Ultrahigh Storage Densities via the Scaling of Patterned Probe Phase-Change Memories

The scaling potential of patterned probe phasechange memory (PP-PCM) cells is investigated, down to single-nanometer dimensions, using physically realistic simulations that combine electrothermal modeling with a Gillespie Cellular Automata (GCA) phase-change model. For this study, a trilayer TiN/Ge2Sb2 Te-5/TiN cell structure (isolated by an SiO2 insulator) was preferred, due to its good performance and practicability, over previously investigated probe-based structures such as those that used diamond-like carbon capping layers or immersion in an inert liquid to protect the phase-change layer (while still allowing for electrical contact). We found that PP-PCM cells with dimensions as small as 5 nm could be successfully amorphized and recrystallized (RESET and SET) using moderate voltage pulses. The resistance window between the RESET/SET states decreased with a reduction in cell dimensions, but it was still more than the order of magnitude even for the smallest cells, predicting that PP-PCM cells are indeed scalable and operable in the sub10-nm region. Most importantly, it was found that the storage density could be increased by cell size scaling with storage densities as high as 10 Tb/in(2) being achieved, which is significantly higher than the storage densities previously reported in the phasechange probe storage, and other probe-based technologies such as thermomechanical, magnetic, and ferroelectric probe storage.