Analysis of the statistics of device-to-device and cycle-to-cycle variability in TiN/Ti/Al:HfO2/TiN RRAMs

In order to study the device-to-device and cycle-to-cycle variability of switching voltages in 4-kbit RRAM arrays, an alternative statistical approach has been adopted by using experimental data collected from a batch of 128 devices switched along 200 cycles. The statistical distributions of switching voltages have been usually studied by using the Weibull distribution. However, this distribution does not work accurately on Al:HfO2-based RRAM devices. Therefore, an alternative approach based on phase-type distributions is proposed to model the forming, reset and set voltage distributions. Experimental results show that in general the phase-type analysis works better than the Weibull one.