Evaluation of metal migration and determination of trace metals after microwave digestion for lithographic materials.

The radioactive tracer technique was applied to investigate the migration of cesium and zinc impurities from bottom antireflective coating (BARC) and photoresist (PR) into underlying substrate. The effects of normal baking temperatures and substrate types were studied. Our results indicated that BARC has higher migration ratios than PR, irrespective of the substrate types and normal baking temperatures. The substrate type did not appear to strongly affect the metal migration ratios. However, water and/or solvent evaporation due to temperature change was found to have a significant effect on metal migration. The diffusion profiles of BARC and PR were depicted based on diffusion equations and the migration ratios. Both the UV/visible spectrometric and the gravimetric methods were successfully implemented to evaluate the feasibility of closed-vessel microwave digestion efficiency for BARC and PR samples. By following the established microwave digestion method and the inductively coupled plasma mass spectrometer (ICPMS) determination, the detection limits obtained for multielements were in the ppb and sub-ppb levels. Except for calcium, the spike recoveries of metals ranged from 91 to 132% and 87 to 125% for BARC and PR, respectively. The analytical results were found to be in reasonably good agreement with the literature values.