The effect of plasma damage and different annealing ambients on the generation of latent interface states

Abstract

p-MOSFETs stressed by (simulated) plasma induced charging were thermally annealed for 20 minutes at 400/spl deg/C in different annealing ambients. After the anneal, the devices were stressed again to reveal latent plasma damage. The charge pumping technique was used to detect interface state generation and charge trapping in the bulk of the oxide. It was found that the plasma stressed interface states are totally annealed by the thermal treatment. However, the interface state generation during the subsequent stress exceeds that of fresh devices. Changing the annealing ambient from forming gas to nitrogen lowers the post-anneal interface states generation rate significantly. Also, the correlation between the plasma charging level and the measured interface state generation has been studied. Although a consistent correlation can be observed for thick gate oxides, this consistency disappears for thinner gate oxides.