Improvement of thin-gate oxide integrity using through-silicon-gate nitrogen ion implantation

A simple and manufacturable technique to improve thin-gate oxide integrity using nitrogen implant through a polycrystalline-silicon (poly-Si) gate MOS structure is described. The Auger depth profile of the film, after 1100°C oxidation cycle, shows nitrogen pile-up at both poly-Si and substrate interfaces, similar to the NH3annealed thermal oxide. Interface-state generation and charge to breakdown under high-field/current stress are significantly improved. Fowler-Nordheim tunneling characteristics and measured capacitance reveal a 3-percent increase in the film thickness. Negative bulk charge trapping is similar to that of thermal oxide film. These properties can be attributed to the formation of the nitrogen-rich layers at both film interfaces, rather than the bulk of the film.