Is the resist sidewall after development isotropic or anisotropic? effects of resist sidewall morphology on LER reduction and transfer during etching

Measurements of the sidewall morphology of commercial resist lines (3D Line Edge Roughness) after lithography and before etching by CD-AFM and SEM show that they exhibit anisotropy in the form of striations perpendicular to line direction. When this anisotropy of post-litho resist sidewalls is included in the models for trimming and pattern transfer proposed in [V. Constantoudis et al., Proc SPIE 7273, 72732J (2009)], then the models predict the beneficial role of trimming process in LER reduction during pattern transfer in agreement with experimental results. Furthermore, experimental and simulation studies show that the CD-AFM measurements of the 3D Line Width Roughness may overestimate the correlation length. Taking into account this finding in the model for trimming, we found that model predictions approach further the experimental results.

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