Fundamental drift of parameters in chalcogenide phase change memory

Abstract

We present the data on temporal (t) drift of parameters in chalcogenide phase change memory that significantly complement the earlier published results. The threshold voltage Vth and the amorphous state resistance R are shown to drift as ΔVth∝v ln t and R∝tα in broad intervals spanning up to nine decades in time; the drift coefficient v depends on glass parameters and temperature, but does not depend on device thickness. We have demonstrated that drift saturates at long enough times that can be shorten with temperature increase. All available data on drift dynamics are fully consistent with the classical double-well-potential model, which gives simple analytical expressions for the observed temporal dependencies including numerical parameters.

Role of activation energy in resistance drift of amorphous phase change materials

“…A divergent explanation was proposed by Karpov et al [29], suggesting a volume change of the amorphous phase change material due to differences in the volumetric mass densities of the amorphous and the crystalline phase (∼6%) to be responsible for drift. By employing the general concept of the doublewell potential for the atomic potential of metastable glasses to chalcogenide alloys [30] and the resulting relaxation characteristics the authors proposed a correlation between volume change of the amorphous phase and the time evolution of the resistance [29].…”

“…In the literature the majority of experiments are done in melt-quenched amorphous phase change memory cells. These previous studies showed that different read out voltages and currents as well as varying RESET states can all influence the resistance drift behavior [10,25,27,29,33,34]. Former works also indicated a potential influence of the surrounding dielectric material encapsulating the phase change material in a cell on the drift behavior [35].…”

“…By employing the general concept of the doublewell potential for the atomic potential of metastable glasses to chalcogenide alloys [30] and the resulting relaxation characteristics the authors proposed a correlation between volume change of the amorphous phase and the time evolution of the resistance [29].…”

Aging mechanisms in amorphous phase-change materials

“…PCMs are used as the active part of non-volatile memory devices 5,6 , which exploit the fast and reversible switch between a conductive crystalline structure and an amorphous phase that displays a higher electrical resistivity. On aging, the resistivity of the amorphous state for a large number of such systems [7][8][9] increases even further. This 'resistance drift' impedes the realization of multilevel memories.…”

Carbon doping induced Ge local structure change in as-deposited Ge2Sb2Te5 film by EXAFS and Raman spectrum

“…15 The higher RESET current, 16 will hinder its potential commercial applications in low-power consumption electronic devices. In addition, the exhibiting aging phenomenon of amorphous state, where the resistivity of the amorphous state increases with time, 17 will impede the realization of multilevel memories. To overcome the mentioned disadvantages in GST material, carbon dopants were introduced, resulting in a higher crystallization temperature, a reduction of RESET current, a relatively low resistance drift and an improved cycling endurance.…”