Outgassing of photoresists in extreme ultraviolet lithography

Abstract

The outgassing characteristics of 100 nm thick films of several commercial photoresists were investigated during and after exposure to lithographically relevant doses of extreme ultraviolet lithography radiation. Three positive tone and two negative tone chemically amplified deep ultraviolet resists were evaluated that are commercially available. The amount and chemical composition of the outgassed species was determined by quartz crystal microbalance and quadrupole mass spectrometry. Outgassed species identified were products from acid catalyzed or photochemical cleavage reactions involving protecting groups, and products from the decomposition of photoacid generator molecules. t-butyl ester protected positive resist based on tetra polymers of methacrylates (IBM version 2.1) outgassed during exposure, and t-butoxy carbonyl protected positive resist based on polyhydroxystyrene (APEX-E) outgassed during and after exposure. Outgassing from t-butyl ester positive resist based on an ESCAP type polymer (UV6) and from negative resists (SAL 605 and NTS-4A4) was below detection limits in our experiments.