Maintaining reproducible plasma reactor wall conditions: SF₆ plasma cleaning of films deposited on chamber walls during Cl₂/O₂ plasma etching of Si

The removal of silicon oxychloride films deposited on the chamber walls during Cl₂/O₂ plasma etching of Si using an SF₆ plasma was studied using multiple surface and plasma diagnostic techniques. Focus was on the changes in the gas phase and in the chemical composition of the silicon oxychloride film as it is removed by F atoms in an SF₆ plasma. Films depositing and species adsorbing on the chamber walls during the deposition and cleaning steps were detected by a real time, in situ diagnostic probe. The radicals in the discharge were detected by optical emission spectroscopy (OES) while stable gas species present in the exhaust of the reactor were detected through gas phase FTIR absorption spectroscopy. Simultaneous monitoring of the walls and the gas phase yielded insights into the cleaning mechanism of the silicon oxychloride deposits by SF₆ plasma.