Differences in radical generation due to chemical bonding of gas molecules in a high-density fluorocarbon plasma: Effects of the C=C bond in fluorocarbon gases

Abstract

We investigated the differences in radical generation due to chemical bonding of fluorocarbon gas molecules in the plasma. We found that dissociation of the C=C bond is five times easier than that of the C–C bond in a fluorocarbon gas plasma. As a result, a C2F4 plasma could generate a higher density of CF2 radicals than a C4F8 plasma. Additionally, the same dissociation processes occurred in the C3F6 and C5F8 plasma, which both have the C=C bond and C–C bond in their molecules. In the C3F6 plasma, the density of generated CF2 radicals was 3.5 times higher than that for CF or CF3 radicals, whose radical densities were the same. The C5F8 gas plasma mainly produced CF2 and CF radicals, and the CF radical density was higher in comparison to other fluorocarbon gas plasmas.