Structural and chemical evolution of fluorocarbon coatings on reactor walls and their run-to-run impacts on film deposition in C₄F₈/Ar/N₂ plasma processing

Although unintentional contamination of the inner chamber wall during repeated plasma processing can substantially affect semiconductor device performance, the quantitative impact of chamber wall conditions remains underexplored. To bridge this gap, in this study, the effects of repeated identical deposition processes on the chamber wall and their subsequent influence on plasma behavior and the properties of films deposited on substrates were investigated. With each run, the wall-deposited film gradually thickened, eventually saturating at approximately 5 μm. Throughout this wall contamination process, driven by polymer deposition, the film thicknesses at the center and edge of the bottom substrate followed distinct trends. Notably, the film at the substrate edge, located closer to the chamber wall, exhibited considerable variation in both thickness and chemical composition. These results suggest that plasma–wall interactions, intensified by the accumulation of wall deposits, led to the release of C_xF_y species from the contaminated chamber wall, thereby enhancing film growth at the substrate edge. Chemical analyses revealed that the proportions of carbon-containing groups such as CF₂, C CF₂, and C = C decreased in the wall-deposited film but increased in the film formed at the substrate edge. Furthermore, the plasma–wall interaction altered the radial distribution of reactive species in the plasma: The CF₂ density at the radial edge increased fourfold, while the F density decreased by 29 %. These findings underscore the critical role of plasma–wall interactions in modulating film deposition characteristics.