The influence of surface currents on pattern-dependent charging and notching

Surface charge dissipation on insulator surfaces can reduce local charging potentials thereby preventing ion trajectory deflection at the bottom of trenches that leads to lateral sidewall etching (notching). We perform detailed Monte Carlo simulations of pattern-dependent charging during etching in high-density plasmas with the maximum sustainable surface electric field as a parameter. Significant notching occurs for a threshold electric field as low as 0.5 MV/cm or 50 V/μm, which is reasonable for the surface of good insulators. The results support pattern-dependent charging as the leading cause of notching and suggest that the problem will disappear as trench widths are reduced.