抄録
Photo-acid generators (PAC's) are vital components in the formulation of deep-UV chemically amplified resists. A new series of α-substituted-2-nitrobenzyl arylsulfonate PAG's was synthesized. Because the thermal stability of these PAG's correlates with the upper limit of the post-exposure bake (PEB) temperature of resists formulated with these, a study of the thermal stability was done looking at the effect of varying the α-substituent. The best thermal stabilities were obtained by having a bulky electron withdrawing group situated at both the o- and α-positions ofthe 2-nitrobenzyl chromophore. This substitution pattern enhances thermal stabilityby suppressing the nucleophilic displacement reaction of the sulfonate moiety by the nitro group oxygen. When used in resist formulations, PAG's based on these new chromophores conveyed higher thermal stability than was observed for similar PAG's based on the 2-(trifluoromethyl)-6-nitrobenzyl chromophore. Through a study done on the lithographic sensitivities of a series of resists formulated with poly(4-(t-butyoxycarbonyloxy)styrene-sulfone) (PTBOCSS) and the new PAG's, it was found that the quantum yield of acid decreased as the electron withdrawing power of the PAG's α-substituent increased.
