Experimental study and global model of inductively coupled CF4∕O2 discharges

Abstract

Experiments with a Langmuir probe and optical emission spectroscopy combined with actinometry were carried out in inductive CF4∕O2 discharges at three pressures of 8, 15, and 25mTorr. The measured electron energy probability functions are approximately Maxwellian at any oxygen content. The measured electron density decreases with increasing the oxygen in the oxygen content below 20%, beyond which it remains nearly constant. On the other hand, the measured electron temperature is not sensitive to the content. The atomic fluorine density estimated by actinometry increases markedly as oxygen is mixed to CF4 discharges, and then reaches the maximum around the oxygen content of 20%–30%, beyond which it decreases with increasing oxygen content. The atomic oxygen density increases with the increase in the oxygen content except for the oxygen content higher than 90%. A global model for electronegative plasma is used in order to investigate the plasma chemistry in CF4∕O2 discharges assuming the Maxwellian electron energy distribution. The model results are compared with the experimental results, obtaining reasonably good agreement.