A two-year study on the feasibility of High-n Immersion Lithography shows very promising results. This
paper reports the findings of the study.
The evaluation shows the tremendous progress made in the development of second-generation
immersion fluid technology. Candidate fluids from several suppliers have been evaluated. All the
commercial fluids evaluated are viable, so there are a number of options. Life tests have been conducted on
bench top fluid-handling systems and the results referenced to full-scale systems. Parameters such as Dose
per Laser Pulse, Pulse Rate, Fluid Flow Rate, and Fluid Absorbency at 193nm, and Oxygen/Air
Contamination Levels were explored. A detailed evaluation of phenomena such as Last Lens Element
(LLE) contamination has been conducted. Lens cleaning has been evaluated.
A comparison of High-n fluid-based technology and water-based immersion technology shows
interesting advantages of High-n fluid in the areas of Defect and Resist Interaction. Droplet Drying tests,
Resist Staining evaluations, and Resist Contrast impact studies have all been run. Defect-generating
mechanisms have been identified and are being eliminated. The lower evaporation rate of the High-n fluids
compared with water shows the advantages of High-n Immersion.
The core issue for the technology, the availability of High-n optical material for use as the final
lens element, is updated. Samples of LuAG material have been received from development partners and
have been evaluated. The latest status of optical materials and the technology timelines are reported.
The potential impact of the availability of the technology is discussed. Synergy with technologies
such as Double Patterning is discussed. The prospects for <22nm (hp) are evaluated.