POLY[4-[BIS(TRIMETHYLSILYL)METHYL]STYRENE] FOR AN ELECTRON-BEAM RESIST WITH A HIGH-RESOLUTION

Several kinds of organosilicon-containing polymers, based on the poly(4-methylstyrene) [poly(MST)] skeleton (Figure 1), were synthesized to investigate characteristics for electron-beam (EB) resist materials. The glass transition temperature of the monotrimethylsilylated MST polymer [poly(SMS)] was lower than that of poly(MST), while introduction of two trimethylsilyl groups at the methyl group in MST gave a significant increase in the glass transition temperature (T(g) greater-than-or-equal-to 150-degrees-C) of the polymer [poly(BSMS)]. All of these polymers and copolymers with glycidyl methacrylate (GMA) thus obtained showed nega-working properties toward EB exposure. Sensitivity of the resists increased in proportion to their glass transition temperatures rather than to the Si content in the polymer. The contrast parameter gamma, however, increased extremely with increasing silicon content in the polymer. Actually, the gamma-value of poly(BSMS) (M(w) = 1.1 x 10(5), M(w)/M(n) = 1.17) was 8.1, keeping almost the same sensitivity as that of poly(MST). The high gamma-value of poly(BSMS) may be attributable to the unique polymer skeleton in addition to the narrow molecular weight distribution and the high glass transition temperature. Introduction of GMA units in poly(BSMS) resulted in high sensitivity, though the gamma-value decreased.