Improvement in high-k (HfO/sub 2//SiO/sub 2/) reliability by incorporation of fluorine

We demonstrate that negative bias temperature instability (NBTI) of high-k (HfO₂/SiO₂) gate stacks are significantly improved by incorporating fluorine and engineering its concentration profile. We find that F piles up at HfO₂/SiO ₂ interface and diffuses into the underlying SiO₂/Si interface. The HfO₂/SiO₂ stack with F shows significantly less CV hysteresis, positive charge trapping and interface states generation compared to control samples without F under the same negative bias condition. F is believed to form stronger Hf-F and Si-F bonds compared to Hf-H and Si-H bonds which improve the reliability of HfO₂/SiO₂