Organometallic complexes of aluminium, gallium and indium

Details Organometallic complexes of aluminium, gallium and indium Organometallic complexes of aluminium, gallium and indium

1996-04-04

1998-11-10

Nazario-Gonzalez, Porfirio

Coating processes

Coating by vapor, gas, or smoke

Metal coating

556 1, 556176, 427585, 427593, 427587, C23C 1426, C23C 800, C07F 500

Patent

active

058340580

DESCRIPTION:

BRIEF SUMMARY
This application was filed as a request for U.S. examination under 35 U.S.C. .sctn.371 of International application No. PCT/GB94/01696 filed Aug. 2, 1994.
This invention relates to volatile organometallic complexes of aluminium, gallium and indium.
Volatile organometallic compounds of aluminium, gallium and indium, e.g. the aluminium, gallium and indium alkyls, especially trimethyl gallium and triethyl indium, are of considerable interest as volatile sources of aluminium, gallium and indium metal in CVD (chemical vapour deposition) processes. Of particular interest are CVD processes employing a volatile source of aluminium, gallium or indium in the manufacture, by chemical vapour deposition on the surface of a suitable substrate, of compound semi-conductor materials such as gallium arsenide (GaAs), indium arsenide (InAs), indium phosphide (InP), indium aluminium gallium arsenide (InAlGaAs) or wide bandgap material systems such as aluminium, gallium or indium nitride.
Metal alkyls, such as trimethylaluminium, trimethylgallium and triethylindium, are, however, unstable at elevated temperature, pyrophoric and extremely sensitive to air, and are explosively hydrolytic in contact with moisture. Such materials can, therefore, be manufactured and used only under very stringent conditions.
In accordance with the present invention we have discovered that the amidine complexes of aluminium, gallium and indium dialkyls possess good stability at room temperature, are substantially non-pyrophoric, and show excellent thermal stability in the vapour phase. They are, therefore, of high utility as a volatile source of aluminium, gallium and indium in CVD processes of all kinds.
In accordance with the present invention, therefore, there are provided novel organometallic complexes of the formula I preferably methyl or ethyl; and L is an organic ligand containing a amidine ligands are amidines of the formula II: cycloalkyl, optionally including an --NH-- group in the ring, C.sub.3-C.sub.8 cycloalkenyl, phenyl or substituted phenyl containing from 1-3 (C.sub.1 -C.sub.8)alkyl or halo-substituents, trimethylsilyl or halogen, the R' groups being the same or different.
Typical amidine ligands within that formula are N,N'-diphenylbenzamidine, N,N'-di(p-chlorophenyl)acetamidine, N,N'-diphenylformamidine, N,N'-di(p-fluorophenyl)acetamidine, benzamidine, acetamidine, and N,N'-dicyclohexylacetamidine. Other suitable amidine ligands will be apparent to those skilled in the art, as will be methods for the preparation of such amidines.
The amidine complexes of this invention are prepared by reacting a molar excess of the trialkylaluminium, trialkylgallium or trialkylindium compounds, e.g. trimethylaluminium, trimethylgallium or triethylindium with the ligand under anhydrous conditions in vacuo or under an inert atmosphere, preferably, but not necessarily in the presence of an anhydrous hydrocarbon solvent such as toluene or n-hexane. That reaction may be represented as follows: ##STR1##
The alkane (RH) evolved during the course of the reaction is removed preferably continuously, following which the product complex can be recovered by removal of the excess aluminium, gallium or indium trialkyl and the solvent, if present, preferably by distillation in vacuo.
Whilst the alkyl substituents of the aluminium, gallium or indium trialkyl reactant will usually be the same, trialkyls containing different alkyl groups may be used giving rise to complexes of the formula I where the R groups are different.
Aluminium, gallium and indium complexes in accordance with this invention and the preparation thereof is illustrated by the following Examples and by the accompanying drawings. In all the Examples, the reactions were carried out on a vacuum line.
In the drawings
FIG. 1 shows the crystal structure of the dimethylgallium N,N'-diphenylbenzamidine complex.
FIG. 2 shows the thermogravimetric analysis curve of that and various other complexes according to the invention.


EXAMPLE 1



Dimethylgallium N,-N'-diphenylbenzamidine

N,N'-diphenylbenzamidine (0

REFERENCES:
Lechler et al., Journal of Organometallic Chemistry, vol. 359, pp. 1-12, (1989).
Hunsen et al., Journal of Organometallic Chemistry, vol. 145, pp. 277-284, (1978).
Locke et al., Journal of Organometallic Chemistry, vol. 420, pp. 1-12, (1991).

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