Recovery and Drift Dynamics of Resistance and Threshold Voltages in Phase-Change Memories

The electronic behavior of the chalcogenide material used in phase-change memory (PCM) plays a key role in defining the operation voltages and times of the memory cell. In particular, \nthe threshold voltage for electronic switching of the amorphous \nchalcogenide determines the boundary between programming and \nreadout operation, while its resistance allows the recognition of the \nbit status. This paper present a time-resolved analysis of threshold \nvoltage and resistance in a PCM. Both dynamics of threshold voltage and resistance display a fast transient, named recovery behavior, in the first 30 ns after programming. A slower, nonsaturating drift transient is found for longer times. The two transients are discussed referring to electronic and structural rearrangements in the amorphous chalcogenide. Finally, the impact on the device level is considered.