(A) study on characteristics of $SF_6$／$O_2$ capacitive discharge with QMS and Langmuir probe

Abstract

The $SF_6$／$O_2$ CCP plasma is widely used in industry. To measure and control etching characteristic, relation between etching ions/radicals and plasma property are searched. QMS and Langmuir probe are used to measure $n_2, T_e,$ EEDF and positive ion ratio. The experiment is done under fixed pressure of 50 mTorr. Firstly the $SF_6$ mixing ratio in the total gas is changed. Secondly the current applied to the electrode is changed. The relation between $n_e, T_e$ and relative F positive ion density shows discrepancy between the two experiments. However EEDF graph reveals a common underlying relation in the two experiments. By observing electron densities of high energy tail, in-situ monitoring of etching profile is possible.