Study of Ge-Sb-Te and Ge-Te cocktail sources to improve an efficiency of multi-line CVD for phase change memory

In this study, we investigated a deposition of Ge-Sb-Te (GST) and Ge-Te (GT) phase change films using GST and GT cocktail sources to improve the efficiency of multi-line chemical vapor deposition (CVD). Cocktail sources were compounded with the chemical precursors Ge(NMe2)4, Sb(iPr)3, and Te(tBu)2. We controlled experimental conditions, such as deposition and source heating temperature and the number of precursors, and measured their influence using several methods of analysis. Precursor compatibility in the chemical cocktail source was pretested by thermogravimetric analysis. In various experimental conditions, film deposition behavior was observed by plane view and cross-sectional view of scanning electron microscopy and surface roughness was observed by atomic force microscopy. The grain size of the films was analyzed using the software program Image J. The crystallinity at each deposition temperature was measured by X-ray diffraction and was supported by high-resolution transmission electron microscopy. Competitive deposition of the cocktail source was observed at a low deposition temperature. The origin of this phenomenon is discussed in relation to the energy of the CVD process and a solution is proposed. We suggest that this cocktail CVD concept might be a new approach to multi-element deposition in memory processes.