Radiolysis of Poly(acetaldehyde-co-chloral), a Positive E-Beam Resist

Basic study of the radiation chemistry of polymers is needed both for the understanding of interaction of radiation with matter and for various technological applications. In the context of microelectronic lithography, polymers which undergo radiation induced crosslinking or scission are useful as negative or positive resists, respectively. There is a natural amplification of the physical effects of a radiolytic event. In the former case the formation of crosslinks insolubilizes the macromolecules. In the latter case the occurrence of one main chain scission can render the macromolecule more soluble than the parent polymer. Latent images can be developed by these solubility changes. Direct imaging is possible for positive acting resists if radiation cause complete degradation of the polymer into volatile products. Such system may be referred to as self-developing, and has the distinct advantages of simplicity and economy. Radiolysis initiates the unzipping process to convert the entire macro-molecule into its monomer without side reactions. Acetaldehyde and chloral were copolymerized using triethyl aluminum catalyst. Radiolysis in vacuo caused depolymerization with a GM value number of monomers produced per 100 eV of about 4000 to 80 completion. Gamma Radiolysis sensitized by Diphenyl Hexa-fluoro-iodo-phosphate C6H52IPF6 has GM value of 327000. The E-beam sensitivity of ACC is about 3x10 to the -2 csqcm.