High-refractive index nanoparticle fluids for 193-nm immersion lithography

A critical issue preventing the implementation of 193nm immersion lithography (193i) to the 32nm node is the availability of high refractive index (n > 1.8) and low optical absorption fluids. To overcome these issues, we have synthesized high refractive index nanoparticles and introduced them into the immersion fluid to increase the refractive index. Hydrolysis and sol-gel methods have been implemented to grow high refractive index nanoparticles with diameters of 3-4nm. Depending on the synthetic route, it is possible to produce stable suspensions of nanoparticles in either aqueous or organic solvents, making it possible to synthesize a stable high-index immersion fluid.