Chromophore Effect of Non-ionic Photoacid Generators on Resist Performances

Abstract

So far, we have developed and reported a series of novel oxime sulfonate type of photoacid generators (PAG) composed of a fluorenyl chromophore like 2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene (ONPF), which generates a strong acid (nonaflic acid) by light irradiation and is promising for chemically amplified ArF photoresists. They generate a fluorinated alkylsulfonium acid as a strong acid, have high transparency at 193 nm, and show higher hydrophobicity than TPSnf, good solubility in various solvents, and good thermal stability. However, it has been observed that such fluorenyl PAGs did not have a good coating property, and showed a few striation patterns after spin-coating of some formulations. To improve the striation issue while keeping the desirable properties, replacement of the chromophore was examined, and it has been revealed that 8-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluoranthene (PAG A) composed of a fluoranthenyl chromophore and 4''-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-[1,1',4',1'']terphenyl (PAG B) could dramatically improve the coating property and the P-parameter was comparable to that of ONPF. This improvement is due to enhancement of compatibility toward a polymer matrix composed of high carbon content. Therefore, it has been observed that higher carbon content in a PAG molecule provides better coating property.