Impacts of long-term chamber-wall contamination on thin film deposition in N2/Ar/C4F8 plasma processes

It is known that the chamber-wall contamination during C₄F₈-based plasma processes induces changes in plasma properties and/or process results, related to the device performance and process yield [1]. Therefore, it is crucial to maintain the chamber condition stable and also important to study the correlation between chamber-wall contamination and properties of plasma process. In this study, thus, the effects of wall contamination on the deposition processes was investigated using various diagnostic methods. The plasma was generated in an inductively coupled plasma with the mixture of N₂/Ar/C₄F₈ gases. The wall condition was modulated by cyclic contamination over ~ hrs. At each cycle, thin film layer was deposited on a Si substrate and the radial distribution of radical density in the plasma was measured as a function of wall condition. The effects of wall contamination were also evaluated through the analyses of on the film properties deposited on the Si substrate such as film thickness, chemical composition, and etching behavior using O₂ plasma. From the results, it was found that the clean and/or contaminated wall conditions played the role of a radical sink and/or source resulting in the changes of plasma and film properties.