Kinetics of hydrogen atoms in high-density CF4/H2 plasmas studied by (2+1)-photon laser-induced fluorescence spectroscopy

Abstract

We measured the distribution of absolute H atom density in high-density, low-pressure CF4 plasmas with the addition of H2 by (2+1)-photon laser-induced fluorescence spectroscopy. The H atom density had hollow-shaped distributions, i.e., the H atom density adjacent to the chamber wall was higher than that in the plasma column. In addition, when the chamber wall was covered with hydrogenated fluorocarbon film, we detected H atoms without the addition of feedstock H2. These experimental results indicate surface production of H atoms from hydrogenated fluorocarbon film. The surface production rate was sensitive to the property of fluorocarbon film. When the property of fluorocarbon film was unified, the surface production rate increased linearly with the pressure of feedstock H2, suggesting a recycling process of H atoms between gas phase and fluorocarbon film as a mechanism of plasma–surface interaction in CF4/H2 plasmas.