Anomalous etch rates of photoresist with argon dilution of CF4/O2 plasma afterglows

It is shown that the downstream etching of a photoresist with CF4/O2 mixtures can be enhanced by a factor of at least 2 with addition of argon to the gas mixture. Analysis of the oxygen and fluorine atom densities with gas-phase magnetic resonance downstream of the discharge suggests that argon metastables alter the homogeneous chemistry for fluorine atom production as well as the heterogeneous chemistry of photoresist chain scission.