Modeling the amorphous state of phase change memory

A method based on Frenkel-Poole emission is proposed to model the I-V data of the amorphous state (high resistance state) in mushroom-type phase-change memory (PCM) devices. We found the I-V characteristics in the high resistance state are dominated by (i) the size of the amorphous GST (aGST) volume and (ii) the trap density of the amorphized GST material. Neither (i) nor (ii) can't be resolved by the conventional read scheme, which uses a predetermined voltage to measure the PCM cells. We applied the analysis to study a cell with a thin phase change layer (25nm), the phenomena during RESET quenching time, and the resistance drifting at room temperature. With this new and powerful method, detailed changes inside the PCM cells are revealed.