Thermal stress evaluation of a PCRAM material Ge2Sb2Te5

In addition to the huge resistivity changes, the phase-change switching process is accompanied by a significant volume change (Pedersen et al., 2001), which in turn can result in large stresses. This can become a serious reliability issue, particularly in small device cells utilizing under- and over-layers of suitable contact metals. It is important then to evaluate the magnitude and the sign of stress during the phase changes, and to ascertain the effect of capping layers. In this paper, we report distinct stress signatures in a phase change material, Ge₂Sb₂Te₅ (GST). As GST may be integrated in devices with Ti/TiN (for adhesion and diffusion barrier considerations), the stress evolution in such sandwiched structures is addressed