Effect of Slurry pH and H2O2 on Polycrystalline Ge2Sb2Te5 CMP Performance

Abstract

How pH and hydrogen peroxide (H2O2) in colloidal silica-based slurry affect chemical mechanical planarization of polycrystalline Ge2Sb2Te5 (pc-GST) film has been investigated. The polishing rate of pc-GST film increased when the slurry pH decreased or increased from neutral pH. In addition, pc-GST polishing rate was highly affected by adding H2O2, resulting in a high pc-GST polishing rate in the entire pH ranging from 2 to 11. However, a noticeable difference in surface roughness of pc-GST film polished was observed between acidic (pH 2) and alkaline (pH 11) regions. Low RMS of roughness as well as a high polishing rate of pc-GST film was obtained in the acidic pH region with 1wt% H2O2. In contrast, in the alkaline region a high RMS of roughness of pc-GST film was observed owing to enhanced selective corrosion between Ge, Sb, and Te elements. To investigate the different polishing behavior of pc-GST film between acidic and alkaline pH regions, surface characteristics of pc-GST film dipped in acidic or alkaline media were observed by scanning electron microscopy, X-ray photoelectron microscopy, and potentiodynamic measurement.