A theoretical study of scaling behaviour of mushroom PCRAM devices using the Gillespie Cellular Automata Approach

Abstract

We investigate the scaling characteristics of vertical “mushroom” phase change random access memory (PCRAM) cells down to sub-10nm dimensions using an electro-thermal model combined with the Gillespie cellular automata (GCA) phase-transition approach. The size of the amorphous dome formed during the Reset process decreases linearly with simultaneous reduction of the bottom TiN heater width and Ge2Sb2Te5 (GST) phase change layer volume with re-design of the cell geometry required for sub-15nm dimensions. Re-crystallisation of the amorphous dome is primarily nucleation-dominated, however a transition to growth-dominated crystallisation is observed for dimensions below 20nm. The scaling trend features a resistive window of a factor of 10 even for very small dimensions predicting the scalability and operability of mushroom PCRAM cells in the sub-10nm region.