Bastian Trauter

Performance of FlexRay: a fully programmable illumination system for generation of freeform sources on high NA immersion systems

This paper describes the principle and performance of FlexRay, a fully programmable illuminator for high NA immersion systems. Sources can be generated on demand, by manipulating an array of mirrors instead of the traditional way of inserting optical elements and changing lens positions. On demand (freeform) source availability allows for reduction in R&D cycle time and shrink in k1. Unlimited tuning allows for better machine to machine matching. FlexRay has been integrated in a 1.35NA TWINSCAN exposure system. We will present data of FlexRay using measured traditional and freeform illumination sources. In addition system performance qualification data on stability, reproducibility and imaging will be shown. The benefit of FlexRay for SMO enabling shrink is demonstrated using an SRAM example.

Analysis of the uniqueness of an inverse grating characterization method

We propose a method for the characterization of one- and two-dimensional diffraction gratings by means of the measurement of diffraction efficiencies. The method is based on the comparison of measured and calculated efficiencies. For the numerical calculation we use the Rigorous Coupled Wave Analysis RCWA and an optimization algorithm to determine the grating shape that fits best to the measured data. We analyzed in which cases the method is able to determine the grating shape without ambiguity and which measurement parameters should be used. By systematically analyzing a given inverse problem, we try to derive the theoretical limits of the method.