Physical interpretation, modeling and impact on phase change memory (PCM) reliability of resistance drift due to chalcogenide structural relaxation

Chalcogenide materials are extensively used in phase-change memory (PCM) cells, where the ability to electrically change the structural phase from crystalline to amorphous and vice versa is exploited. Although the amorphous phase is quite stable with respect to crystallization, structural relaxation (SR), affecting the concentration of localized states in the band gap, strongly impacts the electrical properties of the amorphous phase even at room temperature. This work combines a previous physics-based model for transport in the chalcogenide glass and a new kinetic model for defect annealing, allowing to quantitatively account for the time and temperature dependences of SR and on its impact on the I-V curve for different read currents. The optimization of readout conditions to minimize the reliability impact is finally discussed.