On the drift behaviors of a phase change memory (PCM) cell

Abstract

This paper presents a HSPICE macromodel of a phase change memory (PCM) by considering the phenomenon of drift behavior as leading to incorrect operation. The model simulates the behavior due to the drift in the resistance and threshold voltage when the cell is not been read or programmed. It considers not only the resistance change by phase (as corresponding to the two phases, amorphous and crystalline), but also the temperature, the crystalline fraction and the continuous profile of the resistance. This electrical based modeling by HSPICE allows to fully characterizing the holding voltage and the continuous behavior of the PCM resistance, while assessing the impact of the programming time of the drifted parameters. The proposed macromodel generates the I-V and R-I plots of a PCM cell at a very small error compared with experimental data. A detailed sensitivity analysis of the electrical parameters of the PCM cell is pursued to show the robust characteristics of the proposed macromodel to capture the variation in parameters due to drift. *

Variable cubic-polynomial memristor based canonical Chua’s chaotic circuit

“…The success of the physical fabrication of the Hewlett Packard (HP) memristor in 2008 has greatly increased researchers' interest in memristors since Leon O. Chua reasoned from symmetry arguments at first in 1971 due to the promising future of the memristor for both of non-volatile memories and neuronmophic applications in nano-scale era [1,2,3,4]. Despite of the interests among researchers, commercially memristors are not expected to be available in a near future due to the technical difficulties involved in nano device fabrication [5].…”

Design and modeling of nonvolatile memories by resistive switching elements

“…The first difference is its circuit simplicity; this feature is evident when considering the multiplier circuits (such as for the computation of 0.1 ) required to simulate the drift behavior of the PCM cell. In [98] this important computational step is also dependent on the simulation time, making the PCM macromodel of [100] more complicated. In the proposed macromodel, a single voltage controlled voltage source (VCVS) is used to generate the drift behavior.…”

“…In the proposed macromodel, a single voltage controlled voltage source (VCVS) is used to generate the drift behavior. The complexity of macromodelling is also reflected in the accuracy, because the additional circuits utilized in [98] generate a larger percentage of error in the simulation process [100]. So for example, the error between simulated and experimental data for the resistance drift grows exponentially as function of T off (at values of T off greater than 500ns the error exceeds 4%).…”

“…As for the drift behaviors of the resistance and threshold voltage, the model of [98] assumes that when the PCM cell is not been programmed, the reset (amorphous) resistance (R a ) increases with time, while the crystalline fraction of the PCM cell (C x ) remains constant [100]. However this is a simplifying assumption used in the macromodel of [98], thus further contributing to the previously described error.…”

“…Therefore, the resistance drift in the proposed macromodel is more accurate and a smaller error with experimental data is encountered. The constant value of the drift exponent is also used in [98] to model the threshold voltage drift of the PCM [100], thus incurring in a similar error also for this drift behavior.…”