Poly(4‐methylstyrene‐co‐chloromethylstyrene): A negative electron beam resist—synthesis and lithography evaluation

Abstract

Synthesis and lithographic characterization of a series of negative acting electron sensitive resists based on poly(4-methylstyrenexo-chloromethylstyrene) are reported. The sensitivity and contrast of these resists were found to depend on the chloroniethylstyrcnc (CMS) content and an optimum value of 5wt% was determined from consideration of parameters associated with the reproducibility of the synthetic method and also the lithographic performance. Both the sensitivity and resolution were found to depend on the molecular weight and CMS content of the copolymer. Several methods of scale up for the synthesis were explored, the route having a very significant influence on the film formation characteristics of the resists. The reactivity ratios of the monomers were measured in order that the compositional drift, which occurs during the synthesis, could be quantified. The effect of solvent composition and molecular weight of the copolymer were explored in relation to the quality of the resulting lithography. These studies have indicated that the copolymer has the potential of being used as a VLSI sub-micron resist with good plasma etch resistance.

Towards Halomethylated Benzene-Bearing Monomeric and Polymeric Substrates

“…Like poly(chloromethylstyrene) (PCMS) [137] and poly(methylphenylsilane) [80], chlorinated polymers of o-, m-, p-methylstyrene, 2,4-and 2,5-dimethylstyrene and 2,4,6-trimethylstyrene found applications as negatively-working electron beam resists in the field of electronics [138][139][140][141]. In such applications, the radiation induced cross-linking via an ethylene bridge and chain scission of the polymer backbones as observed with poly(methylphenylsilane).…”

Synthesis of benzyl chlorine‐free poly(4‐acetoxystyrene) via cationic polymerization followed by Friedel‐Crafts alkylation

“…However, the formed polymers always contain benzyl halogen end‐groups when 1‐phenylethyl chloride (St–Cl)/SnCl 4 /n‐Bu 4 NBr system is used because of the halogen‐exchange between Lewis acids and carbonium ion active centers. It was well known that these highly reactive benzyl halogen end‐groups were instable under basicity, 22,23 thermal treatment 24 and radiation 25‐30 . For example, irradiation leads to the generation of benzyl radicals and Cl radicals which further induce the formation of tertiary radicals in backbones by eliminating HCl, followed by cross‐linking via the recombination of radicals 29,30 .…”