Negative-/positive-bias-instability analysis of the memory characteristics improved by hydrogen postannealing in MANOS capacitors

We report the effect of hydrogen annealing on the gate-leakage-current and switching characteristics of metalaluminanitrideoxidesilicon (MANOS) capacitors by analyzing their negative-/positive-bias instability (NBI/PBI). One sample, namely, A, is annealed with rapid thermal annealing (RTA), and the other sample, namely, B, is first annealed with RTA and then further annealed in a furnace, using a $\hbox{N}-{2}{-}\hbox{H}-{2}$ (98% nitrogen and 2% hydrogen) gas mixture. In the NBI/PBI experiments, the flatband voltage shift $\Delta V-{\rm FB}$ is observed to be smaller, i.e., the gate-leakage-current density is reduced for sample B at gate voltages less than $\pm$3 V, a domain where trap-assisted tunneling is dominant. However, $\Delta V-{\rm FB}$ increases rapidly for the same sample at gate voltages larger than $\pm$6 V, a domain where the modified FowlerNordheim tunneling (MFNT) is dominant, which indicates faster program-and-erase characteristics. These results show that additional hydrogen annealing can improve both device reliability and switching characteristics of the MANOS-type memory by reducing interface traps between the silicon substrate and silicon oxide layers, as well as turn-on voltages for MFNT.