Dependence of resistance drift on the amorphous cap size in phase change memory arrays

Multilevel programming in phase change memories (PCMs) requires understanding of the phenomena which affect the stability of the programmed resistance levels. Although the Ge2Sb2Te5 (GST alloy) crystallization process has been extensively studied, further analysis is needed to characterize the drift of low-field amorphous-GST resistance. In this paper, we carry out a statistical analysis on an array of PCM cells so as to investigate the drift dynamics of intermediate GST resistance states. Our experimental results reveal the dependence of the drift dynamics exponent on the thickness of the amorphous cap inside the GST layer, which is ascribed to the different stresses.