Vacuum ultraviolet absorption spectroscopy for absolute density measurements of fluorine atoms in fluorocarbon plasmas

Absolute densities of fluorine (F) atoms at the ground state (2p5 2P°) were measured in helicon-wave excited high-density CF4 plasmas by vacuum ultraviolet (VUV) absorption spectroscopy. By employing an electron cyclotron resonance CF4 plasma as a light source in the VUV wavelength range, an absorption spectroscopy system with no vacuum windows was constructed. As a result, the density of F atoms was approximately 1×1013 cm−3 for an rf power of 1 kW and a CF4 gas pressure of 2.5 mTorr, which was one-order higher than the density of CFx radicals and was one-order lower than the density of the parent gas.