Measurement of electron temperatures and electron energy distribution functions in dual frequency capacitively coupled CF4/O2 plasmas using trace rare gases optical emission spectroscopy

Measurements of electron temperatures Te and electron energy distribution functions EEDFs in a dual frequency capacitively coupled etcher were performed by using trace rare gas optical emission spectroscopy TRG-OES . The parallel plate etcher was powered by a high frequency 60 MHz “source” top electrode and a low frequency 13.56 MHz “substrate” bottom electrode. Te first increased with pressure up to 20 mTorr and then decreased at higher pressures. Increasing the bottom rf power resulted in higher electron temperatures. Electron temperatures in 90% CF4 +10% O2 plasmas were similar to those in 80% CF4+20% O2 plasmas. EEDF exhibited bi-Maxwellian characteristics with enhanced high energy tail, especially at pressures 20 mTorr. © 2009 American Vacuum Society. DOI: 10.1116/1.3179162