Use of organometallic compounds to deposit thin films from the g

Details Use of organometallic compounds to deposit thin films from the g Use of organometallic compounds to deposit thin films from the g

1991-09-06

1993-05-11

Lusigan, Michael

Coating processes

Coating by vapor, gas, or smoke

Organic coating applied by vapor, gas, or smoke

556 1, 556 13, 556 70, C23C 1600

Patent

active

052099520

DESCRIPTION:

BRIEF SUMMARY
SUMMARY OF THE INVENTION

The invention relates to the use of organometallic compounds containing, as metals, aluminum, gallium or indium for the deposition of thin films or epitactic layers from the gas phase.
The deposition of layers of this type from either pure elements of group III or from III-V combinations, such as, for example, gallium arsenide, indium phosphide or gallium phosphide, can be used to produce electrical, electronic, optical and optoelectronic switching elements, compound semiconductors and lasers. The deposition of these layers is effected from the gas phase.
The properties of these films depend on the deposition conditions and on the chemical composition of the deposited film.
All known methods, such as the metal-organic chemical vapor deposition (MOCVD) method, the photo-metal-organic vapor phase (photo-MOVP) method, in which the substances are decomposed by UV irradiation, the laser chemical vapor deposition (laser CVD) method or the metal-organic magnetron sputtering (MOMS) method, are suitable for the deposition from the gas phase. The advantages over other methods are a controllable layer growth, an exact doping control, simple handling due to the standard- or low-pressure conditions, and production friendliness.
In the MOCVD method, organometallic compounds which decompose at a temperature below 1100.degree. C. with deposition of the metal are employed. Typical apparatus currently used for MOCVD comprise a "bubbler" with an inlet for the organometallic component, a reaction chamber which contains the substrate to be coated, and a source for a carrier gas, which should be inert toward the organometallic component. The "bubbler" is kept at a constant, relatively low temperature, which is preferably above the melting point of the organometallic compound, but far below the decomposition temperature. The reaction or decomposition chamber preferably has a much higher temperature which is below 1100.degree. C., at which the organometallic compound decomposes completely and the metal is deposited. The organometallic compound is converted into the vapor state by the carrier gas and flushed into the decomposition chamber with the carrier gas. The mass flow of the vapor can readily be monitored, and controlled growth of the thin layers is thus also possible.
Hitherto, primarily metal alkyls, such as, for example, trimefhylaluminum, trimethylaluminum or trimethylindium, have been used for gas-phase deposition. However, these compounds are extremely air sensitive, auto-inflammable and in some cases decompose even at room temperature. Complex safety measures are therefore necessary for the preparation, transport, storage and use of these compounds. Some somewhat more stable adducts of metal alkyls with Lewis bases, such as, for example, trimethylamine and triphenylphosphine, are also known (for example described in GB 2,123,422, EP-A 108,469 or EP-A 176,537), but these are only suitable to a limited extent for gasphase deposition due to the lower vapor pressure. Low vapor pressures are frequently attributable to the presence of dimers, trimers or polymers.
The object of the present invention was to find organometallic compounds which are simple to handle and stable at room temperature and which have a sufficiently high vapor pressure so that they are suitable for the various methods of gas-phase deposition.
It has now been found that organometallic compounds of aluminum, gallium and indium, which contain branched or bulky radicals have a suitable vapor pressure and are thus highly suitable for gas-phase deposition. Similar compounds are known from EP-A 0,295,467. However, the compounds described there are usually dimeric and are therefore again not used for deposition from the gas phase, but instead for deposition from the liquid phase.
The invention thus relates to the use of organometallic compounds of the formula I
M is aluminum, gallium or indium,
n is 1, 2 or 3
Y is --NR.sup.2 R.sup.3, --PR.sup.2 R.sup.3, --AsR.sup.2 R.sup.3 or --SbR.sup.2 R.sup.3,
R.sup.1, R.sup.2, R.sup.4 and R.sup.5

REFERENCES:
Mawry, F. et al., Mass Spectrometric Study of the Pyrolysis of Organometallic Precursors Usable in GaAs Vaporphase Epitaxy, Journal of Crystal Growth 91(1988), pp. 97-104.

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