Experimental Techniques for Detection of Components Extracted from Model 193 nm Immersion Lithography Photoresists

Extraction of small molecule components into water from photoresist materials designed for 193 nm immersion lithography has been observed. Leaching of photoacid generator (PAG) has been monitored using three techniques: liquid scintillation counting (LSC); liquid chromatography mass spectrometry (LCMS); and scanning electrochemical microscopy (SECM). LSC was also used to detect leaching of residual casting solvent (RCS) and base. The amount of PAG leaching from the resist films, 30-50 ng/cm 2 , was quantified using LSC. Both LSC and LCMS results suggest that PAG and photoacid leach from the film only upon initial contact with water (within 10 s) and minimal leaching occurs thereafter for immersion times up to 30 min. Exposed films show an increase in the amount of photoacid anion leaching by upward of 20% relative to unexposed films. Films pre-rinsed with water for 30 s showed no further PAG leaching as determined by LSC. No statistically significant amount of residual casting solvent was extracted after 30 min of immersion. Base extraction was quantified at 2 ng/cm 2 after 30 s. The leaching process is qualitatively described by a model based on the inhomogeneities in resist films.