US 5,820,664 AGrant
Precursor Compositions for Chemical Vapor Deposition, and Ligand Exchange Resistant Metal-Organic Precursor Solutions Comprising Same
Issue Date:1998-10-13
•19 Claims
Abstract
A metal source reagent liquid solution, comprising: (i) at least one metal coordination complex including a metal to which is coordinatively bound at least one ligand in a stable complex, wherein the ligand is selected from the group consisting of: .beta.-diketonates, .beta.-ketoiminates, .beta.-diiminates, C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, C.sub.1 -C.sub.8 alkoxy, and fluorinated derivatives thereof; and (ii) a solvent for the metal coordination complex. The solutions are usefully employed for chemical vapor deposition of metals from the metal coordination complexes, such as Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Al, Tl, Er, Sn, Pb, Tm, Bi, and/or Yb. The solvent may comprise glyme solvents, alkanols, organic ethers, aliphatic hydrocarbons, and/or aromatic hydrocarbons. Solutions of the invention having two or more metal coordination complexes are resistant to detrimental ligand exchange reactions which adversely affect the stability and/or volatilizability of the metal complex for CVD applications.
Metadata
Assignee
- Advanced Technology Materials, Inc.
Inventors
- Robin A. Gardiner
- Peter S. Kirlin
- Thomas H. Baum
- Douglas Gordon
- Timothy E. Glassman
- Sofia Pombrik
- Brian A. Vaartstra
Application Information
Application Number:US 4145046
Filing Date:1995-03-31
Priority Date:1990-07-06
Art Unit:171
Classifications
IPC:
C09K 300C23C 1640
Field of Search:
252106423556562182.23287.17;287.19DIG. 1444;55;114;175607
Patent Drawings
This patent does not have any drawings.
Description
Background of the Invention
1. Field of the Invention
The present invention generally relates to metal-organic source reagent compositions of a type which are usefully employed for deposition processes such as chemical vapor deposition (CVD), and to liquid compositions containing same which are resistant to non-degenerative ligand exchange.
2. Description of the Related Art
Chemical vapor deposition of multicomponent material systems requires delivery of multiple source reagents to the CVD reactor. A particularly advantageous way of delivering multiple source reagents is to accurately mix neat liquid source reagents or liquid solutions of source reagents and then flash vaporize the mixture and deliver the resulting vapor to the reactor. It is possible in this situation for the reagents to undergo reactions, either in the liquid phase before vaporization or in the gas phase after vaporization. If these reactions convert a source reagent to an insoluble or non-volatile product, or to a material of different chemical or physical properties, then the elements contained in that product will not reach the substrate and the stoichiometry of the deposited film will be incorrect.
Examples of this problem (wherein Et is ethyl; tBu is tert-butyl; iPr is isopropyl; and thd is tetramethylheptanedionate) include the following:
(i) during deposition of PbZr.sub.x Ti.sub.1-x O.sub.3, using (Et).sub.4 Pb, Zr(OtBu).sub.4, and Ti(OiPr).sub.4 source reagents, ligand exchange between the Zr and Ti reagents resulted in formation of Zr(OiPr).sub.4 (and perhaps other products of which Zr(OiPr).sub.4 is a monomer), which had very low volatility and which condensed in the gas manifold or vaporizer;
(ii) when solutions of Ba(thd).sub.2 and Ti(OiPr).sub.4 were mixed prior to vaporization, an insoluble precipitate was formed, presumably Ba(OiPr).sub.2 ; and
(iii) when solutions of Pb(thd).sub.2 and Ti(OiPr).sub.4 were mixed in butyl acetate, the reagents reacted to form compounds of differing physical properties, such as Pb(OiPr).sub.2 and Ti(OiPr).sub.2 (thd).sub.2.
Another specific example illustrating this problem is the preparation of films of strontium bismuth tantalate and strontium bismuth niobate (SrBi.sub.2 Ta.sub.2 O.sub.9 and SrBi.sub.2 Nb.sub.2 O.sub.9) by CVD for use in non-volatile ferroelectric random access memories. The most commonly used strontium source reagents are .beta.-diketonate complexes such as Sr(thd).sub.2. When a solution is heated containing the following source reagents for deposition of SrBi.sub.2 Ta.sub.2 O.sub.9 :
the ethoxide ligands of the tantalum reagent exchange with the thd ligands of the strontium reagent, leading to the formation of undesirable strontium alkoxide species that have reduced volatility and that can decompose in the vaporization zone. Alternatively, when these reagents are provided separately in bubblers, similar ligand exchange reactions occur in the gas phase; the resulting solids constrict the gas lines or alter the film stoichiometry.
In certain instances, such problems can be avoided by using identical ligands on the metals to make ligand exchange a degenerate reaction (i.e., where the exchanging ligand is identical to the original ligand). Examples of this approach include the use of tetraethylorthosilicate, triethylborate and triethylphosphite for deposition of borophosphosilicate glasses (J. Electrochem. Soc., 1987, 134(2), 430). In many instances, however, this method for avoiding the problem is not possible because the appropriate compound does not exist, is too unstable or involatile to be used for CVD, or otherwise has disadvantageous physicochemical material properties. For example, for deposition of PbZr.sub.x Ti.sub.1-x O.sub.3, a reagent system with identical ligands is problematic because while Pb(thd).sub.2 and Zr(thd).sub.4 are stable and volatile, Ti(thd).sub.4 does not exist and Ti(thd).sub.3 is extremely air sensitive. Similarly, while Ti(OtBu).sub.4 and Zr(OtBu).sub.4 are stable and volatile, Pb(OtBu).sub.2 is thermally unstable at temperatures required for volatilization.
The foregoing problems are also encountered in the circumstance where the metal source reagent is provided in a liquid solution and the solvent contains moieties which react with ligands of the source reagent compound to produce undesirable ligand exchange reaction by-products which display different physical properties and are involatile or insoluble.
Accordingly, it is an object of the present invention to provide improved metal source reagent compositions which are amenable to use in the deposition of corresponding metals and metal oxides.
It is another object of the invention to provide improved metal source reagent compositions in liquid or solution form, to simultaneously deliver the constituent metal(s) to a deposition locus such as a chemical vapor deposition chamber.
It is a further object of the present invention to provide liquid compositions of such type which are resistant to deleterious ligand exchange reactions.
Other objects and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims.
Summary of the Invention
The present invention generally relates to metal-organic source reagent-containing liquid compositions for chemical vapor deposition (CVD) processes involving deposition of the metal in the source reagent. The liquid compositions are stabilized in character, meaning that the metal-organic source reagent therein is resistant to degradation via ligand exchange reactions, e.g., non-degenerative ligand exchanges which adversely affect the chemical identity and suitability of the reagent compositions for CVD applications.
In a broad aspect, the present invention relates to a metal source reagent liquid solution, comprising:
(i) at least one metal coordination complexes, each of such metal coordination complexes including a metal coordinatively binding at least one ligand in a stable complex, wherein such at least one ligand is selected from the group consisting of .beta.-diketonates and .beta.-ketoesters, and their sulfur and nitrogen analogs (i.e., corresponding ligands containing S or N atoms in place of the O atom(s) in the .beta.-diketonates and .beta.-ketoesters); and
(ii) a solvent for such metal coordination complexes.
A generalized formula for each of such metal coordination complexes is
wherein:
M is a metal selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Al, Tl, Er, Sn, Pb, Tm, Bi, and Yb;
A is selected from the group consisting of .beta.-diketonates and .beta.-ketoesters, and their sulfur and nitrogen analogs;
R is selected from the group consisting of C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, and (fully or partially) fluorinated derivatives thereof (i.e., wherein hydrogen substituent(s) of the C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, or C.sub.6 -C.sub.10 aryl ligand, is/are replaced by fluorine substituent(s));
B is selected from the group consisting of polyethers, polyamines, polythiols, bipyridines, glymes, alcohols, crown ethers, crown thioethers, cyclic polyamines (cyclenes), thioglymes, arylthiols, and aliphatic thiols (mercaptans).
Q is hydrocarbyl or halohydrocarbyl, e.g., a ligand selected from the group consisting of C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, and fluorinated derivatives thereof;
a, x, y, and z are stoichiometric coefficients for the ligands A, OR, B, and Q, respectively, wherein a is .gtoreq.1; each of x, y, and z is independently .gtoreq.0; and A.sub.a (OR).sub.x B.sub.y Q.sub.z is in stoichiometric relationship to metal M.
Thus, each of the metal complexes in the solutions of the invention comprises at least one ligand A coordinated to the central atom M of the complex, and M may optionally have additionally coordinated thereto one or more of the ligands OR, B, and Q, in which the resulting complex is appropriately stoichiometrically constituted to define a stable complex.
One class of source reagent complexes usefully employed in reagent solutions according to the invention comprise those of the formula:
wherein:
a, x, M and R are as defined hereinabove;
R.sup.2 and R.sup.3 are independently selected from C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, and fluorinated derivatives thereof; and
G is oxygen, sulfur, or nitrogen moiety of the formula .dbd.NR.sub.b in which Rb is selected from the group consisting of H, C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, and fluorinated derivatives thereof.
The metal utilized as the coordination atom in the complexes of the invention may comprise any suitable metal to which the specific ligand species is coordinatively bondable, and preferably comprises a metal selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Al, Tl, Er, Sn, Pb, Tm, Bi, and Yb. Most preferably, the metal utilized as the coordination atom in the complexes of the invention comprises a metal selected from the group consisting of Mg, Ca, Sr, Ba, Y, La, Ti, Zr, Hf, V, Nb, Ta, Cr, Mn, Ru, Ir, Cu, Al, Sn, Er, Pb, and Bi.
The solvent utilized in the source reagent solutions of the invention may comprise any suitable solvent species, or combination of solvent species, with which the metal complexes are compatible, such as aliphatic hydrocarbons, aromatic hydrocarbons, ethers, esters, nitrites, and alcohols. The solvent component of the solution preferably comprises a solvent selected from the group consisting of: glyme solvents having from 1 to 20 ethoxy --(C.sub.2 H.sub.4 O)-- repeat units; C.sub.2 -C.sub.12 alkanols, organic ethers selected from the group consisting of dialkyl ethers comprising C.sub.1 -C.sub.6 alkyl moieties, C.sub.4 -C.sub.8 cyclic ethers; C.sub.12 -C.sub.60 crown O.sub.4 -O.sub.20 ethers wherein the prefixed C.sub.i range is the number i of carbon atoms in the ether compound and the suffixed O.sub.i range is the number i of oxygen atoms in the ether compound; C.sub.6 -C.sub.12 aliphatic hydrocarbons; C.sub.6 -C.sub.18 aromatic hydrocarbons; organic esters; organic amines; and polyamines.
As used herein, the term "stable complex" means that the metal source complex in a pure state (unexposed to other materials, such as water, oxygen, etc.) is not susceptible to spontaneous degradation or decomposition at 25 degrees Centigrade and 1 atmosphere pressure. The term "complex" is intended to be broadly construed to encompass compounds as well as coordination complexes wherein at least one metal atom is coordinated (covalently, ionically and/or associatively) to at least one organic ligand group.
In another aspect, the present invention relates to a metal source reagent liquid solution, comprising metal source reagent and solvent medium selected from the group, set out in Table I below, consisting of:
wherein when the solvent medium contains multiple components, the percentages specified are percentages by weight, based on the weight of the total solvent medium, and with the percentages of all named solvent components totalling 100%.
In yet another aspect, the present invention relates to a method of forming a metal-containing film on a substrate, comprising providing a metal source reagent solution comprising a metal source reagent and solvent medium of the type described hereinabove, volatilizing the metal source reagent liquid solution to yield a metal source vapor, and contacting the metal source vapor with the substrate, to deposit the metal-containing film thereon.
In a preferred aspect of the invention, the composition of the metal-containing film, metal source reagent, and solvent medium, are selected from the group, set out in Table II below, consisting of:
In yet another aspect, the present invention relates to a source reagent liquid solution comprising:
(i) at least one, and preferably at least two, metal coordination complexes, each of the formula:
wherein:
M is a metal selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Al, Tl, Er, Sn, Pb, Tm, Bi, and Yb;
A is selected from the group consisting of .beta.-diketonates and .beta.-ketoesters, and their sulfur and nitrogen analogs;
R is selected from the group consisting of C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, and (fully or partially) fluorinated derivatives thereof (i.e., wherein hydrogen substituent(s) of the C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, or C.sub.6 -C.sub.10 aryl ligand, is/are replaced by fluorine substituent(s));
B is selected from the group consisting of polyethers, polyamines, polythiols, bipyridines, glymes, alcohols, crown ethers, crown thioethers, cyclic polyamines (cyclenes), thioglymes, arylthiols, and aliphatic thiols (mercaptans).
Q is hydrocarbyl or halohydrocarbyl, e.g., a ligand selected from the group consisting of C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, and fluorinated derivatives thereof;
a, x, y, and z are stoichiometric coefficients for the ligands A, OR, B, and Q, respectively, wherein a is .gtoreq.1; each of x, y, and z is independently .gtoreq.0, and A.sub.a (OR).sub.x B.sub.y Q.sub.z is in stoichiometric relationship to metal M; and
(ii) a solvent for the metal coordination complex(es).
The present invention in another aspect relates to solutions containing compounds comprised of .beta.-diketonate and/or alkoxide ligands having a metal M, e.g., selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Al, Tl, Er, Sn, Pb, Tm, Bi, and Yb, complexed to at least one alkoxide ligand and at least one .beta.-diketonate ligand.
Such compounds may have the general formula:
wherein:
G is oxygen, sulfur, or imide of the formula: .dbd.NR.sub.b, wherein R.sub.b is H, C.sub.1 -C.sub.8 alkyl, or C.sub.1 -C.sub.8 perfluoroalkyl (e.g., trifluoroethyl);
x+y=p where p is the valence of metal M;
x+2y=q where q is the coordination number of the metal M;
R.sup.1 is C.sub.1 -C.sub.6 hydrocarbyl or fluoroalkyl;
R.sup.2 and R.sup.3 are independently selected from C.sub.1 -C.sub.14 hydrocarbyl, C.sub.1 -C.sub.6 alkoxy, and C.sub.2 -C.sub.6 fluoroalkyl groups, wherein hydrocarbyl groups may be selected from C.sub.1 -C.sub.8 alkyl, C.sub.6 -C.sub.10 cycloalkyl, C.sub.2 -C.sub.12 alkenyl and C.sub.6 -C.sub.14 aryl groups, and C.sub.1 -C.sub.6 fluoroalkyl groups may be selected from perfluoroalkyls of 2 through 6 carbons.
As used herein, the following terms have the following meanings: acac=acetylacetonate, more specifically 2,4-pentane dionate; hfacac=hexafluoroacetylacetonate, more specifically 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; tfacac=trifluoroacetylacetonate, more specifically 1,1,1-trifluoro-2,4-pentanedionate; thd=tetramethylheptanedionate, as hereinabove identified, and more specifically 2,2,6,6-tetramethyl-3,5-heptanedionate; fod=fluorodimethyloctanedionate, more specifically 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedionate; hfod=heptafluoro -dimethyloctanedionate; and tg=tetraglyme.
When identified herein by reference to generalized formulas, the copper oxide compound formulas YBaCuO, BaCaCuO, and BiSrCaCuO are intended to be construed to encompass the corresponding stoichiometrically appropriate specific stoichiometries (i.e., specific stoichiometric coefficients w, x, y, and z) of the metal moieties, in relation to the other metal components and the oxygen constituent of such compounds, that yield stable forms of the metal oxide compounds at 25.degree. C. and 1 atmosphere pressure. More generally, various reagents and deposited products may be referred to sometimes hereinafter by alphabetic acronyms based on their constituent elements or moieties, e.g., PZT for lead zirconium titanate, BST for barium strontium titanate, etc., and in such case, such acronymic designations are intended to be broadly construed to encompass all suitable stoichiometric forms of the composition under consideration.
It is to be appreciated that the compositions disclosed herein, in respect of constituent components and/or moieties of such compositions, may comprise, consist, and/or consist essentially of, such constituent components and/or moieties.
Other aspects and features of the invention will be more fully apparent from the ensuing disclosure and appended claims.
Detailed Description of the Invention, and Preferred Embodiments Thereof
The disclosures of the following prior applications and appertaining patents hereby are incorporated herein in their entirety: U.S. application Ser. No. 08/280,143 filed Jul. 25, 1994 and now U.S. Pat. No. 5,536,323; U.S. patent application Ser. No. 07/927,134, filed Aug. 7, 1992 and now abandoned; U.S. patent application Ser. No. 07/807,807, filed Dec. 13, 1991, now issued as U.S. Pat. No. 5,204,314; U.S. patent application Ser. No. 07/549,389, filed Jul. 6, 1990 and now abandoned; U.S. application Ser. No. 08/181,800 filed Jan. 15, 1994 and now U.S. Pat. No. 5,453,494; U.S. application Ser. No. 07/981,141 filed Jul. 22, 1992 and now abandoned; U.S. application Ser. No. 07/615,303 filed Nov. 19, 1990 and now abandoned; U.S. application Ser. No. 07/549,389 filed Jul. 6, 1990 and now abandoned; U.S. application Ser. No. 07/581,631 filed Sep. 12, 1990 in the names of Peter S. Kirlin, et al., and issued Jul. 6, 1993 as U.S. Pat. No. 5,225,561.
The present invention generally relates to metal-organic source reagent compositions having utility for chemical vapor deposition (CVD) processes, and to liquid compositions containing such metal-organic source reagent compositions, which are resistant to deleterious ligand exchange. More specifically, the metal source reagent compositions of the present invention comprise compounds or coordination complexes in which the metal atoms are coordinated to ligand species which are organic in character.
The invention contemplates metal source reagent liquid solutions, comprising: (i) at least one metal coordination complex including a metal, to which is coordinatively bound at least one ligand in a stable complex, wherein the ligand is selected from the group consisting of: .beta.-diketonates, .beta.-ketoiminates, .beta.-diiminates, C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, C.sub.1 -C.sub.8 alkoxy, as well fluorinated derivatives of the foregoing ligands; and (ii) a solvent for such metal coordination complex, preferably a solvent selected from the group consisting of: glyme solvents having from 1 to 20 ethoxy --(C.sub.2 H.sub.4 O)-- repeat units; C.sub.2 -C.sub.12 alkanols, organic ethers selected from the group consisting of dialkyl ethers comprising C.sub.1 -C.sub.6 alkyl moieties, C.sub.4 -C.sub.8 cyclic ethers; C.sub.12 -C.sub.60 crown O.sub.4 -O.sub.20 ethers; C.sub.6 -C.sub.12 aliphatic hydrocarbons; C.sub.6 -C.sub.18 aromatic hydrocarbons; organic esters; organic amines; and polyamines.
The metal constituent of the metal source complexes of the present invention may comprise any suitable metal to which the aforementioned ligands are coordinatable, but preferably the metal is selected from the group comprising Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Al, Tl, Er, Sn, Pb, Tm, Bi, and Yb, and most preferably the coordination metal comprises a metal selected from the group consisting of Mg, Ca, Sr, Ba, Y, La, Ti, Zr, Hf, V, Nb, Ta, Cr, Mn, Ru, Ir, Cu, Al, Sn, Er, Pb, and Bi.
The ligand groups of the metal source complexes in the broad practice of the present invention may be variously substituted to realize a wide variety of materials to optimize volatility, stability and film purity. Preferably, when the metal source reagent comprises a multi-component solution including two or more metal source complexes, the ligands of the various metal source complexes should be either (a) identical to result in degenerative ligand exchange (wherein any ligand exchange involves replacement of the ligand group by the same type ligand from another constituent of the multicomponent solution), or (b) resistant to any detrimental non-degenerative ligand exchange in relation to one another which would substantially impair or preclude the efficacy of the metal source complex for its intended purpose.
The ligand groups that are potentially useful in metal source reagents of the present invention include the ligands which are more fully disclosed in U.S. Pat. No. 5,225,561, the disclosure of which hereby is incorporated herein in its entirety.
The metal source reagents are selected for solution applications on the basis of the following criteria: (i) the metal centers in the coordinated complexes should be as coordinatively saturated as possible, and in such respect multidentate ligands are preferred which occupy multiple coordination sites in the source reagent complex; (ii) the ligands preferably comprise sterically bulky groups such as isopropyl, t-butyl, and neopentyl, which prevent close approach of the metal centers and thus hinder ligand exchange reaction which might otherwise occur; and (iii) each of the individual metal source reagents in the solution has a suitable vapor pressure characteristic, e.g., a vapor pressure of at least 0.001 Torr at the temperature and pressure conditions involved in their volatilization.
The solvent medium employed in source reagent solutions in accordance with the present invention may be any suitable organic solvent which is compatible with the metal complexes in the solution, has moderate volatility, and in which high concentrations of the metal complexes can be dissolved. Such solvent medium may suitably comprise one or more solvent species such as: glymes, aliphatic hydrocarbons, aromatic hydrocarbons, organic ethers (including dialkyl, cyclic and crown ethers), dialkyl esters, alkyl nitriles C(.tbd.NR.sub.b, wherein R.sub.b is H, C.sub.1 -C.sub.8 alkyl, or C.sub.1 -C.sub.8 perfluoroalkyl, e.g., trifluoroethyl), and alkanols. Among these classes of solvents, preferred solvent species include glyme solvents having from 1 to 20 ethoxy --(C.sub.2 H.sub.4 O)-- repeat units; C.sub.2 -C.sub.12 alkanols, organic ethers selected from the group consisting of dialkyl ethers comprising C.sub.1 -C.sub.6 alkyl moieties, C.sub.4 -C.sub.8 cyclic ethers, and C.sub.12 -C.sub.60 crown O.sub.4 -O.sub.20 ethers wherein the prefixed C.sub.i range is the number i of carbon atoms in the ether compound and the suffixed O.sub.i range is the number i of oxygen atoms in the ether compound; C.sub.6 -C.sub.12 aliphatic hydrocarbons; and C.sub.6 -C.sub.18 aromatic hydrocarbons. Particularly preferred crown ethers include 12-crown-4, 15-crown-5, and 18-crown-6 species.
Preferred metal source reagent species include compounds having as constitutent moieties thereof .beta.-diketonate and alkoxide ligands, and a metal selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Al, Tl, Er, Sn, Pb, Tm, Bi, and Yb, wherein the metal is coordinated to at least one alkoxide ligand and at least one .beta.-diketonate ligand.
Illustrative .beta.-diketonate ligands employed in metal source complexes of the present invention include acac, thd, fod, hfod, tfacac, and hfacac.
By way of example, the metal source reagent liquid solutions of the present invention may suitably comprise metal source reagent and solvent medium species identified in Table III set out below.
The metal source reagent solutions of the present invention may be readily employed in CVD applications for forming a metal-containing film on a substrate, by the steps of volatilizing the metal source reagent liquid solution to yield a metal source vapor, and contacting the metal source vapor with the substrate, to deposit the metal-containing film thereon. Illustrative metal source reagent solutions and corresponding metal-containing film compositions are identified in Table II hereinabove in the "Summary of the Invention" section hereof.
One class of source reagent compositions of the present invention includes source reagent liquid solutions comprising:
(i) at least one, and preferably at least two metal coordination complexes, each of the formula:
wherein:
M is a metal selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Al, Tl, Er, Sn, Pb, Tm, Bi, and Yb;
A is selected from the group consisting of .beta.-diketonates and .beta.-ketoesters, and their sulfur and nitrogen analogs;
R is selected from the group consisting of C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, and (fully or partially) fluorinated derivatives thereof (i.e., wherein hydrogen substituent(s) of the C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, or C.sub.6 -C.sub.10 aryl ligand, is/are replaced by fluorine substituent(s));
B is selected from the group consisting of polyethers, polyamines, polythiols, bipyridines, glymes, alcohols, crown ethers, crown thioethers, cyclic polyamines (cyclenes), thioglymes, arylthiols, and aliphatic thiols (mercaptans).
Q is hydrocarbyl or halohydrocarbyl, e.g., a ligand selected from the group consisting of C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, and fluorinated derivatives thereof;
a, x, y, and z are stoichiometric coefficients for the ligands A, OR, B, and Q, respectively, wherein a is .gtoreq.1; each of x, y, and z is independently .gtoreq.0, and A.sub.a (OR).sub.x B.sub.y Q.sub.z is in stoichiometric relationship to metal M; and
(ii) a solvent for the metal coordination complex(es).
Another class of source reagent solutions according to the present invention contain .beta.-diketonate alkoxide compounds having a metal M selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Al, Tl, Er, Sn, Pb, Tm, Bi, and Yb, complexed to at least one alkoxide ligand and at least one .beta.-diketonate ligand, in which the compounds have the following formula:
wherein:
G is oxygen, sulfur, or imide of the formula: .dbd.NR.sub.b, wherein R.sub.b is H, C.sub.1 -C.sub.8 alkyl, or C.sub.1 -C.sub.8 perfluoroalkyl (e.g., trifluoroethyl);
x+y=p where p is the valence of metal M;
x+2y=q where q is the coordination number of the metal M;
R.sup.1 is C.sub.1 -C.sub.6 hydrocarbyl or fluoroalkyl;
R.sup.2 and R.sup.3 are independently selected from C.sub.1 -C.sub.14 hydrocarbyl, C.sub.1 -C.sub.6 alkoxy, and C.sub.2 -C.sub.6 fluoroalkyl groups, wherein hydrocarbyl groups may be selected from C.sub.1 -C.sub.8 alkyl, C.sub.6 -C.sub.10 cycloalkyl, C.sub.2 -C.sub.12 alkenyl and C.sub.6 -C.sub.14 aryl groups, and C.sub.1 -C.sub.6 fluoroalkyl groups may be selected from perfluoroalkyls of 2 through 6 carbons.
R.sup.1 is preferably C.sub.1 -C.sub.6 alkyl, preferably methyl, ethyl, propyl, n-propyl, i-propyl, n-butyl, s-butyl, or t-butyl, and most preferably ethyl, i-propyl, or t-butyl. R.sup.2 and R.sup.3 are preferably selected from the C.sub.2 -C.sub.6 alkyl or cycloalkyl groups t-butyl, s-butyl, i-propyl, cyclohexyl, or neopentyl, and most preferably t-butyl, s-butyl, or isopropyl.
The various source reagent metal complexes of the invention may be readily made by conventional synthetic techniques, including those more fully described in U.S. Pat. No. 5,225,561, the disclosure of which hereby is incorporated herein by reference. The resulting reagent metal complexes may readily be formulated into solution form, by conventional dissolution and solubilization techniques, for subsequent use as CVD source reagents having good shelf life characteristics and which are substantially stable in storage at ambient conditions (e.g., room temperature). The reagent solutions may subsequently be readily vaporized by suitable reagent delivery systems such as those described in U.S. Pat. No. 5,204,314, the disclosure of which also is hereby incorporated herein by reference.
The features and advantages of the invention are more fully shown by the following non-limiting examples, wherein all parts and percentages are by weight unless otherwise expressly stated.
Example 1
Synthesis of Ta(OEt).sub.4 (.eta..sup.2 -thd)
One equivalent (33.9 g) of 2,2,6,6-tetramethyl-3,5-heptanedione (Hthd) was added directly to 74.6 g Ta(OEt).sub.5 in a 500 mL Schlenk flask; both start materials were obtained commercially (Lancaster Chemicals, Inc.). The vessel was heated to 65.degree. C. under a slow nitrogen purge to a bubbler. After 2 hours, the ethanol generated was removed in vacuo to yield 99.8 g of the colorless liquid Ta(OEt).sub.4 (.eta..sup.2 -thd) in quantitative yield, which solidified upon cooling. The compound melted at 26.degree. C. and boiled at approximately 80.degree. C. at 140 mtorr. The .sup.1 H and .sup.13 C NMR spectra in benzene-d.sub.6 were consistent with an octahedral structure composed of two ethoxide ligands in axial positions and a second set of cis-ethoxide ligands in the equatorial plane across from the bidentate .beta.-diketonate: d 5.81 (s, 1H, CH), 4.72 (q, 4H, CH.sub.2), 4.20 (q, 4H, CH.sub.2), 1.34 (tr, 6H, CH.sub.3), 1.14 (tr, 6H, CH.sub.3), 1.13 (s, 18H, t-Bu); .sup.13 C{.sup.1 H} NMR (C.sub.6 D.sub.6) d 199.9 (CO), 92.9 (CH.sub.diket), 68.8 (CH.sub.2 CH.sub.3), 65.4 (CH.sub.2 CH.sub.3), 40.9 (CMe.sub.3), 28.3 (CMe.sub.3), 19.6 (CH.sub.2 CH.sub.3), 19.0 (CH.sub.2 CH.sub.3).
Example 2
Synthesis of Ta(OiPr).sub.4 (.eta..sup.2 -thd)
A nine-fold excess of isopropanol (170 mL) was added to 33.6 g Ta(OEt).sub.4 (.eta..sup.2 -thd). The solution was heated at 60.degree. C. for 45 min, following which the volatiles were removed in vacuo. The ligand exchange procedure was repeated a second time to yield 36.8 g of white, crystalline Ta(O-i-Pr).sub.4 (.eta..sup.2 -thd) in quantitative yield. The product was purified by sublimation at 100.degree. C. at 150 mtorr. The compound melted at 149.degree. C. The .sup.1 H and .sup.13 C NMR spectra in benzene-d.sub.6 were consistent with an octahedral structure composed of two isopropoxide ligands in axial positions and a second set of cis-isopropoxide ligands in the equatorial plane across from the bidentate b-diketonate: d 5.81 (s, 1H, CH), 5.10 (sept, 2H, CH), 4.51 (sept, 2H, CH), 1.38 (d, 12H, Me), 1.20 (d, 12H, Me), 1.17 (s, 18H, t-Bu); .sup.13 C{.sup.1 H} NMR (C.sub.6 D6) d 199.4 (CO), 93.0 (CH.sub.diket), 75.0 (CHMe.sub.2), 71.4 (CHMe.sub.2), 40.8 (CMe.sub.3), 28.3 (CMe.sub.3), 26.4 (CHMe.sub.2), 25.8 (CHMe.sub.2).
Example 3
Synthesis of Nb(OEt).sub.4 (.eta..sup.2 -thd)
The procedure of Example 1 is followed, using Nb(OEt).sub.5 as starting material rather than the tantalum ethoxide. One equivalent of 2,2,6,6-tetramethyl-3,5-heptanedione (Hthd) is added directly to Nb(OEt).sub.5 in a Schlenk flask. The vessel is heated to about 65.degree. C. under a slow nitrogen purge to a bubbler. After 2 hours the ethanol generated is removed in vacuo to yield Nb(OEt).sub.4 (.eta..sup.2 -thd) in quantitative yield.
Example 4
Synthesis of Nb(OiPr).sub.4 (.eta..sup.2 -thd)
A nine-fold molar excess of isopropanol is added to Nb(OEt).sub.4 (.eta..sup.2 -thd). The resulting solution is heated at 60.degree. C. for 45 min, following which the volatiles are removed in vacuo. The ligand exchange procedure is repeated a second time to yield solid Nb(O-i-Pr).sub.4 (.eta..sup.2 -thd) in quantitative yield. The product is purified by sublimation at 100.degree. C. at 150 mtorr.
Example 5
Deposition of Niobia Film
Nb(O-i-Pr).sub.4 (.eta..sup.2 -thd) is used to deposit Nb.sub.2 O.sub.5 ("niobia") on a silicon wafer held at 400.degree. C. in a CVD reactor. The Nb reagent is contained in a vessel ("bubbler") held at 185.degree. C. and Ar gas is flowed through the vessel at 100 sccm. Pressure in the "bubbler" is controlled at 80 torr using a manual throttle valve. Oxygen is flowed to the reactor through a separate manifold at 300 sccm. Total pressure in the reactor is 1 torr and partial pressure of the Nb reagent in the reactor is 0.03 torr. Deposition rate is approximately 0.04 mm/minute.
Example 6
Deposition of Tantala Film
Ta(O-i-Pr).sub.4 (thd) is used to deposit Ta.sub.2 O.sub.5 (tantala) on a fused silica (glass) envelope of a high intensity lamp by chemical vapor deposition. The glass surface is held at 450.degree. C. in a CVD reactor. The Ta(O-i-Pr).sub.4 (thd) compound is dissolved in an organic solvent and this liquid solution is pumped to a vaporization zone of the reactor held at 200.degree. C. where Ar carrier gas is also introduced at 100 sccm. At the vaporizer zone the solvent evaporates, the Ta compound sublimes and the gaseous reagents and Ar then flow to the chemical vapor deposition reactor. Oxygen is flowed to the reactor through a separate manifold at 300 sccm. Total pressure in the reactor is 1 torr and the deposition rate is 0.065 mm/minute.
Example 7
Deposition of Nb:BST
Nb(O-i-Pr).sub.4 (.eta..sup.2 -thd) is used to deposit Ba.sub.1-x Sr.sub.x Ti.sub.1-y Nb.sub.y O.sub.3 (Nb:BST) on a platinum metal layer on a silicon wafer in a CVD reactor. The metal layer will act as a bottom electrode in a capacitor and the Nb:BST film will have a high dielectric constant with dc low leakage current density. The platinum surface is held at 650.degree. C. Nb(O-i-Pr).sub.4 (.eta..sup.2 -thd) reagent is dissolved in an organic solvent along with Ba(thd).sub.2 -tetraglyme, Sr(thd).sub.2 -tetraglyme and Ti(OPr).sub.2 (thd).sub.2, and this liquid solution is pumped to a vaporization zone held at 220.degree. C. where Ar carrier gas is also introduced at 600 sccm. The solution is stable and no detrimental levels of ligand exchange occured between the metallorganic compounds in the liquid phase or gas phase. At the vaporization zone the solvent evaporates and the Bi, Sr, and Ti compounds sublime and pass into the vapor phase. The gaseous reagents and Ar then flow to the CVD reactor. A mixture of oxygen and nitrous oxide is flowed to the reactor through a separate manifold at 300 sccm each. Total pressure in the reactor is 0.700 torr and the (Nb:BST) is efficiently deposited.
Example 8
Deposition of Bi.sub.2 SrTa.sub.2 O.sub.9
Ta(O-i-Pr).sub.4 (thd) is used to deposit Bi.sub.2 SrTa.sub.2 O.sub.9 on platinum metal layer on a silicon wafer in a CVD reactor. The Bi.sub.2 SrTa.sub.2 O.sub.9 film will form a ferroelectric capacitor with remanent polarization that can be switched greater than 10.sup.12 times. The Bi.sub.2 SrTa.sub.2 O.sub.9 is deposited at 650.degree. C. Ta(O-i-Pr).sub.4 (thd) is dissolved in an organic solvent along with triphenylbismuth and Sr(thd).sub.2 -tetraglyme and this liquid solution is pumped to a vaporization zone held at 200.degree. C. where Ar carrier gas is also introduced at 100 sccm. The solution is stable and no detrimental ligand exchange occured between the metallorganic compounds in the liquid or gas phase. At the vaporization zone the solvent evaporates and the Bi, Sr, Na compounds sublime. The gaseous reagents and Ar then flow to the chemical vapor deposition reactor. A mixture of oxygen and nitrous oxide is flowed to the reactor through a separate manifold at 300 sccm each. Total pressure in the reactor is 2.1 torr and the Bi.sub.2 SrTa.sub.2 O.sub.9 is deposited at useful rates.
Example 9
Growth of GMR Oxide Films on LaAlO.sub.3 (100), NdGaO.sub.3 (110), and MgO (100) Substrates by CVD
La.sub.x Ca.sub.1-x MnO.sub.3 films were grown on LaAlO.sub.3 (100), NdGaO.sub.3 (110), and MgO (100) substrates by CVD in the CVD system that is shown schematically in FIG. 1. Tris(tetramethylheptanedionato)lanthanum (La(thd).sub.3), bis(tetramethylheptanedionato)calcium (Ca(thd).sub.2), and tris(tetramethylheptanedionato)manganese (Mn(thd).sub.3), all of which were purchased commercially (Strem Chemicals), were used as precursor materials. These three organic compounds, in appropriate amounts, were mixed and dissolved in a single organic solution of 25:1 butyl acetate:tetraglyme under an inert atmosphere. The concentrations of La(thd).sub.3, Ca(thd).sub.2 and Mn(thd).sub.3 in the solution were 0.033, 0.017, and 0.05 moles/liter of solution, respectively. During deposition, the solution was constantly injected into a vaporizer by a liquid pump and the vapors were carried immediately into a chemical vapor deposition reactor by nitrogen gas. The films were deposited at a constant pressure of 1.5 Torr and at a substrate temperature ranging from 600.degree. C. to 700.degree. C. Both oxygen and nitrous oxide were used as oxidants.
The films were characterized and showed a high transition temperature T.sub.c in the as-deposited films, probably due to the higher oxygen partial pressure in the CVD process. The highest T.sub.c attained was 300 K. The peak value of resistivity r is observed to decrease from 34 m.OMEGA.-cm to 12 m.OMEGA.-cm in the film with T.sub.c =300 K. Post annealing of these films in 1 atm of O.sub.2 further reduced r and increased T.sub.c. The oxygen content plays an important role in controlling the carrier concentration. All of the films prepared at different substrate temperatures between 600.degree. and 750.degree. C. were highly (001) oriented. The grain size of films decreased as the substrate temperature decreased without a degradation of crystallinity determined by XRD in this temperature range. There was no correlation found between grain size and cusp temperature or magnetoresistance of the films. The preferred orientation of the films appear to affect on the temperature dependence of resistivity as shown in the case of a (LaCa)MnO3 film deposited on MgO substrate. A lower .DELTA.R/R.sub.H effect of as-deposited (LaCa)MnO3 films by MOCVD than that of annealed (LaCa)MnO3 films prepared by laser deposition is probably due to a relatively low resistivity of these MOCVD films.
Example 10
Growth of Zirconium Titanate
A number of PZT runs were performed with the objectives of optimizing vaporizer conditions and achieving desired film stoichiometry, from Zr(thd).sub.4 and Ti(O-iPr).sub.4 source reagents. The CVD reactor was constructed to permit preheating of the carrier gas using heat tape around an in-line filter, and the delivery system for vaporization and transport of the source reagent vapor was arranged and constructed in accordance with the disclosure of U.S. Pat. No. 5,204,314.
Initial experiments employed as the solvent a mixture of THF:tetraglyme in the ratio of 9:1. It was found that the effect of carrier gas preheat was minimal. Vaporizer temperature was a much stronger variable with increased vaporization temperature giving somewhat more consistent vaporization as judged by monitoring the pressure of the vaporizer behind the frit (vaporization element). Lower temperatures (T.sub.vap =215.degree. C.) resulted in more erratic vaporizer pressure. In addition, increased relative Zr content in the solution caused wide swings in vaporizer pressure as the run progressed, even at T.sub.vap =230.degree. C. (Total Zr content in all cases has been held at 0.15 to 0.145 moles/liter solution to prevent delivery tube clogging which was experienced at higher Zr concentrations.)
One variable studied in the test was the addition of isopropanol to the solvent. In such modification, the solvent used was THF:isopropanol:tetraglyme in the ratio of 8:2:1. IPA affected the process remarkably favorably in respect of the desired film composition. Zr incorporation efficiency increased to the point where films of Zr.sub.x Ti.sub.1-x O.sub.4 were produced. The deposition conditions were held constant during all of the experiments, evidencing the fact that transport of Zr is significantly enhanced by the addition of IPA to the THF/tetraglyme solvent. This suggested that ligand exchange may have played a role, e.g., with the reaction Zr(thd).sub.4 .fwdarw.Zr(OiPr).sub.x (thd).sub.4-x, leading to more volatile species. It was also observed that the swings in vaporizer pressure decreased (at T.sub.vap =230.degree. C. and with 40 mm frits) with the modified solvent. Ligand exchange may also have led to the provision of all liquid precursors at the vaporizer temperature rather than solid as is the case for Zr(thd).sub.4.
Example 11
Growth of BiSrTa
Transport experiments for Bi--Sr--Ta were conducted in a CVD reactor to roughly determine vaporizer operating conditions, following which two Ta compounds were evaluated. The first was Ta(OiPr).sub.4 (thd), for which three vaporizer temperatures were investigated. The best condition was found to be 200.degree. C. A second Ta compound, Ta.sub.2 (OEt).sub.4 (thd) also was tried under the same transport conditions, as summarized in Table IV below.
Ta(OiPr).sub.4 (.eta..sup.2 -thd)
The 180.degree. C. experiment resulted in a steep rise in pressure behind the frit, presumably due to unsublimed material (likely Sr(thd).sub.2) which was consistent with the fact that the pressure behind the frit recovered by 93% to nearly its initial value in about 1.5 hours.
The 200.degree. C. experiment had a steep initial pressure rise, followed by the lowest steady-state rise of any of the conditions tried. A relatively low pressure recovery after the experiment (29%) indicated that some decomposition of metalorganic material occurred at the frit.
The 220.degree. C. experiment behaved similarly to the 200.degree. C. experiment with two exceptions: the steady state rise was >2X.times. higher and a steep pressure rise occurred at the end of the experiment (.about.2 hours) which was accompanied by a clog in the delivery tube at the frit. The clog disappeared as the vaporizer cooled overnight and a significant amount (about a 5 mm dia. lump) of white material was present on top of the frit. This may have been due to the reagent being sucked into the vaporizer from the delivery tube (with some leakage through the 20 psi check valve) from which the solvent had evaporated. An NMR analysis was conducted on the material, and it showed BiPh.sub.3 and Ta(OiPr).sub.4 (thd) precursors in about their original ratios but no Sr(thd).sub.2.
The frit residue was analyzed qualitatively by x-ray fluorescence (XRF). The results showed that the amount of Bi and Ta left on the frit increased with increasing vaporizer temperature, as expected.
Ta(OEt).sub.4 (.eta..sup.2 -thd)
This compound appeared fairly well behaved until near the end of the transport experiment, where a significant rise in pressure behind the frit occurred, accompanied by a clog in the delivery system. This clog disappeared within minutes of shutting off the solution flow. Vaporizer pressure recovered by about 62% after the experiment.
Several films were deposited on Pt/Ta/SiO.sub.2 /Si during the transport experiments. Deposition at 750.degree. C. susceptor temperature resulted in a film that was poorly crystallized. In contrast, films deposited at 800.degree. C. showed strong XRD peaks. Interestingly, all films had a striped appearance across the wafer indicating changing thickness. This may be attributable to a macroscopic manifestation of ledge motion during growth of the compound which is known to be a layered structure. Fringes were observed moving across the wafer at the early stages of growth.
Example 12
Growth of BaTiO.sub.3 from Ti(OR).sub.2 (thd).sub.2
A source reagent mixture of Ti(OR).sub.2 (acac).sub.2 and Ba(thd).sub.2 in solvent medium was found to experience ligand exchange, resulting in mixed Ba(.beta.-diketonate).sub.2 species that display a reduced volatility. Use of Ti(OR).sub.2 (thd).sub.2 in place of Ti(OR).sub.2 (acac).sub.2 resulted in degenerate ligand exchange that was transparent to the vaporization and CVD deposition process.
Example 13
Growth of Bi.sub.2 SrTa.sub.2 O.sub.9 Using Ta(OEt).sub.4 (thd)
The combination of reagents Ta(OEt).sub.5 and Sr(thd).sub.2 also resulted in ligand exchange when the ligands were dissolved in solvent medium, as in Example 12. By using Ta(OEt).sub.4 (thd) the aforementioned exchange problem is alleviated in solution. This enables a reproducible transport and CVD process.
The Ta(OEt).sub.4 (thd) and Sr(thd).sub.2 solution can be used for depositing SrTaO or Bi.sub.2 SrTa.sub.2 O.sub.9 materials.
Example 14
Growth of BaTiO.sub.3 or BST Using Ti(OR).sub.2 (thd).sub.2
The source reagent combination of Ti(OR).sub.4 and Ba(thd).sub.2 can undergo ligand exchange as described in Examples 12 and 13. Use of Ti(OR).sub.2 (thd).sub.2 as the Ti reagent alleviates the exchange problem in solution. The latter solution can be used for the formation of BaTiO or BaSrTiO films.
Example 15
Growth of PbTiO.sub.3
The source reagent combination of Ti(OR).sub.4 and Pb(thd).sub.2 can also result in ligand exchange in solution. Using Ti(OR).sub.2 (thd).sub.2 eliminates the ligand exchange with the Pb reagent. The latter solution is useful for deposition of PbTiO.sub.3 or PbZrTiO.sub.3 (PZT) films.
Example 16
Growth of YBCO
Y(thd).sub.3, Ba(thd).sub.2, and Cu(thd).sub.2 were dissolved in an appropriate solvent to enable the facile vaporization and gas-phase transport of the precursors into the reaction zone. The volatility and transport characteristics of the reagents are primarily governed by the thd ligands and the temperature of the heated vaporization zone of the liquid delivery system. These solutions can be used for Y.sub.x Ba.sub.y Cu.sub.z O film growth.
Example 17
Growth of YBCO
Various metal (.beta.-diketonates) are dissolved in the desired solvent to provide compatible solubilities. For example, Cu(thd).sub.2 or Cu(hfacac).sub.2 reagents are used in tandem with the similar Y(thd).sub.3 or Y(hfacac).sub.3 reagents, respectively, to realize comparable solubilities of widely differing metals.
Example 18
CVD of Aluminum--Addition of Solvent to Decrease Precursor Viscosity
An inert solvent is added to a "neat" liquid or reagent being used for film growth. Dimethyl aluminum hydride (dimer) is a viscous liquid that yields high-purity aluminum films. Liquid delivery is facilitated by dilution in an inert organic solvent, such as hexane or toluene. The dilute solution is easily transported to the vaporization zone for deposition. Other organic solvents with a suitable boiling point can be used with equal success.
Example 19
Solvent System to Optimize Liquid Delivery of Reactants for CVD
A solvent is chosen, such that preferential boiling of the solvent does not occur without volatilization of the reagent. This allows maximum volatilization of the reagent to be realized without detrimental clogging of the vaporizer. For example, the use of a tetrahydrofuran-isopropanol mixture is advantageous for the delivery vaporization of Bi(Ph).sub.3 and Ta(OiPr).sub.4 (thd).
Example 20
Use of Additive to Increase Reactant Solubility for LP CVD
Acetone, tetrahydrofuran, dimethoxyethane (DME) or dimethylformamide (DMF) are added to a solution containing Ba(thd).sub.2 to maximize its solubility.
Example 21
Use of Polyethers to Improve Suitability for LP CVD
Various compositions were made up of reagent solutions, including: addition of 4-glyme to Ba(thd).sub.2 ; addition of polyamines for Ba(thd).sub.2 ; addition of polyether alcohols to enhance thermal stability of reagents; and addition of 18-crown-6 to enhance the thermal stability of the reagents.
Example 22
Use of Solvent to Lower Freezing Point of Low-Melting Solid
Ta(OEt).sub.5 has a melting point of .about.21.degree. C. Liquid delivery of this material requires a lowering of the freezing point to maintain a liquid in the bubbler and throughout the process system. Lowering the freezing point is achieved by addition of ethanol to the `neat` Ta(OEt).sub.5 used to grow Ta.sub.2 O.sub.5 films. The ethanol does not have a deterimental effect on the reagent, the liquid delivery or the reagent and/or the CVD growth process.
Example 23
Addition of Solvent to Depress Freezing Point of Low Melting Solids
Ti(OiPr).sub.4, m.p. of 20.degree. C., is mixed with i-PrOH to lower the melting point. MgAl.sub.2 (OiPr).sub.8, m.p. 40.degree. C., is mixed with iPrOH to lower the melting point. Ta(OEt).sub.4 (thd), m.p.=26.degree. C., is mixed with EtOH to lower the melting point.
Example 24
Liquid Delivery of Cu Reagents--Solvent Coordination for Altering Complex Properties
A solvent is chosen to maximize dissolution of a reagent based upon the solubility of that precursor in a given solvent. However, the solvent may be chosen to provide a solvated complex which exhibits different physical properties after solvation. Cu(hfacac).sub.2 hydrate is exceedingly soluble in alcoholic solvents because the water is displaced and the alcohol coordinates to the metal center. Isolation of the solvated complex yields materials with different physical properties. Thus, the solvent is chosen to alter the physical and chemical properties of the reagent being used for film growth.
This same concept can be extended to a wide variety of other reagents which can be solvated to provide complexes of different physico-chemical properties for use in CVD. For example, tetrahydrofuran (THF) may be added to a solution to increase the solubility of Cu(thd)2 therein.
Example 25
Use of Additive to Increase Reactant Stability for LP CVD
Tetraglyme was added to Ba(thd).sub.2 (tetraglyme) solution to enhance thermal stability of the reagent composition.
Example 26
Addition of Excess Lewis Base to Increase Reactant Stability During LP CVD
Lewis base copper(I) .beta.-diketonate complexes are useful for copper CVD. However, the Lewis base may be easily liberated from the molecule resulting in premature decomposition and clogging of the vaporizer. To combat this problem, excess Lewis base is added. Similarly, excess Lewis base can be added to stop the formation of a less volatile dinuclear species and eliminate precipitation in the vaporizer. For example, liberation of 3-hexyne from 3-hexyne Cu(hfacac) leads to the formation of a dinuclear complex, 3-hexyne Cu(hfacac)!.sub.2, which is a solid at room temperature. The formation and precipitation of this dinuclear solid can be controlled by forcing this equilibrium in the reverse direction. Thus, excess 3-hexyne not only enhances the thermal stability, but eliminates formation of a less volatile solid precipitate, which can lead to clogging and decomposition in the vaporizer.
Example 27
Addition of Polyether or Polyamine to Reduce Hydrolysis of Reactant During LP CVD
The coordination of H.sub.2 O to Ba(thd).sub.2 on thermal vaporization may be reduced or eliminated by coordinating a stronger Lewis Base to the barium center.
While the invention has been described herein with reference to specific embodiments, features and aspects, it will be recognized that the invention is not thus limited, but rather extends in utility to other modifications, variations, applications, and embodiments, and accordingly all such other modifications, variations, applications, and embodiments are to be regarded as being within the spirit and scope of the invention.
Claims
Post-issuance certificates present
The text shown below may not reflect later post-issuance changes.
What is claimed is:
1. A metal source reagent solution having utility for chemical vapor deposition in the manufacture of semiconductor device structures, said metal source reagent solution consisting essentially of: (i) at least one metal coordination complex including a metal selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Tl, Er, Pb, Tm, Bi, and Yb, to which is coordinatively bound at least one ligand in a stable complex, wherein the ligand is selected from the group consisting of: .beta.-diketonates, .beta.-ketoiminiates, .beta.diiminates, C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, C.sub.1 -C.sub.8 alkoxy, and fluorinated derivatives thereof; and (ii) a solvent for said metal coordination complex, selected from the group consisting of glymes, aliphatic hydrocarbons, aromatic hydrocarbons, organic ethers, organic esters, alkyl nitriles, alkanols, organic amines, and polyamines.
2. A metal source reagent liquid solution according to claim 1, comprising a multi-component solution including at least two said metal source complexes.
3. A metal source reagent liquid solution according to claim 2, wherein the ligands of the metal source complexes are either (a) identical to result in degenerative ligand exchange, or (b) resistant to non-degenerative ligand exchange in relation to one another.
4. A metal source reagent liquid solution according to claim 1, wherein the solvent comprises at least one solvent species selected from the group consisting of: glymes, aliphatic hydrocarbons, aromatic hydrocarbons, ethers, esters, nitrites, and alcohols.
5. A metal source reagent liquid solution according to claim 1, wherein the solvent comprises an organic ether selected from the group consisting of dialkyl, cyclic and crown ethers.
6. A metal source reagent liquid solution according to claim 1, wherein the solvent comprises an alkyl nitrile of the formula: C.tbd.NR.sub.b, wherein R.sub.b is H, C.sub.1 -C.sub.8 alkyl, or C.sub.1 -C.sub.8 perfluoroalkyl.
7. A metal source reagent liquid solution according to claim 1, wherein the solvent comprises at least one solvent species selected from the group consisting of: glyme solvents having from 1 to 20 ethoxy -(C.sub.2 H.sub.4 O)- repeat units; C.sub.2 -C.sub.12 alkanols, organic ethers selected from the group consisting of dialkyl ethers comprising C.sub.1 -C.sub.6 alkyl moieties, C.sub.4 -C.sub.8 cyclic ethers, and C.sub.12 -C.sub.60 crown O.sub.4 -O.sub.20 ethers wherein the prefixed C.sub.i range is the number i of carbon atoms in the ether compound and the suffixed O.sub.i range is the number i of oxygen atoms in the ether compound; C.sub.6 -C.sub.12 aliphatic hydrocarbons; and C.sub.6 -C.sub.18 aromatic hydrocarbons.
8. A metal source reagent liquid solution according to claim 1, wherein the solvent comprises a crown ether selected from the group consisting of 12-crown-4, 15- crown-5, 18-crown-6, and 24-crown-8 crown ethers.
9. A metal source reagent solution having utility for chemical vapor deposition in the manufacture of semiconductor device structures, said metal source reagent solution consisting essentially of (i) at least one metal coordination complex including a metal coordination atom selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Tl, Er, Sn, Pb, Tm, Bi, and Yb, to which is coordinately bound in a stable complex at least two different ligands selected from the group consisting of: .beta.-diketonates, .beta.-ketoiminates, .beta.-diiminates, C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, C.sub.1 -C.sub.8 alkoxy, and fluorinated derivatives thereof; and (ii) a solvent for said metal coordination complex selected from the group consisting of glymes, aliphatic hydrocarbons, aromatic hydrocarbons, organic ethers, organic esters, alkyl nitriles, alkanols, organic amines, and polyamines.
10. A metal source reagent liquid solution according to claim 9, wherein the metal coordination atom comprises a metal selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Al, Tl, Er, Sn, Pb, Tm, Bi, and Yb.
11. A metal source reagent liquid solution according to claim 9, wherein the metal coordination atom is coordinated to at least one alkoxide ligand and at least one .beta.-diketonate ligand.
12. A metal source reagent liquid solution according to claim 9, wherein the metal coordination atom is coordinated to a .beta.-diketonate ligand selected from the group consisting of acac, thd, fod, hfod, tfacac, and hfacac.
13. A metal source reagent liquid solution according to claim 9, wherein the solvent comprises at least one solvent species selected from the group consisting of: glyme solvents having from 1 to 20 ethoxy -(C.sub.2 H.sub.4 O)- repeat units; C.sub.2 -C.sub.12 alkanols, organic ethers selected from the group consisting of dialkyl ethers comprising C.sub.1 -C.sub.6 alkyl moieties, C.sub.4 -C.sub.8 cyclic ethers; C.sub.12 -C.sub.60 crown O.sub.4 -O.sub.20 ethers wherein the prefixed C.sub.i range is the number i of carbon atoms in the ether compound and the suffixed O.sub.i range is the number i of oxygen atoms in the ether compound; C.sub.6 -C.sub.12 aliphatic hydrocarbons; C.sub.6 -C.sub.18 aromatic hydrocarbons; organic esters; organic amines; and polyamines.
14. A metal source reagent liquid solution according to claim 9, wherein the solvent is selected from the group consisting of tetrahydrofuran, alkyl acetate, tetraglyme and C.sub.3 -C.sub.8 alkanols.
15. A metal source reagent liquid solution having utility for chemical vapor deposition in the manufacture of semiconductor device structures, said metal source reagent solution consisting essentially of metal source reagent(s) and solvent medium selected from the group consisting of: Metal Source Reagent(s) Solvent Medium ______________________________________ Al(thd).sub.3 80-98% tetrahydrofuran and 2-20% tetraglyme Al(OR).sub.3 80-98% tetrahydrofuran and 2-20% tetraglyme Ba(thd).sub.2 (tetraglyme) 85-99% butyl acetate and 1-15% tetraglyme Ca(thd).sub.2 (tetraglyme) Cu(thd).sub.2 Ba(thd).sub.2 (tetraglyme) 85-98% butyl acetate and 1-15% tetraglyme Sr(thd).sub.2 (tetraglyme) Ti(OiPr).sub.2 (thd).sub.2 Sr(thd).sub.2 (tetraglyme) 75-95% isopropanol with 5-25% tetraglyme Ca(thd).sub.2 (tetraglyme) Cr(thd).sub.3 80-98% tetrahydrofuran with 2-20% tetraglyme Er(thd).sub.3 85-99% butyl acetate and 1-15% tetraglyme Ir(acac).sub.3 butyl acetate or Ir(thd).sub.3 La(thd).sub.3 tetrahydrofuran (MeO).sub.3 P.dbd.O MgAl.sub.2 (OiPr).sub.8 isopropanol Nb(OiPr).sub.4 thd 45-88% tetrahydrofuran 10-35% isopropanol 2-20% tetraglyme Pb(thd).sub.2 80-98% tetrahydrofuran with 2-20% tetraglyme La(thd).sub.3 Ti(OiPr).sub.2 (thd).sub.2 Pb(thd).sub.2 80-98% tetrahydrofuran with 2-20% tetraglyme Ti(OiPr).sub.2 thd.sub.2 Pb(thd).sub.2 45-88% tetrahydrofuran Zr(thd).sub.4 10-35% isopropanol 2-20% tetraglyme Pb(thd).sub.2 45-88% tetrahydrofuran Zr(thd).sub.4 10-35% isopropanol Ti(OiPr).sub.2 (thd).sub.2 2-20% tetraglyme Ru(acac).sub.3 butyl acetate or Ru(thd).sub.3 Sn(alkyl).sub.2 (J-diketonate).sub.2 butyl acetate wherein alkyl = C.sub.1 -C.sub.18 alkyl Sn(acetate).sub.2 butyl acetate or 85-99% butyl acetate/ 1-15% tetraglyme Sr(thd).sub.2 (tetraglyme) 45-88% tetrahydrofuran BiPh.sub.3 10-35% isopropanol Ta(OiPr).sub.4 (thd) 2-20% tetraglyme Ta(OEt).sub.5 1% ethanol solution O.dbd.Ti(thd).sub.2 !.sub.n butyl acetate wherein n is 1 or 2 Y(thd).sub.3 isopropanol Y(thd).sub.3 butyl acetate/tetraglyme Ba(thd).sub.2 Cu(thd).sub.2 Zr(thd).sub.4 80-98% tetrahydrofuran and 2-20% tetraglyme Y(thd).sub.3 O.dbd.Zr(thd).sub.2 !.sub.n butyl acetate wherein n is 1 or 2 or butyl acetate/tetraglyme ______________________________________ wherein when the solvent medium contains multiple solvent components, the percentages specified are percentages by weight, based on the weight of the total solvent medium, and with the total percentage of all solvent compositions being 100% and wherein R is selected from the group consisting of C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, and fluorinated derivatives thereof wherein at least one hydrogen substituent is replaced by fluorine.
16. A source reagent liquid solution having utility for chemical vapor deposition in the manufacture of semiconductor device structures, said metal source reagent solution consisting essentially of: (i) at least one metal coordination complex of the formula: wherein: M is a metal selected from the group consisting of Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, Nb, Cr, W, Pm, Mn, Re, Sm, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Tl, Er, Pb, Tm, Bi, and Yb; A is selected from the group consisting of .beta.-diketotiates and .beta.-ketoesters, and their sulfur and nitrogen analogs; R is selected from the group consisting of C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, and fluorinated derivatives thereof, wherein hydrogen substituent(s) of the C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15, cycloalkenyl, or C.sub.6 -C.sub.10 aryl ligand is/are replaced by fluorine substituent(s); B is selected from the group consisting of polyethers, polyamines, polythiols, bipyridines, glymes, alcohols, crown ethers, crown thioethers, cyclic polyamines (cyclenes), thioglymes, arylthiols, and aliphatic thiols (mercaptans); Q is hydrocarbyl or halohydrocarbyl; A, x, y and z are stoichiometric coefficients for the ligands A, OR, B and Q, respectively, wherein A is .ltoreq.1; each of X, Y, and Z is independently .gtoreq.0; and A.sub.a (OR).sub.x B.sub.y Q.sub.z is in stoichiometric relationship to metal M; and (ii) a solvent for the metal coordination complexes selected from the group consisting of glymes, aliphatic hydrocarbons, aromatic hydrocarbons, organic ethers, organic esters, alkyl nitrites, alkanols, organic amines, and polyamines.
17. A metal source reagent composition having utility for chemical vapor deposition in the manufacture of semiconductor device structures, said metal source reagent solution consisting essentially of (i) a metal source reagent in (ii) solvent medium selected from the group consisting of glymes, aliphatic hydrocarbons, aromatic hydrocarbons, organic ethers, organic esters, alkyl nitriles, alkanols, organic amines, and polyamines, wherein the metal source reagent comprises at least one .beta.-diketonate alkoxide compound including a metal M selected from the group consisting of Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Pr, V, Nb, Ta, Nd, Cr, W, Pm, Mn, Re, Sm, Fe, Ru, Eu, Co, Rh, Ir, Gd, Ni, Tb, Cu, Dy, Ho, Tl, Er, Sn, Pb, Tm, B, and Yb, coordinated to at least one alkoxide ligand and at least one .beta.-diketonate ligand, and having the formula; wherein; G is oxygen, sulfur, or imide of the formula: .dbd.NR.sub.b, wherein R.sub.b is H, C.sub.1 -C.sub.8 alkyl, or C.sub.1 -C.sub.8 perfluoroalkyl; x+Y=p where p is the valence of metal M; x=2y=q where q is the coordination number of metal M; R.sup.1 is C.sub.1 -C.sub.6 hydrocarbyl or fluoroalkyl; and R.sup.2 and R.sup.3 are independently selected from the group consisting of C.sub.1 -C.sub.14 hydrocarbyl, C.sub.1 -C.sub.6 alkoxy, and C.sub.2 -C.sub.6 fluoroalkyl groups.
18. A solution according to claim 17, wherein hydrocarbyl is selected from the group consisting of the group consisting of C.sub.1 -C.sub.8 alkyl, C.sub.6 -C.sub.10 cycloalkyl, C.sub.2 -C.sub.12 alkenyl and C.sub.6 -C.sub.14 aryl groups, and C.sub.2 -C.sub.6 fluoroalkyl groups is selected from perfluoroalkyls of 2 through 6 carbons.
19. A metal source reagent liquid solution having utility for chemical vapor deposition in the manufacture of semiconductor device structures, said metal source reagent solution consisting essentially of: (i) at least one metal coordination complex including a metal to which is coordinatively bound at least one ligand in a stable complex, wherein the ligand is selected from the group consisting of: .beta.-diketonates, .beta.-ketoiminates, .beta.-diiminates, C.sub.1 -C.sub.8 alkyl, C.sub.2 -C.sub.10 alkenyl, C.sub.2 -C.sub.15 cycloalkenyl, C.sub.6 -C.sub.10 aryl, C.sub.1 -C.sub.8 alkoxy, and fluorinated derivatives thereof; and (ii) a solvent for said metal coordination complex, selected from the group consisting of: (A) 9:1 tetrahydrofuran/tetraglyme; (B) 8:2:1 tetrahydrofuran/isopropanol/tetraglyme; and (C) 25:1 butyl acetate/tetraglyme.
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