Determination of Plasma Parameters in a Dual-Frequency Capacitively Coupled CF ₄ Plasma Using Optical Emission Spectroscopy

Optical emission spectroscopy measurements of dual-frequency capacitively coupled CF 4 plasmas were carried out. The gas temperature (T _g ) was acquired by fitting the optical emission spectra of a CF B−X system in 201∼206 nm. The atomic fluorine concentration and the electron temperature (T _e ) were obtained by trace rare gas optical emission spectroscopy and a modified Boltzmann plot technique, respectively. It was found that the gas temperature was about 620±30 K at 50 mTorr and the atomic fluorine concentration increased while the electron temperature decreased with increasing gas pressure and power of high frequency (60 MHz). With increasing low frequency (2 MHz) power, the electron temperature also increased, but the atomic fluorine concentration was insensitive to this change. The generation and disappearance mecha- nisms of F atoms are discussed.