Spectroscopic diagnostics of CF4‐O2 plasmas during Si and SiO2 etching processes

The emission intensities in the range of 2000-8000 Å of CF, CF 2, O, F, CO, CO+, and CO2 produced in CF 4/O2 radio-frequency discharges, operated at 1 Torr of pressure and 50 W of power input, have been used to follow the etching process of Si and SiO2, as a function of the CF4/O2 feed composition. The addition of small amounts of nitrogen or argon to the plasma mixtures has permitted the determination of the effect of the oxygen addition to the gas feed on the electron densities of the plasma for a wide range of electron energies. The relative concentration profiles of F and O, as well as of CO and CO2, have been determined with this technique, as a function of the oxygen content in the feed. The important role played by atomic F as active etchant for both Si and SiO2 substrates has been confirmed.