This paper assesses the progress of Step and Scan systems towards "Production 250nm Lithography". Advantages of the Step and Scan technique are discussed.
The relationships between NA, wavelength, resolution, and depth of focus are examined. The lithographic performance of the new generation Deep-UV Step and Scan system with high-NA optics is presented. Data is provided from electrical probe linewidth metrology and SEM analysis. Linewidth control of 27nm (3 sigma) is demonstrated over a large field size of 650mm2 for 350nm features. A 250nm resolution capability is shown.
The family of Step and Scan systems, I-Line--Deep-UV--Very- Deep-UV, is reviewed in the context of progress towards 250nm lithography . The impact of Phase Shift Masks is highlighted . Particular attention is paid to the effect of partial coherence on the depth of focus achievable with Phase Shift Masks. Examples of 250nm lithography in a single level resist system are presented . It is indicated that optical lithography will continue to be the dominant lithographic technique down to sub-250nm lithography and that Step and Scan technique will be a critical factor in maintaining this dominance.