期刊
LANGMUIR
卷 26, 期 6, 页码 3911-3917出版社
AMER CHEMICAL SOC
DOI: 10.1021/la903212c
关键词
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资金
- National Science Foundation [CHE-0415652]
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [0911197] Funding Source: National Science Foundation
The initial surface chemistry and growth mechanisms of the atomic layer deposition (ALD) of metallic copper on SiO2 surfaces are investigated using an amidinate precursor (copper(I) di-sec-butylacetamidinate, [Cu((BU)-B-s-amd)](2)) and molecular hydrogen, using in situ Fourier transform infrared spectroscopy together with calculations based on density functional theory, we show that the initial surface reaction of [Cu(Bu-s-amd)](2) with hydroxylated SiO2 takes place by displacement of one of the sec-butylacetamidinate ligands at a surface -OH site, thus forming a Si-O-Cu-(Bu-s-amd) surface species, evident by the stretching vibrations of Si-O-Cu and the chelating -NCN- bonds. Molecular hydrogen exposure during a subsequent pulse dissociates most of the sec-butylacetamidinate ligands bound to surface Cu, which releases free amidine vapor, leaving Cu atoms free to agglomerate on the surface and thus opening more reactive sites for the next [Cu(Bu-s-amd)](2) pulse. Copper agglomeration is evident in the IR absorbance spectra through the partial recovery of the intensity of SiO2 optical phonon modes upon H-2 reduction, which was lost after the reaction of [Cu(Bu-s-amd)](2) with the initial SiO2 surface. The thermally activated ligand rearrangement from a bridging to a monodentate structure occurs above 220 degrees C through hydrogenation of the ligand by surface hydroxyl groups after exposure to it [Cu(Bu-s-amd)](2) pulse, As Cu particles grow with further ALD cycles, the activation temperature is lowered to 185 degrees C, and hydrogenation of the ligand takes place after H-2 pulses, catalyzed by Cu particles on the surface. The Surface ligand rearranged into a monodentate structure call be removed during subsequent Cu precursor or H-2 Pulses. Finally, we postulate that the attachment of dissociated ligands to the SiO2 surface during the [Cu(Bu-s-amd)](2) pulse call be responsible for carbon contamination at the surface during the initial cycles of growth, where the SiO2 surface is not yet completely covered by copper metal.
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