Thermomechanical Analysis on the Phase Stability of Nitrogen-Doped Amorphous Ge2Sb2Te5 Films

Abstract

The phase stability of amorphous Ge2Sb2Te5 (GST) films affects the performance and reliability of phase change memory (PRAM) devices. The viscosity and the glass forming ability of nitrogen (N)-doped amorphous GST films were investigated in terms of thermomechanical behavior using wafer curvature measurements. The viscosity which increased by two orders of magnitude was observed in the N-doped amorphous GST film by measuring the stress relaxation accompanied by bimolecular structural relaxation. The glass forming ability (ΔTx), difference between the glass transition temperature (Tg) and the crystallization temperature (Tc), of GST increased as the nitrogen contents increased. These increases in the viscosity and ΔTx indicate the retardation of atomic diffusion in amorphous GST and the stabilization of the amorphous phase.