The rational design of bleachable non-chemically amplified DUV photoactive compounds

Abstract

Photoactive compounds have been designed, synthesized and characterized for deep ultraviolet non-chemically amplified resist applications. These resist materials may have potential use in next generation 257 nm mask fabrication. Mask fabrication requires stringent linewidth specifications over long post-coat and post-exposure bake delays. Lithography simulation and imaging experiments have been done to determine the lithographic performance of resists formulated with these new photoactive compounds. Previously studied chromophores, 7 substituted 3-diazo 4-hydroxycoumarin and N-substituted 3-diazo-2,4-piperidione, both have the transparency, bleaching and exposure rate kinetics in the DUV that are analogous to those exhibited by the diazonaphthoquinone chromophore at 365 nm. The sulfonate linkages attached to these photoactive compounds provide dissolution rate inhibition of novolak that is very similar to the diazonaphthoquinone-sulfonates. The trifunctional diazopiperidione that incorporates three sulfonate linkages provides more efficient inhibition per chromophore than the corresponding bisfunctional photoactive compound. The diazocoumarin based novolak resist demonstrates image reversal (negative tone) with the use of a post-exposure bake. The post-exposure bake causes the exposed photoactive compound to decarboxylate, which dramatically reduces its solubility in aqueous base. The trifunctional diazopiperidione provides the best overall imaging results due to almost complete bleaching and high contrast. © 2001 SPIE - The International Society for Optical Engineering.