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 (ΔV_TH) at identical NBTI over-drive 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 (ΔN_it) in the sub-1-nanometer EOT devices, with ZrO₂ devices showing about one order of magnitude lower ΔN_it than HfO₂ device. However, the ΔN_it contribution to the total ΔV_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.