Depth dependence of resist line-edge roughness: Relation to photoacid diffusion length

We report the results of an experimental and simulation study of the correlation between line-edge roughness (LER) and height along the sidewall for resists patterned with electron-beam lithography. The characterization has been performed using atomic force microscopy with carbon nanotube tips and scanning electron microscopy. Experimental results generally support that LER depends on resist height and aerial image modulation. Finally, percolation simulation results based on stochastic modeling are compared with experimental results, and allow us to set an upper limit of 3–5 nm on acid diffusion length.