Development and characterization of 193-nm ultra-thin resist process

The lithographic performance of a single layer 193nm resist platform, Sumitomo PAR707, was evaluated for 100nm node patterns for thicknesses ranging from 313nm to 60nm. We first demonstrated that the standard resist formulation could not be used for sub-200nm thicknesses because of unacceptable line edge roughness (LER). We then evaluated the influence of the concentration of photo acid generator (PAG) in the resist formulation of LER over the thickness range of 313nm to 60nm. High PAG loading was found to decrease LER significantly for sub-200nm thicknesses. Using the optimal formulation for minimal LER for a given thickness, process latitudes for 100nm node patterns were determined. The overall dose-focus latitudes were found to remain very close for all thicknesses, with slightly larger latitude for thicker imaging layers.