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

Abstract

The emission intensities in the range of 2000–8000 Å of CF, CF₂, O, F, CO, CO⁺, and CO₂ produced in CF₄/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.