Multi-Level Storage in Lateral Phase-Change Memory: from 3 to 16 Resistance Levels

Here, we report multi-level storage (MLS) in multi-layer (ML) and single-layer (SL) phase-change memories (PCM). For the former ML-PCM device, the active medium with two layers of chalcogenide consists of a top 30 nm TiN/180 nm SbTeN/20 nm TiN/bottom 120 nm SbTeN stacked multi-layer. Three stable and distinct resistance states are demonstrated in both static and dynamic switching characteristics of the multi-layer devices. For the latter SL-PCM device, the active medium with only one layer of chalcogenide consists of a top 50 mu TiN/150 nm SbTeN. We demonstrate that the number of distinguishable resistance levels can readily reach 16 and even higher. These levels in this study result from the initial threshold switching and the subsequent current-controlled crystallization induced by Joule heating. Therefore, the latter memory allows the creation of many distinct levels, thus enabling the low-cost ultra-high-density non-volatile memory.