Modeling of programming and read performance in phase-change memories - Part II: Program disturb and mixed scaling approach

The scaling analysis of phase-change memory (PCM) cells is an essential step toward validation as a competitive technology in terms of array density and current consumption. While the current scaling has been addressed in a companion paper, we focus here on the thermal crosstalk, namely, the temperature increase in 1 bit in the array while an adjacent cell is being programmed by a high-current reset pulse. This parasitic heating may lead to partial crystallization in the amorphous phase and to a consequent resistance decrease after cycling. Our analysis shows that the thermal crosstalk strongly depends on the scaling approach used, e.g., isotropic or nonisotropic scaling. A new mixed-scaling option for PCM cells is proposed, which provides the maximum decrease of programming current compatible with the reliability requirements deriving from the thermal crosstalk. The effects of this new scaling approach on the programmed volume and data retention are finally addressed.