gas was purged from the system by argon purging for 10 seconds. Step 3: Reducing gas 202 was introduced into the film-forming chamber 100. The precursor thin film formed in step 1 was reacted with the reducing gas 202 for 15 seconds at a system pressure of 100 Pa to form a bismuth metal thin film. Step 4: Unreacted reducing gas 202 and by-product gases were purged from the system by argon purging for 10 seconds.

[0122] Comparative Example 1: A thin film was produced using the same procedure as in Example 1, except that tris(dimethylamino)bismuth was used as the comparative compound for the first thin film-forming source M1, and the ALD apparatus shown in FIG. 1 was used. The heating temperature of the source container 101 in step 1 was changed to 70°C. The composition of the resulting thin film was analyzed using X-ray diffraction and X-ray photoelectron spectroscopy. The thin film was found to be a bismuth metal thin film, but the residual carbon content in the thin film was 20 atom % and the residual oxygen content was less than 1 atom %. Furthermore, the thickness of the thin film was measured using X-ray reflectivity or spectroscopic ellipsometry. The thin film formed on the substrate had a thickness of 400 Å, and the film thickness obtained per cycle was 0.4 Å.

[0123] Comparative Example 2 A thin film was produced using the same procedure as in Example 2, except that tris(dimethylamino)bismuth was used as the comparative compound M1 of the first thin film-forming raw material, and the ALD apparatus shown in FIG. 1 was used. The heating temperature of the source container 101 in step 1 was changed to 70°C. The composition of the resulting thin film was analyzed using X-ray diffraction and X-ray photoelectron spectroscopy. The thin film was found to be a bismuth metal thin film, but the residual carbon content in the thin film was 25 atom% and the residual oxygen content was less than 1 atom%. Furthermore, the film thickness was measured using X-ray reflectivity or spectroscopic ellipsometry. The thin film formed on the substrate had a thickness of 400 Å, and the film thickness obtained per cycle was 0.4 Å.

[0124] The film formation results of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 are shown in Table 1 below.

[0125]

[0126] From the above, it was confirmed that the thin film manufacturing method of the present invention can form a high-purity bismuth metal thin film with a high film deposition rate, a uniform film thickness, and little residual carbon. Furthermore, the bismuth metal thin film manufactured by the thin film manufacturing method of the present invention has a significantly thick film thickness per cycle, suggesting that the thin film manufacturing method of the present invention can achieve high productivity.

[0127] REFERENCE SIGNS LIST 100 Film formation chamber 101 Source material container 102 Vaporization chamber 103 Heater 104 Mass flow controller (MFC) 105 Radio frequency (RF) power supply 106 RF matching system 107 Vacuum pump 108 Automatic pressure controller 109 Cold trap 201 Carrier gas 202 Reducing gas 203 Exhaust 204 Purge gas M1 First thin film forming source material M2 Second thin film forming source material S Substrate

Claims

1. A method for producing a thin film, comprising the steps of: forming a bismuth metal thin film using a bismuth compound represented by the following general formula (1) and at least one selected from Bi(SiMe3)3 and a reducing gas: (In general formula (1), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms; R 2 , R 3 and R 4 each independently represents an alkyl group having 1 to 3 carbon atoms.

2. A method for producing a thin film according to claim 1, comprising the steps of: introducing a first source gas obtained by vaporizing a first thin film forming source material containing a bismuth compound represented by general formula (1) into a film formation chamber, and depositing the bismuth compound in the first source gas on a surface of a substrate to form a precursor thin film; and introducing a second source gas obtained by vaporizing a second thin film forming source material containing Bi(SiMe3)3 or the reducing gas into a film formation chamber, and reacting the precursor thin film with the bismuth compound in the second source gas or the reducing gas to form a bismuth metal thin film.

3. A method for producing a thin film according to claim 1, comprising the steps of: introducing a second source gas obtained by vaporizing a second thin film forming source material containing Bi(SiMe3)3 into a film formation chamber, and depositing a bismuth compound in the second source gas on a surface of a substrate to form a precursor thin film; and introducing a first source gas obtained by vaporizing a first thin film forming source material containing a bismuth compound represented by general formula (1) into a film formation chamber, and reacting the precursor thin film with the bismuth compound in the first source gas to form a bismuth metal thin film.

4. A method for producing a thin film according to claim 2 or 3, further comprising, after the step of forming the bismuth metal thin film, a step of introducing a reducing gas into a film formation chamber and reacting the bismuth metal thin film with the reducing gas to highly purify the bismuth metal thin film.

5. A set of thin film forming raw materials comprising: a first thin film forming raw material containing a bismuth compound represented by the following general formula (1); and a second thin film forming raw material containing Bi(SiMe3)3. (In general formula (1), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms; R 2 , R 3 and R 4 each independently represents an alkyl group having 1 to 3 carbon atoms.

6. A set of thin film forming materials according to claim 5 for forming a bismuth metal thin film.

Images