Evolution of cell resistance, threshold voltage and crystallization temperature during cycling of line-cell phase-change random access memory

Doped SbTe phase change (PRAM) line cells produced by e-beam lithography were cycled 100 million times. During cell cycling the evolution of many cell properties were monitored, in particular the crystalline and amorphous resistance, amorphous resistance drift exponent, time-dependent threshold voltage, threshold voltage as a function of RESET pulse height, crystallization temperature, and activation energy of crystal growth. The power of the present approach is that all these properties were measured simultaneously during the life of single cells. The evolution of the cell properties can be summarized by (i) an initialization phase characterized by settle-in effect of the material surrounding the programmable region, (ii) a usable life phase where initially the cell properties remain fairly constant until after ∼5 × 105 cycles decomposition of the programmed region caused degradation of the cell properties, and (iii) finally an end of life phase where the cell is stuck in the SET state after typically 10...