Monte Carlo simulations of charging and profile evolution in patterned antenna structures during etching in high-density plasmas reveal a rapid change in the potential of the lines at end point, which causes a surge in electron tunneling through thin gate oxides and possibly charging damage. The condition of the substrate (grounded vs. floating) determines the magnitude of the surge and whether it will be followed by a steady-state current until all lines of the pattern become disconnected. A reduction in damage is possible by controlling the substrate condition, which may be assessed through notching experiments.