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than PMMA with equivalent molecular weights. In addition, our PMCN-A homopolymer is nearly identical in sensitivity to the P(MCN-co-MMA) systems recently reported by Stilhvagon et al. (9). Curiously, they find that Q is 8 • 10 -6 C/cm 2 and constant for copolymers ranging from 6 to 47% in MCN composition. These results may be attributed to some other factor than radiation G value, because G(s) increases from 1.2 to 3.85 or 3.34 in going from 9 to 100% MCN. This is important and Ouano (10) and others ( 11) have shown that the dissolution rate increases, for irradiated PMMA cannot be accounted for by molecular weight decreases alone. At high radiation exposures, the PMMA dissolution rates are more dependent upon polymer microporosity or entrapped organic volatiles than molecular weight. We propose here that the polymer microporosity or the amount of entrapped volatile products decreases as the G(s) value steadily increases over the 0-100% MCN polymer composition range. Thus, the net result is a constant e-beam resist sensitivity. This proposal is reasonable, because PMCN has no ester side group to be radiolytically removed to produce gaseous products (CO, CO2, CH4, etc.) which increase microporosity which leads to enhanced dissolution rates. Furthermore, CN group removal is not thermodynamically favorable (12). In contrast to irradiated PMMA, PMCN dissolution rates are probably determined more by radiation-induced molecular weight changes. We plan to rigorously test this hypothesis in the near future by volatile product and dissolution rate measurements.

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Poly(methyl α‐chloroacrylate) (PMCA) and the copolymers of methyl methacrylate and methyl α‐chloroacrylate (poly(MMA‐co‐MCA)) have been reported recently to be more susceptible to radiation degradation than poly(methyl methacrylate) (PMMA). In this paper we report our studies of PMCA and poly(MMA‐co‐MCA) as electron‐sensitive positive resists. It has been found that both PMCA and the copolymers are more sensitive than PMMA. Using mixtures of dimethylformamide and 2‐propanol as developers, the sensitivities of PMCA and poly(MMA‐co‐MCA) (38 mole percent MCA) have been found to be 1 × 10−5 and 6 × 10−6 coulomb/cm2, respectively. It has also been found that crosslinking predominates in PMCA when the electron dose exceeds 6 × 10−4 coulomb/cm2.