Focused-ion-beam direct structuring of fused silica for fabrication of nano-imprinting templates

A dual beam scanning electron microscopy (SEM)/focused-ion-beam (FIB) system was used to pattern fused silica coated with a thin Cr layer. Features were characterised by atomic force microscopy (AFM) and SEM. The milled depth, surface roughness and the evolution of feature profiles as a function of ion fluence were investigated. It was found that the milled depth in fused silica substrates was linearly dependent on the ion fluence within the studied range. Features topography measurement revealed that after removing completely the Cr layer, an increase of the ion fluence resulted in a slight rise of surface roughness, however, the maximum root mean square (RMS) values were still less than 2.5 nm. More importantly, compared with the roughness of an unprocessed area on the substrate, an improvement of the surface finish of about 300% was obtained. The results demonstrated that FIB technology could be an alternative solution for producing nano-imprinting templates.