Effects of Chamber Wall Contamination Levels on Plasma Properties in Long-Term C4F8/Ar Plasma Deposition Processes

CxFy-based gas discharges can lead to process deviations due to severe contamination of the inner chamber wall. However, the extent of wall contamination and the variation in plasma properties relative to process operation time in CxFy-based plasmas remain unclear. Therefore, in this study, the degree of wall contamination depending on the process time and its effects on plasma properties were evaluated. The thickness of the wall-deposited polymer increased to 5.78 mu m after 8 h and remained constant until 12 h. In contrast, since the thickness for every 2 h-process under a clean-wall condition was approximately 1.85 mu m, the total summed thickness for the 12 h-process exceeded 11 mu m. This difference in thickness suggests that the interaction between the plasma and contaminated wall limited further wall contamination during the deposition process. In addition, plasma parameters, such as CF2 density, varied with the level of wall contamination. Up to 8 h, the CF2 density decreased by 20 % but did not show significant changes beyond that point. These results indicate that the balance between radical loss to the wall and radical generation from the contaminated wall and/or suppressed deposition on the wall influences plasma parameters.