The morphology and chemistry evolution of fused silica surface after Ar/CF4 atmospheric pressure plasma processing

In order to reveal the plasma etching processes on fused silica, the surface characterizations of fused silica after Ar/CF4 atmospheric pressure plasma processing were investigated. The morphology and chemistry evolution of fused silica surface were analyzed by AFM and XPS respectively. The AFM micrographs exhibited the three-dimensional surface topography and the RMS roughness changed with the increase of the material removal depth. The surfaces appeared to become smoother when the plasma etching occurred on the surface top layer. However, after the chemically modified layer was removed, etching resulted in the formation of a series of pits. During extended etching, the individual pits coalesced with one another, and the coalescence provided a means of reducing the depth of subsurface damage and the RMS roughness. The XPS results illustrated that small amount of radicals including C-CFn and CF-CFn could be introduced onto the fused silica surface during the Ar/CF4 plasma process, the fluorocarbon radicals were generated during CF4 plasma ionization. And the changes in relative concentration of the fluorocarbon radicals C-CFn with the removal depth were also studied.