Reduction of topography dependent charging with low electron temperature plasma

In simple terms, topography dependent charging (TDC) or electron shading results from the directionality difference between ions and electrons bombarding a surface with topography. In addition to directionality, the ion and electron energy distribution functions (IEDF and EEDF, respectively) also play important roles in charging by this mechanism. Experimentally, Fujiwara et al. (1995) reported that lowering electron temperature T_e reduces TDC, as demonstrated by the notching effect. For the ions, the importance of the IEDF was implied early by the observed dependence of notching on bias voltage (Ogino et al., 1995) and frequency (Fujiwara et al., 1994). In terms of theory, the Stanford group (Kinoshita et al., 1996) followed by the Cal Tech group (Hwang et al., 1997) have developed TDC simulators which predict the effects of the IEDF on this form of charging. Using the former simulator with the addition of EEDF calculations, this paper gives a more detailed description of how increasing the low energy electron population reduces topography dependent charging