Drift-driven investigation of phase distribution in phase-change memories

Multi-level programming in Phase-Change Memories (PCMs) requires adequate understanding of the phenomena affecting the stability of the programmed levels. Although crystallization in GST (Ge₂Sb₂Te₅) has been extensively studied, further analysis is needed to understand the phase distribution in intermediate states between the amorphous and the crystalline GST. In this paper, we carry out a drift-driven analysis on a PCM array to investigate phase distribution of intermediate resistance states obtained with partial-SET programming. The analysis shows that the phase distribution after a partial-SET pulse can be more conveniently described by means of a parallel-like model having a crystalline path inside an amorphous cap.