Improvement of the Si-SiO2 interface stress resistance of thin gate oxides after channel ion implantation

The effect of phosphorus and boron ion implantation into silicon dioxide films is examined with regard to the resistance of the Si-SiO₂ interface under high field constant current stress conditions. Phosphorus and boron ions of various doses and energies have been implanted through a 35 nm thick oxide. The interface stress resistance is found to decrease with increasing ion dose and increase with implant energy. However, at high energies, the stress resistance of the boron implanted samples is significantly less than the phosphorus equivalents due to the creation of a second interface trap level. Post-implant annealing increases the interface stress resistance but the best performance is observed for the case of sacrificial oxidation.