Roughness analysis of lithographically produced nanostructures: off-line measurement and scaling analysis

The aim of this paper is to obtain a method for line-edge roughness (LER) detection and characterization for lithographically produced nanostructures based on the analysis of top-down scanning electron microscope (SEM) images. For the line-edge detection, an off-line image analysis algorithm is developed, while for the LER characterization the detected edges are analyzed according to the scaling theory to reveal the type of edge roughness (such as self-affinity or quasiperiodicity). As a consequence one determines the best and most complete set of roughness descriptors. The experimental line-edges of two photoresists are examined and show a self-affine structure, similar to the lithographically produced surfaces of negative and positive tone photoresists [Microelectron, Eng., 61/62 (2002) 793]. Therefore, the best LER descriptors for them should be the σ value (root mean square value of the edge points), the correlation length ξ and the roughness exponent α which is connected to the fractal dimension DF (α = 2 - DF). Finally, the dependencies of these descriptor on image analysis parameters are also investigated.