PREPARATION AND PROPERTIES OF SI-CONTAINING COPOLYMER FOR NEAR-UV RESIST .1. POLY(N-(4-HYDROXYPHENYL)MALEIMIDE-ALT-PARA-TRIMETHYLSILYLSTYRENE)

A new negative near-UV photoresist consisting of poly(N-(4-hydroxyphenyl) maleimidealt-p-trimethylsilylstyrene) (PHMS) and a naphthoquinonediazide ester was developed. PHMS was synthesized by solution free-radical polymerization of the comonomers with azobisisobutyronitrile (AIBN) in 1,4-dioxane at 60-degrees-C. The preparation of PHMS in terms of reaction time, thermal initiator, and solvent was evaluated; and a series of different molecular weight copolymers were prepared. PHMS was 1 : 1 in composition and was predominantly alternating. These copolymers dissolved in a wide range of solvents (including 5% tetramethylammonium hydroxide). The thermal properties of these copolymers were investigated by DSC and TGA. The chain-stiffening effect of the maleimide group played an important role in effecting high thermal resistance. Near-UV exposure was carried out using a Canon PLA-501F contact printer. High resolution negative images were obtained which had resistance to thermal deformation at 330-degrees-C and above. The developed patterns exhibited good adhesion to the silicon substrates without the use of an adhesion promoter. The lithographic applications of a bilayer photoresist system in which the prepared resist was used as the top imaging layer were examined. It is supposed that if PHMS was used as a binder for a diazonaphthoquinone sulfonate (NDS) photochemically, positive images would be obtained; however, on the contrary, negative images were observed. It is proposed that photocrosslinking occurred in the PHMS main chain.