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.
Abstract-This paper describes a novel filtering method (FIMER) to extract three critical yield loss components: gross yield loss from parametric problems or from clustering of defects, repeated yield loss from mask defects or from lithography margin, and random yield loss mainly from particles. It is shown by simulation that FIMER is not only superior to the conventional windowing method in extracting repeated yield loss but also accurately extracts gross yield loss and random yield loss. The simulation studies show that the three components are extracted with an error equal to or less than 5% by optimizing threshold and filter weights, which are the major parameters in FIMER.
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