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Novel polymers containing polyhedral oligomeric silsesquioxane (POSS) pendant groups have been synthesized and evaluated as components of 157 nm resist formulations. Random copolymers of polymerizable, ethyl-POSS containing monomers with various acrylates, including tert-butyl methacrylates, were first used in positive, aqueous base-developable resist formulations and evaluated at thicknesses in the range of 100 nm. Copolymers with optimized monomer composition do not present strong self-organization phenomena and provide materials with good film forming properties, and high sensitivity at 157 nm (1-10 mJ/cm2 under open field exposure). Process studies reveal strong influence of thermal processing conditions and development concentrations on swelling of unexposed and underexposed resist areas. Similar results are obtained from Dissolution Rate Monitoring (DRM) studies. A typical process selected for selling reduction includes pre-exposure and post-exposure bakes at 160°C (2 minutes) and selection of low strength developers. High resolution patterning under these conditions has shown potential for sub 130 nm lithography upon further material optimization. On the other hand, pattern transfer studies have shown that 100 nm thick films of POSS containing materials, having the same silicon content as the ones evaluated for high resolution 157 nm lithography, provide the necessary oxygen plasma resistance for use as bilayer resists. X-ray photoelectron spectroscopy (XPS) was used for surface characterization before plasma etching. Both XPS and angular XPS characterization have revealed that the POSS moieties tend to segregate preferentially on the free surface of the films.
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