Abstract
High-index immersion lithography beyond water can be an enabler for the 32nm node. For several years researchers have tried to find or develop higher index lens element, immersion fluid and resist. A high index lens material has been developed that is suitable for implementation as the final lens element. The development of high index immersion fluid and resist remains, and this will require breakthroughs in materials development. An intermediate index fluid has been developed but will only enable 1.55NA immersion lithography. To achieve 1.70NA a fluid with a refractive index approaching 1.80 at 193nm will be required. Additionally a compatible resist with an index of about 1.9 will be required. The development of these materials with extreme refractive indices is particularly challenging due to the limitations of variables that can affect the index without compromising other required properties. This paper reviews the successes and failures in the search for these higher index fluids and resist materials, and the most likely path to success using high index nanoparticles.
