Novel Interface Nitridation Process for Thin Gate Oxides

This paper presents a novel thin (100–200 Å) gate dielectric film, which exhibits improved properties as compared to control pure thermal oxides. The film is obtained by thermal nitridation of the silicon wafers in pure ammonia, followed by high temperature oxide (HTO) deposition, and an anneal in oxygen ambient (“reoxidation”). It was found that these dielectrics exhibit excellent electrical characteristics under Fowler-Nordheim tunneling stress, such as a relatively large charge-to-breakdown (Qbd), considerable reduction in charge trapping, reduction of interface state generation (ΔDit), and a significant improved resistance to transconductance (g_m) degradation. The novel dielectric layer is of potential use for the fabrication of reliable ultrathin gate oxide films for standard CMOS technology and particularly for non-volatile programmable memories.