Radiolysis study of highly sensitive positive and self-developing polymeric resists

Radiolysis studies were carried out on four different halogenated polymeric resists: (1) poly(haloalkyl methacrylates) and copolymers with methyl methacrylate, (2) copolymers of MCA and trihaloethyl methacylate (TFEMA, TCEMA), (3) poly(p-substituted α-methylstyrenes), and (4) poly(monochloracetaldehyde). Homopolymers and copolymers of various halogenated methacrylates were synthesized by radical bulk polymerization. Copolymer compositions were determined by elemental analysis, and the reactivity ratios of comonomers were obtained by Yezrielev's method. The molecular weights of the gamma-irradiated polymers were obtained by GPC. Thermal properties of these polymers have been studied by TGA and DSC. The radiolysis volatile products were analyzed by GC/MS. Quantitative ESR was used to identify the radicals as well as to obtained G(r) values. Based on the G values, ESR and GC/MS, the radiolysis mechanisms were proposed for each system. It has been found that dissociative electron capture plays a key role in the radiolysis of these halogenated methacrylate polymers, especially chlorine containing polymers. The dry-etching resistance of PMCAD can be enhanced by inducing crosslinking in unexposed areas of the resist material. A process similar to image reversal was proposed. Plasma etching resistance was determined by sample weight loss versus etching time. Addition of bisazidoformate crosslinkers improve the dry etching resistance of PMCAD substantially, but it also decreases the radiation sensitivity to certain degree