Effect of CMP on the Te Segregation in Ge2Sb2Te5 Films

Abstract

The surface characteristics of a Ge2Sb2Te5 chalcogenide layer after the chemical mechanical polishing (CMP) process was examined by X-ray diffraction, Auger electron microscopy and optical profiling to identify the dominant CMP mechanism of the new memory material. The platen speeds and applied pressure were varied up to 60 m/s and 4 psi, respectively, to understand the CMP variable effect on the surface quality of Ge2Sb2Te5 layer. The amount of Te hillock and surface roughness increased with increasing platen speed and applied pressure of CMP. Te segregation was the main cause of the increasing surface roughness. Stress and thermal effects were observed through the CMP-induced phase transformation from FCC to HCP and Te segregation. The surface properties of the Ge2Sb2Te5 thin films showed a strong correlation with phase transformation and Te segregation. The results show that the surface quality can be improved by reducing the platen speed and pressure. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.025203jes] All rights reserved.