Method for producing metal or semi-metal films

Abstract

The present invention belongs to the field of methods for preparing inorganic metal- or semi-metal-containing films, which methods comprise: (a) depositing a metal- or semi-metal-containing compound from a gaseous state onto a solid substrate, and (b) contacting the solid substrate in a gaseous state with a compound of the general formula (I), (II) or (III), wherein A is NR, NR2, PR, PR2, O, OR, S or SR, E is N, NR, P, PR, O or S, n is 1, 2 or 3, R is an alkyl, alkenyl, aryl or silyl group, and R' is hydrogen, an alkyl, alkenyl, aryl or silyl group, and A, E and n are selected so that the compound of the general formula (I), (II) or (III) is electrically neutral.

Description

[0001] The invention belongs to the field of methods for producing inorganic metal or semi-metal films on substrates, in particular atomic layer deposition methods.

[0002] With the continuous miniaturization, for example in the semiconductor industry, the demand for thin inorganic films on substrates increases, while the quality requirements for these films become more stringent. Metallic or semi-metallic films are used for different purposes, such as barrier layers, conductive structures or capping layers. Several methods for producing metallic or semi-metallic films are known. One of them is the deposition of film-forming compounds from the gaseous state on the substrate. In order to make the metal or semi-metal atoms gaseous at mild temperatures, volatile precursors must be provided, for example by complexing the metal or semi-metal with suitable ligands. These precursors need to be stable enough to evaporate, but on the other hand, they need to be reactive enough to react with the deposited surface.

[0003] EP 3 121 309 A1 discloses a method for depositing aluminum nitride films from a tris(dialkylamino)aluminum precursor. However, this precursor is not sufficiently stable for applications requiring high-quality films.

[0004] In order to convert the deposited metal or semi-metal complex into a metal or semi-metal film, it is usually necessary to expose the deposited metal or semi-metal complex to a reducing agent. Hydrogen is usually used to convert the deposited metal or semi-metal complex into a metal or semi-metal film. Although hydrogen works quite well as a reducing agent for relatively noble metals such as copper or silver, it does not produce satisfactory results for more electropositive metals such as titanium or aluminum.

[0005] WO 2013 / 070702A discloses a method for depositing metal films using aluminum hydride coordinated by diamine as a reducing agent. Although this reducing agent generally produces good results, for some demanding applications, a higher vapor pressure, stability and / or reduction potential is required.

[0006] D.Mukherjee et al. disclosed an alane complex with a chelating ligand in Chemical Communications, Vol. 53 (2017), pp. 3593-3496. However, since the compound is only used for organic synthesis in solution, its applicability to the preparation of inorganic metal or semi-metal films has not been recognized by the authors.

[0007] Therefore, the object of the present invention is to provide a method for preparing inorganic metal or semimetal containing films with fewer impurities in the film. The materials of the method should be easy to handle; in particular, they should be able to be evaporated with as little decomposition as possible. In addition, the materials of the method should not decompose on the deposition surface under the process conditions, but at the same time they should be sufficiently reactive to participate in surface reactions. All reaction by-products should be volatile to avoid film contamination. In addition, the method should be adjustable so that the metal or semimetal atoms in the materials of the method are volatile or are incorporated in the film. In addition, the method should be universal, so that it can be applied to produce a wide range of different metals (including electropositive metal or semimetal films).

[0008] These objects are achieved by a method for preparing an inorganic metal or semi-metal film, the method comprising:

[0009] (a) depositing a metal or semi-metal compound from a gaseous state onto a solid substrate, and

[0010] (b) contacting a solid substrate with a compound of formula (I), (II) or (III) in a gaseous state:

[0011]

[0012] wherein A is NR, NR2, PR, PR2, O, OR, S or SR,

[0013] E is N, NR, P, PR, O or S,

[0014] n is 1, 2, or 3,

[0015] R is an alkyl group, an alkenyl group, an aryl group or a silyl group, and

[0016] R' is hydrogen, alkyl, alkenyl, aryl or silyl, and

[0017] A, E and n are selected such that the compound of formula (I), (II) or (III) is electrically neutral.

[0018] The invention further relates to the use of compounds of the general formula (I), (II) or (III) as reducing agents in vapour deposition processes.

[0019] Preferred embodiments of the invention can be found in the description and the claims. Combinations of different embodiments fall within the scope of the invention.

[0020] The method according to the present invention is suitable for preparing inorganic metal or semi-metal films. In the context of the present invention, inorganic refers to a material containing at least 5% by weight, preferably at least 10% by weight, more preferably at least 20% by weight, and especially at least 30% by weight of at least one metal or semi-metal. Inorganic films usually contain only carbon in the form of carbide phases, including mixed carbide phases such as nitride carbide phases. The carbon content of carbon that does not belong to the carbide phase in the inorganic film is preferably less than 5% by weight, more preferably less than 1% by weight, and especially less than 0.2% by weight. Preferred examples of inorganic metal or semi-metal films are metal or semi-metal nitride films, metal or semi-metal carbide films, metal or semi-metal carbonitride films, metal or semi-metal alloy films, intermetallic compound films, or films containing mixtures thereof.

[0021] The film prepared by the method according to the present invention contains a metal or a semimetal. The film may contain one metal or a semimetal or more than one metal and / or a semimetal. Metals include Li, Be, Na, Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Cs, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os Ir, Pt, Au, Hg, Tl, Bi. Semimetals include B, Si, Ge, As, Sb, Se, Te. Preferably, the metal or semimetal is more electropositive than Cu, more preferably more electropositive than Ni. The metal or semimetal is, in particular, Ti, Ta, Mn, Mo, W, Ge, Ga, As, In, Sb, Te, Al or Si.

[0022] The solid substrate can be any solid material. These include, for example, metals, semimetals, oxides, nitrides, and polymers. The substrate can also be a mixture of different materials. Examples of metals are aluminum, steel, zinc, and copper. Examples of semimetals are silicon, germanium, and gallium arsenide. Examples of oxides are silicon dioxide, titanium dioxide, and zinc oxide. Examples of nitrides are silicon nitride, aluminum nitride, titanium nitride, and gallium nitride. Examples of polymers are polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyamide.

[0023] The solid substrate may have any shape. These include thin plates, films, fibers, particles of various sizes and substrates with grooves or other depressions. The solid substrate may have any size. If the solid substrate has a particle shape, the size of the particles may be less than 100 nm to several centimeters, preferably 1 μm to 1 mm. In order to avoid that the particles or fibers adhere to each other when the metal-containing or semi-metallic compound is deposited thereon, it is preferably kept moving. This can be achieved, for example, by stirring, by a rotary drum or by a fluidized bed technique.

[0024] According to the invention, a solid substrate is contacted in the gas phase with a compound of the general formula (I), (II) or (III). R' in the compound of the general formula (I), (II) or (III) is hydrogen, alkyl, alkenyl, aryl or silyl, preferably hydrogen or alkyl, in particular hydrogen, methyl or ethyl. R' may be identical or different from one another. Preferably, all R' are identical.

[0025] The alkyl group may be straight chain or branched. Examples of straight chain alkyl groups are methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl. Examples of branched alkyl groups are isopropyl, isobutyl, sec-butyl, tert-butyl, 2-methylpentyl, neopentyl, 2-ethylhexyl, cyclopropyl, cyclohexyl, indanyl, norbornyl. Preferably, the alkyl group is a C1-C8 alkyl group, more preferably a C1-C6 alkyl group, in particular a C1-C4 alkyl group, such as a methyl, ethyl, isopropyl or tert-butyl group.

[0026] Alkenyl contains at least one carbon-carbon double bond. The double bond may include the carbon atom through which R' is bonded to the rest of the molecule, or its position may be further away from the position where R' is bonded to the rest of the molecule. Alkenyl may be straight chain or branched. Examples of straight chain alkenyls in which the double bond includes the carbon atom that bonds R' to the rest of the molecule include 1-vinyl, 1-propenyl, 1-n-butenyl, 1-n-pentenyl, 1-n-hexenyl, 1-n-heptenyl, 1-n-octenyl. Examples of straight chain alkenyls in which the double bond is further away from the position where R' is bonded to the rest of the molecule include 1-n-propen-3-yl, 2-butene-1-yl, 1-butene-3-yl, 1-butene-4-yl, 1-hexene-6-yl. Examples of branched alkenyl groups in which the double bond includes the carbon atom that binds R' to the rest of the molecule include 1-propene-2-yl, 1-n-butene-2-yl, 2-butene-2-yl, cyclopentene-1-yl, cyclohexene-1-yl. Examples of branched alkenyl groups in which the double bond is located further away from the position where R' is bound to the rest of the molecule include 2-methyl-1-butene-4-yl, cyclopentene-3-yl, cyclohexene-3-yl. Examples of alkenyl groups with more than one double bond include 1,3-butadiene-1-yl, 1,3-butadiene-2-yl, cyclopentadiene-5-yl.

[0027] Aryl includes aromatic hydrocarbon radicals, for example phenyl, naphthyl, anthracenyl, phenanthrenyl and heteroaromatic radicals, for example pyrrolyl, furanyl, thienyl, pyridyl, quinolyl, benzofuranyl, benzothienyl, thienothiphenyl. Several of these radicals or combinations of these radicals are also possible, for example biphenyl, thienophenyl or furanthiphenyl. Aryl can be substituted, for example, by halogens such as fluorine, chlorine, bromine, iodine; by pseudohalogens such as cyanide, cyanate, thiocyanate; by alcohol; by alkyl or alkoxy chains. Aromatic hydrocarbons are preferred, more preferably phenyl.

[0028] Silyl is a silicon atom with 3 substituents usually. Preferably, silyl has the formula SiX3, wherein X is independently hydrogen, alkyl, aryl or silyl. It is possible that all three X are identical, or two X are identical and the remaining X is different, or all three X are different from each other, preferably all X are identical. Alkyl and aryl are as described above. The example of silyl includes SiH3, methylsilyl, trimethylsilyl, triethylsilyl, tri-n-propylsilyl, triisopropylsilyl, tricyclohexylsilyl, dimethyl tert-butylsilyl, dimethylcyclohexylsilyl, methyl diisopropylsilyl, triphenylsilyl, phenylsilyl, dimethylphenylsilyl, pentamethyldisilyl.

[0029] A in the compounds of the general formula (I) or (II) is NR, NR2, PR, PR2, O, OR, S or SR, i.e. a nitrogen atom with one or two substituents R, a phosphorus atom with one or two substituents R, an oxygen atom, an oxygen atom with one substituent R, a sulfur atom or a sulfur atom with one substituent R. R is an alkyl, alkenyl, aryl or silyl group. The same definition applies to the above R'. Preferably, R is an alkyl or silyl group, more preferably a methyl, ethyl, isopropyl, sec-butyl, tert-butyl or trimethylsilyl group, in particular a methyl or ethyl group. All A in the compounds of the general formula (I) or (II) may be identical or different from each other.

[0030] E in the compounds of the general formula (II) or (III) is N, NR, P, PR, O or S, i.e. a nitrogen atom, a nitrogen atom having one substituent R, a phosphorus atom, a phosphorus atom having one substituent R, an oxygen atom or a sulfur atom. The same definitions as described above for R apply. All E in the compounds of the general formula (II) or (III) may be identical to or different from one another.

[0031] It is possible that all R and R' are individual substituents. Alternatively, it is possible that two R or two R', or one R and one R' together form a ring, preferably a 4-8 membered ring, in particular a 5 or 6 membered ring.

[0032] According to the invention, n (which is the number of hydrogen atoms bonded to the aluminum atom) in the compounds of the general formula (I), (II) or (III) is 1, 2 or 3, preferably 1 or 2, in particular 1.

[0033] According to the present invention, A, E and n are selected so that the compound of general formula (I), (II) or (III) is electrically neutral. If A is NR, PR, O or S, A provides anion donor atoms for the ligand, while if A is NR2, PR2, OR or SR, it provides neutral donor atoms. If E is N or P, E provides anion donor atoms, while if E is NR, PR, O or S, it provides neutral donor atoms. In order to make the compound of general formula (I), (II) or (III) electrically neutral, the number of anion donor atoms plus the number of hydrogen atoms bonded to the aluminum atom needs to be 3 to compensate for the Al2O3. 3+ The charge of an atom.

[0034] Preferably, the compound of formula (I) is one of the following formulae.

[0035]

[0036] Preferred examples of compounds of the formula (I) with reference to these formulae are given in the table below.

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043] Et represents ethyl.

[0044] The synthesis of some compounds of the general formula (I) is described, for example, by C. Jones in Journal of the Chemical Society, Dalton Transactions, Vol. 1996, pp. 829-833.

[0045] Preferably, the compound of formula (II) is one of the following formulae.

[0046]

[0047]

[0048] Preferred examples of compounds of the formula (II) with reference to these formulae are given in the table below.

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] Et represents an ethyl group, and Ph represents a phenyl group.

[0056] Preferably, the compound of formula (III) is one of the following formulae.

[0057]

[0058]

[0059]

[0060] Preferred examples of compounds of the formula (III) with reference to these formulae are given in the table below.

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068] Et represents ethyl and Ph represents phenyl.

[0069] Preferably, R has no hydrogen atom in the 1-position, i.e. R has no hydrogen atom on the atom which is bound to the nitrogen or oxygen atom, which is therefore in the β position relative to the aluminum atom. Also preferably, R" has no hydrogen atom in the 1-position. More preferably, both R' and R" have no hydrogen in the 1-position. Examples are alkyl groups having two alkyl side groups in the 1-position, i.e. 1,1-dialkylalkyl groups, such as tert-butyl, 1,1-dimethylpropyl; alkyl groups having two halogens in the 1-position, such as trifluoromethyl, trichloromethyl, 1,1-difluoroethyl; trialkylsilyl groups, such as trimethylsilyl, triethylsilyl, dimethyl-tert-butylsilyl; aryl groups, in particular phenyl or alkyl-substituted phenyl groups, such as 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl. Alkyl groups having no hydrogen atom in the 1-position are particularly preferred.

[0070] The molecular weight of the compound of formula (I), (II) or (III) is preferably not more than 1000 g / mol, more preferably not more than 800 g / mol, even more preferably not more than 600 g / mol, in particular not more than 500 g / mol.

[0071] Preferably, the compound of the general formula (I), (II) or (III) has a melting point of -80 to 125° C., preferably -60 to 80° C., even more preferably -40 to 50° C., in particular -20 to 20° C. Advantageously, the compound of the general formula (I), (II) or (III) melts to give a clear liquid which remains unchanged up to the decomposition temperature.

[0072] Preferably, the compound of formula (I), (II) or (III) has a decomposition temperature of at least 80° C., more preferably at least 100° C., in particular at least 120° C., for example at least 150° C. The decomposition temperature is usually not more than 250° C. The compound of formula (I), (II) or (III) has a high vapor pressure. Preferably, the vapor pressure is at least 1 mbar at a temperature of 200° C., more preferably 150° C., in particular 120° C. Typically, the temperature at which the vapor pressure is 1 mbar is at least 50° C.

[0073] The compounds of the general formula (I), (II) or (III) used in the process according to the invention are used in high purity in order to achieve optimal results. High purity means that the substances used contain at least 90% by weight, preferably at least 95% by weight, more preferably at least 98% by weight and in particular at least 99% by weight of metal-containing or semimetallic compounds or compounds of the general formula (I), (II) or (III). The purity can be determined by elemental analysis in accordance with DIN 51721 (Prüfung fester Brennstoffe-Bestimmung des Gehaltes an Kohlenstoff und Wasserstoff-Verfahren nach Radmacher-Hoverath, August 2001).

[0074] The compound of the general formula (I), (II) or (III) is brought into contact with the solid substrate from the gaseous state. It can be made gaseous, for example, by heating it to a high temperature. In any case, a temperature lower than the decomposition temperature of the compound of the general formula (I), (II) or (III) must be selected. The decomposition temperature is the temperature at which the original compound of the general formula (I), (II) or (III) begins to change its chemical structure and composition. Preferably, the heating temperature is 0-300° C., more preferably 10-250° C., even more preferably 20-200° C., in particular 30-150° C.

[0075] Another method for making a compound of formula (I), (II) or (III) gaseous is direct liquid injection (DLI), for example as described in US2009 / 0226612A1. In this method, the compound of formula (I), (II) or (III) is usually dissolved in a solvent and sprayed in a carrier gas or vacuum. If the vapor pressure and temperature of the compound of formula (I), (II) or (III) are high enough and the pressure is low enough, the compound of formula (I), (II) or (III) becomes gaseous. Various solvents can be used, provided that the compound of formula (I), (II) or (III) shows sufficient solubility in the solvent, for example at least 1 g / l, preferably at least 10 g / l, and more preferably at least 100 g / l. Examples of these solvents are coordinating solvents, such as tetrahydrofuran, dihydrofuran, Solvent mixtures are also suitable.

[0076] Alternatively, the compound of formula (I), (II) or (III) can be converted to a gaseous state by direct liquid evaporation (DLE), for example as described by J. Yang et al. (Journal of Materials Chemistry, 2015). In this method, the compound of formula (I), (II) or (III) is mixed with a solvent, for example a hydrocarbon such as tetradecane, and heated to a temperature below the boiling point of the solvent. By evaporating the solvent, the compound of formula (I), (II) or (III) is converted to a gaseous state. This method has the advantage of not forming particulate contaminants on the surface.

[0077] Preferably, the compound of formula (I), (II) or (III) is made gaseous under reduced pressure. In this way, the method can usually be carried out at a lower heating temperature, resulting in reduced decomposition of the compound of formula (I), (II) or (III). It is also possible to use increased pressure to push the gaseous compound of formula (I), (II) or (III) toward the solid substrate. Inert gases such as nitrogen or argon are usually used as carrier gases for this purpose. Preferably, the pressure is from 10 bar to 10 -7 mbar, more preferably 1 bar to 10 -3 mbar, in particular 1-0.01 mbar, for example 0.1 mbar.

[0078] Typically, the compound of the general formula (I), (II) or (III) is used as a reducing agent in the process. According to the invention, the metal- or semi-metal-containing compound is deposited from the gaseous state onto a solid substrate, which is then contacted with the compound of the general formula (I), (II) or (III). Typically, the metal- or semi-metal-containing compound is reduced to a metal, a metal nitride, a metal carbide, a metal carbonitride, a metal alloy, an intermetallic compound or a mixture thereof. In the context of the present invention, the metal film is a film having a high electrical conductivity (typically at least 10 4 S / m, preferably at least 10 5 S / m, especially at least 10 6 S / m) of metal or semi-metal film.

[0079] The compound of the general formula (I), (II) or (III) has a low tendency to form permanent bonds with the surface of the solid substrate with the deposited metal- or semi-metal-containing compound. Therefore, the metal- or semi-metal-containing film is hardly contaminated by reaction by-products of the compound of the general formula (I), (II) or (III). Preferably, the metal- or semi-metal-containing film contains less than 5% by weight, more preferably less than 1% by weight, in particular less than 0.5% by weight, for example less than 0.2% by weight of nitrogen in total.

[0080] The metal or semi-metal compound contains at least one metal or semi-metal atom. Metals include Li, Be, Na, Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Cs, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os Ir, Pt, Au, Hg, Tl, Bi. Semi-metals include B, Si, Ge, As, Sb, Se, Te. Preferably, the metal or semi-metal compound contains a metal or semi-metal having an electropositive property greater than Cu, more preferably a metal or semi-metal having an electropositive property greater than Ni. In particular, the metal- or semi-metal-containing compound comprises Ti, Ta, Mn, Mo, W, Ge, Ga, As, In, Sb, Te, Al or Si. More than one metal- or semi-metal-containing compound may be deposited onto the surface simultaneously or successively. If more than one metal- or semi-metal-containing compound is deposited on the solid substrate, all metal- or semi-metal-containing compounds may contain the same metal or semi-metal or different metals or semi-metals, preferably they contain different metals or semi-metals.

[0081] Any metal or semimetal compound that can be converted into a gaseous state is suitable. These compounds include alkyl metals or semimetals such as dimethyl zinc, trimethyl aluminum; metal alkoxides, such as tetramethoxy silicon, tetraisopropoxy zirconium or tetraisopropoxy titanium; metal or semimetal cyclopentadienyl complexes, such as pentamethylcyclopentadienyl trimethoxy titanium or di(ethylcyclopentadienyl) manganese; metal or semimetal carbenes, such as tri(neopentyl)neopentyl tantalum or bisimidazolidinyl chloride ruthenium; metal or semimetal halides, such as aluminum trichloride, tantalum pentachloride, titanium tetrachloride; , molybdenum pentachloride, germanium tetrachloride, gallium trichloride, arsenic trichloride or tungsten hexachloride; carbon monoxide complexes, such as chromium hexacarbonyl or nickel tetracarbonyl; amine complexes, such as bis(tert-butylimino)bis(dimethylamino)molybdenum, bis(tert-butylimino)bis(dimethylamino)tungsten or tetrakis(dimethylamino)titanium; diketonate complexes, such as tris(acetylacetonato)aluminum or bis(2,2,6,6-tetramethyl-3,5-heptanedione)manganese. Preferred are metal or semimetal halides, in particular aluminum chloride, aluminum bromide and aluminum iodide. Preferred metal or semimetal compounds have a molecular weight of at most 1000 g / mol, more preferably at most 800 g / mol, in particular at most 600 g / mol, for example at most 500 g / mol.

[0082] The method is preferably carried out as an atomic layer deposition (ALD) method and comprises the following sequence:

[0083] (a) depositing a metal or semi-metal compound from a gaseous state onto a solid substrate, and

[0084] (b) contacting the solid substrate with the deposited metal or semimetal compound with a compound of formula (I), (II) or (III). Preferably, the sequence comprising (a) and (b) is performed at least 2 times, more preferably at least 5 times, even more preferably at least 10 times, in particular at least 50 times. Typically, the sequence comprising (a) and (b) is performed no more than 1000 times.

[0085] It is generally preferred to purge the substrate and its surroundings with an inert gas each time the solid substrate is exposed to the gaseous metal- or semimetal-containing compound or the compound of formula (I), (II) or (III). Preferred examples of inert gases are nitrogen and argon. The purge may be for 1 second to 1 minute, preferably 5-30 seconds, more preferably 10-25 seconds, and especially 15-20 seconds.

[0086] Preferably, the temperature of the substrate is 5 to 40°C higher than the position where the metal or semimetal compound becomes gaseous, for example 20°C. Preferably, the temperature of the substrate is room temperature to 400°C, more preferably 100-300°C, for example 150-220°C.

[0087] Preferably, after depositing the metal- or semi-metal-containing compound on the solid substrate and before contacting the solid substrate with the deposited metal- or semi-metal-containing compound with the compound of formula (I), (II) or (III), the solid substrate with the deposited metal- or semi-metal-containing compound is contacted with an acid in the gaseous state. Without being bound by theory, it is believed that the protonation of the ligands of the metal- or semi-metal-containing compound facilitates its decomposition and reduction. Suitable acids include hydrochloric acid and carboxylic acids, preferably carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid or trifluoroacetic acid, in particular formic acid.

[0088] Alternatively, the aluminum can be deposited from a compound of the general formula (I), (II) or (III). In this case, the compound of the general formula (I), (II) or (III) is adsorbed on the surface of the solid substrate, for example because reactive groups such as OH groups are present on the surface of the solid substrate or the temperature of the solid substrate is sufficiently high. Preferably, the adsorbed compound of the general formula (I), (II) or (III) is decomposed.

[0089] The decomposition can be carried out in various ways. The temperature of the solid substrate can be raised above the decomposition temperature. In this case, the process is a chemical vapor deposition (CVD) process. The solid substrate is usually heated to a temperature of 300-1000°C, preferably 350-600°C.

[0090] Furthermore, the deposited compound of the general formula (I), (II) or (III) can be exposed to a plasma such as an oxygen plasma, a hydrogen plasma, an ammonia plasma or a nitrogen plasma; an oxidant such as oxygen, oxygen radicals, ozone, nitrous oxide (N2O), nitrogen oxide (NO), nitrogen dioxide (NO2) or hydrogen peroxide; ammonia or ammonia derivatives such as tert-butylamine, isopropylamine, dimethylamine, methylethylamine or diethylamine; hydrazine or hydrazine derivatives such as N,N-dimethylhydrazine; a solvent such as water, an alkane or tetrachloromethane; or a boron compound such as borane. The choice depends on the chemical structure of the desired layer. For aluminum oxide, it is preferred to use an oxidant, a plasma or water, in particular oxygen, water, oxygen plasma or ozone. For aluminum nitride, it is preferred to use ammonia, hydrazine, a hydrazine derivative, a nitrogen plasma or an ammonia plasma. For aluminum boride, it is preferred to use a boron compound. For aluminum carbide, it is preferred to use an alkane or tetrachloromethane. For aluminum carbide nitride, it is preferred to use a mixture containing an alkane, tetrachloromethane, ammonia and / or hydrazine.

[0091] The method is preferably carried out by atomic layer deposition (ALD) method, comprising the following sequence:

[0092] (c) contacting a solid substrate with a compound of formula (I), (II) or (III), and

[0093] (d) decomposing the adsorbed compound of formula (I), (II) or (III). Preferably, the sequence comprising (c) and (d) is performed at least 2 times, more preferably at least 5 times, even more preferably at least 10 times, in particular at least 50 times. Typically, the sequence comprising (c) and (d) is performed no more than 1000 times.

[0094] In this case, the temperature of the substrate is preferably 5 to 40° C., for example 20° C. higher than the position where the metal or semimetal compound becomes gaseous. Preferably, the temperature of the substrate is room temperature to 400° C., more preferably 100-300° C., for example 150-220° C.

[0095] If in the method according to the invention, the temperature of the substrate is maintained below the decomposition temperature of the metal-containing or semi-metal compound, a monolayer will usually be deposited on the solid substrate. Once the molecules of the metal-containing or semi-metal compound are deposited on the solid substrate, the possibility of further deposition on top of it will usually be small. Therefore, the deposition of the metal-containing or semi-metal compound on the solid substrate preferably represents a self-limiting process step. The typical layer thickness of the self-limiting deposition process step is 0.01-1nm, preferably 0.02-0.5nm, more preferably 0.03-0.4nm, in particular 0.05-0.2nm. The layer thickness is usually measured by ellipsometry, as described in PAS 1022DE (Referenzverfahren zur Bestimmung von optischen unddielektrischen Materialeigenschaften sowie der Schichtdicke dünner Schichtenmittels Ellipsometrie; February 2004).

[0096] The exposure of the substrate to the compound of formula (I), (II) or (III) or the metal- or semi-metal-containing compound can be from a few milliseconds to a few minutes, preferably from 0.1 seconds to 1 minute, in particular from 1 to 10 seconds. The longer the solid substrate is exposed to the compound of formula (I), (II) or (III) or the metal- or semi-metal-containing compound at a temperature below the decomposition temperature of the compound of formula (I), (II) or (III) or the metal- or semi-metal-containing compound, the more regular the film formed is and the fewer defects it has.

[0097] A particular advantage of the process according to the invention is that the compounds of the general formula (I), (II) or (III) are very versatile, so that the process parameters can be varied within wide ranges. The process according to the invention therefore includes CVD processes and ALD processes.

[0098] According to the method of the present invention, an inorganic metal or semi-metal film is obtained. The film may be only a metal monolayer, or thicker, such as 0.1nm to 1μm, preferably 0.5-50nm. The film may contain defects such as holes. However, these defects usually account for less than half of the surface area covered by the film. The film preferably has a very uniform film thickness, which means that the film thickness at different positions on the substrate varies very little, usually less than 10%, preferably less than 5%. In addition, the film is preferably a conformal film on the surface of the substrate. Suitable methods for determining film thickness and uniformity are XPS or ellipsometry.

[0099] The film obtained by the method according to the present invention can be used for electronic components. The electronic component can have structural features of various sizes, for example 100nm to 100μm, for example 10nm, 14nm or 22nm. The method of forming a film for an electronic component is very particularly suitable for very fine structures. Therefore, electronic components with a size less than 1μm are preferred. Examples of electronic components are field effect transistors (FETs), solar cells, light emitting diodes, sensors or capacitors. In optical devices such as light emitting diodes or light sensors, the film obtained by the method according to the present invention is used to increase the refractive index of the layer that reflects light.

[0100] The preferred electronic component is a transistor. Preferably, the film is used as a chemical barrier metal in a transistor. A chemical barrier metal is a material that reduces diffusion from adjacent layers while maintaining electrical connectivity.

Claims

1. A method for preparing an inorganic metal or semi-metal film, comprising: (a) depositing a metal or semi-metal compound from a gaseous state onto a solid substrate, and (b) contacting a solid substrate with a compound of formula (I), (II) or (III) as a reducing agent in a gaseous state: wherein A is NR, NR2, PR, PR2, O, OR, S or SR, E is N, NR, P, PR, O or S, n is 1, 2, or 3, R is an alkyl group, an alkenyl group, an aryl group or a silyl group, and R' is hydrogen, alkyl, alkenyl, aryl or silyl, and A, E and n are selected so that the compound of formula (I), (II) or (III) is electrically neutral, wherein the metal- or semi-metal-containing compound contains Ti, Ta, Mn, Mo, W, Ge, Ga, As, In, Sb, Te, Al or Si.

2. The process according to claim 1, wherein R is methyl, ethyl, isopropyl, sec-butyl, tert-butyl, or trimethylsilyl.

3. The method according to claim 1, wherein R has no hydrogen atom at position 1.

4. The method according to claim 2, wherein R has no hydrogen atom at position 1.

5. The method according to claim 1, wherein n is 1 or 2.

6. The method according to claim 2, wherein n is 1 or 2.

7. The method according to claim 3, wherein n is 1 or 2.

8. The method according to claim 4, wherein n is 1 or 2.

9. The process according to any one of claims 1 to 8, wherein the compound of general formula (I), (II) or (III) has a melting point of -80 to 125°C.

10. The process according to any one of claims 1 to 8, wherein the metal- or semimetal-containing compound is a halide of a metal or semimetal.

11. The method according to claim 9, wherein the metal- or semi-metal-containing compound is a halide of a metal or semi-metal.

12. The method according to any one of claims 1 to 8, wherein the inorganic metal or semi-metal film contains a metal, a metal nitride, a metal carbide, a metal carbonitride, a metal alloy, an intermetallic compound or a mixture thereof.

13. The method according to claim 11, wherein the inorganic metal or semi-metal film contains a metal, a metal nitride, a metal carbide, a metal carbonitride, a metal alloy, an intermetallic compound or a mixture thereof.

14. The method according to any one of claims 1 to 8, wherein the sequence of steps (a) and (b) is performed at least twice.

15. The method according to claim 13, wherein the sequence of (a) and (b) is performed at least twice.

16. The method according to any one of claims 1 to 8, wherein the method is an atomic layer deposition method.

17. The method according to claim 15, wherein the method is an atomic layer deposition method.

18. A process according to any one of claims 1 to 8, wherein the compound of formula (I), (II) or (III) has a molecular weight of not more than 600 g / mol.

19. The method according to claim 17, wherein the compound of formula (I), (II) or (III) has a molecular weight of not more than 600 g / mol.

20. The process according to any one of claims 1 to 8, wherein the compound of the general formula (I), (II) or (III) has a vapor pressure of at least 1 mbar at a temperature of 200°C.

21. The process according to claim 19, wherein the compound of the general formula (I), (II) or (III) has a vapor pressure of at least 1 mbar at a temperature of 200°C.

22. The method according to any one of claims 1 to 8, wherein the inorganic metal- or semi-metal-containing film contains less than 5% by weight of nitrogen.

23. The method of claim 21, wherein the inorganic metal or semi-metal containing film contains less than 5 weight percent nitrogen.

24. Use of a compound of the general formula (I), (II) or (III) as defined in any one of claims 1 to 9 as a reducing agent in a vapour deposition process.

25. Use according to claim 24, wherein the vapor deposition process is an atomic layer deposition process.

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