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

Abstract

We demonstrate that negative bias temperature instability (NBTI) of high-k (HfO/sub 2//SiO/sub 2/) gate stacks are significantly improved by incorporating fluorine and engineering its concentration profile. We find that F piles up at HfO/sub 2//SiO/sub 2/ interface and diffuses into the underlying SiO/sub 2//Si interface. The HfO/sub 2//SiO/sub 2/ 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 HfO/sub 2//SiO/sub 2/.