Effects Of Acid Diffusion And Resist Molecular Size On Line Edge Roughness For Chemically Amplified Resists In Euv Lithography: Computational Study

Stochastic simulations are performed to analyze the effects of acid diffusion and resist molecular size on pattern profiles for chemically amplified resists in EUV lithography. In the simulation, polymer chains are formed by random connection of monomer units. The acid diffusion and the acid reaction with polymers in the post exposure bake are introduced by the random-walk model. Simulation results show that the inhomogeneous acid generation and diffusion more largely affects the pattern roughness than polymer molecular size for both deprotection and cross-linking types of resists. At high doses, the line edge roughness (LER) increases with increasing polymerization degree of resist polymer. In such condition, the acid distribution becomes uniform and molecular size affects the LER. On the other hand, at low doses, the LER decreases with increasing polymerization degree. That is because the larger polymer molecule is less sensitive to inhomogeneous distribution of acid accompanying low doses.