The resolution limit of the resist silylation process in i-line lithography

The resolution limit of the resist silylation process in an i-line stepper was considered. The method was developed to render the silylated layer visible and was applied to measure the thickness of the silylated layer. The silylated profile is compared with the exposure energy profile and there is good agreement. This result indicates that the degradation of contrast in the silylation is negligible. The dry development process does not limit the resolution because no microloading effect is observed down to the 0.25-µm slit. The degradation of contrast due to optical diffraction is concluded to be essential for determining the resolution. The resolution limit of 0.35 µm in 0.75-µm resist thickness is demonstrated by simulation and experiment.