Abstract
A feasibility study is being conducted on the subject of extending the resolution capability of immersion lithography exposure systems with high-n fluids to 35nm and below. Fluids, for evaluation, are available from chemical vendor companies such as DuPont, Mitsui, and JSR. The new fluids have a refractive index of approximately 1.65. This makes it possible to design optics with a numerical aperture of 1.55, which is a 17% extension on the highest numerical aperture possible with water-based immersion lithography.
The feasibility study has examined all the key factors associated with the possible introduction of high index immersion lithography. These aspects include: fluid handling challenges; UV exposure impact on fluid performance; fluid recycling to mitigate the effects of UV exposure; fluid interaction with resist; and the mechanisms involved in the generation of stains and imaging defects. Imaging tests using interference printing to define profiles in resist at 29nm L/S are reported.
To complete the analysis, the progress in enabling developments such as final lens element optical materials is reported, and the potential position for the technology in the lithography roadmap is discussed.
