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New Liquid Precursors for Chemical Vapor Deposition

Published online by Cambridge University Press:  10 February 2011

Roy G. Gordon ,
Feng Chen ,
Nicholas J. Diceglie Jr ,
Amos Kenigsberg Jr ,
Xinye Liu ,
Daniel J. Teff  and
John Thornton
Roy G. Gordon
Affiliation:
Harvard University Chemical Laboratories, Cambridge, Massachusetts 02138
Feng Chen
Affiliation:
Harvard University Chemical Laboratories, Cambridge, Massachusetts 02138
Nicholas J. Diceglie Jr
Affiliation:
Harvard University Chemical Laboratories, Cambridge, Massachusetts 02138
Amos Kenigsberg Jr
Affiliation:
Harvard University Chemical Laboratories, Cambridge, Massachusetts 02138
Xinye Liu
Affiliation:
Harvard University Chemical Laboratories, Cambridge, Massachusetts 02138
Daniel J. Teff
Affiliation:
Harvard University Chemical Laboratories, Cambridge, Massachusetts 02138
John Thornton
Affiliation:
Harvard University Chemical Laboratories, Cambridge, Massachusetts 02138
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Abstract

New precursors have been found for chemical vapor deposition (CVD) of many metal oxides. Each precursor is a mixture formed by randomly attaching a selected set of organic groups, such as the isomers of the butyl group, to a metal 2,4-pentanedionate (also known as acetylacetonate) in place of the methyl groups of the 2,4-pentanedionate ligand. Most of these new mixed metal beta-diketonates are liquids at room temperature, whereas the corresponding metal 2,4-pentanedionates are solids. In the cases where they were solids or viscous liquids, small amounts of organic solvents were added to reduce the viscosity. We have so far prepared mixed beta-diketonate precursors for barium, strontium, calcium, magnesium, aluminum, indium, tin, lead, bismuth, titanium, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, manganese, iron, ruthenium, cobalt, nickel, copper, zinc, yttrium, lanthanum and cerium.

Liquid sources are much more convenient for CVD than solid sources. These liquid mixtures or solutions were vaporized by ultrasonically nebulizing the liquid into a flow of hot nitrogen carrier gas preheated to 150–250 °C. These vapor mixtures were mixed with air or oxygen and flowed over substrates heated typically to 350–450 °C. Films of the corresponding metal oxide (or carbonate, in the case of barium, strontium and calcium) were deposited on substrates of silicon or glass. Gas pressures from 20–760 Torr were used.

Because a common set of ligands is used for each of these metal precursors, they can be mixed as liquids or vapors without any precipitation due to ligand exchange reactions. To demonstrate their use in forming mixed metal oxides, we have prepared films of ferroelectric barium titanate. This method should be applicable to other mixed metal oxides of current interest, such as high dielectric constant strontium titanate, ferroelectric bismuth strontium tantalate, superconducting yttrium barium copper oxide, refractory yttrium zirconium oxide, second-harmonic generating barium borate, metallic lanthanum strontium cobalt oxide and magnetoresistive lanthanum strontium manganate.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 495: Symposium W – Chemical Aspects of Electronic Ceramics Processing , 1997 , 63
Copyright
Copyright © Materials Research Society 1998

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References

REFERENCES

1. Specific examples of preparative procedures for similar ligands are given in Inorganic Syntheses, for chromium(III) in 5, pp. 130–131 (1957) and 24, pp. 183–184 (1986); for cobalt(III) in 5, pp. 188–189 (1957); for rare earth metals in 11, pp. 94–98 (1968); for cerium(IV) in 12, pp. 77–78 (1970) and 23, pp. 147–8 (1985); for manganese(III) in 23, pp. 148–149 (1985); for iron(II) in 31, pp. 267–269 (1997); for copper(II) in 23, pp. 146–147 (1985); for beryllium in 2, pp. 17–20 (1946); and for calcium, strontium and barium in 31, pp. 1–7 (1997).Google Scholar
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