Important factors contributing to line-edge roughness (LER) of chemically amplified resists are, among others, acid diffusion, and photoresist polymer molecular weight (M W). Their effects on the final LER are combined and simulations indicated that acid diffusion can be the major LER modifying factor. Acid-diffusion increases LER overall in a chemically amplified resist in comparison with a conventional one under the same deprotection fraction. In addition, extremely high values of acid-diffusion range can result in smaller LER for higher M W polymers. Under normal acid diffusion conditions, the effect M W on LER is seen to be of secondary importance. Explanations are given based on the critical ionization model for the resist film dissolution, and experimental verification is done with top-down scanning electron microscope (SEM) images for extreme-ultraviolet lithography (EUVL) photoresist.

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