Postexposure bake sensitivity

Brominated poly(l-trimethylsilylpropyne) is an example of a substituted polyacetylene that is suitable for bilevel-resist processes (34). Requiring both exposure and postexposure bake (PEB) steps, samples of the polypropyne having a mole fraction of bromine from 0.1 to 0.2 per monomer unit exhibit sensitivities in the order of 25 mj/cm. Submicrometer resolution has been demonstrated, and etching-rate ratios relative to hard-baked photoresist planarizing layers are —1 25. 

Figure 8. Sensitivity curves for brominated derivatives of poly(TMSP) after postexposure baking for 1 h at 140 °C. Sample designations are explained in the caption to Figure 2.

The rate of acid generation from BTf was larger than that of diphenyliodonium triflate(ITf). Deprotection of poly(tert-butyloxycarbonyloxystyrene) (tBOCHS) with BTf was 3 times faster than that with ITf after postexposure bake at same temperature. BTf with higher sensitivity and thermal stability may be expected to be PAG of diazo compounds applicable to microlithography resists. 

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