Bulk oxide charge and slow states in Si-SiO2 structures generated by RIE-mode plasma

The damage induced in a thin SiO₂-Si system after an exposure to O₂ and N₂ plasma working in the reactive ion etching (RIE) mode has been studied. A generation of a large density (up to ~5×10¹²cm^-2 in the first 15 s plasma exposure) of positive oxide charge in bulk traps as well as in slow states has been established. The RIE damage effects become highly process dependent as the plasma time increases-the fixed oxide charge first increases and then slows down or even turns around depending on discharge conditions. It is suggested that the relative contribution of the two main plasma components (ion bombardment and vacuum UV photons) at different discharge regimes is the reason for the appearance or the absence of the “turn-around” effect. It is established that the combination O₂ plasma-low pressure is critical for the degradation of the plasma treated samples. The results reveal a strong linear correlation between leakage current detected and plasma created positive charge