Multilevel Storage in Lateral Top-Heater Phase-Change Memory

A lateral top-heater phase-change memory (LTH-PCM) is proposed and investigated for multilevel storage (MLS). The active layers are composed of a 50-nm-thick TiN layer as a top heater and a 150-nm-thick SbTeN layer. A number of intermediate levels, which are induced by electric currents, are exhibited in experimental results. They are distinct and very stable. The reversible switching of multilevels is successfully demonstrated in the LTH-PCM device. The MLS results from the gradual enlargement of crystalline region between electrodes by Joule heating according to our analysis.