Improved NBTI Reliability With Sub-1-Nanometer EOT ZrO2 Gate Dielectric Compared With HfO2

The negative bias temperature instability (NBTI) reliability of sub-1-nanometer equivalent oxide thickness (EOT) ZrO2 and HfO2 dielectrics with metal gate is investigated. The threshold voltage shift (Delta V-TH) at identical NBTI overdrive stress conditions is observed to be lower in ZrO2 than in HfO2 field-effect transistors. Ring oscillator charge pumping is applied to determine interface trap generation (Delta N-it) in the sub-1-nanometer EOT devices, with ZrO2 devices showing about one order of magnitude lower Delta N-it than HfO2 device. However, the Delta N-it contribution to the total Delta V-TH is very limited in sub-1-nanometer EOT devices, as the recoverable component from the pre-existing bulk defects dominates the whole NBTI degradation. Pulsed Id-Vg technique is applied to analyze the pre-existing bulk defects in those sub-1-nanometer EOT devices, and lower pre-existing bulk defect density is shown in ZrO2, which decisively reduces NBTI in ZrO2 gate dielectric.