MONTE-CARLO SIMULATION AND MEASUREMENT OF SILICON REACTIVE ION ETCHING PROFILES

A two-dimensional plasma etching model based on the SIMBAD Monte Carlo thin-film growth simulation program has been modified to include ion- enhanced etch processes. The modified program has been applied to a st udy of sidewall passivation in the etching of silicon in a CF4/O2 plas ma. Experimentally measured mask undercut in the etching of 0.8-mum-wi de lines was reduced from 150 angstrom/min to virtually zero with an i ncrease in oxygen from 8% to 45% of total gas flow. The corresponding decrease in etch rate was from about 750 to 325 angstrom/min. Simulati ons account for this change based on competition between oxidation and flourine etching of the silicon surface. Reactive gases follow collis ionless trajectories at the simulation scale and have a high probabili ty of diffuse re-emission following contact with the surface. This sim ulation method extends current profile simulation capabilities for a w ell-known etching chemistry.