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The development of novel resists that can match the challenges posed by the next generation of lithography partly hinges on our ability to develop new methods for extracting spatial information with sub-nm precision at each step of the lithographic process. This is particularly important for EUV resists, which tend to suffer from the seemingly inescapable trade-off between improving photon sensitivity and resolution, while reducing line edge roughness (LER). The strategies used to optimize this trade-off rely on tailoring the physicochemical mechanisms that take place before the final development of the resists, thus finding a way to characterize the structure of their latent image is critical to future progress.
To meet some of these challenges, resonant x-ray scattering (ReXS) has emerged as a powerful technique which leverages the chemical contrast that exists between exposed and unexposed regions before the final development step in order to produce the average cross-sectional profile of the latent image with sub-nm precision. Most recently, the ReXS technique was demonstrated in a grazing incidence configuration by leveraging contrast in the carbon element’s local chemistry in order to extract the latent image of a patterned chemically amplified resist (CARs) directly on a silicon substrate[1]. In this work, we show how this capability may be extended to extract chemical contrast from other active elements in a given resist and expand on the potential benefits and drawbacks (i.e. beam damage, experimental configurations, and LER sensitivity) of performing such measurements both before and after the post-exposure baking step has taken place. Finally, we will present comparisons between the latent image profile collected at various resonant x-ray energies and the final developed structure corresponding to a variety of modern commercial resists used both for e-beam and EUV lithography. Such unique spatiochemical information should provide useful guidelines for both the synthesis and processing of the next generations of resist materials.
[1] G. Freychet, I.A. Cordova, T. McAfee, D. Kumar, R.J. Pandolfi, C. Anderson, P. Naulleau, C. Wang, A. Hexemer, Using resonant soft x-ray scattering to image patterns on undeveloped resists, SPIE2018.
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