Broadband extreme ultraviolet zeroth order scatterometry for nanostructure metrology

The continuous shrinkage of critical dimensions in nanofabrication demands nanometrology at the relevant resolution, which can be achieved using short-wavelength light sources. Most industrial metrology uses periodic structures for process control, exploiting diffraction to probe the fabrication quality of actual device structures. Here, we introduce a table-top high-harmonic generation extreme-ultraviolet scatterometry with broadband illumination. Our method exploits the spectrally resolved 0^th diffraction order of the extreme-ultraviolet light, which, while lacking spatial-encoded information, carries valuable spectral information and offers high diffraction efficiency. The use of relative reflectivity removes the need for absolute calibration, and rigorous coupled-wave analysis simulations underpin a library-based reconstruction approach, yielding single-nanometer accuracy for groove height and 10 nm accuracy for critical dimensions. Our work demonstrates broadband extreme-ultraviolet high-harmonic-generation 0^th order scatterometry that delivers fast, reliable, non-destructive metrology for structures with at-wavelength features, providing sensitivity and accuracy for details far below the diffraction limit.