Effect of Substrate Temperature on Surface Properties of Ge2Sb2Te5 Film during Chemical Mechanical Polishing

In this study, the effect of substrate temperature on the surface properties of Ge2Sb2Te5 (GST) during chemical mechanical polishing (CMP) was investigated. During the CMP process, the substrate temperature of our GST film was controlled from 12 to 35 degrees C. The amount of Te hillocks and the surface roughness of the GST film increased with increasing substrate temperature. The surface roughness was related to the thermal effects of the CMP process. Furthermore, the grain size of the GST film polished at a temperature much lower than the annealing temperature changed because of frictional heat. The material removal rate of the GST film did not noticeably change with substrate temperature up to 21 degrees C, but it decreased with a further increase in substrate temperature. The material removal rate of the GST film showed strong correlations with the oxidation ability of the GST film and the unreacted amount of Te. The results of the CMP process showed that the surface quality and material removal rate of a GST film during CMP can be improved by reducing substrate temperature. (C) 2012 The Japan Society of Applied Physics