Fig. 1. ARCNL’s current and future research^[5]

Fig. 2. Simple schematic diagram of the gas high-order harmonic spectrum

Fig. 3. Generation of quasi-phase matching in the HHG-EUV, modulated hollow-core fibres used to implement quasi-phase matching with period of 1 mm, inner diameter of 150 μm, and modulation depth of 10 μm (left), experimentally measured HHG spectra for straight (blue) and modulated (red) fibres (right)^[27]

Fig. 4. High-power EUV light source generation experimental setup, nonlinear compression and subsequent high-order harmonic generation experimental setup (left), HHG spectrum optimized with krypton (right), with each harmonic line having the corresponding average power, and spatial envelope output of the XUV beam (inset)^[3]

Fig. 5. Progress of the current state-of-the art high photon flux HHG sources, HHG sources based on Ti∶Sa driving lasers are shown in red, while those based on fiber laser systems are shown in blue, HHG sources based on enhancement cavities are shown in black^[37]

Fig. 6. Schematic drawing of EUV mask (left)^[41] and typical defects in an EUV mask (right)^[42]

Fig. 7. Extreme ultraviolet lithography mask defect review system (EMDRS) of SAMSUNG corporation, based on HHG-EUV source^[43]

Fig. 8. Coherent scatterometry microscope (CSM) based on the HHG-EUV source^[51]

Fig. 9. Schematic diagrams of the EMCI system set-up^[58]. (a) EMCI optical setup, the beam source is preselected by a Z-fold EUV multilayer reflector, focused by a spherical multilayer mirror, then reflected onto the sample by a flat folding mirror, the diffraction patterns in the far field is recorded on the EUV detector; (b) light matter interaction of the EUV mask in EMCI, exit wave in the near filed contains shadow effects and multi-scattering effects of the 3D EUV mask sample which are simultaneously propagated to the far field and recorded by the EUV detector

Fig. 10. Schematic of RAPTR-CDI. The inset shows a diagram of the two samples imaged, topped with their visible microscope images, the tantalum was deposited by physical vapor deposition, and the top layer of copper was electroplated^[82]

Fig. 11. Height maps of the uncoated and Al-coated samples, both the coated EUV and AFM images show high aspect-ratio artifacts where debris is located on the surface of the sample^[82]

Fig. 12. Experimental overview and nanostructure imaging^[90]. (a) Schematic diagram of amplitude- and phase-sensitive imaging reflectometer, which can non-destructively generate large-area, spatially and depth-resolved layers; (b)(c) enlarged views of the EUV gas chromatography phase reconstruction of the positive sample before and after the precise implementation of 3D tilt plane correction and total variation (TV); (d) amplitude reconstruction over the entire wide field of view; (e)(f) characteristic reflectivity versus angle curves of several materials at a wavelength of 30 nm, demonstrating the sensitivity of EUV light to material composition

Fig. 13. Spatially resolved and composition-sensitive 3D nanostructure characterization^[90]. (a) Higher-doped structure; (b)(c) composition and depth reconstruction in low-doped and higher-doped substrates, phase-sensitive imaging reflectometer is sensitive to most parameters in this model, some parameters are determined through correlation imaging; (d) zoom-out and zoom-in (inset) of fully reconstructed sample, different colors correspond to different materials

Fig. 14. Concept and far-field detection schematic diagram of extreme ultraviolet/soft X-ray scattering measurement tools for wafer inspection^[94]

Fig. 15. 3D structure scattering measurement of wafer^[94]. (a) Schematic diagram of measured Intel GAA wafer, with the average recess etching varying among the 8 wafers due to etching time; (b) diffraction pattern measured from the GAA; (c) data driven inference based on 8 wafers with varying recess etch time