Anionic living polymerization of 4‐[bis(trimethylsilyl)methyl]styrene and its properties as a resist material

An anionic polymerization of 4‐[bis(trimethylsilyl)methyl]styrene (BSMS) proceeded homogeneously to give a polymer with a narrow molecular weight distribution (MWD; Mw/Mn = 1.06–1.07) even at 20°C. The relative lower propagating rate owing to the electron‐donating character of the para standing bis(trimethylsilyl)methyl group in BSMS (σ—π hyperconjugation) plays an important role for formation of the poly(BSMS) with a narrow MWD, even at a high polymerization temperature. Poly(BSMS) thus obtained had a high silicon content (24.1 wt%) and a fairly high glass transition temperature (140–150°C). Properties as an electron‐beam resist for poly(BSMS) were investigated. The polymer was found to be a negative‐type resist with a high contrast value (γ = 4.7) and a sensitivity about twice on high as poly(styrene). These facts may be attributable to the high Tg content, the narrow molecular weight distribution, and the characteristic structure of poly(BSMS).