A Dielectric Sheet Covering Rough Surface to Enhance the Uniformity of Plasma Treatment: A Modelling Study

The surface morphology has significant influence on the surface treatment effect of plasma. When plasma is used to treat rough surfaces, electric field distortion will lead to uneven discharge, resulting in poor surface treatment effect. We present a method to improve the surface discharge uniformity of a rough surface by covering a dielectric sheet above the rough surface. The results of 2-dimensional fluid model indicate that this method can change the spatial distribution of surface discharge. The average fluxes of reactive species onto the surface increase, which means that the dielectric layer can improve the intensity of surface discharge. Meanwhile, the maximum/minimum values of the fluxes reduce, indicating that the uniformity of the surface fluxes is improved. To comply with practical applications, rough surfaces with different height of protrusions are further studies. For two different height arrangements of protrusions, namely high-short-high and short-high-short, the introduction of dielectric sheet benefits to the uniformity of surface treatment. The effects of the permittivity of dielectric layer and the distance between layer and rough surface on the surface discharges are also discussed. The results in this paper could contribute to better understanding of the plasma surface treatment in industrial production.