Poly(alkenylsilane sulfone)s as positive electron beam resists for two‐layer systems

Alternating copolymers of sulfur dioxide and vinyltrimethylsilane (VTMS) and terpolymers with allyltrimethylsilane (ATMS) and 1‐butene have been synthesized by low‐temperature, free radical‐initiated polymerization. The co‐polymers with VTMS were soluble but hydrolytically unstable. Whereas the copolymer from ATMS was insoluble, terpolymers containing less than 75 mol‐percent ATMS (relative to butene) were soluble in a variety of organic solvents. Moreover, they were stable against hydrolysis and had good film forming properties. Their electron beam sensitivity was 1.5 °C/cm² at 20 keV. and their contrast was ∼2. The terpolymers have been used as a top imaging layer in a two‐layer resist system to transfer half‐micron features into a 1.2μm‐thick Novolac planarizing layer by oxygen reactive ion etching (O₂, RIE).