Impact of Thermoelectric Effects on Phase Change Memory Characteristics

Joule heating in phase change memory (PCM) controls programming characteristics, read disturb, and programming disturb. To optimize the energy consumption and reliability of PCM, a thorough understanding of Joule heating as a function of the electrical operation of the device is thus strongly required. This paper presents a comprehensive characterization of thermoelectric (TE) effects in PCM operated at positive and negative voltage polarity. The impact of polarity was studied for all major temperature-dependent properties of the PCM device, namely, melting, crystallization, ion migration, threshold switching, and holding. It was demonstrated that heating is less efficient under negative voltage, compared with positive voltage. It was also shown that the positive and negative voltages needed to induce all above phenomena display a universal correlation. We propose a unified finite-element model for the PCM, which correctly accounts for the observed polarity-dependent heating and the universal voltage characteristics. The impact of isotropic scaling on TE is finally addressed.