Silicon Nitride Resistive Memories

ABSTRACT SiN x is an attractive resistance switching material for ReRAM applications due to its physicochemical properties. By modifying the ratio between N and Si, the microstructure of the SiN x is affected, rendering it possible to change the operation characteristics and the performance of SiN x ReRAMs, including SET and RESET voltages, the dielectric strength, conductivity and noise. Stoichiometric and N‐rich SiN x RRAMs demonstrate self‐compliance characteristics during the RESET. In addition, N‐rich SiN x RRAMs switch to the LRS on average 6% faster, and stoichiometric SiN x have the best breakdown characteristics. Si doping of SiN x resulted in higher SET voltages with low variability, while doping with O decreased the RESET voltages significantly. O doping also resulted in a conduction mechanism that is governed by electron variable range hopping. The effect of the wafer substrate is studied as well, comparing SOI to bulk Si wafers, with ReRAMs on SOI having improved endurance due to the reduction of the current overshoot during the RESET. Finally, the formation of the conductive filament is explored extensively and was found to be composed of nitrogen vacancies, which explains how different N/Si ratios affect the behavior of the SiN x ReRAMs, since they lead to different defect concentrations in the dielectric.