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 sigma value (root mean square value of the edge points), the correlation length xi and the roughness exponent alpha which is connected to the fractal dimension D-F (alpha = 2 - D-F). Finally, the dependencies of these descriptors on image analysis parameters are also investigated. (C) 2003 Elsevier Science B.V. All rights reserved.