A potential candidate for the new generation lithography beyond EUV is La/B4C multilayer optics for λ = 6.x nm. Achieving the highest possible reflectance at near normal (1.5°) incidence requires substantial practical improvement of the structural perfection of the multilayers. Pure La/B4C multilayers suffer from the formation of relatively thick interlayer at the interfaces. We have found that N-ion and N2 gas treatment of the multilayer interfaces strongly reduces interlayer formation and therefore enhances the multilayer optical contrast which leading to increase of the reflectivity at 6.x nm. The wavelength dependence of the La/B4C and LaN/B4C multilayer reflectivity has been studied in order to investigate the spectral properties of multilayers near B-absorption edge. Calculation of the maximal reflectance for La/B4C and LaN/B4C reflectivity for various wavelengths (figure 1) predicts significant gain in reflectance near the B absorption edge. We will present the influence of N-ions treatment on reflectivity properties of La/B4C multilayers near the B absorption edge and discuss the effect on throughput of an entire lithography system.
|Place of Publication||Veldhoven|
|Publication status||Published - 2011|