[摘要]：Mask contributors to line-edge roughness (LER) have recently been shown to be an issue of concern for both the accuracy of current resist evaluation tests as well the ultimate LER requirements for the 22 nm production node. Problems arise from mask absorber LER as well as mask multilayer roughness leading to random phase variations in the reflected beam. Not only do these mask contributors effect the total measured LER in resist but they also have an impact on LER spatial scaling characteristics such as power spectral density and the related descriptors of correlation length and roughness exponent. Understanding how these metrics respond to mask effects may lead to an experimental mechanism for evaluating the importance of mask contributors to observed LER in resist. Here the authors present a detailed study of mask-induced LER spatial characteristics. The authors further describe the influence of illumination conditions and defocus on the metrics and compare the results to those expected from intrinsic resist LER. The results show power spectral density analysis to be a promising technique for distinguishing mask and resist contributors to LER.
