Pulse-induced crystallization in phase-change memories under set and disturb conditions

Abstract

We introduce a new technique to study the crystallization process in phase-change memory. By this technique, crystallization is characterized in the ON-state at extremely low currents, allowing to extend the time scale of crystallization times to more than two decades. To describe the pulse-induced crystallization in the set regime, we develop a finite-element method model based on localized conduction in the amorphous phase and non-Arrhenius crystallization kinetics. The range of crystallization times is then extended to even lower currents in the subthreshold regime, where the model allows describing the crystallization kinetics thus providing the physics-based prediction of read disturb.

Impact of Thermoelectric Effects on Phase Change Memory Characteristics

“…The time needed for ion migration in the OFF-state was defined at the crossing with the threshold resistance R * = 50 M . These measurements highlight the relevance of ion migration for read disturb reliability, similar to voltage-accelerated drift and crystallization [10]. Fig.…”

“…The curves are almost symmetric, showing an exponential increase of current with voltage [8] (Poole-Frenkel regime) toward threshold switching, taking place at threshold voltage V T and threshold current I T [9]. Device readout is carried out in the region below I T (OFF-state), while the region above I T (ON-state) is exploited for program operation [10]. We performed bipolar R read at I read = ±1 nA, and we verified that the R measured at positive and negative polarities was the same.…”

“…A larger V is needed for set transition at V < 0. and constant pulsewidth t P = 170 ns. To allow the characterization of programming curve below V T , the voltage pulse was anticipated by a short pulse (t P < 20 ns) with amplitude above V T , with negligible impact on GST crystallization [10]. The cell was prepared in the reset state before every programming pulse.…”

Reconfigurable Writing Architecture for Reliable RRAM Operation in Wide Temperature Ranges

“…Together with the consumed power, the circuit working temperature describes the dynamics of the conductive filament heating processes [10]. Consequently, characteristics such as switching speed [11] or data-retention ability [12] highly depend on the system working temperature. To the end of our knowledge, until [11] no driver had dealt with temperature caused problems.…”

“…At the same time, this partial selection produces a leakage phenomena that should be addressed [27], [28]. More in depth information about how this stress affects data retention can be found in [12], [29], [30].…”