Acid amplifiers: proton transfer or direct acid formation

Wu-Song Huang; Ranee W. Kwong; Wayne M. Moreau

doi:10.1117/12.388344

23 June 2000 Acid amplifiers: proton transfer or direct acid formation

Wu-Song Huang, Ranee W. Kwong, Wayne M. Moreau

Author Affiliations +

Proceedings Volume 3999, Advances in Resist Technology and Processing XVII; (2000) https://doi.org/10.1117/12.388344
Event: Microlithography 2000, 2000, Santa Clara, CA, United States

Abstract

Acid Amplifiers (AA) such as tosylate protected diols are additives to chemically amplified resist (CA) which can generate additional acid during postexposebake. The primary acid formed from the photoacid generator (PAG) induces further acid formation in a 'dark reaction' by the acidolysis of the tosylate acid amplifier. Gains of 2 to 10X in photospeed have been reported by the addition of AA. We have investigated tosylate and camphor sulfonate pinane diols as acid amplifiers in a ketal (KRS-XE) polyhydroxystyrene (PHS) based CA resist and found gains in DUV photospeed or for electron beam exposures. The acid amplifiers gave speed increases of a 1.5 - 2X when used in excess of 2 - 5X mole % of the primary acid generator of triphenylsulfonium triflate. The acid from the AA additive can also be formed directly by the irradiation of the AA in the film. This occurs primarily by the sensitization by the phenolic portion of PHS. The pinanediol tosylate alone was not as efficient as acid source as the triphenylsulfonium PAG. The acid amplifiers also showed thermal lability in the PHS resist film to directly form acid in baking > 100 C. Thus, the host polymer in this case of PHS can affect both the sensitivity and thermal stability of the added acid amplifier. The considerations of the design and use of AA should weigh the thermal stability of the AA, the strength of acid formed from the primary AG, the direct formation of acid from irradiation of the AA, and the strength of the acid produced from the acid amplifier.

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Wu-Song Huang, Ranee W. Kwong, and Wayne M. Moreau "Acid amplifiers: proton transfer or direct acid formation", Proc. SPIE 3999, Advances in Resist Technology and Processing XVII, (23 June 2000); https://doi.org/10.1117/12.388344

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