Improvement of dielectric strength of TiSix-polycide-gate system by using rapidly nitrided oxides

We discuss two approaches to improve the dielectric strength of TiSi_x-polycide-gate systems which have a 100-nm-thick poly-Si and a 9.9-nm-thick oxide. (1) A 25-nm-thick intermediate WSi_y layer is effective, while keeping the sheet resistance lower than 2 Ω/□. (2) Rapid nitridation of oxides is very effective. A slight nitridation only for 60 s at 900-950°C makes the systems free from low-field breakdown and increases Q_BD successfully. On the other hand, too long nitridation reduces Q_BD. A thin oxide nitrided by lamp-heated rapid thermal annealing is very promising in future VLSI applications.