Organoindium compounds

Details Organoindium compounds Organoindium compounds

2003-01-17

2004-01-20

Nazario-Gonzalez, Porfirio (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heavy metal containing

C427S252000, C427S593000, C438S680000, C438S681000

Reexamination Certificate

active

06680397

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to the field of organometallic compounds. In particular, the present invention relates to the certain indium compounds suitable for use in indium vapor deposition processes.
Metal films may be deposited on surfaces, such as non-conductive surfaces, by a variety of means such as chemical vapor deposition (“CVD”), physical vapor deposition (“PVD”), and other epitaxial techniques such as liquid phase epitaxy (“LPE”), molecular beam epitaxy (“MBE”), and chemical beam epitaxy (“CBE”). Chemical vapor deposition processes, such as metalorganic chemical vapor deposition (“MOCVD”), deposit a metal layer by decomposing organometallic precursor compounds at elevated temperatures, i.e., above room temperature, either atmosphere pressure or at reduced pressures.
A wide variety of metals may be deposited using such CVD or MOCVD processes. See, for example, Stringfellow,
Organometallic Vapor Phase Epitaxy: Theory and Practice,
Academic Press, 2
nd
Edition, 1999, for an overview of such processes. For example, indium is used in a variety of metal films produced by epitaxial growth, particularly in the manufacture of electronic devices such as integrated circuits and light emitting diodes (“LEDs”). Exemplary indium containing metal films include indium-phosphide (“InP”), indium-gallium-arsenide (“InGaAs”), indium-gallium-aluminum-phosphide (“InGaAlP”), indium-gallium-arsenic-phosphide (“InGaAsP”), indium-gallium-arsenide/gallium-arsenide/aluminum-gallium-arsenide (“InGaAs/GaAs/AlGaAs”), indium-arsenide (“InAs”), indium-antimonide (“InSb”) and indium-arsenic-bismuthide (“InAsBi”).
Metal layers and alloy layers are typically formed in CVD or MOCVD processes by the decomposition of one or more precursor compounds. A wide variety of precursor compounds may be used. In conventional CVD processes, suitable precursor compounds must have a sufficient vapor pressure to allow them to be transported to the deposition chamber. From ease of handling and transportation to the deposition chamber, liquid precursor compounds are preferred.
A number of indium compounds are known as CVD and/or MOCVD precursors. Solid trimethylindium is the conventional precursor of choice for use in the manufacture of indium-containing semiconductors. However, this compound imposes several problems during the growth of indium-containing alloys because of inconsistency in the compound's evaporation rate when a conventional bubbler-type container is used in the delivery system. Such inconsistency in the vapor phase concentration of trimethylindium has been attributed to a) reduction in the surface area of the solid trimethylindium with the progress of growth, b) formation of voids or channels in the solid trimethylindium that offer only minimal contact with the carrier gas, c) sublimation of the trimethylindium to regions of the delivery system inaccessible to the carrier gas flow, and d) recrystallization of the trimethylindium leading to changes in its surface area that prohibit evaporation.
Various attempts have been tried to overcome these difficulties, but have had limited success. These have included reversing the direction of carrier gas flow, depositing the indium precursor on an inert porous solid support, suspending the precursor in a liquid medium, suspending the precursor in another alkylindium and using hybrid organoindium compounds instead of trimethylindium. For example, U.S. Pat. No. 4,720,560 (Hui et al.) discloses hybrid organometallic compounds having the formula MRx where x=2-4; the Rs are independently selected from hydrogen, lower alkyl, phenyl, alkyl substituted phenyl, cyclopentadienyl, or alkyl substituted cyclopentadienyl; M is an element of Groups 2B or 3A of the periodic table, bismuth, selenium, tellurium, beryllium and magnesium; wherein at least 2 of the Rs are different. The only indium compounds disclosed in this patent are dimethylethylindium and diethylmethylindium. These indium compounds have not achieved commercial success because they do not have a sufficiently high vapor pressure and because they do not exist as a single species. Both dimethylethylindium and diethylmethylindium exist as an equilibrium with trimethylindium and triethylindium, such equilibrium being temperature dependent. Such an equilibrium mixture is disadvantageous because during the vapor deposition process, the more volatile trimethylindium will be consumed first, and the less volatile triethylindium second. However, because of the differences (mismatch) in vapor pressure between these compounds, a lesser volume of triethylindium may be transported to the deposition chamber, thus adversely affecting the quality of the indium film deposited.
Though trimethylindium is a solid, it is the only indium compound to achieve commercial success because of its higher vapor pressure. Methods of providing trimethylindium in liquid form have been sought. For example, a solution of trimethylindium in a solvent has been sold commercially. This may be problematic in that impurities in the solvent or the solvent itself may contaminate the deposited indium film. Trimethylindium has also been dissolved in tri(C
3
-C
5
)alkylindiums. See, e.g., U.S. Pat. No. 5,502,227, which discloses a solution of trimethylindium dissolved in a high boiling tri(C
3
-C
5
)alkylindium, such as tripropylindium, tri-n-butylindium or tri-iso-butylindium. Such higher boiling trialkylindiums are reported to be more advantageous solvents than organic solvents as any impurities would have been removed during purification of the trialkylindium or else they would react with the trialkylindium before the addition of the trimethylindium. However, such approach requires a higher temperature during deposition, such as 17° to 40° C., in order to keep the equilibrium shifted such that trimethylindium is the predominate compound.
Another problem with trimethylindium is that films (pure indium or indium alloys) grown from trimethylindium suffer from high carbon incorporation. Triethylindium is used in applications where indium films having low carbon content are desired. Indium films grown from triethylindium have a lower carbon content than films grown from trimethylindium. One problem with triethylindium is that it has a lower vapor pressure than trimethylindium and consequently has a lower concentration in the vapor phase. Triethylindium is not suitable for forming indium alloys, such as indium phosphide.
There is thus a need for liquid indium compounds having sufficient vapor pressure to be suitable for use as a CVD and/or MOCVD indium precursor compound.
SUMMARY OF THE INVENTION
It has been surprisingly found that certain trialkylindium compounds are liquids at room temperature, are discrete species and have sufficient vapor pressure suitable for use as CVD and/or MOCVD indium precursor compounds.
In one aspect, the present invention provides an indium compound having the formula Bg
1
Bg
2
InR, wherein Bg
1
and Bg
2
are bulky alkyl groups each having at least three carbons, and R is a (C
1
-C
4
)alkyl, where R and Bg
1
are different. Such indium compound is particularly suitable for use as a CVD and/or MOCVD precursor compound.
In a second aspect, the present invention provides a method for depositing a film including indium on a substrate including the steps of: a) conveying a trialkylindium compound of the formula Bg
1
Bg
2
InR, wherein Bg
1
and Bg
2
are bulky alkyl groups each having at least three carbons, and R is a (C
1
-C
4
)alkyl, where R and Bg
1
are different, in the gaseous phase to a deposition chamber containing the substrate; b) decomposing the trialkylindium compound in the deposition chamber; and c) depositing a film including indium on the substrate.
In a third aspect, the present invention provides a method for manufacturing an electronic device including the step of depositing a film including indium on an electronic device substrate including the steps of: a) conveying a trialkylindium compound of the formula Bg
1
Bg
2
InR, wherein Bg
1
and Bg
2
are bulky alkyl g

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