Forming nitrided gate oxides by nitrogen implantation into the substrate before gate oxidation by RTO

Nitrogen was implanted into the Si-substrate at an energy of 20 keV with doses of 1×10¹³ cm^-2, 1×10 ¹⁴ cm^-2, and 1×10¹⁴ cm^-2 . After implantation, oxides were grown by rapid thermal oxidation on nitrogen implanted wafers with and without an anneal step before oxidation. The gate oxide growth rate and the nitrogen peak concentration at the SiO₂/Si interface (measured by SIMS) can be controlled by the nitrogen implant dose. An implant anneal with RTP after implantation results in a significant decrease of nitrogen concentration at the surface or interface. However, an implant anneal also significantly decreases surface roughness and crystal defects in the substrate after N⁺-implantation, as shown by AFM and TEM measurements. By using the nitrogen implantation with the lowest dose (1×10¹³ cm^-2) the Q_BD-values can be slightly increased