Catalysis in organometallic CVD of thin metal films

A process for CVD including plasma enhanced and laser induced CVD using one or more precursor film forming metal compounds as the major film forming metal precursor, for example organotungsten, which is admixed with minor amounts of a precursor catalytic metal compound, for example, an organoplatinum compound, as a precursor to a catalytic metal in the presence of hydrogen gas to provide improved purity of deposited metal films having residual amounts of the catalytic metal incorporated therein.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to chemical vapor deposition (CVD) of thin metal 
films, and in particular to the catalyzed removal of heteroatoms during 
the deposition of metals from precursor film forming metal compounds in 
the presence of hydrogen. 
2. Description of the Prior Art 
The deposit of thin coatings of metals onto various substrates are 
important in several industries. For example, one of the most important 
applications is in the production of integrated circuits in the 
microelectronics industry. In this respect, one of the most important 
criteria is the purity of the deposited thin metal film. The presence of 
even small amounts of carbon, oxygen and other heteroatom contaminants can 
markedly affect the performance of the finished electronic component. 
The term "heteroatom" as used herein and in the appended claims is meant to 
include all atoms except metal atoms. 
Various methods have been used for purposes of depositing a thin metal 
coating onto a substrate including for example precipitation from liquid 
solution, sputtering, and chemical vapor deposition (CVD), and plasma 
enhanced CVD. 
In addition to purity, it is often desirable to selectively deposit a metal 
film on a portion of the surface of a semiconductor or other electronic 
component. This is particularly the case for purposes of providing 
interconnects to various circuit elements which require selective 
deposition in small voids in the substrate surface of the electronic 
component. 
The use of liquid solution precipitation of precursor compounds followed by 
metal deposition has some advantages. However, it has generally been 
unsatisfactory for purposes of complete and contiguous deposition since it 
is difficult to insure that the solution will penetrate the small voids 
which are necessary to insure film quality and proper adherence to the 
substrate. Additionally, the purity of the deposited coating is often not 
as high as is necessary for some commercial applications. Sputtering has 
also been rejected in many instances since the quality of the coating as 
well as the uniformity of the coating has often been less than 
commercially acceptable. Also, this method requires that the extra metal 
introduced be chemically etched away in subsequent treatments. 
Chemical vapor deposition, has provided more uniform deposition of thin 
metal films and is more reliable for conformal coverage in the deposition 
of metal films on convoluted surfaces. Despite the advantages of CVD, the 
degree of purity of the deposited metal films has often been less than 
desired. 
Chemical vapor deposition has produced films which have been contaminated 
with unacceptable levels of carbon and oxygen and other heteroatoms that 
are derived from decomposition of hydrocarbon and oxocarbon moieties of 
the volatile CVD precursor compounds. 
These precursor compounds are typically organometallic compounds with 
hydrocarbon, carbonyl, and hydride ligands that are used in organometallic 
chemical vapor deposition processes (OMCVD). 
For instance, the use of metal carbonyl compounds in CVD applications 
typically introduces carbon and oxygen contaminants. Localized laser 
heating at high temperatures of small deposited metal "dots" as shown by 
Houle et al in their work with deposited tungsten appears to essentially 
clean in the center with impurities on the periphery of the dot area. 
The three major chemical processes for achieving CVD can be generally 
classified as reduction, thermal decomposition, and displacement. 
Reduction involves exposing the volatile metal compound during or after 
deposition on the substrate to hydrogen or equivalent reducing gas. 
Theoretically, the hydrogen reacts with the nonmetal portion of the 
compound to yield volatile hydrocarbon byproducts and to leave the metal 
film behind on the substrate. 
Thermal decomposition involves heating the substrate to cause the 
hydrocarbon portion of the volatile metal compound to decompose to 
volatile hydrocarbons and leave the surface of the substrate while leaving 
the metal on the surface. 
Displacement involves use of a surface material or surface absorbed species 
on the substrate to react with the volatile metal compound to yield 
volatile byproducts and deposit metal on the exposed surface. 
All of the above techniques suffer from the introduction of impurities 
during the decomposition reaction of the precursor metal compound or to 
produce corrosive byproducts in depositing the metal film. 
In recent years, improved purity of thin metal films deposited by CVD 
involved the use of organometallics as the volatile compound. See Gozum, 
J. et al., "`Tailored` Organometallics as Precursors for the Chemical 
Vapor Deposition of High-Purity Palladium and Platinum Thin Films," J. Am. 
Chem. Soc., 110, 2688 (1988). 
In the above referenced article bis(allyl)palladium, 
bis(2-methylallyl)palladium, and (cyclopentadienyl)(allyl) palladium were 
investigated for CVD at 250.degree. C. and 10.sup.-4 Torr. The 
cyclopentadienyl compound yielded CVD palladium films having about 5 mol % 
residual carbon as a contaminant. However, it was also found that at a 
similar temperature and pressure, the cyclopentadienyl complex 
CPPtMe.sub.3 [(cyclopentadienyl)(trimethyl)platinum(IV)] produced high 
quality platinum films that were not significantly contaminated with 
carbon. In some cases a large amount of carbon is incorporated by the 
process. For example, titanium carbide films have been deposited using 
tetraneopentyltitanium (Ti[CH.sub.2 C(CH.sub.3).sub.3 ].sub.4) at 
approximately 350.degree. C. The deposited Ti contained sufficient carbon 
to form a separate TiC phase. 
Organometallic compounds have also been evaluated for other purposes. For 
example, in Egger, K., "Cyclopentadienyl-Metal Complexes II. Mass 
Spectrometric and Gas Phase Kinetic Studies on the Thermal Stability and 
the Structure of (CH.sub.3).sub.3 Pt-C.sub.5 H.sub.5," J. Organometallic 
Chemistry, 24, 501 (1970), the structure of 
[cyclopentadienyl(trimethyl)platinum(IV)] was reported. The article 
concluded that the cyclopentadienyl group was .pi. bonded. Studies of the 
hydrogenation of (1,5 cyclooctadiene) dimethylplatinum has also been 
reported. Miller, T. et al., "Heterogeneous, Platinum-Catalyzed 
Hydrogenation of (Diolefin)dialkylplatinum(II) Complexes: Kinetics," J. 
Am. Chem. Soc., 3146 (1988) (and two subsequent articles by the same 
author). Hydrogenation of nickelocene ((C.sub.5 H.sub.5).sub.2 Ni) has 
also been reported. Kaplin, Y. et al., "Decomposition of Nickelocene in 
Presence of Hydrogen," UDC 547.1'174, c. 1980 Plenum Publishing Corp., 
translated from Zhurnal Obshchei Khimii, 50, 118 (1980). None of these 
articles, however, report any special benefits of using these compounds in 
CVD. 
In our newly issued patent U.S. Pat. No. 5,130,172 there is described the 
low temperature deposition of organometallic compounds onto substrates. 
The process includes coating onto various substrates such as glass or 
silicon, at least one metal that can readily cycle between two oxidation 
states and that is also a hydrogenation catalyst capable of facilitating 
the hydrogenation of hydrocarbon ligands of precursor organometallic 
compounds. During the process the substrate is maintained at a relatively 
low temperature in the range of about room temperature up to about 
190.degree. C. depending on the substrate. 
The precursor organometallic compound of our patent which is vaporized or 
dissolved has the general formula 
EQU L.sub.n MR.sub.m 
wherein L is hydrogen, ethylene, allyl, methylallyl, butadienyl, 
pentadienyl, cyclopentadienyl, methycyclopentadienyl, cyclohexadienyl, 
hexadienyl, cycloheptatrienyl, or derivatives of said compounds having at 
least one alkyl side chain having less than five carbon atoms, 
M is a metal which can readily cycle between two oxidation states and can 
catalyze hydrogenation of hydrocarbon ligands of the organometallic 
compound such as cobalt, rhodium, iridium, nickel, palladium, platinum, 
osmium, ruthenium. 
R is methyl, ethyl, propyl, or butyl, 
n is a number from 0 to the valence of said metal, 
m is a number from 0 to the valence of the metal, and m plus n must equal 
the valence of the metal. 
During the process the substrate is continuously exposed to hydrogen gas 
and the organometallic compound at a temperature in the range of about 
room temperature to about 190 .degree. C. depending on the organometallic 
compound. During the course of reaction, a layer of the metal from the 
organometallic compound is deposited on the surface of the substrate which 
at the same time catalytically hydrogenates the hydrocarbon ligand of the 
organometallic compound to provide significant purity of the deposited 
metal compared with prior art processes. In the above process, the best 
results were obtained using CpPtMe.sub.3 or MeCpPtMe.sub.3. 
A particular advantage of the process is that in most cases the process 
takes place at a relatively low temperature and the carbon impurity can be 
kept as low as 3.5 mol % or less. 
However, following the above process using a heated substrate of, for 
example, silicon or glass and an organometallic compound wherein the metal 
is comprised of a refractory metal such as tungsten and in the presence of 
hydrogen gas, it has been found that the deposited tungsten metal is 
contaminated significantly with carbon, as much as 30 mol % to 40 mol % 
depending on the reaction conditions. Thus, the presence of the hydrogen 
reducing gas is insufficient in the case of tungsten organometallics to 
prevent the contamination of the deposited tungsten film with carbon. 
Thus, it is an object of the invention to provide a method for depositing 
metal films, and especially tungsten metal films by both liquid and gas 
phase CVD. Such metal films contain significantly reduced heteroatom 
contaminants than hitherto possible. As used herein and in the appended 
claims the term "liquid CVD" refers to use of a solution deposited 
precursor compound in the CVD process. 
It is a further object of the invention to provide a thin metal film, 
especially tungsten having up to 5-10 mol % of another catalytic metal 
such as platinum, and other Group VIII transition metals such as 
ruthenium, osmium, cobalt, rhodium, iridium, nickel, and palladium. 
It is a further object of the invention to provide a process for the 
deposit of tungsten and/or other metals having dissolved therein or 
alloyed with, or heterogeneously admixed, one or more of the above 
catalytic metals. 
It is also an object of the invention to provide a process wherein tungsten 
and/or other metals can be deposited on a substrate from precursor film 
forming metal compounds and the purity improved by including precursor 
catalytic metal compounds which catalyze the removal of carbon from the 
deposited tungsten and other metal films and at the same time remain as a 
dissolved portion of the tungsten or other metal films, or at the metal 
surface or at grain boundaries. 
It is a further object of the invention to provide a process for 
controlling the amount of heteroatom such as carbon in the deposit of 
metal films in which one precursor would introduce carbon during metal 
deposition while another precursor would deposit the pure metal. Such 
depositions can be simultaneous or sequential. 
It is another object of the invention to provide metal films comprising a 
mixture of two metals with up to 10 mol % of a catalytic metal. 
It is a further object of the invention to provide a method for the laser 
induced deposition of pure metal films using precursor film forming metal 
compounds and precursor catalytic metal compounds in the presence of 
hydrogen gas wherein the laser beam is directed on the substrate at an 
incident angle ranging from perpendicular to parallel. 
It is also an object of the invention to provide a process for deposition 
of pure metals from precursor film forming metal compounds in the presence 
of precursor catalytic metal compounds and hydrogen gas wherein the 
precursor catalytic metal compound is first deposited on the substrate 
from a solvent solution followed by evaporation and thermal decomposition 
to leave the catalytic metal on the substrate, followed by CVD deposition 
of a metal from precursor film forming metal compounds in the presence of 
hydrogen gas. The above process is referred to herein and in the claims as 
"liquid CVD". 
It is also an object of the invention to provide processes for the 
deposition of pure metal films onto substrates by various combinations of 
gas CVD and liquid CVD processes using precursor film forming metal 
compounds and precursor catalytic metal compounds in the presence of 
hydrogen gas. 
It is also an object of the invention to selectively deposit metals onto a 
substrate using precursor film forming metal compounds and catalytic 
amounts of a precursor catalytic metal compound in the presence of 
hydrogen gas. In this manner, the process can be used to provide a 
patterned deposition of metals either from the gas phase deposition, 
either sequentially or simultaneously or by the liquid phase deposition of 
precursor compounds to deposit either the metals or catalytic metals or 
both or all sequentially or simultaneously. 
SUMMARY OF THE INVENTION 
The invention includes the deposition of a thin layer of tungsten and other 
metals onto a substrate with greatly improved purity levels. 
The process includes using one or more precursor film forming metal 
compound as the major film forming metal precursor, for example 
organotungsten, which is admixed with minor amounts of a precursor 
catalytic metal compound, for example, an organoplatinum compound, as a 
precursor to a catalytic metal in the presence of hydrogen gas and wherein 
the substrate is heated to bring about deposition of the film forming 
metal and catalysis by the catalytic metal for removal of carbon and other 
heteroatom contaminants as volatile hydrocarbon byproducts from the 
deposited metal film. 
The invention process also includes the liquid phase deposition of the 
precursor followed by metal deposition as well as gas phase deposition, 
sequentially or simultaneously to control and or to tailor deposited metal 
films and metal admixtures. Laser induced CVD and plasma enhanced CVD are 
also included in the invention. 
The invention also includes the improved purity metal films, especially 
tungsten metal films having relatively minor amounts of a catalytic metal 
dissolved, admixed, or alloyed therein.

DETAILED DESCRIPTION OF THE INVENTION 
It is intended that any procedure normally followed for chemical vapor 
deposition (CVD) or liquid vapor deposition can be used in carrying out 
the process of the invention. Deposition by means of laser photodeposition 
is also used and is an additional process element of the invention. 
Preferably, a reaction chamber is used having a means for introduction of 
gaseous substances. If desired, the reaction chamber can be provided with 
a window made of a special quartz material such as Spectrosyl.TM. or 
Carbosyl.TM. which permits the passage of infrared light for purposes of 
heating of the substrate. 
The reaction chamber also includes a susceptor or other support for holding 
the substrate onto which the tungsten is to be deposited. 
The substrates, for example, can be comprised among others of glass, fused 
silica, sapphire (001), silicon (100) and GaAs (100). Cleaning of the 
substrates by degreasing, acid or other etching prepares the surface of 
the substrate for the deposition process by removing impurities which can 
interfere with the deposition process. 
The process is particularly suitable for deposition of metals which are 
capable of resisting high temperatures and which preferentially form 
refractory carbides in the presence of carbon. Such metals of greatest 
interest include tungsten, molybdenum, niobium, and tantalum due to their 
low electrical resistivity. Of lesser interest are hafnium, thorium, 
titanium, uranium, vanadium, and zirconium due to their high electrical 
resistivity, although the invention process can be used advantageously to 
improve the purity of these and other deposited metal films for a variety 
of other applications. 
The precursor film forming metal compounds, for example, 
bis(cyclopentadienyl)dihydrotungsten, (C.sub.5 H.sub.5).sub.2 WH.sub.2, 
and the precursor catalytic metal compounds, for example CpPtMe.sub.3 are 
each separately mixed with helium, argon or other inert gas preferably to 
the point of saturation. The two gases are then preferably mixed together, 
as in a manifold, prior to introduction into the reaction chamber. The use 
of the inert gas prevents premature decomposition, especially of the 
precursor catalytic metal compounds in the presence of hydrogen gas. 
Alternatively, the precursor film forming metal compounds can be introduced 
with a stream of hydrogen gas, while the more reactive precursor catalytic 
metal compound is preferably introduced by a stream of inert gas. 
Hydrogen gas is separately introduced into the reaction chamber, preferably 
near to the substrate. Excellent results have been obtained using 
approximately equal volume portions of the hydrogen gas and the mixture 
taken as a whole of the inert gas saturated with the precursor film 
forming metal compounds and the inert gas saturated with the precursor 
catalytic metal compounds . 
Saturation of the inert gas is effected by passage of the inert gas over 
the precursor film forming metal compounds or over the precursor catalytic 
metal compounds. 
The relative amounts of the precursor film forming metal compounds and the 
precursor catalytic metal compounds are controlled by the flow rates. The 
precursor catalytic metal compounds are included to provide up to 10 mol 
%, with from 0.1-5 mol % being most preferred. The exact amount will 
depend upon the identity of the precursor film forming metal compounds and 
of the precursor catalytic metal compounds used. 
All of the gases are preferably directed in a stream across the surface of 
the substrate. The substrate is heated to and maintained at a temperature 
sufficiently high to cause decomposition of the precursor film forming 
metal compounds. The exact temperature will depend upon the identity and 
chemical, thermal, and stability makeup of the compounds used under the 
reaction conditions. A temperature of approximately 
200.degree.-400.degree. C., has given good results using in the case of 
(C.sub.5 H.sub.5).sub.2 WH.sub.2 on various substrates. 
Heating of the substrate is preferably by means of an infrared lamp which 
is focused through the quartz window in order to specifically heat the 
substrate. 
The precursor film forming metal compound gas mixture and the precursor 
catalytic metal compound gas mixture are preferably prewarmed to a 
temperature of approximately 60.degree. C. 
The pressure within the reaction chamber during the reaction can be ambient 
but is more preferably a dynamic vacuum so that the stream of gases is 
constantly passing over and contacting the substrate surface onto which 
the film forming metal such as tungsten and the catalytic metal, such as 
platinum are being continuously deposited. 
In some cases, a preliminary surface treatment with the catalytic metal is 
feasible. Alternatively, the catalytic metal deposited from the catalytic 
metal precursor in the early part of the CVD process is sufficient to 
yield relatively pure metal film. 
In some cases the precursor metal compound or compounds and/or the 
precursor catalytic metal compound can be introduced into a plasma in 
plasma-enhanced CVD processes. 
The precursor from which the film forming metal is deposited is one or more 
vaporizable or soluble precursor film forming metal compounds having the 
formula L.sub.n MR.sub.m. The precursor film forming metal compounds is 
included as a major component of a gas mixture which is admixed with a 
minor amount of at least one vaporizable precursor catalytic metal 
compound having the formula 
EQU L.sub.n M'R.sub.m 
In the above formulas, L is a .pi.-bonding organic ligand such as ethylene, 
allyl, methylallyl, butadienyl, pentadienyl, cyclopentadienyl, 
methycyclopentadienyl, cyclohexadienyl, hexadienyl, cycloheptatrienyl, or 
alkyl or alkyl silyl or fluorinated derivatives of such compounds having 
sufficient volatility of the precursor metal compound to be of utility in 
CVD or liquid CVD; 
M is a precursor metal such as a transition metal, Ti (titanium), Zr 
(zirconium), Hf (hafnium), V (vanadium), Nb (niobium), Ta (tantalum), Cr 
(chromium), Mo (molybdenum), W (tungsten), Mn (manganese), Re (Rhenium), 
Fe (iron), Ru (ruthenium), Os (osmium), or a main group metal such as Al 
(aluminum), Ga (gallium), In (indium), Si (silicon), Ge (germanium), Sn 
(tin), or a lanthanide or actinide metal such as La (lanthanum), Nd 
(neodymium), Sm (samarium), U (uranium), Pu (plutonium; 
M' is a metal selected from the group of metals that can catalyze 
hydrogenation and hydrogenolysis reactions of unsaturated and saturated 
organic ligands, L and R, to yield volatile byproducts and also can 
catalyze the hydrogenation of surface carbon to methane as in 
Fischer-Tropsch catalysis in the presence of hydrogen, and consisting 
among others of the Group VIII transition metals of Co (cobalt), Rh 
(rhodium), Ir (iridium), Ni (nickel), Pd (palladium), Pt (platinum), Fe 
(iron), Ru (ruthenium), and and Os (osmium); 
R is a G-bonding ligand radical such as hydrogen, methyl, ethyl, n- or iso- 
propyl, n-, sec-, or t- butyl, benzyl, phenyl, and silylated and 
fluorinated derivatives having sufficient volatility or solubility of the 
precursor metal compound to be of utility in CVD or liquid CVD; 
n is a number from 0 to the valence of said metal, 
m is a number from 0 to the valence of the metal, where m plus n allow a 
stable configuration of the precursor metal compound to allow the 
precursor compound to be either volatile or soluble. 
Examples of the precursor film forming metal compounds include but are not 
limited to: 
bis(cyclopentadienyl)dihydromolybdenum, (C.sub.5 H.sub.5).sub.2 MoH.sub.2 ; 
bis(cyclopentadienyl)(ethylene)molybdenum, (C.sub.5 H.sub.5).sub.2 
MoC.sub.2 H.sub.2 ; tris(butadiene)molybdenum, (C.sub.4 H.sub.6).sub.3 Mo; 
tris(cyclobutadienyl)molybdenum, (C.sub.4 H.sub.4).sub.3 Mo; 
dicylopentadienyltrihydroniobium, (C.sub.5 H.sub.5).sub.2 NbH.sub.3 ; 
bis(cyclopentadienyl)niobiumborohydride, (C.sub.5 H.sub.5).sub.2 NbH.sub.2 
BH.sub.2 ; bis(cyclopentadienyl)hydro(ethylene)niobium, (C.sub.5 
H.sub.5).sub.2 NbHC.sub.2 H.sub.2 ; bis(cyclopentadienyl)allylniobium, 
(C.sub.5 H.sub.5).sub.2 NbC.sub.3 H.sub.4 ; pentamethyltantalum, Ta 
(CH.sub.3).sub.5 ; bis(cyclopentadienyl)trihydrotantalum, (C.sub.5 
H.sub.5).sub.2 TaH.sub.3 ; bis(cyclopentadienyl)trimethyltitanium, 
(C.sub.5 H.sub.5).sub.2 Ti(CH.sub.3).sub.3 ; titanocene borohydride, 
(C.sub.5 H.sub.5).sub.2 TiH.sub.2 BH.sub.2 ; 
bis(cyclopentadienyl)dimethyltitanium, (C.sub.5 H.sub.5).sub.2 
Ti(CH.sub.3).sub.2 ; bis(cyclopentadienyl)methylvanadium, (C.sub.5 
H.sub.5).sub.2 VCH.sub.3 ; 1,1'-dimethylvanadocene, (C.sub.5 H.sub.4 
CH.sub.3).sub.2 V; bis(2,4-dimethylpentadienyl)vanadium, (C.sub.5 H.sub.3 
(CH.sub.3).sub.2).sub.2 V; bis(cyclopentadienyl)dihydrotungsten, (C.sub.5 
H.sub.5).sub.2 WH.sub.2 ; trisbutadienetungsten, (C.sub.4 H.sub.6).sub.3 
W; hexamethyl tungsten, (CH.sub.3).sub.6 W; and 
bis(cyclopentadienyl)(cyclobutadiene)zirconium, (C.sub.5 H.sub.5).sub.2 
ZrC.sub.4 H.sub.4. 
Examples of the precursor organocatalyst metal compound comprise among 
others: 
CpPtMe.sub.3 ; CpPt(allyl); CpPt(methylallyl); MeCpPt(methylallyl); 
CpPt(CO)CH.sub.3 ; MeCpPt(CO)CH.sub.3 ; bisallylPd; 
(methylallyl)Pd(allyl); bis(2-methylallyl)palladium; 
(cyclopentadienyl)(allyl)palladium; (CH.sub.3 C.sub.5 H.sub.4)PtMe.sub.3 ; 
(C.sub.3 H.sub.5).sub.3 Rh; (C.sub.3 H.sub.5).sub.3 Ir; CpIr(hexadiene); 
(C.sub.5 H.sub.5)Ir(C.sub.6 H.sub.8); (C.sub.5 
(CH.sub.3).sub.5)Ir(ethylene).sub.2 ; (C.sub.5 H.sub.7)Ir(C.sub.8 
H.sub.8); (CH.sub.3 C.sub.5 H.sub.4).sub.2 Ni; 
(cyclopentadienyl)(cyclohexadienyl)cobalt, (C.sub.5 H.sub.5)Co(C.sub.6 
H.sub.7); (CH.sub.3 C.sub.5 H.sub.4)Co(MeCp); (C.sub.5 H.sub.5)CoCp; 
(cyclobutadienyl)(cyclopentadienyl)cobalt, (C.sub.4 H.sub.4)CoC.sub.5 
H.sub.5 ; bis(cyclopentadienyl)cobalt; (C.sub.5 H.sub.5).sub.2 Co; 
bis(methylcyclopentadienyl)cobalt, (CH.sub.3 C.sub.5 H.sub.4).sub.2 Co; 
cyclopentadienyl(1,3-hexadienyl)cobalt, (C.sub.5 H.sub.5)CoC.sub.6 H.sub.7 
; (cyclopentadienyl)(5-methyl-cyclopentadienyl)cobalt, (C.sub.5 
H.sub.5)CoC.sub.5 H.sub.4 CH.sub.3 ; (C.sub.5 H.sub.5)Co(CO).sub.2 ; 
(C.sub.6 H.sub.8)CoCp; bis(ethylene)(pentamethylcyclopentadienyl)cobalt, 
((CH.sub.3).sub.5 C.sub.5)Co(C.sub.2 H.sub.2).sub.2 ; triallylchromium, 
(C.sub.3 H.sub.4).sub.3 Cr; bis(cyclopentadienyl)chromium, (C.sub.5 
H.sub.5).sub.2 Cr; (cycloheptatrienyl)(cyclopentadienyl)chromium, (C.sub.7 
H.sub.7)Cr(C.sub.5 H.sub.5); bis(cyclopentadienyl)iron, (C.sub.5 
H.sub.5).sub. 2 Fe; (2,4-cyclohexadienyl)(cyclopentadienyl)iron, (C.sub.6 
H.sub.7)Fe(C.sub.5 H.sub.5); 
(cyclopentadienyl)(methylcyclopentadienyl)iron, (C.sub.5 
H.sub.5)Fe(C.sub.5 H.sub.4 CH.sub.3);bis(methylcyclopentadienyl)iron, 
(CH.sub.3 C.sub.5 H.sub.4).sub.2 Fe; 
(cycloheptatrienyl)(cyclopentadienyl)manganese, (C.sub.5 
H.sub.5)Mn(C.sub.7 H.sub.8); (benzene)(cyclopentadienyl)manganese, 
(C.sub.5 H.sub.5)Mn(C.sub.6 H.sub.6); ethenylosmocene, (C.sub.5 
H.sub.5)Os(C.sub.5 H.sub.4 CHCH.sub.2); 1,1'-dimethylosmocene, (C.sub.5 
H.sub.4 CH.sub.3).sub.2 Os; vinylosmocene, (C.sub.5 H.sub.5)O.sub.5 
(C.sub.5 H.sub.4 CH.sub.2 CH.sub.3); bis(cyclopentadienyl)hydridorhenium, 
(C.sub.5 H.sub.5).sub.2 ReH; hexamethylrhenium, (CH.sub.3).sub.6 Re; 
HRe(CO).sub.5 ; cyclopentadienyl(methylcyclopentadienyl)ruthenium, 
(C.sub.5 H.sub.5)Ru(C.sub.5 H.sub.4 CH.sub.3); ruthenocenylacetylene, 
(C.sub.5 H.sub.5)Ru(C.sub.5 H.sub.4 CCH); vinylruthenocene, (C.sub.5 
H.sub.5)Ru(C.sub.5 H.sub.4 CHCH.sub.2); 
bis(methylcyclopentadienyl)ruthenium, Ru(CH.sub.3 C.sub.5 H.sub.4).sub.2 ; 
ethylruthenocene, (C.sub.5 H.sub.5)Ru(C.sub.5 H.sub.4 CH.sub.2 CH.sub.3). 
Examples of the preferred precursor film forming metal compounds include: 
bis(cyclopentadiene)dihydrotungsten, (C.sub.5 H.sub.5).sub.2 WH.sub.2 ; 
trisbutadienetungsten, (C.sub.4 H.sub.6).sub.3 W. 
The preferred precursor catalytic metal compounds are: 
CpPtMe.sub.3 or MeCpPtMe.sub.3. 
By the term "soluble" as used herein and in the appended claims is meant to 
have sufficient solubility to enable the precursor compound to be 
dissolved in an organic solvent. Examples of such organic solvents 
includes among others hexane, cyclohexane, tetrahydrofuran, 
1,2-dimethoxyethane, acetonitrile, and the like. 
The solution is applied to the surface of the substrate and the solvent 
removed by evaporation. Thermal heating and/or laser induced decomposition 
in the presence of hydrogen gas and the catalytic metal causes the metal 
film to be formed. 
The precursor film forming metal compounds for metal film forming are 
included in major amounts with relatively minor amounts of the precursor 
catalytic metal compounds. With respect to the amount of the precursor 
catalytic metal compounds, there can be included up to about 10 mol %. 
The invention will be more easily understood by reference to the following 
examples which are presented for the purpose of illustrating the invention 
and are in no way intended to constitute a limitation thereof. 
EXAMPLE 1 
PREATION OF PRECURSOR FILM FORMING METAL COMPOUNDS AND PRECURSOR 
CATALYTIC METAL COMPOUNDS 
The following precursor film forming metal compounds and precursor 
catalytic metal compounds were prepared: 
(a) CpPtMe.sub.3 
(b) (CH.sub.3 C.sub.5 H.sub.4)PtMe.sub.3 
(c) (C.sub.3 H.sub.5).sub.3 Rh 
(d) (C.sub.3 H.sub.5).sub.3 Ir 
(e) HRe(CO).sub.5 
(f) (CH.sub.3 C.sub.5 H.sub.4).sub.2 Ni 
(g) (C.sub.5 H.sub.5).sub.2 CoCP 
(h) (C.sub.5 H.sub.5)Co(C.sub.6 H.sub.7); 
(i) (CH.sub.3 C.sub.5 H.sub.4)Co(MeCp); 
where Cp is cyclopentadienyl; Me is methyl; (C.sub.6 H.sub.7) is 
cyclohexadiene; and MeCp is methylcyclopentadiene. 
Compound (a) was prepared from PtMe.sub.3 I and NaCp using the procedure 
described in Robinson, S. and Shaw, B., J. Chem. Soc., 277, 1529 (1965), 
except that toluene was used instead of benzene as the solvent, and the 
reaction was started at -77.degree. C. The yield obtained was 52%. 
Compound (a) was also obtained using the Robinson and Shaw procedure. 
Compound (b) was prepared as follows: 445 mg PtMe.sub.3 I in 25 ml ethyl 
ester dried over potassium and benzene was added dropwise at -78.degree. 
C. under nitrogen to 1.5 ml of approximately 1.1 M MeCpNa. The solution 
was slowly raised back to room temperature over 12 hours while stirring. 
Ethyl ether and THF were removed at -20.degree. to -30.degree. C., leaving 
an oily residue that sublimed at room temperature. A cold finger at 
-15.degree. C. gave 62 mg of a yellow compound. The residue was extracted 
with pentane and filtrated in air. The pentane was removed at -20.degree. 
C. 
Compound (c) was prepared as follows: 100 mg RhCl.sub.3 anhydrous was 
stirred in 50 ml ethyl ether dried over potassium and benzophenone and 
added to a ten times excess of allylMgCl (2.0 M in THF (Aldrich)). After 
stirring for 12 hours, dry ice was added to the decomposed excess 
allylMgCl, and the mixture was dried under vacuum at -15.degree. C. 
Pentane was then used to exhaust the residue and pentane was removed at 
about 5 degrees centigrade by water evaporation. After sublimation (cold 
finger at temperature of running water, flask at room temperature), a 
yellow solid formed on the cold finger. 
Compound (d) was prepared as follows: 0.200 g IrCl.sub.3 in 4 ml toluene 
was dried and added dropwise under argon gas to 3.4 ml of 2M allylMgCl in 
THF (Aldrich) at -78 degrees C. The black IrCl.sub.3 remained undissolved. 
The solution was then raised to room temperature and heated on a water 
bath to 50.degree. C. for 10 hours. The solution was dark and no 
precipitate formed. A few lumps of dry ice were added to destroy any 
remaining Grignard reagent. Solvent was removed at 0.degree. C. under 
10.sup.-2 torr vacuum. 50 ml pentane was used to extract the product from 
the raw product, and the pentane was removed at 15.degree.-20.degree. C. 
and 10.sup.-2 torr to give the crude product. The crude product was then 
purified by sublimation at 15 torr and 50.degree. C. with a cold finger 
at 10.degree. C. for about 30 minutes. 
Compounds (e) to (i) were prepared using similar procedures. 
EXAMPLE 2 
DEPOSITION OF TUNGSTEN IN THE PRESENCE OF HYDROGEN AND AN ORGANOPLATINUM 
CATALYST 
The reaction materials were prepared from precursors. The organotungsten 
compound, Cp.sub.2 WH.sub.2 was prepared from WCl.sub.6 following the 
procedure outlined by M. L. H. Green, J. A. McCleverty, L. Pratt and G. 
Wilkinson, J. Chem. Soc., 4854 (1961); see also Organometallic Syntheses, 
J. J. Eisch and R. B. King, Eds., Vol. 1, Transition Metal Compounds, R. 
B. King, Ed. (Academic Press, New York, N.Y., 1965) 79. 
The precursor CpPtMe.sub.3 was prepared from K.sub.2 PtCl.sub.6 according 
to the method described by Z. Xue, H. Thridandam, H. D. Kaesz and R. F. 
Hicks, Chem. Mater., 4, 162 (1992). Alternatively, the CpPtMe.sub.3 can be 
purchased directly from Strem Chemical Company, Newburyport, Mass. 
The reaction chamber was comprised of a glass tube having a diameter of 2.5 
cm. The tungsten was deposited on both glass and silicon (100) substrates. 
Prior to deposition, the glass was washed in ethylene chloride and 
methanol, rinsed in deionized water, and dried in air. The silicon wafers 
were similarly prepared but deionized after water rinsing, also included 
etching for 10 seconds in 10% by volume hydrofluoric acid, rinsing again 
in water, and then drying in air. 
The substrate was placed within the glass tube. The section of the tube 
containing the substrate which was about 3 cm long, was heated to 
380.degree..+-.20.degree. C. by means of heating tape wrapped uniformly 
around the tube. 
The Cp.sub.2 WH.sub.2 was placed 5 cm upstream of the substrate and was 
heated to 100.degree.-150.degree. C. by a resistance heater located 
directly underneath the tube. At these temperatures the vapor pressure of 
Cp.sub.2 WH.sub.2 is .about.0.01 Torr. During the deposition period, 
hydrogen was fed at 8 cm.sup.3 /min, and argon was fed at 16 cm.sup.3 
/min. The argon was passed through a glass frit containing CpPtMe.sub.3 at 
23.degree. C. so that the argon became saturated with 0.045 Torr of the 
precursor catalytic metal compound. 
The argon and the hydrogen were purified prior to reaction by passing 
through a deoxygenating catalyst (OXYSORB.TM., Altec Associates, Inc.) and 
13X molecular sieves. The relative ratios or percentages by volume of the 
Cp.sub.2 WH.sub.2 and CpPtMe.sub.3 were 90/10 mol %. The gases were flowed 
over the substrate for a period ranging from 6 to 20 hours. 
Using the silicon (100) substrates, it was found that tungsten decomposed 
more readily than on the glass substrates. For example, the glass surface 
was covered with a transparent brown layer of material after 6 hours of 
deposition. After the same amount of time, the silicon was covered with a 
uniform, highly reflective metal film. 
It was estimated that the growth rate of the films was between 0.05 and 
0.15 .ANG./s. The films exhibited excellent adherence to the silicon as 
demonstrated by the fact that they could not be removed by cellophane tape 
application. 
The structure and composition of the deposited W/Pt films were analyzed by 
X-ray diffraction, scanning electron microscopy, and Auger electron 
spectroscopy with depth profiling. A 4-point probe was used to determine 
the sheet resistivity and a depth profiling measurement yielded the 
thickness of the films deposited. 
It was found that the deposited films are amorphous and comprised of 
100-500 .ANG. clusters as shown by scanning electron micrographs. It was 
also found that the clusters could be converted into microcrytallites by 
annealing in hydrogen at 750.degree. C. 
FIG. 2 shows an Auger depth profile of the W/Pt film. The bulk film is 
sputtered from 20 to 140 minutes after which the Si signal appears due to 
sputtering of the silicon substrate. FIG. 2 does not show the atomic 
contribution from the silicon. The film produced was found to contain 
89.6% W, 3.3% Pt, 5.3% C, and 1.8% O. It is believed that this is the 
highest purity tungsten film ever produced from the thermal decomposition 
of an organotungsten precursor. 
It is believed that the high purity is a consequence of the catalytic 
hydrogenation and hydrogenolysis of the hydrocarbon ligands by the 
codeposited platinum. 
The above results demonstrate that increased purity of tungsten films can 
be effected by including small amounts of CpPtMe to improve the purity of 
transition metal films obtained by chemical vapor deposition of precursor 
film forming metal compounds. 
EXAMPLE 3 
DEPOSITION OF TUNGSTEN FROM ORGANOTUNGSTEN IN THE ABSENCE OF A PRECURSOR 
CATALYST METAL COMPOUND 
This example is presented for purposes of comparison only and is not in 
accordance with the process of the invention. 
The procedure of Example 2 was repeated except that tungsten was deposited 
from Cp.sub.2 WH.sub.2 in the presence of hydrogen but without the 
presence of an organoplatinum catalyst. 
Hydrogen was fed to the reactor upstream of the precursor at 2 cm.sup.3 
/min (at 20.degree. C.). 
X-ray diffraction, scanning electron microscopy, and Auger electron 
spectroscopy with depth profiling was also used to analyze the structure 
and composition of the W films deposited. A four-point probe was used to 
measure sheet resistivity and film thickness was determined with depth 
profiling measurements. 
The film thickness was 1,450 .ANG.. 
FIG. 1 shows the X-ray diffraction pattern of tungsten film deposited on 
silicon (100) after annealing in hydrogen at 750.degree. C. for 21/2 
hours. As shown, the sharp lines near 2.theta.=40.degree., 58.degree., 
73.degree., and 87.degree. are due to W metal. A silicon substrate shows a 
broad peak at 69.degree.. No peaks were found for tungstensilicide. 
It was found that the sheet resistivity of the unannealed W films averaged 
54.+-.4 .mu..OMEGA..cm. This is compared with the value for bulk tungsten 
metal of 5.6 .mu..OMEGA..cm. It is believed that the high resistivity is 
probably due to the amorphous nature of the deposit as well as the poor 
contact between adjacent metal clusters. 
Table 1 shown below compares the compositions of W/Pt films deposited 
according to example 2 and W films deposited according to example 3. 
An examination of Table 1 indicates that when tungsten is deposited without 
the organoplatinum catalyst, the composition of the film is 71.8% W, 25.1% 
C, and 3.1% O. Thus, there is significantly decreased carbon contamination 
(25.1% C compared to 5.3% C) and decreased contamination with oxygen (3.1% 
O compared to 1.8% O) when the precursor catalytic metal compound is 
codeposited with the tungsten precursor. 
These results demonstrate the advantage of including small amounts of 
CpPtMe.sub.3 or equivalent precursor catalytic metal compounds for 
codeposition to enhance the purity of transition metal films obtained by 
chemical vapor deposition. 
EXAMPLE 4 
LASER PHOTODEPOSITION 
Using the reaction chamber substantially as described in Example 3, glass, 
silicon, fused silica, sapphire (001), and GaAs (100) substrates are 
deposited with tungsten using Cp.sub.2 WH.sub.2 and CpPtMe.sub.3 in the 
presence of hydrogen. 
The substrates are prepared in the same manner as described in Example 3. 
A stream of argon gas is separately passed over crystals of Cp.sub.2 
WH.sub.2 and over crystals of CpPtMe.sub.3 to saturate the argon gas with 
the respectively compounds. 
Hydrogen gas is introduced into the reaction chamber in proximity to a 
laser beam, and gas flow is parallel to the surface of the substrate. 
All photolyses are carried out at atmospheric pressure with the laser beam 
perpendicular to the surface. An alternative deposition using the laser 
beam parallel to the surface to induce a gas phase reaction that surface 
deposits metal can also be used as well as laser beam deposition at angles 
between parallel and perpendicular to the surface. 
The laser is a 308 nm line of a XeCl excimer laser or the 351 and 364 nm 
lines of an argon ion laser. 
The deposition is first carried out by irradiating a circle 1 mm in 
diameter with 2.6 mJ/pulse at 10 Hz using the 308 nm band. Visible mirrors 
are formed on the substrates in about 10 minutes. The deposited films have 
a thickness of about 1000 angstroms. 
Photodeposition is carried out under CW conditions with fluences of 4-5 
mW/mm.sup.2 at laser wave lengths of 351 and 364 nm. Using the same flow 
rates, mirror-like deposits are observed in about 10 minutes. 
Analysis of the films using Auger electron spectroscopy showed 
substantially the same pure films as obtained following the process of 
Example 3. 
The substrate is patterned using a mask and a 40 mm lens for the laser. The 
image is focussed below the surface of the substrate in order to minimize 
the focus, and hence deposition, on the cell windows. Successful patterned 
depositions are obtained. 
Laser induced and plasma enhanced metal deposition can also be used in 
combination with various combinations of gas phase CVD and liquid CVD as 
above described. 
Various modifications of the invention are contemplated which will be 
obvious to those skilled in the art and which can be resorted to without 
departing from the spirit and scope of the invention as defined in the 
following appended claims.