Polystyrene-tetrathiofulvalene

Figure 39. Polystyrene-tetrathiofulvalene resist. The sensitizer is a perhaloaliphatic such as CBr. Exposure results in salt formation in the exposed areas of the resist film.

PSTTF is based on polystyrene that has been functionalized through appendage of a tetrathiofulvalene side-chain. The resist is spin-coated from a solution which contains a sensitizer substance, typically a perhaloalkane... 

It was indicated earlier that swelling limits resolution in solvent-developed negative resists. It was also intimated that swelling effects could be minimized if there were a sufficient polarity change between the exposed and non-exposed areas of the type mentioned in the previous discussion of the PBOCST system. A similar principle was utilized by Hofer et al., (145-146) at IBM, based on ion pair formation. The resist consists of a polystyrene polymer to which tetrathiofulvalene (TTF) units have been attached. When spun down with an acceptor such as CBr4, a complex is formed which, on irradiation, undergoes an electron transfer reaction to form an ion pair ... 

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