Dry Etching of Ge2Sb2Te5 Thin Films into Nanosized Patterns Using TiN Hard Mask

Abstract

We investigated dry etching methods for the patterning of nanosized Ge2Sb2Te5 (GST) patterns using high-density helicon plasma etching system. It was found that GST patterns of 10-nm-order size could not be formed in a suitable way owing to the damage of undesirable under-cut when the etching process was performed in gas mixtures of Ar/Cl2 using a SiO2 hard mask. In this work, a hard mask of TiN was therefore chosen for employing a CF4-based gas mixture for GST etching, in which the gas mixing ratios of Ar/Cl2 and Ar/CF4 were carefully controlled for TiN and GST patterning processes, respectively. Using these optimized patterning conditions, tens-of-nanometer-sized GST line and square-dot patterns could be successfully obtained with good profiles and uniformity.