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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 24, Number 11
BKCSDE 24(11)
November 20, 2003 

Preparation of Al2O3 Thin Films by Atomic Layer Deposition Using Dimethylaluminum Isopropoxide and Water and Their Reaction Mechanisms
Ki-Seok An, Wontae Cho, Kiwhan Sung, Sun Sook Lee, Yunsoo Kim
Aluminum oxide, Atomic layer deposition (ALD), Dimethylaluminum isopropoxide, Surface chemical reaction
Al2O3 thin films were grown on H-terminated Si(001) substrates using dimethylaluminum isopropoxide [DMAl:(CH3)2AlOCH(CH3)2], as a new Al precursor, and water by atomic layer deposition (ALD). The selflimiting ALD process by alternate surface reactions of DMAI and H2O was confirmed from measured thicknesses of the aluminum oxide films as functions of the DMAI pulse time and the number of DMAI-H2O cycles. Under optimal reaction conditions, a growth rate of ~1.06 Å per ALD cycle was achieved at the substrate temperature of 150 ℃. From a mass spectrometric study of the DMAI-D2O ALD process, it was determined that the overall binary reaction for the deposition of Al2O3 [2 (CH3)2AlOCH(CH3)2 + 3H2O → Al2O3 + 4CH4 + 2HOCH(CH3)2] can be separated into the following two half-reactions:(A) AlO‡H* + (CH3)2AlO†CH(CH3)2  Al-O‡-Al[O†CH(CH3)2]* + CH4↑(B) Al[O†CH(CH3)2]* + H2O‡  AlO‡H* + HO†CH(CH3)2↑ where the asterisks designate the surface species. Growth of stoichiometric Al2O3 thin films with carbon incorporation less than 1.5 atomic % was confirmed by depth profiling Auger electron spectroscopy. Atomic force microscopy images show atomically flat and uniform surfaces. X-ray photoelectron spectroscopy and cross-sectional high resolution transmission electron microscopy of an Al2O3 film indicate that there is no distinguishable interfacial Si oxide layer except that a very thin layer of aluminum silicate may have been formed between the Al2O3 film and the Si substrate. C-V measurements of an Al2O3 film showed capacitance values comparable to previously reported values.
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