Effect of CMP on the Te segregation in Ge ₂Sb ₂Te ₅ films

The surface characteristics of a Ge ₂Sb ₂Te ₅ 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 ms and 4 psi, respectively, to understand the CMP variable effect on the surface quality of Ge ₂Sb ₂Te ₅ 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 Ge ₂Sb ₂Te ₅ 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.