First Insight Into the Lifetime Acceleration Model of High-$k$$\hbox{ZrO}_{2}/\hbox{SiO}_{2}/\hbox{ZrO}_{2}$ Stacks for Advanced DRAM Technology Nodes

Long-term reliability results over six orders of magnitude in time are presented showing that the voltage acceleration model for ZrO2/SiO2/ZrO2 exhibits an exponential dependence with voltage, down to 2 V. The voltage acceleration parameter gamma is between 10 and 15 V-1, depending on the biasing polarity. Soft-breakdown behavior (SILC) is evident prior to the onset of hard breakdown as a result of barrier lowering or charge accumulation in the high- k film. Under ac stress conditions, this SILC branch is lowered in magnitude, translating to a gain in lifetime to breakdown.