Formation of Ultrathin Nitrided SiO₂ Oxides by Direct Nitrogen Implantation into Silicon

A nitridation technique is proposed for ultrathin, SiO₂ oxides in deep submicron CMOS technology, which involves direct implantation of molecular nitrogen (N₂) into the silicon substrate. N₂ ions were implanted into silicon at different doses and energies, through a 150 A thick screen oxide. In this study the effect of implanted N atoms on silicon oxidation, and SiO₂ oxide nitridation process have been studied. Two groups of the N₂-implanted wafers were used: wafers from one group were annealed prior to the screen oxide removal, whereas wafers of the other group did not receive this anneal. It is shown that nitridation can be achieved both ways, allowing this technique to be easily integrated into a semiconductor IC fabrication process.