THE INFLUENCE OF MASK THICKNESS ON CHARGING DAMAGE DURING OVERETCHING

Feature-scale charging simulations during gate electrode overetching i n high-density plasmas reveal that the thickness of the insulating mas k plays a critical role in charging damage, When thinner masks are use d. the electron irradiance of the conductive part of the sidewalls inc reases, causing the charging potentials of the polysilicon lines to de crease, thus reducing the probability for catastrophic tunneling curre nts through the underlying oxide. Simultaneously, changes in the charg ing potential distribution at the bottom SiO2 surface cause a signific ant perturbation in the local ion dynamics which. in turn. adversely a ffects notching. Notches are predicted to form everywhere in a line-an d-space structure, even when the lines are electrically isolated. The results suggest that the trend toward thinner (hard) masks-to keep the aspect ratio low as device dimensions shrink-should reduce oxide fail ure but at the cost of more severe notching. (C) 1997 American Institu te of Physics.