Effect of Resistance Drift on the Activation Energy for Crystallization in Phase Change Memory

Abstract

The crystallization properties of phase-change memory (PCM) in the presence of thermal disturbances are investigated with a novel micro-thermal stage. It is found that the recrystallization time due to thermal disturbances significantly varies depending on how the PCM cell drifts. The longer crystallization time is obtained following additional resistance drift, which can be described by an increase of the effective activation energy for crystallization. The possibility of achieving better retention in a PCM cell by allowing the PCM cell to drift for a longer time is demonstrated in this work. The activation energy changes at a rate of more than 1 eV/decade with varying time intervals below a second. As the ambient temperature gets higher, the effect of resistance drift on the crystallization process is diminished with respect to the dominant crystallization process which has a higher crystal growth rate at elevated ambient temperatures.