The effect of water-contact and evaporation on the roughness of photoresist for immersion lithography

The effect of water-contact time on the roughness increment of patterned photoresist (AZ5214) was investigated by AFM analysis and the reason for the roughness increment was studied by the gravimetric experiment and the ellipsometry method. New method for calculating RMS line edge roughness from AFM raw data and the model of immersion lithography for experimentation were established. From the gravimetric experiments, it was confirmed that the diffusion of water into photoresist film is ruled by Fick's law. It was suggested that the amount of the swelling which follows the diffusion of water would be the reason for the roughness increment during rapid evaporation of water. As a result, the roughness of both the patterned line edge and the surface were proportioned in the root of water-contact time at the initial time and it was the same as the results in previous gravimetric experiments.