The unique solution to the stress reduction of Ge2Sb2Te5 phase-change material was known to cap a layer with an inherently huge compressive stress. Here, another approach to stress reduction was firstly presented in view of the compositional change of Ge2Sb2Te5; due particularly to O diffusion. During thermal cycles, the radius changes were measured using 4 kinds of samples and calculated their stress-changes using the Stoney equation. In the case of basic specimens, more O in Ge2Sb2Te5 and a larger stress-change were observed as the cycling temperature increased. In the rest of the samples, the stress-change was reduced compared with the basic one, only when a capping layer on Ge2Sb2Te5 blocked the O penetration effectively. The stress increase by O diffusion was considered to be due to the lattice distortion of Ge2Sb2Te5.

Stress Reduction of Ge2Sb2Te5 by Inhibiting Oxygen Diffusion. Y.S.Park, J.W.Lim, W.S.Yang, S.Y.Lee, S.M.Yoon, B.G.Yu: Materials Transactions, 2008, 49[9], 2107-11