Study of the treatment's homogeneity in plasma assisted chemical vapour deposition by atmospheric pressure dielectric barrier discharge

Dielectric Barrier Discharge (DBD) appears to be a promising technology to perform surface treatments at atmospheric pressure, particularly for the treatments of large-dimension flat objects for on-line industrial applications. Besides the fact of allowing short treatment times, the advantage of atmospheric pressure is the suppression of constraints correlated to the implementation of vacuum devices necessary for low pressure treatments. But at the present time, if this technology showed its ability for the surface cleaning, it is not still the case for thin film deposition over large surfaces, due to an insufficient homogeneity of the deposited layers. This lack of homogeneity is the main present problem limiting the use of DBD in PACVD. The study of the layer's uniformity leads us to search links between the internal physical phenomena inside the reactor and the layer's properties. This paper is focused to the study of the spatial homogeneity of SiOx thin films deposited over large surfaces by using an atmospheric pressure DBD with N2/O2/HMDSO gas mixture. The results presented in this paper show that it is possible to understand the homogeneity variations of deposited layers by simultaneously making the link between the deposited power in plasma (taking into account both the energy per pulse and the pulse repetition frequency) and the gas hydrodynamics in the flow boundary layer.