Full-field exposure tools for immersion lithography

Abstract

Immersion lithography is becoming a realistic method of high resolution pattern generation for semiconductor manufacturing. Nikon has a roadmap of full-field immersion exposure tools starting with an Engineering Evaluation Tool (EET, NA=0.85), succeeded with production models of S609B (NA=1.07) and S6xx (NA=1.30). EET was constructed in 2004, and is being used for evaluation of immersion technology and process development. With EET, focus, stepping, overlay and across-wafer CD uniformity data are demonstrated to be better or equivalent to dry tools, while the depth of focus (DOF) is significantly improved as expected. A remarkable point is the defectivity result with EET. We have detected no bubbles and a negligible level of “immersion specific” defects even with hydrophobic top coat. A production model S609B will have the NA=1.07 optics, which will be the highest NA of “all refractive optics”, and will be shipped at 2005/4Q. S6xx, with planned shipment timing is 2006/2H, will have NA=1.30 catadioptric optics, whose NA will be the highest NA of “water-immersion”. Both S609B and S6xx will be equipped with loss-less polarized illuminators, which will enable 50nm L/S with S609B and 42nm L/S with S6xx. Resist and top coat are studied from the viewpoints of chemical contamination and scanning properties. Tentative specifications are proposed for leaching of PAG and amines against chemical contamination. As for scanning properties, static contact angle was found to be not a good parameter; instead, sliding angle is proposed.