Deposition of ternary oxide films containing ruthenium and alkali earth metals   

The present application is a continuation application of U.S. Non-provisional application Ser. No. 12/411,782, filed Mar. 26, 2009, which claims the benefit of U.S. Provisional Application No. 61/039,516, filed Mar. 26, 2008, each being incorporated herein by reference in its entirety for all purposes.

1. Field of the Invention

This invention relates generally to compositions, methods and apparatus for use in the manufacture of semiconductor, photovoltaic, LCD-TFT, or flat panel type devices. More specifically, the invention relates to methods and compositions for depositing ternary oxide films on a substrate.

2. Background of the Invention

As the design and manufacturing of semiconductor devices continues to evolve, the semiconductor industry is constantly seeking new and novel methods of depositing films onto substrates, such that the resulting film will have certain sought after properties. One example of these properties can be found in metal electrodes to be employed in advanced CMOS technologies together with high-k dielectric films. For the next generation nodes, ruthenium is considered as the best candidate for electrode for FeRAM and DRAM applications, and potentially for MRAM. One reason for this is that the resistibility of ruthenium is lower than iridium and platinum. Additionally, even RuO2 has better conductivity than the two corresponding metal oxides in the case where a metal layer is in contact with high-k layers. Recent researches mentioned the use of ruthenium-based materials, CaRuO3, SrRuO3 and BaRuO3, as an electrode for ferroelectric applications. Ternary oxides such as ARuO3 (A=Ca, Sr and Ba) complexes show perovskite crystal structure and could be grown epitaxially on several types of insulation oxide layers. Hence, it is thought that ARuO3 films may be suitable to be deposited on gate stack structures. Furthermore, such films have suitable metallic conductivity.

As the size of chip becomes smaller and smaller, each layer deposited thereon should be thinner and thinner, making deposition techniques such as chemical vapor deposition (CVD) or atomic layer deposition (ALD) desirable to deposit these layers.

A large variety of Ru precursors are available and many have been studied in CVD or ALD mode. However, most of them have recurrent drawbacks: low vapor pressure (e.g. 0.25 Torr at 85° C. for Ru(EtCp)2), high impurity contents of the obtained films (e.g. carbon and oxygen in most of the cases), long incubation time, poor adherence, and non-uniformity in deep trenches.

In some cases, precursors are not liquid and need to be dissolved in a solvent or mixture of solvents to allow an easy delivery of the vapors to the reaction chamber Moreover, the solvents that are used are usually toxic and/or flammable and their usage brings many constraints (safety aspects, environmental issues). Besides, the use of precursors with melting points higher than 20° C. implies many additional constraints during the process deposition (heating of the delivery lines to avoid condensation of the precursor at undesired locations) and during the transportation.

The number of known strontium and barium precursors available for vapor deposition is low compared to ruthenium. Many strontium and barium precursor are solid with a high melting point (above 200° C.), and their vapor pressure is low, which generates throughput and equipment issues. Stability may also a problem because the temperature at which the precursor reacts with an oxidizing agent corresponds to its decomposition temperature.

Consequently, there exists a need for ruthenium precursors with good reactivity and incubation time properties, which can be combined with alkali earth metal precursors which have a melting point less than about 200° C. to form ternary oxide films, and which precursors may be dissolved in a suitable solvent to aid in the deposition process.

SUMMARY

In an embodiment, a method for forming a ternary oxide film on one or more substrates comprises providing at least one substrate disposed in a reactor. A ruthenium precursor in vapor form is introduced into the reactor, where the ruthenium precursor is either ruthenium tetraoxide or a precursor with the general formula:

(L)mRu(L′)n

wherein L is an unsaturated, cyclic or linear, η4-η6 type hydrocarbon ligand; L′ is a linear or branched ligand, independently selected from a carbonyl, an amidinate, a β-diketonato, an alkyl, an alkoxy, hydrogen, an alkylamino; a halogen; diketimine; an enaminoketones; diazabutadiene; ethyleamine; or formamidine; and 0≦n or m≦3. An alkali earth metal precursor in vapor form is introduced into the reactor, where the alkali earth metal precursor has the general formula:

A(RxCp)2R′y

wherein A is either calcium, strontium, or barium; R is a linear or branched ligand selected from a C1-C4 alkyl group, an alkoxy, a silyl, or a halogen; R′ is a linear or cyclic hydrocarbon ligand which contains N, P, or O; 0≦x≦5; and 0≦y≦2. At least part of the ruthenium and alkali earth metal precursors are deposited to form a ternary oxide film on at least one of the substrates.

Other embodiments of the current invention may include, without limitation, one or more of the following features: the L ligand comprises a substituted or unsubstituted ligand selected from: butadiene; butadienyl; cyclopentadiene; cyclopentadienyl; pentadiene; pentadienyl; hexadiene; hexadienyl; cyclohexadiene; cyclohexadienyl; heptadiene; heptadineyl; norbornadiene; octadiene; cylcooxtadiene; and cyclooctadienyl; the R′ ligand comprises a ligand selected from: tetrahydrofuran; dioxane; dimethoxyethane; dimethoxyethane; and pryridine; the alkali earth metal precursor has a melting point less than about 100° C., and is preferably a liquid at about 25° C.; the ruthenium precursor is selected from: ruthenium tetraoxide; ruthenium(cyclopentadienyl)2; ruthenium(methylcyclopentadienyl)2; ruthenium(ethylcyclopentadienyl)2; ruthenium(isopropylcyclopentadienyl)2; ruthenium(CO)3(1-methyl-1,4-cyclohexadien2); ruthenium(2,6,6-trimethylcyclohexadienyl)2; ruthenium(dimethylpentadienyl)2; (cyclopentadienyl)ruthenium(dimethylpentadienyl); (ethylcyclopentadienyl)ruthenium(dimethylpentadienyl); ruthenium(toluene)(1,4-cyclohexadiene); (cyclopentadienyl)ruthenium(amidinate); and ruthenium(CpMe5)(iPr-amindate). the alkali earth metal precursor is selected from: Ca(MeCp)2(THF)z; Sr(MeCp)2(THF)z; Ba(MeCp)2(THF)z; Ca(MeCp)2(DME)z; Sr(MeCp)2(DME)z; Ba(MeCp)2(DME)z Ca(MeCp)z; Sr(MeCp)z; Ba(MeCp)z; Ca(EtMeCp)2(THF)z; Sr(EtCp)2(THF)z; Ba(EtCp)2(THF)z; Ca(EtCp)2(DME)z; Sr(EtCp)2(DME)z; Ba(EtCp)2(DME)z; Ca(EtCp)z; Sr(EtCp)2, Ba(EtCp)2, Ca(iPrCp)2(THF)n, Sr(iPrCp)2(THF)z; Ba(iPrCp)2(THF)z; Ca(iPrCp)2(DME)z; Sr(iPrCp)2(DME)z; Ba(iPrCp)2(DME)z; Ca(iPrCp)2, Sr(iPrCp)2, Ba(iPrCp)2, Ca(iPr3Cp)2(THF)z; Sr(iPr3Cp)2(THF)z; Ba(iPr3Cp)2(THF)z; Ca(iPr3Cp)2(DME)z; Sr(iPr3Cp)2(DME)z; Ba(iPr3Cp)2(DME)z; Ca(iPr3Cp)2, Sr(iPr3Cp)2, Ba(iPr3Cp)2, Ca(tBuCp)2(THF)z; Sr(tBuCp)2(THF)z; Ba(tBuCp)2(THF)z; Ca(tBuCp)2(DME)z; Sr(tBuCp)2(DME)z; Ba(tBuCp)2(DME)z; Ca(tBuCp)2, Sr(tBuCp)2, Ba(tBuCp)2, Ca(tBu3Cp)2(THF)z; Sr(tBu3Cp)2(THF)z; Ba(tBu3Cp)2(THF)z; Ca(tBu3Cp)2(DME)z; Sr(tBu3Cp)2(DME)z; Ba(tBu3Cp)2(DME)z; Ca(tBu3Cp)2, Sr(tBu3Cp)2, and Ba(tBu3Cp)2; and wherein 0≦z≦3; the alkali earth metal precursor is initially supplied dissolved in a solvent, and the solvent has a boiling point greater than the melting point of the precursor; the solvent has a boiling point greater than 100° C., preferably greater than about 150° C.; an oxygen containing reactant is introduced into the reactor, and the reactant is selected from: O2; O3; H2O; H2O2; N2O; NO; NO2; and mixtures thereof; the ternary oxide film is deposited through either a chemical vapor deposition (CVD) process or through an atomic layer deposition process; the deposition process is performed at a temperature between 100° C. and about 500° C.; and the ternary film is treated post deposition in an oxidizing atmosphere, and the treatment is at a temperature higher than that of the deposition process.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

Certain terms are used throughout the following description and claims to refer to various components and constituents. This document does not intend to distinguish between components that differ in name but not function.

As used herein, the term “alkyl group” refers to saturated functional groups containing exclusively carbon and hydrogen atoms. Further, the term “alkyl group” may refer to linear, branched, or cyclic alkyl groups. Examples of linear alkyl groups include without limitation, methyl groups, ethyl groups, propyl groups, butyl groups, etc. Examples of branched alkyls groups include without limitation, t-butyl. Examples of cyclic alkyl groups include without limitation, cyclopropyl groups, cyclopentyl groups, cyclohexyl groups, etc.

As used herein, the abbreviation, “Me,” refers to a methyl group; the abbreviation, “Et,” refers to an ethyl group; the abbreviation, “t-Bu,” refers to a tertiary butyl group; and the abbreviation “Cp” refers to a cyclopentadienyl group.

As used herein, the term “independently” when used in the context of describing R groups should be understood to denote that the subject R group is not only independently selected relative to other R groups bearing different superscripts, but is also independently selected relative to any additional species of that same R group. For example in the formula MR1x(NR2R3)(4-x) where x is 2 or 3, the two or three R1 groups may, but need not be identical to each other or to R2 or to R3. Further, it should be understood that unless specifically stated otherwise, values of R groups are independent of each other when used in different formulas.

Embodiments of the present invention provide novel methods and compositions for the deposition of a ternary oxide film on a substrate. In general, the compositions and methods utilize a ruthenium precursor and an alkali earth metal precursor.

In some embodiments, the ruthenium precursor may have the general formula:

where M is ruthenium; L is a substituted or unsubstituted ligand selected from butadiene, butadienyl, cyclopentadiene, cyclopentadienyl, pentadiene, pentadienyl, hexadiene, hexadienyl, cyclohexadiene, cyclohexadienyl, heptadiene, heptadineyl, norbornadiene, octadiene, cylcooxtadiene, and cyclooctadienyl; L′ is a linear or branched ligand selected from a carbonyl, a carbine, an amidinate, a β-diletonato, an alkyl, an alkoxy, hydrogen, an alkylamino; a halogen; diketimine; an enaminoketones; diazabutadiene; ethyleamine; and formamidine; and 0≦n or m≦3.

In some embodiments the alkali earth metal precursor may have the general formula:

wherein A is calcium, strontium, or barium; R is a linear or branched ligand selected from an alkyl group (e.g. Me, Et, nPr, IPr, nBu, tBu), an alkoxy, a silyl and a halogen; R′ is a linear or cyclic hydrocarbon ligand which contains N, P or O (e.g. tetrahydrofuran, dioxane, dimethoxyethane, dimethoxyethane, pyridine); and 0≦y≦2.

In some embodiments, either the ruthenium precursor or the alkali earth metal precursor may be dissolved in a solvent. In these embodiments, the solvent should have a boiling point greater than 100° C., preferably greater than about 150° C. The solvent may be distilled under an inert gas (e.g. nitrogen, argon, etc) to remove moisture and/or dissolved oxygen. Typically, the solvent should have good affinity with the precursors at room temperature, and have as a property a boiling point greater than the melting point of the precursor itself. Table 1 lists an non-exhaustive list of suitable solvents.

TABLE 1 Examples of solvents Vis- cosity Formula b.p. Density [cP] @ Name (F.W.) [C.] [g/cm3] 25 C. Octane C8H8 (114.23) 125 0.7 0.51 Toluene C6H5CH3 (92.14) 111 0.87 0.54 Xylene C6H4(CH3)2 (106.16) 138.5 0.86 0.6 Mesitylene C6H3(CH3)3 (120.2) 165 0.86 0.99 Ethylbenzene C6H5C2H5 (106.17) 136 0.87 0.67 Propylbenzene C6H5C3H7 (120) 159 0.86 0.81 Ethyl toluene C6H4(CH3)(C2H5) (120.19) 160 0.86 0.63 Ethylcyclohexane C6H11C2H5 (112) 132 0.78 Propylcyclohexane C6H11C3H7 (126.1) 156.8 0.79 0.85 Tetrahydrofuran C4H8O (72.11) 66 0.89 0.46 Dioxane C4H8O2 (88.11) 101.1 1.03 1.2 1,2-diethoxyethane C2H5O(CH2)2OC2H5 121 0.8 (118.17) Diethylene glycol CH3O(CH2)2O(CH2)2OCH3 162 0.95 1.1 dimethylether (134.2) Ethoxybenzene C6H5OC2H5 (122.17) 173 0.96 1.1 Pyridine

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