JART VCM v1b

The JART VCM v1b var model represents an extension of the JART VCM v1b model which additionally considers device-to-device and cycle-to-cycle variability. The ECD can be seen in Fig. 1. The physical equations are the same as in the v1b model. Device-to-device variability is achieved through parameter variation of specific parameters during initialization of the devices and cycle-to-cycle variability is achieved through modification of the same parameters during the simulation run [1]. Characteristic figures used to describe VCM cells include the I-V characteristic, which can be used to determine the range for LRS and HRS as well as the ranges of SET and RESET voltages. Experimental I-V sweeps for a current compliance of 100 μA are shown in Fig. 2 (a) whereas Fig. 2 (b) shows the simulation result. Both sweeps were performed using the same sweep rate (1 V/s) and the same stop voltages for SET and RESET of ±1.3 V. The SET voltages are between −0.45 V and −0.75 V, while the RESET voltages are between 0.45 V and 0.65 V. Fig. 2 (c) shows the measured SET delays, i.e. the time required to switch the cell into the LRS for a voltage pulse of a specific height between −0.6 V and −1.1 V. Fig. 2 (d) shows the simulated SET kinetics. The variability model reproduces the non-linearity as well as the multiple orders of magnitude variation in the SET time. Fig. 2 (e) shows a more complex experiment, which could be reproduced using the proposed model, namely the RESET kinetics for different initial LRS. For this experiment, the devices were first SET using different SET voltages which resulted in different LRS states. Afterward, a RESET kinetic was measured from those different LRS. Fig. 2 (g) shows the measured endurance characteristic over 1000 SET-RESET cycles. The LRS turns out to be very stable at around 3 kΩ, while the HRS varies between 30 kΩ and 100 kΩ with only a few outliers above 100 kΩ. Fig. 4 (h) shows the simulated endurance behavior over 1000 cycles. The LRS again is rather stable with a slightly larger variability than the experiment around 3 kΩ, while the HRS varies between 20 kΩ and 100 kΩ.