Impact of recoiled-oxygen-free processing on 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, a Si substrate without recoiled oxygen is essential in forming high-quality SiON gate dielectrics of less than 1.5 nm.