Copolymers of methacrylic acid and itaconic acid derivatives as thermally crosslinkable electron resists

Abstract

This thesis describes the preparation and lithographic evaluation of copolymers of methyl methacrylate, dimethyl itaconate and α - methyl styrene with derivatives of methacrylic acid or itaconic acid as thermally crosslinkable electron resists. A number of promising materials, including copolymers, terpolymers and mixtures of two types of copolymer have been identified, and have been demonstrated to be capable of sub 500nm resolution.

Statistical copolymers have been found to show a general variation in resist properties with copolymer composition. This has been discussed in terms of the variation in the proportion of crosslinking groups present, and in changes in radiation sensitivity and solvent development behaviour with copolymer composition.

It has been shown that the exposure dose required to first solubilise the resist can be very much less than that required for the development of high resolution resist features. Experimental results obtained in this work are compared to a theory originally published to describe the solubilisation of lignin from plant tissues, whereby gel degradation can be conceptually treated as the reverse of network formation.