Surface smoothing of diamond membranes by reactive ion etching process

This paper describes a procedure based on reactive ion etching developed to reduce the surface roughness of CVD diamond thin films. The technique involves etching a bilayer made up of diamond and a planarizing SiO2 layer in an SF6-O-2 plasma mixture. Etching conditions have been determined which yield equal rates for both diamond and the SiO2 coverlayer and favour the removal of diamond peaks. Smoothed surfaces have been characterized by SEM, AFM and XPS: the results exhibit a significant decrease in roughness. This novel technique offers promising prospects for polishing thin diamond membranes for X-ray lithography applications without the removal of significant amounts of diamond material. The optical transmittance of diamond membranes, mainly affected by light scattering due to surface roughness, is significantly improved using this method of planarization.