A study on the angular dependence of the etch and the redeposition rates in plasma etching using a faraday cage

摘要

Etching experiments were made in a CF_4 plasma with SiO_2 substrate located in a Faraday cage set on the cathode in a TCP etcher. The SiO_2 substrates were fixed on sample-holder slopes which have different angles to the cathode. The substrate was subject to only etching by incident ions, redeposition from the SiO_2 bottom plate, or a simultaneous etching and redeposition depending on the design of Faraday cages. Both the etch and the redeposition rates were measured changing the slanted angle of the sample holder, #PHI#, and the incident ion energy. The etch rate changed linearly with cos#PHI#, regardless of ion incident energies. On the other hand, the redeposition rate changed with 1-cos#PHI# for high ion energies (400 and 800 eV) but with 1-cos#PHI#)~2 for low energy (100 eV). The net etch rate observed by simultaneous etching and redeposition was different from the sum of individual rates for etching and redeposition.