Characterization of plasma charging damage in ultrathin gate oxides

Abstract

Charging damage induced in oxides with thickness ranging from 8.7 to 2.5 nm is investigated. Results of charge-to-breakdown (Q/sub bd/) measurements performed on control devices indicate that the polarity dependence increases with decreasing oxide thickness at room temperature and elevated temperature (180/spl deg/C) conditions. As the oxide thickness is thinned below 3 nm, the Q/sub bd/ becomes very sensitive to the stressing current density and temperature. Experimental results show that severe antenna effects would occur during plasma ashing treatment in devices with gate oxides as thin as 2.6 nm. It is concluded that the negative plasma charging and high process temperature are the key factors responsible for the damage.