In this paper the design of radiation sensitive polymeric imaging systems is reviewed. Advances in design have led to systems that function on the basis of radiation-induced changes in the polarity of polymer repeating units rather than cross-linking. These new systems offer improved resolution, since they do not swell during development. Improvement in sensitivity has been achieved by designing systems that incorporate chemical amplification. The design principles leading to amplification and examples of systems that demonstrate amplification are presented.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.93.24.73 Downloaded on 2015-01-05 to IP
Poly[p-(formyloxy)styrene] is prepared by chemical modification of poly(p-hydroxystyrene) or free-radical-initiated polymerization of the corresponding monomer.Unlike poly(p-acetoxystyrene), which undergoes a partial photochemical Fries rearrangement, poly[p-(formyloxy)styrene] decarbonylates smoothly when exposed to UV irradiation in solution or in the solid state. The difference in reactivity between the two acylated polymers is likely due to the lower stability of the formyl radical which is formed in the first stage of the photo-Fries reaction. In addition, while uniform irradiation of a 1-pm film of poly(p-acetoxystyrene) is impossible because of the formation of a strongly absorbing and UV stabilizing polymer at the surface of the exposed film, poly[p-(formyloxy)styrene] can be used in microlithographic processes to produce highresolution relief images. The images can be developed with positive or negative tone by differential dissolution of the exposed and unexposed areas of the polymer film by using solvents of appropriate polarities.
A mechanistic hypothesis is presented which explains the radiation chemistry of poly(methy1 a-haloacry1ate)s. In order to test the hypothesis poly(methy1 a-trifluoromethylacrylate) PMTFMA was synthesized together with copolymers of methyl methacrylate (MMA), and the a-trifluoromethyl analog. The mechanistic hypothesis predicts that PMTFMA should have a higher G scission than PMMA and that it should have no crosslinking propensity. This prediction was verified by experiment. Imaging of PMTFMA a s a positive e-beam resist is also presented. The new material is a more sensitive resist than PMMA.
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