Negative Electron Resists for Direct Device Lithography: I . Initial Material Survey

Abstract

Copolymers of glycidyl methacrylate (GMA) and various halostyrene monomers have been prepared and evaluated as negative electron resists to be used for direct device fabrication. The copolymerization kinetics of glycidyl methacrylate and halostyrene were found to be similar for 2‐chlorostyrene (2CS), 3‐chlorostyrene (3CS), 4‐chlorostyrene, and mixed isomers of chloro‐ and bromostyrene. Both the chemical composition and molecular parameters of the polymers were dependent only on polymerization conditions. Bromostyrene copolymers with GMA had a higher sensitivity although poorer dry etching characteristics than equivalent CS copolymers. Copolymers of 3CS and GMA exhibited a decreasing sensitivity and increasing contrast with increasing 3CS content. Dry etching performance increased with increasing 3CS content. Poly (glycidyl methacrylate‐co‐3‐chlorostyrene) with 0.50 mole fraction 3‐chlorostyrene can be reproducibly synthesized and most nearly meets the requirements for direct wafer fabrication.