Stress Reduction of Ge₂Sb₂Te₅ by Inhibiting Oxygen Diffusion

Abstract

The unique solution to the stress reduction of Ge₂Sb₂Te₅ phase-change material has been known to cap a layer with an inherently huge compressive stress. In this paper, another approach to the stress reduction is firstly presented in view of the compositional change of Ge₂Sb₂Te₅, particularly due to oxygen diffusion. During thermal cycles, we measured the radius changes using four kinds of samples and calculated their stress-changes using Stoney equation. In case of basic specimen, more oxygen in Ge₂Sb₂Te₅ and larger stress-change are observed as cycling temperature increases. In the rest of samples, the stress-change is reduced compared with the basic one, only when a capping layer on Ge₂Sb₂Te₅ blocks the oxygen penetration effectively. The stress increase by the oxygen diffusion is considered to be due to the lattice distortion of Ge₂Sb₂Te₅.