Computational Analysis of Rupture-Oxide Phase-Change Memory Cells

The potential of rupture-oxide mushroom phase-change memory cells is assessed through 2-D finite element analysis using electro-thermal models with temperature-dependent material parameters, coupled with a circuit model for access transistors. The mushroom cell structure used for the simulations consists of a 100-nm thick ${\rm Ge}_{2}{\rm Sb}_{2}{\rm Te}_{5}$ layer separated from a 20-nm wide TiN bottom heater by a 3-nm thick ${\rm SiO}_{2}$ rupture-oxide layer. The ruptured oxide is modeled as a conductive filament through the oxide layer at the center of the heater. The effects of supply voltage, gate voltage, access transistor width, filament diameter and resistivity are studied using a read/reset/read sequence enabled by a dynamic amorphization model. The simulation results show that rupture-oxide cells can be operated with smaller voltages, currents and transistor widths compared to their conventional counterparts for the same resistance contrast. Moreover, it is shown that the cell performance is further improved for narrower and more resistive filaments.