Recoiled-oxygen-free processing for 1.5 nm SiON gate-dielectric in sub-100-nm CMOS technology

We have developed high-quality 1.5-nm-SiON gate dielectrics using recoiled-oxygen-free processing. We found that oxygen recoiling from a sacrificial oxide during ion implantation or defects induced by recoiled oxygen change the growth mechanism of SiON gate dielectrics of less than 2 nm and degrade the controllability of film thickness, film quality, and device electrical characteristics. PMOSFETs using the recoiled-oxygen-free process and As-implantation for the channel have better controllability of gate dielectric thickness, up to one-third less gate leakage current, a hundred times more reliable TDDB characteristics, and a 20% improvement in drain current compared to the conventional process. Thus, an Si substrate without recoiled oxygen is essential in forming high-quality SiON gate dielectrics of less than 1.5 nm. In addition, we will show that anneal before SiON gate dielectric formation removes the recoiled oxygen from the Si substrate and improves controllability of the gate SiON gate dielectric thickness.