Performance of FlexRay, a fully programmable Illumination system for generation of Freeform Sources on high NA immersion systems

In this paper the principle and performance of FlexRay, the first fully programmable illuminator for a high NA immersion system, will be described. Arbitrary 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. This next generation illuminator is developed to give lithographers easy access to the enhanced process windows as predicted by state of the art Source Mask Optimization software (SMO) and to give virtually unlimited source tuning capability that can be used to improve matching or correct for example mask bias errors. To evaluate the performance of FlexRay, the illuminator has been integrated in a 1.35NA TWINSCAN exposure system. We will present data of the key characteristics of FlexRay using measured traditional and freeform illumination sources. The benefit of FlexRay for SMO is demonstrated using some application examples for memory and logic. We will show data on process window increase with SMO and enhanced proximity matching by making use of the pupil tuning capability of FlexRay.