A new imaging technique enables nondestructive, 3D characterization of nanostructures, their composition, and interfaces.

Imaging using coherent extreme-ultraviolet (EUV) light provides exceptional capabilities for the characterization of the composition and geometry of nanostructures by probing with high spatial resolution and elemental specificity. We present a multi-modal tabletop EUV imaging reflectometer for high-fidelity metrology of nanostructures. The reflectometer is capable of measurements in three distinct modes: intensity reflectometry, scatterometry, and imaging reflectometry, where each mode addresses different nanostructure characterization challenges. We demonstrate the system’s unique ability to quantitatively and non-destructively measure the geometry and composition of nanostructures with tens of square microns field of view and sub-nanometer precision. Parameters such as surface and line edge roughness, density, nanostructure linewidth, and profile, as well as depth-resolved composition, can be quantitatively determined. The results highlight the applicability of EUV metrology to address a wide range of semiconductor and materials science challenges.

We present a versatile, ptychographic phase-sensitive imaging EUV reflectometer that can nondestructively image samples with spatial, depth and compositional resolution, with sensitivities to dopant levels and interface quality.

Ptychography implemented with coherent high-harmonic (HHG) sources enables high-resolution, high-fidelity imaging of nanostructures and biosystems. However, when driven by mid-infrared lasers to generate light at higher photon energies, HHG inherently produces a broadband quasi-continuum, which is less suited for coherent imaging compared with a single harmonic order. Consequently, experiments typically select a narrow bandwidth of ≈1%, leaving most of the HHG photons unused, increasing exposure times. In this work, we demonstrate broadband ptychography utilizing an extreme UV (EUV) continuum centered at 92 eV, with a bandwidth of up to 7.9 eV (a relative bandwidth of ~9%). By focusing the HHG beam to a sub-micrometer spot size to relax the temporal coherence constraints, and utilizing a multi-wavelength ptychographic reconstruction algorithm, we achieve a spatial resolution of 42 nm, which is near the diffraction limit of ~30 nm for our setup. To the best of our knowledge, this represents the broadest spectral bandwidth successfully employed to date for EUV ptychography, with the potential to increase the usable photon flux by up to an order of magnitude relative to previous approaches. In the future, broadband soft X-ray ptychography can be used to image hydrated samples around the carbon K-edge and magnetic textures at the L-edges of transition metals.

An analysis of blind ptychography that provides predictions of error and the reconstructed field-of-view (FOV) is presented. The utility of this analysis is demonstrated with a new approach called dual-grid ptychography that maximizes the FOV.