Photochemical Studies on Bottom Anti-Reflective Coatings

The photochemical behavior of 193-nm photosensitive bottom anti-reflective coatings (BARCs) were studied. The effects of exposure dose, post-exposure bake (PEB) temperature, PAG size, and BARC thickness on contrast and the decrosslinking process was investigated. Using higher PEB temperatures improve the BARC contrast. Smaller photogenerated acids diffuse more freely throughout the crosslinked polymer. The decrosslinking process had an energy of activation associated with it and is controlled by the exposure dose and PEB temperature. An optimum BARC thickness for lithography was located at the first reflectivity maximum in the reflectivity curve. At this thickness, the best contrast and lower D50 values are obtained. Lithographic evaluations at these BARC thicknesses using a photoresist showed good performance on 150-nm L/S (1:1.5) on both silicon and silicon dioxide substrates.