Mechanism of Surface Charging Effects on Etching Profile Defects

Surface charging effects on the etching profile defects during silicon (Si) and polycrystalline silicon (poly-Si) etching in non-uniform plasmas were experimentally demonstrated and their mechanisms were studied using an electrostatic ion trajectory simulator and a newly developed surface potential probe. Profile tilt and bowing were found in Si etching, while undercut and shouldering were observed in poly-Si etching. The trajectory simulation and the directly measured charging potential showed that these profile defects were induced by the potential difference between the etching materials and the charged insulating mask and were dependent on the mask patterns. The profile results agreed well with the gate oxide damage results which were also successfully explained by the surface charging.