Enhanced Performance of Phase Change Memory Cell Element by Initial Operation and Non-Cumulative Programming

A phase change memory (PCM) device, based on the Ge₂Sb₂Te₅ (GST) material, is fabricated using the standard 0.18−μm CMOS technology. After serials of detailed experiments on the phase transition behaviors, we find that the RESET process is strongly dependent on the state of the inactive area and the active area affects the SET process dramatically. By applying a 5−mA current-voltage (I-V) sweep as initial operation, we can reduce the voltage drop beyond the active area during the RESET process and the overall RESET voltage decreases from 3 V plus to 2.5 V. For the SET operation, a non−cumulative programming method is introduced to eliminate the impact of randomly formed amorphous active area, which is strongly related to the threshold switching process and SET voltage. Combining the two methods, the endurance performance of the PCM device has been remarkably improved beyond 1×10⁶ cycles.