For the prediction of abnormal etching profiles, an ion trajectory prediction system has recently been developed. In this system, sheath modeling was combined with the on-wafer monitoring technique for accurate prediction. This system revealed that sidewall conductivity strongly affects the charge accumulation and ion trajectory in high-aspect-ratio holes. It was also found that the accumulated charge in adjacent holes is one of the reasons for the generation of twisting profiles according to analysis using the system. We presume that the prediction system is an effective tool for developing nanoscale fabrication.