A surface-silylated single-layer resist using chemical amplification for deep UV lithography: IIIb. optimization of PAG and its content

A thick single layer of poly(vinyl phenol) containing PAG was surface-silylated uniformly with HMDS. When TPS-SbF6 and TPS-Tf were used as the PAG, surface sublayer thickness was 130-200 nm and 60-150 nm, and O-2 RIE durability was 10-31 and 18-43, respectively. The SSS Resist was patterned by DUV exposure, chemically amplified desilylation during PEB, wet development with TMAH, and O-2 RIE blanking to form a positive-tone image with a high aspect ratio. The optimum sensitivity was 3 mJ/cm(2) with TPS-SbF6 at 2.7 mol% loading and 2 mJ/cm(2) with TPS-Tf at 6.3 mol% loading. The sensitivity with TPS-Tf was higher than that with TPS-SbF6, since TPS-Tf is less bulky, of larger diffusion constant, and has longer catalytic chain length of desilylation. The amount of TPS-Tf, appropriate for the optimum sensitivity was larger than that of TPS-SbF6, which was considered in conjunction with light absorption, acid generation by the PAG acid-catalyzed desilylation, and dissolution inhibition by the remaining PAG unreacted.