Feature profile evolution during shallow trench isolation etch in chlorine-based plasmas. II. Coupling reactor and feature scale models

A two-dimensional numerical fluid model was developed to investigate the effects of reactor design on the radial profiles of plasma species, namely, etch products and positive ions, during shallow trench isolation etching in Cl2 O2 Ar inductively coupled plasmas. Specifically, the dual-coil and dual gas-feed designs of the reactor were examined. The former parameter was determined to be effective in tailoring the radial ion flux profile at pressures higher than 20 mT, while the latter parameter was shown to alter the etch product transport in the convection-dominant flow regime. Coupling of the reactor scale model to a feature scale model allowed investigation of minor center to edge variations in the etched feature profile. This hybrid model suggests that the general radial decrease in the etch depth seen from a set of design of experiments is caused by an inherent decrease in the spatial distribution of chlorine radicals. In addition, the increase in the silicon sidewall angle from center to edge can be qualitatively explained by the radial profile of the etch products. ? 2008 American Vacuum Society.