Negative Resist for i-Line Lithography Utilizing Acid Catalyzed Silanol-Condensation Reaction

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Abstract
Negative resist systems composed of a novolak resin, diphenylsilanediol (Ph2Si(OH)2) and an acid generator are investigated for i-line lithography. The reaction in this resist system is based on an acid-catalyzed condensation reaction; the acid produced in the exposed area induces a condensation reaction of Ph2Si(OH)2 during post-exposure baking. The condensation product, siloxane, acts as an aqueous-base dissolution inhibitor, while silanol compounds in unexposed areas work as dissolution accelerators. The resist composed of a novolak resin, Ph2Si(OH)2 and 2-naphthoylmethyl-tetramethylenesulfonium hexafluoroantimonate (NMTMS-SbF6) shows a sensitivity of about 200 mJ/cm2 at 365 nm. This sensitivity is lower than that at 248 nm when triphenylsulfonium triflate (Ph3S+OTf-) is used as an acid generator, which can be ascribed to the low quantum yield of acid generation from NMTMS-SbF6. Using this resist, 0.3 µm space patterns with 1 µm film thickness were obtained by combining an i-line stepper with a phase-shifting mask.

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