Normal incidence collector for LPP sources with integrated debris mitigation

The leading candidate for the manufacture of next generation semi-conductor devices is extreme ultraviolet lithography, with laser-produced plasmas as a candidate 13.5nm light source. A primary challenge for continuous operation is elimination of the debris load on the collector, without compromising the radiation intensity at the intermediate focus. A novel combination of thermal management and debris mitigation is developed in order to reduce the deformation and degradation of collector optics. This patent-pending novel debris mitigation technique enables the continuous operation of the source. The paper shows atomic force microscope measurements of the collector surface deposition. The debris mitigation system run at 50% design operating condition gives 90% debris mitigation effectiveness. The average temperature of the cooled collector is 36.5 degrees C at the design point, with a peak-to-peak difference of 0.8 degrees C. The collector geometry, after being adapted to compensate the thermal deformation, yields a spot size of 30 mu m at IF. Computational simulations, using ETH's multi-scale computational tools, complement the presented experimental results.