Stoichiometric Ge₂Sb₂Te₅ (GST) films were deposited on TiN/Si, chemically or thermally grown SiO₂/Si, atomic-layer-deposited TiO₂/Si and Al₂O₃/Si substrates using a shower-head type 8-inch-scale plasma-enhanced ALD reactor at a wafer temperature of 200^oC. Ge(i-C₄H₉)₄, Sb(i-C₃H₇)₃, and Te(i-C₃H₇)₂ were used as the Ge, Sb and Te precursors, respectively. In order to confirm whether the ALD or CVD reaction took place, the precursor purge and precursor injection times were independently varied. It appeared that the incorporation of Ge was ALD-like whereas those of Sb and Te were of CVD nature at 200^oC. For investigating the nucleation and growth behaviors on each substrate, chemical composition and area layer density of the film were investigated by an X-ray fluorescence analyzer. The structure, cross-section and surface morphology of GST film were investigated by X-ray diffraction, field-emission scanning electron microscopy and atomic force microscopy. The X-ray diffraction showed that the as-deposited GST films on the TiN and TiO₂ substrates have an fcc structure with (200) preferred growth directions. They also have fcc structure but with (111) preferred directions on SiO₂ and Al₂O₃ substrates. There was negligible incubation period with high nucleation density for the growth on the TiN and TiO₂ substrates. On the contrary, GST films on SiO₂ and Al₂O₃ substrates showed island-type growth behavior and appears to have a rather long incubation period. Among the three components, Sb showed the best nucleation behavior on the various substrates. Ge and Te incorporation on the pre-deposited Sb layer was more efficient so that uniform and stoichiometric GST films were obtained when Sb layer was used as the nucleation layer. However, the films growth still showed the strongly substrate surface dependent behaviors. Step coverage on 3-dimensional hole structure was also investigated.

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