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Protective top coats and top antireflective coatings (ARCs) are frequently used in conjunction with chemically amplified resists. Top coats provide resistance to airborne contamination, and are particularly important where charcoal filtration is not available in the processing area. They are also useful in environments where delay times between process steps are not precisely controlled. Conductive top coats can be used for e-beam applications to reduce charging and image placement errors. Top ARCs are used to reduce reflections at the resist/air interface, thereby lowering the amplitude of the swing curve. All of these materials are applied on top of the photoresist after the postapply bake. In this article we report that depending on the subsequent processing conditions, top coatings can significantly impact the lithographic performance of the photoresist. Alterations in development rate, optical proximity effects, resist profile, and postexposure bake latitude have been observed as a result of processing with an additional top film. The primary mechanism responsible for these changes is an alteration of the diffusion characteristics of the photo acid generator during the deprotection step. © 1998 American Vacuum Society.