Improved NBTI Reliability With Sub-1-Nanometer EOT ${rm ZrO}_{2}$ Gate Dielectric Compared With ${rm HfO}_{2}$

摘要

The negative bias temperature instability (NBTI) reliability of sub-1-nanometer equivalent oxide thickness (EOT) ${rm ZrO}_{2}$ and ${rm HfO}_{2}$ dielectrics with metal gate is investigated. The threshold voltage shift $(Delta{V}_{rm TH})$ at identical NBTI over-drive stress conditions is observed to be lower in ${rm ZrO}_{2}$ than in ${rm HfO}_{2}$ field-effect transistors. Ring oscillator charge pumping is applied to determine interface trap generation $(Delta{N}_{rm it})$ in the sub-1-nanometer EOT devices, with ${rm ZrO}_{2}$ devices showing about one order of magnitude lower $Delta{N}_{rm it}$ than ${rm HfO}_{2}$ device. However, the $Delta{N}_{rm it}$ contribution to the total $Delta{V}_{rm TH}$ 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 ${rm ZrO}_{2}$, which decisively reduces NBTI in ${rm ZrO}_{2}$ gate dielectric.