Evolution of resist roughness during development: stochastic simulation and dynamic scaling analysis

The study of surface-roughness evolution of resist films during development may elucidate the material origins of line-edge roughness. We use a stochastic simulator of resist development and analyze the resulting surface roughness evolution with dynamic scaling theory in polymers with homogeneous and inhomogeneous local dissolution behavior. In all cases, a power-law increase of root mean square (rms) roughness and correlation length is found. In homogenous polymers, a slow rms roughness increase is reported and the scaling exponents are shown to obey the dynamic scaling hypothesis of Family-Viscek. Dissolution inhomogeneity is inserted on a monomer scale (using copolymers), on a chain scale (using mixture of copolymers), or on a film scale by the activation of photo acid generator (PAG) molecules and the concomitant acid diffusion. Our simulator predicts that any kind of inhomogeneity may cause much larger rms roughness than homogeneous solubility. Furthermore, PAG-induced inhomogeneity results in a faster increase and larger values of roughness compared to chain-level inhomogeneity and this, in turn, leads to larger values compared to polymers with monomer-scale inhomogeneity. The differences in roughness are abruptly magnified when one reduces the resist solubility to levels in the range of the "clearing dose." A comparison with experimental results shows good agreement with the simulation predictions. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3497580]