Basic Techniques of Increasing Resolution of Photopolymerizable Compositions

Abstract

Photopolymerizing liquid compositions via a radical mechanism and enabling the formation of products with a thickness ranging from ten to several hundred micrometers and the linear dimensions of elements of several micrometers are considered. They are mixtures of organic oligomers and monomers, and the correlation time of the rotational motion of a paramagnetic probe (2,2,6,6-tetramethyl-4-oxypiperidine-1-oxyl) in them is (4–6) × 10^–10 s. Only photopolymerizable compositions (PPCs) with such a correlation time can simultaneously provide the highest values of the photopolymerization rate, light sensitivity, and photolithography resolution. Their core components consist of a photoinitiator generating free radicals through Norrish type I reaction and a highly efficient inhibitor of radical polymerization. An ultimately high resolution of optical lithography can be achieved by using PPCs in which polymerization proceeds via a terminationless mechanism, no increase in light scattering is observed upon exposure, and in which a polymerization inhibiting system is present, but with limitations placed on the diffusion of the inhibitor. Systems in which polymerization proceeds via a microheterogeneous mechanism are not suitable for this purpose. The possibility of creating such PPCs arises from the phenomena of stopping chemical reactions and leveling reactive capacity.