Mitigating X-ray-Induced Damage in CD-SAXS Metrology of EUV Resists.

Accurate characterization of nanoscale features in photoresist patterns is critical for advancing extreme ultraviolet lithography. Critical-dimension small-angle X-ray scattering (CD-SAXS) enables reconstruction of nanoscale patterns from angle-dependent scattering data, but measurements of organic, chemically active materials, such as photoresists, are strongly limited by beam-induced damage. Here, we demonstrate that CD-SAXS can be successfully applied to organic resists when X-ray exposure is carefully managed to mitigate beam damage. We quantify beam-induced damage in multiple resist systems by monitoring diffraction pattern evolution under continuous X-ray exposure, establishing a fluence threshold of ∼1000 photons/nm2 at 16.1 keV for the resist systems and measurement conditions investigated. We evaluate complementary strategies to extend the usable measurement window: reversing the sample orientation to exploit beam attenuation by the substrate (about sixfold dose reduction), increasing the photon energy, and reducing the angular sampling density.