Process dependence of roughness in a positive-tone chemically amplified resist

Line edge roughness becomes an important factor in linewidth control as lithographic dimensions approach the 0.1 μm region. In order to understand different contributions to roughness, we explored the relationship between roughness and deprotection in the case of a positive chemically amplified resist. Experiments show that the roughness of the remaining resist depends on process history and it is not a simple function of the degree of deprotection. Scaling analysis of atomic force microscopy images shows that an equal degree of deprotection yields a self-affine rough surface with constant fractal dimensions which imply a similar surface morphology, but with a different standard deviation. The correlation between sidewall and top surface roughness is also discussed.