Metal compounds for ALD applications

Abstract

The present invention relates to scandium complexes and a method of using these complexes as precursors for deposition of scandium containing films, in particular by atomic layer deposition.

Description

[0001] Metal Compounds for ALD Applications

[0002] Field

[0003] The present invention relates to scandium complexes and a method of using these complexes as precursors for deposition of scandium containing films, in particular by atomic layer deposition.

[0004] Background Art

[0005] Metal-containing films are used in semiconductor and electronics applications. Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) have been applied as the main deposition techniques for producing thin films for semiconductor devices. These methods enable the achievement of conformal films (metal, metal oxide, metal nitride, metal silicide, and the like) through chemical reactions of metal-containing compounds (precursors). The chemical reactions occur on surfaces which may include metals, metal oxides, metal nitrides, metal silicides, and other surfaces. In CVD and ALD, the precursor molecule plays a critical role in achieving high quality films with high conformality and low impurities. The precursor needs to have an appropriate vapor pressure and sufficient thermal stability. Furthermore, it needs to be vaporizable in a stable supply amount for forming a thin film by CVD or ALD method. The temperature of the substrate in CVD and ALD processes is an important consideration in selecting a precursor molecule. The precursor molecules should preferably be stable at typical substrate temperatures, e.g. in the range of 150 to 600 °C. Furthermore, the preferred precursor is capable of being delivered to the reaction vessel in a liquid or gaseous phase. The liquid phase of precursors at volatilization temperature generally provides a more uniform delivery of the precursor to the reaction vessel than solid phase precursors. While it is sufficient that the precursor is a liquid at delivery temperature, it is preferable that the precursor is a liquid at room temperature or close to room temperature. This has the advantage that condensation is less likely to occur if there is any cold spot in the precursor delivery system. Furthermore, the handling of a compound which is a liquid at or slightly above room temperature is technically easier, e.g. the filling of the vessels from which the precursor is applied.

[0006] The ALD process deposits thin layers of solid materials using two or more different vapor phase precursors. The surface of a substrate onto which the film is to be deposited is exposed to a dose of vapor of a first precursor. Then any excess unreacted vapor from that precursor is pumped away, e.g. by inert gas purges. Next, a vapor dose of a second precursor is brought to the surface and allowed to react. This cycle of steps can be repeated to build up thicker films. One particularly important aspect of this process is that the ALD reactions are self-limiting in that only a certain maximum thickness can form in each cycle, after which no further deposition occurs during that cycle, even if excess reactant is available. Because of this self-limiting character, ALD reactions produce coatings with highly uniform thicknesses not only on flat substrate surfaces, but also into narrow holes and trenches as well as other three-dimensional surfaces, which renders this technique indispensable for the semiconductor industry.

[0007] Thin films containing scandium have enormous technological significance for the semiconductor industry. Such thin films can contain metallic scandium or scandium compounds, such as scandium(lll) oxide SC2O3, scandium(lll) sulfide SC2S3, scandium(lll) nitride ScN or mixed metal materials comprising scandium. Due to increasing demand for highly conformal, very thin films containing scandium for semiconductor manufacturing processes, particularly for the deposition of dielectric films, it would be advantageous to have highly volatile compounds with a low melting point having a low and wide ALD window as precursors for ALD of scandium containing films. ALD of scandium containing films has been employed for the deposition of electrically insulating materials with high dielectric constants (high-k dielectrics) as gate insulators in high-speed transistors as well as ultrathin gate interlayers in the integration of new channel materials and high performance capacitors.

[0008] Metal amidinate (AMD) complexes are generally known as precursors for the deposition of scandium containing films via ALD. For example, W02004 / 046417 discloses the use of volatile metal amidinates for ALD applications and embraces a large variety of metals and a large variety of differently substituted amidinate ligands wherein the amidinate ligand can be substituted e.g. by alkyl, aryl, alkynyl, etc.. The examples disclose complexes with various transition metals and main group metals, wherein the amidinate ligands are substituted with iso-propyl, secbutyl and / or tert-butyl groups. No examples with scandium are disclosed. Furthermore, it is suggested to use longer alkyl chains and / or alkyl chains with more than one stereoisomer as substituents on the amidinate to lower the melting point.

[0009] US2023 / 0058025A1 discloses scandium amidinate complexes, in particular scandium acetamidinate complexes wherein the substituents on each nitrogen atom of a ligand are different from each other. The compound disclosed in the examples, Sc(Amd-Me,Et)3, i.e. tris(N-methyl-N’-ethyl-acetamidinato)scandium, has a melting point of 67 °C, and the Tso% in TGA (temperature of 50% weight loss) is at 215 °C. There is considerable decomposition during evaporation, as can be seen from a residue which cannot be evaporated. No complexes with formamidinate ligands are disclosed in the examples.

[0010] KR10-2614467B1 discloses various scandium amidinate complexes some of which are liquid at room temperature. Two complexes are disclosed in the examples, Sc(Et2nPr-AMD)3, i.e. tris(N,N’-diethyl-butanoic-amidinato)scandium, and Sc(Et2Et-AMD)3, i.e. tris(N,N’-diethyl-propionic-amidinato)scandium.

[0011] Further scandium amidinate complexes are known, e.g. tris(N,N’-diisopropyl-acet- amidinato)scandium from P. de Rouffignac et al., Electrochemical and Solid State Letters 2006, 9(6), F45-F48, or tris(N,N’-diethyl-acetamidinato)scandium from H. Wang et al., Electrochemical and Solid State Letters 2009, 12(4), G13-G15 or K.

[0012] H. Kim et al., Applied Physics Letters 2006, 89, 133512. These materials show higher evaporation temperatures. Furthermore, tris(N,N’-diisopropyl- formamidinato)scandium is commercially available. This compound has a melting point of 269 °C.

[0013] In a method of forming a thin-film through the vaporization of a compound, such as the CVD or ALD method, important properties that the compound to be used as a thin-film forming precursor (reactant) is required to have are as follows: its vapor pressure is high; its melting point is low, and the compound is preferably a liquid at or slightly above room temperature; its thermal stability is high; and the compound can produce a high-quality thin-film with high productivity, i.e. the reactivity towards the surface, the co-reactant and the deposited material is high and the reactions are clean, i.e. the reactions do essentially not produce any undesired byproducts on the surface. As discussed above, there is still room for improvement with respect to the scandium compounds of the prior art. Accordingly, an object of the present invention is to provide novel compounds, which have high vapor pressures, low melting points, and can produce high-quality thin-films with high productivity when used as a thin-film forming raw material as compared to the related-art scandium compounds.

[0014] Surprisingly, it was found that scandium complexes comprisinig specific alkyl substituted formamidinate ligands could significantly decrease the melting temperature as well as in particular the evaporation temperature of the scandium complexes compared to the scandium complexes known in the prior art. These compounds furthermore have appropriate thermal stability and volatility and can be employed in a CVD or ALD method to form a scandium containing film. Such compounds are therefore the subject of the present invention.

[0015] Summary

[0016] The disclosed and claimed subject matter is directed to a compound of the following formula (1):

[0017] Formula (1) wherein RN1, RN2are on each occurrence, identically or differently, ethyl or n- propyl and wherein the compound can be partially or completely deuterated.

[0018] Each of the groups [RN1N-CH-NRN2] in the compound of formula (1) is referred as a “ligand” or “formamidinate ligand”.

[0019] The disclosed and claimed subject further includes compositions and formulations comprising the compound of formula (1), methods of using the compound of formula (1) as precursor for deposition of scandium containing films, and scandium containing films derived from the compound of formula (1).

[0020] Detailed description

[0021] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0022] The use of the terms "a", "an", "the" and similar referents in the context of describing the disclosed and claimed subject matter (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms ( / .e., meaning “including, but not limited to”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it was individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the disclosed and claimed subject matter and does not pose a limitation on the scope of the disclosed and claimed subject matter unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosed and claimed subject matter. The use of the term “comprising” or “including” in the specification and the claims includes the narrower language of “consisting essentially of’ and “consisting of.”

[0023] Embodiments of the disclosed and claimed subject matter are described herein, including the best mode known to the inventors for carrying out the disclosed and claimed subject matter. Variations of those embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the disclosed and claimed subject matter to be practiced otherwise than as specifically described herein. Accordingly, the disclosed and claimed subject matter includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosed and claimed subject matter unless otherwise indicated herein or otherwise clearly contradicted by context.

[0024] The compound according to the present invention is also referred to as “precursor” or “reactant” when the use of the compound in CVD or ALD deposition techniques is described.

[0025] For ease of reference, “microelectronic device” or “semiconductor device” corresponds to semiconductor wafers having integrated circuits, memory, and other electronic structures fabricated thereon, and flat panel displays, phase change memory devices, solar panels and other products including solar substrates, photovoltaics, and microelectromechanical systems (MEMS), manufactured for use in microelectronic, integrated circuit, or computer chip applications. Solar substrates include, but are not limited to, silicon, amorphous silicon, polycrystalline silicon, monocrystalline silicon, CdTe, copper indium selenide, copper indium sulfide, and gallium arsenide on gallium. The solar substrates may be doped or undoped. It is to be understood that the term “microelectronic device” or “semiconductor device” is not meant to be limiting in any way and includes any substrate that will eventually become a microelectronic device or microelectronic assembly.

[0026] As defined herein, the term “barrier material” corresponds to any material used in the art to seal the metal lines, e.g., copper interconnects, to minimize the diffusion of said metal, e.g., copper, into the dielectric material. Preferred barrier layer materials include tantalum, titanium, ruthenium, hafnium, and other refractory metals and their nitrides and silicides.

[0027] “Substantially free” is defined herein as less than 0.001 wt%. “Substantially free” also includes 0.000 wt%. The term “free of” means 0.000 wt%. As used herein, "about" or “approximately” are intended to correspond to within ± 5% of the stated value.

[0028] In all such compositions, wherein specific components of the composition are discussed in reference to weight percentage (or “weight %” or “wt%”) ranges including a zero lower limit, it will be understood that such components may be present or absent in various specific embodiments of the composition, and that in instances where such components are present, they may be present at concentrations as low as 0.001 wt%, based on the total weight of the composition in which such components are employed. All percentages of the components are weight percentages and are based on the total weight of the composition, that is, 100%.

[0029] Moreover, when referring to the compositions described herein in terms of weight % or wt%, it is understood that in no event shall the wt% of all components, including non-essential components, such as impurities, add to more than 100 wt%. In compositions “consisting essentially of” recited components, such components may add up to 100 wt% of the composition or may add up to less than 100 wt%. Where the components add up to less than 100 wt%, such composition may include some small amounts of a non-essential contaminants or impurities. For example, in one such embodiment, the formulation can contain 2 wt% or less of impurities. In another embodiment, the formulation can contain 1 wt% or less than of impurities. In a further embodiment, the formulation can contain 0.05 wt% or less than of impurities. In other such embodiments, the constituents can form at least 90 wt%, more preferably at least 95 wt% , more preferably at least 99 wt%, more preferably at least 99.5 wt%, most preferably at least 99.9 wt%, and can include other ingredients that do not or not significantly affect the deposition process. Otherwise, if no significant non- essential impurity component is present, it is understood that the composition of all essential constituent components will essentially add up to 100 wt%.

[0030] Any reference to “one or more” or “at least one” includes “two or more” and “three or more” and so on.

[0031] The headings employed herein are not intended to be limiting; rather, they are included for organizational purposes only.

[0032] In a preferred embodiment of the invention, the three formamidinate ligands in the compound of formula (1) are identical. It is therefore preferred that all groups RN1are identical and all groups RN2are identical. RN1and RN2can be the same or different, but preferably RN1and RN2are the same. In a further preferred embodiment, RN1is ethyl.

[0033] Suitable combinations of RN1and RN2are the compounds of Table 1.

[0034] Table 1 :

[0035] Particularly preferred is the compound 1 , i.e. compound with RN1= RN2= ethyl.

[0036] It is preferable that the compound of formula (1) or the preferred embodiments is essentially free of impurities. This refers in particular to metal impurities, organic by-products and halogen impurities. The content of each of the impurity metal elements is preferably 10 ppm or less, more preferably 1 ppm or less, and the total content thereof is preferably 50 ppm or less, more preferably 10 ppm or less. The total content of the impurity halogens is preferably 100 ppm or less, more preferably 10 ppm or less, and most preferably 1 ppm or less.

[0037] The compound of formula (1) and the preferred embodiments can be synthesized by reaction of an appropriate scandium precursor ScX3wherein X is a counteranion, such as halogen (F, Cl, Br, I, preferably Cl), triflate or tosylate, with the desired formamidinate salt, such as LifAMD, NafAMD or KfAMD, preferably LifAMD, where fAMD stands for the correspondingly substituted formamidinate. The formamidinate salt can be prepared in situ from the corresponding formamidine by deprotonation in a solvent, wherein polar or non-polar aprotic solvents, such as THF, dioxane, diethylether, methyl-tert-butylether, dibutylether, hexane, pentane or toluene or mixtures thereof, are preferred.

[0038] The present invention is therefore further directed to a method of manufacturing a compound of formula (1) or the preferred embodiments wherein a compound ScX3wherein X is a counterion, preferably F, Cl, Br, I, triflate or tosylate and particularly preferably Cl, is reacted with a formamidinate salt, preferably a Li, Na or K salt and particularly preferably a Li salt.

[0039] Method of Use

[0040] The disclosed compounds can be used as precursors (reactants) for the deposition of scandium containing films using any chemical vapor deposition process known to those of skill in the art. The precursor for forming a thin film, also referred to as “thin film forming precursor” comprises the compound according to the present invention and optionally further compounds, depending on the production process to which the precursor is applied. For example, when a thin film containing only scandium as a metal is produced, the thin film forming precursor of the present invention is free of metal compounds other than the compound represented by the general formula (1). Meanwhile, when a thin film containing two or more kinds of metals is produced, the thin film forming precursor of the present invention may contain a compound containing a desired metal in addition to the compound represented by the general formula (1). The thin film forming precursor of the present invention may further contain an organic solvent. As described above, the physical properties of the compound represented by the general formula (1) are suitable for serving as the precursor for a CVD method, and hence the thin film forming precursor of the present invention is useful as a CVD precursor. In particular, the thin-film forming precursor of the present invention is particularly suitable for an ALD method because the compound represented by the general formula (1) has a self-limiting reaction behavior at the surface, i.e. is not reacting with the adsorbed surface precursor species.

[0041] As used herein, the term “chemical vapor deposition process” (CVD) refers to any process wherein a substrate is exposed to one or more volatile precursors, which react and / or decompose on the substrate surface to produce the desired deposition. As used herein, the term “atomic layer deposition process” (ALD) refers to a selflimiting (e.g., the amount of film material deposited in each reaction cycle is constant), sequential surface chemistry that deposits films of materials onto substrates of varying compositions. Although the precursors, reagents and coreagents used herein may be sometimes described as “gaseous,” it is understood that the precursors can be either liquid or solid at room temperature and / or at elevated temperature and are transported with or without an inert gas into the reactor via direct vaporization, bubbling or sublimation. In some case, the vaporized precursors can pass through a plasma generator. The term “reactor” as used herein, includes without limitation, the reaction chamber (reaction vessel, deposition chamber).

[0042] Chemical vapor deposition processes in which the disclosed and claimed compounds can be utilized as precursors include, but are not limited to, those used for the manufacture of semiconductor type microelectronic devices, such as ALD, CVD, pulsed CVD, plasma enhanced ALD (PEALD) and / or plasma enhanced CVD (PECVD). Examples of suitable deposition processes for the method disclosed herein include, but are not limited to, cyclic CVD (CCVD), MOCVD (Metal Organic CVD), thermal chemical vapor deposition, plasma enhanced chemical vapor deposition (“PECVD”), high density PECVD, photon assisted CVD, plasma-photon assisted (“PPECVD”), cryogenic chemical vapor deposition, chemical assisted vapor deposition, hot-filament chemical vapor deposition, CVD of a liquid polymer precursor, deposition from supercritical fluids, low energy CVD (LECVD), roll-to-roll ALD, spatial ALD and atmospheric pressure ALD. In certain embodiments, the scandium containing films are deposited via atomic layer deposition (ALD), plasma enhanced ALD (PEALD) or plasma enhanced cyclic CVD (PECCVD) process.

[0043] In one embodiment, the scandium containing film is deposited using an ALD process. In another embodiment, the scandium containing film is deposited using a CCVD process. In a further embodiment, the scandium containing film is deposited using a thermal CVD process. Suitable substrates on which the disclosed and claimed precursors can be deposited are not particularly limited and vary depending on the intended final use. For example, the substrate may be chosen from oxides, such as HfC>2 based materials, TiC>2 based materials, ZrC>2 based materials, rare earth oxide-based materials, ternary oxide-based materials, etc., or from nitride-based materials. Other substrates may include solid substrates, such as metal substrates (e.g., Au, Pd, Rh, Ru, W, Al, Ni, Ti, Co, Pt), metal silicide containing substrates (e.g., TiSi2, CoSi2, and NiSi2), metal nitride containing substrates (e.g., TaN, TiN, WN, TaCN, TiCN, TaSiN, and TiSiN), semiconductor materials (e.g., Si, SiGe, GaAs, InP, diamond, GaN, and SiC), insulators (e.g., SiO2, Si3N4, SiON, HfO2, Ta2Os, ZrO2, TiO2, AI2O3, and barium strontium titanate), and combinations thereof. Preferred substrates include TiN, Ru and Si type substrates.

[0044] In such deposition methods and processes, usually a co-reactant is used, such as an oxidizing agent. An “oxidizing agent” in the sense of this application is understood to mean a chemical compound which transfers oxygen to the scandium containing film. The oxidizing agent is typically introduced in gaseous form. Examples of suitable oxidizing agents include, but are not limited to, oxygen gas, water vapor, ozone, oxygen plasma, or mixtures thereof.

[0045] Further possible co-reactants are reducing agents, such as H2, H2 plasma, hydrazine or aminoboranes, nitrogen-containing co-reactants, such as hydrazine, NH3, N2 or N2 plasma, sulfur-containing co-reactant, such as H2S or elemental sulfur, or peroxides, such as H2O2 or HOOtBu.

[0046] The deposition methods and processes may also involve purge steps, which are usually done by using one or more purge gases. The purge gas, which is used to purge away unconsumed reactants and / or reaction byproducts, is an inert gas that does not react with the precursors and with the formed thin film. Exemplary purge gases include, but are not limited to, argon (Ar), nitrogen (N2), helium (He), neon (Ne), and mixtures thereof. For example, a purge gas, such as Ar, is supplied into the reactor at a flow rate ranging from about 10 to about 2000 seem for about 0.1 to 10000 seconds, thereby purging the unreacted material and any byproduct that may remain in the reactor.

[0047] The deposition methods and processes require that energy be applied to the at least one of the precursors according to the present invention, co-reactants or combination thereof to induce reaction and to form the scandium containing film or coating on the substrate. Such energy can be provided by, but not limited to, temperature (thermally induced), plasma, pulsed plasma, helicon plasma, high density plasma, inductively coupled plasma, X-ray, e-beam, photon, remote plasma methods, and combinations thereof. In some processes, a secondary RF frequency source can be used to modify the plasma characteristics at the substrate surface. When utilizing plasma, the plasma-generated process may include a direct plasma-generated process in which plasma is directly generated in the reactor, or alternatively a remote plasma-generated process in which plasma is generated outside of the reactor and supplied into the reactor.

[0048] When utilized in such deposition methods and processes, suitable precursors, such as the compounds of the present invention, may be delivered to the reaction chamber, such as a CVD or ALD reactor, in a variety of ways. A preferred method of delivering the precursors to the reaction chamber is by vaporization of the precursor, e.g. either by vacuum driven thermal vaporization or by active vaporization using a carrier gas. In other instances, a liquid delivery system or a combined liquid delivery and flash vaporization process unit may be employed to enable low volatility materials to be volumetrically delivered, which leads to reproducible transport and deposition without thermal decomposition of the precursor. The precursor compositions described herein can be effectively used as reagents via direct liquid injection (DLI) or via vacuum driven vaporization to provide a vapor stream of these metal precursors into an ALD or CVD reactor. Vacuum driven vaporization is the preferred method of delivery for the precursors according to the present invention.

[0049] When used in these deposition methods and processes, the disclosed and claimed compounds may include hydrocarbon solvents which are particularly desirable due to their ability to be dried to sub-ppm levels of water. Exemplary hydrocarbon solvents that can be used in the precursors include, but are not limited to, toluene, mesitylene, cumene (isopropylbenzene), p-cymene (4-isopropyl toluene), 1 ,3- diisopropylbenzene, octane, dodecane, 1,2,4-trimethylcyclohexane, n- butylcyclohexane, and decahydronaphthalene (decalin). The disclosed and claimed compounds can also be stored and used in stainless steel containers. In certain embodiments, the hydrocarbon solvent is a high boiling point solvent or has a boiling point of 100 °C or greater. The disclosed and claimed compounds can also be mixed with other suitable metal compounds, which can be utilized as precursors, and the mixture used to deliver both metals simultaneously for the growth of a binary metal-containing films. A flow of argon and / or other gas may be employed as a carrier gas to help deliver a vapor containing at least one of the disclosed and claimed precursors to the reaction chamber during the precursor pulsing. When delivering the precursors, the reaction chamber process pressure is between 1 and 50 torr, preferably between 5 and 20 torr.

[0050] Substrate temperature can be an important process variable in the deposition of high-quality scandium containing films. Typical substrate temperatures range from about 100 °C to about 550 °C. Higher temperatures can promote higher film growth rates, but might result in bulk CVD rather than ALD. Furthermore, there is the risk at higher substrate temperatures that the precursor desorbs from the substrate, thus resulting in lower growth rates. If the substrate temperature is not high enough, the temperature might be too low for a sufficient reaction of the precursor with the surface, which also results in lower growth rates, and / or the precursor might condense on the surface resulting in increasing growth rates.

[0051] In view of the forgoing, those skilled in the art will recognize that the disclosed and claimed subject matter further includes the use of the disclosed and claimed compounds as precursors in chemical vapor deposition (CVD) processes as follows.

[0052] In one embodiment, the disclosed and claimed subject matter includes a method for forming a scandium containing film on at least one surface of a substrate that includes the steps of:

[0053] (a) providing the at least one surface of the substrate in a reaction vessel; and

[0054] (b) forming a scandium containing film on the at least one surface by a deposition process selected from a chemical vapor deposition (CVD) process and an atomic layer deposition (ALD) process using at least one compound of formula (1) or the preferred embodiments as precursor of a scandium source compound for the deposition process.

[0055] In a further aspect of this embodiment, the method includes introducing at least one co-reactant into the reaction vessel. A co-reactant is a reactant which is used in addition to the precursor of the present invention for the deposition of the scandium containing film. In a further aspect of this embodiment, the method includes introducing at least one co-reactant into the reaction vessel where the at least one co-reactant is selected from the group of water, oxygen (O2), oxygen plasma, ozone (O3), NO, N2O, NO2, CO, CO2 and combinations thereof. These coreactants are typically used for forming a metal oxide thin film. In another aspect of this embodiment, the method includes introducing at least one co-reactant into the reaction vessel where the at least one co-reactant is selected from the group of ammonia, hydrazine, monoalkylhydrazine, dialkylhydrazine, nitrogen, nitrogen / hydrogen, ammonia plasma, nitrogen plasma, nitrogen / hydrogen plasma, and combinations thereof. These co-reactants are typically used for forming a metal nitride thin film, but ammonia, hydrazine, monoalkylhydrazine, dialkylhydrazine, ammonia plasma, and combinations thereof, might also be used for forming a metallic film. In another aspect of this embodiment, the method includes introducing at least one co-reactant into the reaction vessel where the at least one co-reactant is selected from the group of hydrogen, hydrogen plasma, a mixture of hydrogen and helium, a mixture of hydrogen and argon, hydrogen / helium plasma, hydrogen / argon plasma, boron-containing compounds, silicon-containing compounds and combinations thereof. These co-reactants are typically used for forming metallic film, i.e. formation of the elemental metal.

[0056] In one embodiment, the disclosed and claimed subject matter includes a method of forming a scandium containing film via an atomic layer deposition (ALD) process or ALD-like process that includes the steps of:

[0057] (a) providing a substrate in a reaction vessel;

[0058] (b) introducing into the reaction vessel one or more of the compounds of formula (1) or the preferred embodiments as precursor;

[0059] (c) a purging step, in particular purging the reaction vessel with a first purge gas;

[0060] (d) introducing into the reaction vessel a co-reactant;

[0061] (e) a purging step, in particular purging the reaction vessel with a second purge gas;

[0062] (f) sequentially repeating steps (b) through (e) until a desired thickness of the scandium containing film is obtained.

[0063] Depending on the desired composition of the produced scandium containing thin film, the steps (b), (c), (d) and (e) may also be repeated with a second co-reactant in step (d) and optionally a third or further co-reactant and a purging step with the third purge gas and optionally a fourth or further purge gases.

[0064] Furthermore, it is possible in step (b) to introduce two or more precursors, wherein at least one precursor is a compound of formula (1) or the preferred embodiments. These two or more precursors may be introduced as a mixture from the same container or may be introduced from different containiers. Furthermore, it is possible in step (d) to introduce two or more co-reactants. These two or more co-reactants may be introduced as a mixture from the same source vessel or may be introduced from different containers.

[0065] In a further aspect of this embodiment, the co-reactant is one or more of an oxygencontaining co-reactant selected from water, O2, oxygen plasma, O3, NO, N2O, NO2, CO, CO2 and combinations thereof. In another aspect of this embodiment, the coreactant is one or more of a nitrogen-containing co-reactant selected from ammonia, hydrazine, monoalkylhydrazine, dialkylhydrazine, nitrogen, nitrogen / hydrogen, ammonia plasma, nitrogen plasma, nitrogen / hydrogen plasma and mixture thereof. In another aspect of this embodiment, the co-reactant is selected from hydrogen, hydrogen plasma, a mixture of hydrogen and helium, a mixture of hydrogen and argon, hydrogen / helium plasma, hydrogen / argon plasma, boron-containing compounds, silicon-containing compounds and combinations thereof. In a further aspect of this embodiment, the method the first and second purge gases are each independently selected one or more of argon, nitrogen, helium, neon, and combinations thereof. Additionally or alternatively, vacuum may be applied for one or more purging steps. In a further aspect of this embodiment, the method further includes applying energy to at least one of the precursor, the co-reactant, the substrate, and combinations thereof, wherein the energy is one or more of thermal, plasma, pulsed plasma, helicon plasma, high density plasma, inductively coupled plasma, capacitively coupled plasma, X-ray, e-beam, photon, remote plasma methods and combinations thereof. In a preferred aspect of this embodiment, step (b) of the method includes introducing into the reaction vessel the precursor using thermal energy and vacuum. In a further aspect of this embodiment, step (b) of the method further includes introducing into the reaction vessel the precursor using a stream of carrier gas to deliver a vapor of the precursor into the reaction vessel. In a further aspect of this embodiment, step (b) of the method further includes use of a solvent medium comprising one or more of toluene, mesitylene, isopropylbenzene, 4- isopropyl toluene, 1 ,3-diisopropylbenzene, octane, dodecane, 1,2,4- trimethylcyclohexane, n-butylcyclohexane, and decahydronaphthalene and combinations thereof.

[0066] The shape of the substrate is not particularly limited and can be, for example, a plate shape, a spherical shape, a fibrous shape, or a scaly shape. The surface of the substrate may be planar, or may have a three-dimensional structure such as a trench structure. In addition, examples of the above-mentioned production conditions include a reaction temperature (substrate temperature), a reaction pressure, and a deposition rate. The reaction temperature is preferably from room temperature to 500 °C, more preferably from 100 °C to 300 °C. In addition, the reaction pressure is preferably from 10 Pa to an atmospheric pressure in the case of the thermal CVD or the optical CVD, and is preferably from 10 Pa to 2,000 Pa in the case of using plasma. For ALD, the pressure of a system (in the film formation chamber) when this step is performed is preferably from 1 Pa to 10,000 Pa, more preferably from 10 Pa to 1,000 Pa.

[0067] In addition, the deposition rate may be controlled by the supply conditions (vaporization temperature and vaporization pressure) of the precursor, the reaction temperature, and the reaction pressure. When the deposition rate is large, the characteristics of a thin-film to be obtained may deteriorate. When the deposition rate is small, a problem may occur in productivity. Accordingly, for CVD processes, the deposition rate is preferably from 0.01 nm / min to 100 nm / min, more preferably from 1 nm / min to 50 nm / min. In addition, in the case of the ALD method, the deposition rate is controlled by the number of cycles so that a desired film thickness may be obtained. In an ALD process, typical deposition rates are from 0.01 nm / cycle to 0.2 nm / cycle, more typically from 0.05 nm / cycle to 1.3 nm / cycle. Further, as the above-mentioned production conditions, there are given a temperature and a pressure when the thin-film forming precursor is vaporized to obtain a precursor gas. The step of vaporizing the thin-film forming precursor to obtain a precursor gas may be performed in the precursor vessel or in the vaporization chamber. In any case, it is preferred that the thin-film forming precursor of the present invention be evaporated at a temperature between 0 °C and 150 °C. In addition, when the thin-film forming precursor is vaporized to obtain a precursor gas in the precursor vessel or in the vaporization chamber, the pressure in the precursor vessel and the pressure in the vaporization chamber are each preferably from 1 Pa to 10,000 Pa.

[0068] In addition, in the method of producing a thin-film of the present invention, after the thin-film deposition, annealing treatment may be performed under an inert atmosphere, an oxidizing atmosphere, or a reducing atmosphere in order to obtain more satisfactory electrical characteristics. The temperature for annealing is from 200 °C to 1,000 °C, preferably from 250 °C to 500 °C.

[0069] Brief description of the drawings Fig. 1 shows the TGA curves for various compounds according to the invention as well as comparative scandium compounds.

[0070] Fig. 2 shows the thermal stability study for Sc(Et2-fAMD)3 on Si(100) with 10 nm scandium oxide, as described in ALD Example 1.

[0071] Fig. 3 shows the saturation study of Sc(Et2-fAMD)3 on Si(100) with native oxide at 200 °C, 250 °C and 300 °C, as described in ALD Example 2.

[0072] Fig. 4 shows the temperature dependency of the Sc(Et2-fAMD)3 / O3 process on Si(100) with native oxide, as described in ALD Example 3.

[0073] Examples

[0074] Reference will now be made to more specific embodiments of the present disclosure and experimental results that provide support for such embodiments. The examples are given below to more fully illustrate the disclosed subject matter and should not be construed as limiting the disclosed subject matter in any way.

[0075] It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed subject matter and specific examples provided herein without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter, including the descriptions provided by the following examples, covers the modifications and variations of the disclosed subject matter that come within the scope of any claims and their equivalents.

[0076] Materials and Methods:

[0077] All solvents and starting materials were purchased from Sigma-Aldrich unless otherwise indicated.

[0078] General synthetic procedure:

[0079] In a Schlenk flask, the respective amidine (AMDH) (3eq) to prepare the below described complexes was dissolved in THF and cooled to -78 °C. n-Butyl lithium (nBuLi), 1.6 M in hexane (3 eq), was added dropwise to the solution. The mixture was allowed to warm up to room temperature and was stirred for 2 h. The mixture was cooled to 0 °C and was transferred slowly via a cannula into a 0 °C cold solution of scandium chloride (ScCh) (1 eq.) in THF. After addition, the reaction mixture was stirred at room temperature overnight. The solvent was removed under reduced pressure and the crude mixture was extracted in toluene. The suspension was filtered, and solvent of the filtrate was removed under reduced pressure. The crude product was distilled or sublimed under the below given conditions to obtain spectroscopically pure complexes. In the following, fAMD stands for formamidinate, MeAMD for acetamidinate, EtAMD for propionic- amidinate and nPrAMD for butanoic-amidinate. The employed amidines are known in the literature.

[0080] Example 1 : Sc(Et2-fAMD)3

[0081] Tris(N,N’-diethyl-formamidinato)scandium; compound of formula (1) with RN1= RN2= ethyl.

[0082] 1H NMR (500 MHz, C6D6) 6 8.08 (s, 3H), 3.14 (q, J = 7.2 Hz, 12H), 1.18 (t, J = 7.2 Hz, 18H).

[0083] TGA: Ti% = 98 °C, Tso%=196 °C, mRest<1 %

[0084] DSC. Tmelting point—27 C, Tdecomposition onset—350 °C

[0085] Vapor Pressure: Lg(p(Pa)) = -2988.7(1 / T(K)) + 10.219 T orr = 96 °C

[0086] Example 2: Sc(nPr2-fAMD)s

[0087] Tris(N,N’-di-n-propyl-formamidinato)scandium; compound of formula (1) with RN1= RN2= n-propyl.

[0088] 1H NMR (500 MHz, C6D6) 6 8.10 (s, 3H), 3.11 (t, J = 6.8 Hz, 12H), 1.58 (h, J = 7.2

[0089] Hz, 12H), 0.96 (t, J = 7.4 Hz, 18H).

[0090] TGA: Ti% = 128 °C, T50%= 231 °C, mRest< 1 %

[0091] DSC. Tmelting point— —22 C, Tdecomposition onset—287 °C

[0092] Vapor Pressure: Lg(p(Pa)) = -3457.2(1 / T(K)) + 10.534 TiTorr = 138 °C

[0093] Comparative Example 1 : Sc(Et,Me-MeAMD)3

[0094] Tris(N-methyl-N’-ethyl-acetamidinato)scandium; compound according to US 2023 / 0058025 A1 , corresponding to a compound of formula (1) with RN1= methyl, RN2= ethyl, but having a methyl substituent on the carbon atom.

[0095] 1H NMR (500 MHz, C6D6) 5 3.24 - 3.10 (m, 6H), 3.01 - 2.93 (m, 9H), 1.62 - 1.51 (m, 9H), 1.38 - 1.21 (m, 9H).

[0096] TGA: Ti% = 123 °C, T50%= 215 °C, mRest= 9.3 %

[0097] DSC. Tmelting point — 76 C, Tdecomposition onset — 265 °C (no clear peak)

[0098] Vapor Pressure: Lg(p(Pa)) = -3832.7(1 / T(K)) + 11.868 TiTorr = 120 °C

[0099] Comparative Example 2: Sc(Et2-EtAMD)s Tris(N,N’-diethyl-propionic-amidinato)scandium; compound according to

[0100] KR 102614467 B1 , corresponding to a compound of formula (1) with RN1= RN2= ethyl, but having an ethyl substituent on the carbon atom.

[0101] 1H NMR (500 MHz, C6D6) 5 3.24 (q, J = 7.2 Hz, 12H), 2.16 (q, J = 7.7 Hz, 6H), 1.27 (t, J = 7.2 Hz, 18H), 1.00 (t, J = 7.7 Hz, 9H).

[0102] TGA: Ti% = 116 °C, Tso% = 243 °C (determined under the same conditions as for examples 1 and 2; 232 °C under conditions according to prior art), m^st < 1 % Tmeiting point > room temperature

[0103] Comparative Example 3: Sc(Et2-nPrAMD)s

[0104] Tris(N,N’-diethyl-butanoic-amidinato)scandium; compound according to KR 102614467 B1 , corresponding to a compound of formula (1) with RN1= RN2= ethyl, but having an n-propyl substituent on the carbon atom.

[0105] TGA: Tso% = 246 °C (according to prior art).

[0106] Comparative Example 4: Sc(iPr2-fAMD)s

[0107] Tris(N,N’-di-iso-propyl-formamidinato)scandium; commercial compound, corresponding to a compound of formula (1) with RN1= RN2= isopropyl.

[0108] 1H NMR (500 MHz, C6D6) 5 8.18 (s, 3H), 3.17 (hept, J = 6.4 Hz, 6H), 1.23 (d, J = 6.5 Hz, 36H).

[0109] TGA: Ti% = 151 °C, T50% = 236 °C, mRest< 1 %

[0110] DSC. Tmeiting point — 269 C, Tdecomposition onset — 390 C, further endothermic peak at 146 °C.

[0111] Vapor Pressure: Lg(p(Pa)) = -4283.7(1 / T(K)) + 12.176 TiTorr = 153 °C

[0112] Analysis by TGA

[0113] TGA curves were determined for the compounds of examples 1 and 2 and comparative examples 1 , 2 and 4. The samples were heated with a heating ramp of 10 K min-1at an Ar flow of 20 ml min-1. The sample mass of each compound was 10 mg for the TGA experiment. The TGA curves are shown in Figure 1.

[0114] Discussion of results

[0115] The evaporation temperature (Tso%, i.e. temperature for 50 % mass loss) is compared in Table 1 for the inventive compounds as well as the comparative compounds. As can be seen for comparative example 2, the value cited in the prior art differs from the measured value, but it is known that the value depends from the exact conditions used for the TGA analysis. As the TGA for examples 1 and 2 and comparative examples 1, 2 and 4 is done under identical conditions, the obtained values can be directly compared to each other.

[0116] The inventive compounds have the advantage over the compound of comparative example 1 that they can be evaporated essentially without decomposition, which becomes evident from a residual mass of less than 1 %. In contrast, there is considerable decomposition of the compound of comparative example 1, which can be seen from a residual mass of more than 9 % (see also Figure 1).

[0117] The inventive compounds furthermore have the advantage over the compounds of comparative examples 2, 3 and 4 that they have a lower evaporation temperature, which is particularly pronounced for the compound of example 1.

[0118] The inventive compound 2 is the only compound which is liquid at room temperature while compound 1 has a melting point slightly above room temperature and the compounds of comparative examples 1, 2 and 4 are solid at room temperature. The only other reported compound which is liquid at room temperature in KR 102614467 B1 is the compound in comparative example 3 which however has a lower volatility than the compound in comparative example 2. Thus, inventive compound 2 is the most volatile Sc complex which is also liquid at room temperature.

[0119] Table 1. Comparison of the formamidinate compounds of Examples 1 and 2 with the compounds from comparative examples 1 to 4 in terms of 50 % mass loss (Tso%). value according to prior art value according to own measurements under same conditions as for examples 1 and 2 and comparative examples 1 and 4 ALD Experiments

[0120] Experimental:

[0121] The depositions were carried out using a Picosun R-200 Advanced tool on 2” Si(100) wafers with native oxide. The precursor Sc(Et2-fAMD)3 was used, with a delivery temperature set to 100 °C and an argon carrier gas flow of 10 seem. Ozone (O3) was used as the co-reactant, generated by an Anseros COM-AD-04 ozone generator at 50% power and an O2 flow of 800 seem. The tool is equipped with a Film Sense FS-1 in-situ ellipsometer to monitor the process, and the film thickness is determined using a Cauchy model. The refractive index was determined from ex-situ measurements and set to 1.94. The film thickness of the deposited films was further examined via ex-situ ellipsometry using a J. A. Woollam M2000D ellipsometer. Measurements were taken at five points on the 2” wafer at three different angles (65°, 70°, and 75°), and both the thickness and refractive index were determined using an oscillator model. The median of the measurements was used to optimize the process.

[0122] ALD Example 1 : Thermal Stability of Sc(Et2-fAMD)s

[0123] For this experiment, the Si(100) wafers with native oxide were first coated with 10 nm scandium oxide, as described in example 3. These scandium oxide coated wafers were used as the substrates for the thermal stability study. In this experiment Sc(Et2-fAMD)3 precursor vapors were delivered to the deposition chamber in a pulsed mode separated by argon purge. For the thermal stability study, Sc(Et2-fAMD)3 was pulsed for 1 s followed by a 70 s Ar purge without using a co-reactant. This pulsing sequence was repeated 50 times. The point at which growth is observed indicates thermal decomposition at the surface (CVD-like growth). Growth was monitored using an in-situ ellipsometer, and the thickness was determined by subtracting the initial precursor absorption from the final thickness. While no growth was observed at 250°C and 300°C, a slight increase was noted over 50 cycles at 350°C. This trend was further confirmed by a clear decomposition of the precursor at a process temperature of 400°C, which resulted in measurable film growth. Thus, the precursor Sc(Et2-fAMD)3 is stable up to 300°C in the ALD process. Fig. 2 shows the result of the thermal stability study.

[0124] ALD Example 2: Saturation study of Sc(Et2-fAMD)s

[0125] In this experiment scandium oxide films were deposited by atomic layer deposition method comprising the following steps: a. providing Si substrate in a reaction vessel; b. introducing into the reaction vessel Sc(Et2-fAMD)3 precursor; c. purging the reaction vessel with argon; d. introducing into the reaction vessel ozone; e. purging the reaction vessel with argon; and f. sequentially repeating steps b through e until a desired thickness of the scandium-containing film is obtained.

[0126] A saturation study of Sc(Et2-fAMD)3 was conducted at 200 °C, 250 °C, and 300 °C. In the study, the precursor pulse time was varied between 0.5 s and 7 s, while the rest of the ALD cycle times were held constant to yield the following pulse / purge sequence: x s (precursor pulse) / 70 s (precursor purge) / 3 s (ozone pulse) / 30 s (ozone purge). At all three investigated temperatures, the precursor reached saturation with a 1 s pulse time, showing very little variation in the measured thicknesses at different pulse times, both in-situ and ex-situ. At a deposition temperature of 200 °C, the precursor saturated with a GPC of 0.43 A; at 250 °C with 0.64 A; and at 300 °C with 0.92 A, thereby proving the ALD-like self-limiting behavior of Sc(Et2-fAMD)3. Fig. 3 shows the results of the saturation study.

[0127] ALD Example 3: Temperature Dependency of the Sc(Et2-fAMD)s / ozone process

[0128] In this experiment scandium oxide films were deposited by atomic layer deposition method comprising the following steps: a. providing Si substrate in a reaction vessel; b. introducing into the reaction vessel Sc(Et2-fAMD)3 precursor; c. purging the reaction vessel with argon; d. introducing into the reaction vessel ozone; e. purging the reaction vessel with argon; and f. sequentially repeating steps b through e until a desired thickness of the scandium-containing film is obtained.

[0129] To demonstrate the temperature dependency of the Sc(Et2-fAMD)3 / C>3 process, the deposition temperature was varied between 150 °C and 400 °C using a 1 s precursor pulse followed by a 70 s purge, while ozone was pulsed for 3 s followed by a 30 s purge. A strong temperature dependency was observed, as the GPC consistently increased with higher deposition temperatures. The following growth rates were found: 0.27 A cycle-1at 150 °C, 0.43 A cycle-1at 200 °C, 0.64 A cycle-1at 250 °C, 0.92 A cycle-1at 300 °C, 1.10 A cycle-1at 350 °C and 1.26 A cycle-1at 400 °C. Growth rates above 1 A / cycle were observed only above 350 °C, when Sc(Et2-fAMD)3 begins to decompose, typically leading to increased growth rates. Fig. 4 shows the results of the temperature dependency study.

Claims

Claims1. Compound of formula (1):Formula (1 ) wherein the symbols used are as follows:RN1, RN2are on each occurrence, identically or differently, ethyl or n-propyl which can also be partially or fully deuterated.

2. Compound according to claim 1, characterized in that all three formamidinate ligands are identical.

3. Compound according to claim 1 or 2, selected from the compounds with(a) RN1= RN2= ethyl;(b) RN1= ethyl and RN2= n-propyl; and(c) RN1= RN2= n-propyl.

4. Method of manufacturing a compound according to one or more of claim 1 to3, characterized in that a compound ScX3with X = F, Cl, Br, I, triflate or tosylate is reacted with a formamidinate salt.

5. Use of a compound according to one or more of claim 1 to 3 for the deposition of a scandium containing film.

6. Method for forming a scandium containing film on at least one surface of a substrate, comprising the steps:(a) providing at least one surface of the substrate in a reaction vessel; and(b) forming a scandium containing film on the at least one surface by a deposition process selected from a chemical vapor deposition (CVD) process and an atomic layer deposition (ALD) process using at least one compound according to one or more of claim 1 to 3 as precursor of a scandium source compound for the deposition process.

7. Method according to claim 6, further comprsing introducing into the reaction vessel at least one co-reactant.

8. Method according to claim 7, characterized in that the co-reactant is selected from the group of water, oxygen, oxygen plasma, ozone, NO, N2O, NO2, CO, CO2, ammonia, hydrazine, monoalkylhydrazine, dialkylhydrazine, nitrogen, nitrogen / hydrogen, ammonia plasma, nitrogen plasma, nitrogen / hydrogen plasma, hydrogen, hydrogen plasma, a mixture of hydrogen and helium, a mixture of hydrogen and argon, hydrogen / helium plasma, hydrogen / argon plasma, boron-containing compounds, silicon-containing compounds and combinations thereof.

9. Method for forming a scandium containing film via an atomic layer deposition (ALD) process or ALD-like process, the method comprising the steps of:(a) providing a substrate in a reaction vessel;(b) introducing into the reaction vessel one or more compounds according to one or more of claims 1 to 3 as precursor;(c) a purging step, in particular purging the reaction vessel with a first purge gas;(d) introducing into the reaction vessel a co-reactant;(e) a purging step, in particular purging the reaction vessel with a second purge gas;(f) sequentially repeating steps (b) through (e) until a desired thickness of the scandium containing film is obtained.

10. Method according to claim 9, characterized in that at least one co-reactant in step (d) is selected from water, O2, O3, NO, N2O, NO2, CO, CO2, ammonia, hydrazine, monoalkylhydrazine, dialkylhydrazine, nitrogen, nitrogen / hydrogen, hydrogen, a mixture of hydrogen and helium, a mixture of hydrogen and argon, hydrogen / helium plasma, boron-containing compounds, silicon- containing compounds and combinations thereof or a plasma of these coreactants.

11. Method according to one or more of claims 6 to 10, characterized in that the compound according to one of more of claims 1 to 3 is introduced into the reaction vessel by vaporization using thermal energy and vacuum.

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