Correlation between proton dynamics and line edge roughness in chemically amplified resist for post-optical lithography

Abstract

In chemically amplified (CA) resists for electron beam (EB) and extreme ultraviolet (EUV) lithographies, acids (a pair of proton and counteranion) generated upon exposure are utilized for resist pattern formation. As protons and counteranions are separately generated during the exposure, they initially have different spatial distributions. In this work, the authors investigated the effects of proton dynamics during the recombination between protons and counteranions and subsequent acid diffusion during postexposure bake on the line edge roughness (LER) formation of the latent image. The proton dynamics and acid diffusion were simulated by a Monte Carlo technique based on diffusion under Coulomb potential induced by many-body charged species. Based on the results shown here, the correlation between the linewidth and LER as a function of exposure dose and the concentration of base additives are discussed in terms of proton and acid trajectories. The obtained aspects not only provide detailed insight into the nature of reaction mechanism in CA-EB (EUV) resist but also would be of help in the development of resists and the optimization of process conditions.