Experiments and Global Model Analysis of Inductively Coupled CF4/O2/Ar Plasmas

Abstract

Measurements using a Langmuir probe and optical emission spectroscopy combined with actinometry are carried out in inductively coupled CF4/O2/Ar discharges at total pressures lower than 30 mTorr for Ar contents ranging from 10 to 90%. The measured structure of the electron energy probability functions can be changed from being Druyvesteyn-like to being Maxwellian-like as Ar content decreases. The electron density measured at each fixed Ar content gradually decreases with increasing O2 content, whereas the measured electron temperature is not sensitive to O2 content. The atomic fluorine density measured at each fixed Ar content reaches its maximum when the ratio (ROC) of O2 content to the sum of CF4 and O2 contents is around 0.2, beyond which it decreases with increasing ROC. The atomic fluorine density measured at ROC = 0.2 remains constant for Ar contents lower than 60%, beyond which it monotonically decreases with increasing Ar content. These results are shown to be in reasonably good agreement with the predictions of the global model for electronegative plasma.