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 study of sidewall passivation in the etching of silicon in a CF4/O2 plasma. Experimentally measured mask undercut in the etching of 0.8‐μm‐wide lines was reduced from 150 A/min to virtually zero with an increase in oxygen from 8% to 45% of total gas flow. The corresponding decrease in etch rate was from about 750 to 325 A/min. Simulations account for this change based on competition between oxidation and flourine etching of the silicon surface. Reactive gases follow collisionless trajectories at the simulation scale and have a high probability of diffuse re‐emission following contact with the surface. This simulation method extends current profile simulation capabilities for a well‐known etching chemistry.