Mechano-chemical AFM nanolithography of metallic thin films: A statistical analysis

A mechano-chemical atomic force microscope (AFM) nanolithography on a metallic thin film (50 nm in thickness) covered by a spin-coated soft polymeric mask layer (50–60 nm in thickness) has been introduced. The surface stochastic properties of initial grooves mechanically patterned on the mask layer (grooves before chemical wet-etching) and the lithographed patterns on the metallic thin film (the grooves after chemical wet-etching) have been investigated and compared by using the structure factor, power spectral density, and AFM tip deconvolution analyses. The effective shape of cross section of the before and after etching grooves have been determined by using the tip deconvolution surface analysis. The wet-etching process improved the shape of the grooves and also smoothed the surface within them. We have indicated that relaxation of the surface tension of the deposited mask layer after the AFM scribing is independent from surface density of the grooves and also their length scale. Based on the statistical analysis, it was found that increase of the width of the grooves after the wet-etching and also relaxation of surface tension of the mask layer resulted in a down limit in the size of the metallic nanowires made by the combined nanolithography method. An extrapolation of the analyzed statistical data has indicated that, in this method, the minimum obtainable width and length of the metallic nanowires are about 55 nm and 2 μm, respectively.