Ti diffusion in chalcogenides: a ToF-SIMS depth profile characterization approach

Ge2Sb2Te5 (GST) is one of the most promising chalcogenide materials for phase-change memory devices, which are potential candidates for the future generation of non-volatile memories. The goal of this work was to investigate the inter-diffusion properties of the Ti-GST system upon annealing, by means of ToF-SIMS depth profile characterization. A double stack (Ti-GST-Ti) and a single stack (Ti-GST) have been considered, both as virgin samples (as-deposited) and post-annealed at 673 K for 10 s in pure N, atmospher. Two basic results have been found: (a) the annealed sample looked clearly affected by Ti diffusion throughout the whole GST layer; (b) the initial GST layer composition was dramatically altered as Te diffused as well as reacted with Ti, forming a Ti-Te compound (most likely as Te2Ti). As a consequence, pronounced inter-diffusion of Ti and Te has been observed, resulting in a substantial reduction of the Te content of the original GST layer. (C) 2004 Elsevier B.V. All rights reserved.