New Photoresist Based on Amorphous Low Molecular Weight Polyphenols

Abstract

We have investigated the possibility of amorphous low molecular weight polyphenols as a chemically amplified positive-tone electron-beam (EB) resist. Two low molecular weight polyphenols, 4,4'-methylenebis[2-[di(2-methyl-4-hydroxy-5-cyclohexylphenyl)]methyl] phenol (3M6C-MBSA), and 4,4'-methylenebis[2-[di(4-hydroxy-2,5-dimethylphenyl)]methyl]phenol (25X-MBSA) as a base matrix, and poly(p-hydroxystylene) (PHS) with a weight average molecular weight of 8400 as a reference were selected. Those phenol groups were protected by 1-ethoxyethyl groups to control the dissolution rate of these materials in 0.26 N tetramethylammonium hydroxide (TMAH) aq. developer. Etching rates under CF4/CHF3/He mixed gas process, dissolution rates with the developer, sensitivities with EB exposure, resolution and surface roughness were evaluated. The resist based on 3M6C-MBSA showed the excellent pattern profile and 60 nm lines and spaces (lines/spaces=1/1) resolution. And, even 50 nm lines and spaces pattern was partially resolved. In addition, as compared with PHS, smaller surface roughness of 3M6C-MBSA films was observed by AFM measurement.