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We demonstrate temporally multiplexed multibeam ptychography implemented for the first time in the EUV, by using a high harmonic based light source. This allows for simultaneous imaging of different sample areas, or of the same area at different times or incidence angles. Furthermore, we show that this technique is compatible with wavelength multiplexing for multibeam spectroscopic imaging, taking full advantage of the temporal and spectral characteristics of high harmonic light sources. This technique enables increased data throughput using a simple experimental implementation and with high photon efficiency.

Recent advances in structured illumination are enabling a wide range of applications from imaging to metrology, which can benefit from advanced beam characterization techniques. Solving uniquely for the spatial distribution of polarization in a beam typically involves the use of two or more polarization optics, such as a polarizer and a waveplate, which is prohibitive for some wavelengths outside of the visible spectrum. We demonstrate a technique that circumvents the use of a waveplate by exploiting extended Gerchberg–Saxton phase retrieval to extract the phase. The technique enables high-resolution, wavefront-sensing, full-field polarimetry capable of solving for both simple and exotic polarization states, and moreover, is extensible to shorter wavelength light.

Multiple beam ptychographic imaging with an extreme ultraviolet high harmonic light source is demonstrated through simultaneous spectral and temporal multiplexing. This method is experimentally straightforward to implement and ideal for hyperspectral functional imaging of nanosystems

Nanostructuring on length scales corresponding to phonon mean free paths provides control over heat flow in semiconductors and makes it possible to engineer their thermal properties. However, the influence of boundaries limits the validity of bulk models, while first principles calculations are too computationally expensive to model real devices. Here we use extreme ultraviolet beams to study phonon transport dynamics in a 3D nanostructured silicon metalattice with deep nanoscale feature size, and observe dramatically reduced thermal conductivity relative to bulk. To explain this behavior, we develop a predictive theory wherein thermal conduction separates into a geometric permeability component and an intrinsic viscous contribution, arising from a new and universal effect of nanoscale confinement on phonon flow. Using both experiments and atomistic simulations, we show that our theory is valid for a general set of highly-confined silicon nanosystems, from metalattices, nanomeshes, porous nanowires to nanowire networks. This new analytical theory of thermal conduction can be used to predict and engineer phonon transport in boundary-dominated nanosystems, that are of great interest for next-generation energy-efficient devices.

Coherent Fourier scatterometry (CFS) via laser beams with a Gaussian spatial profile is routinely used as an in-line inspection tool to detect defects on, for example, lithographic substrates, masks, reticles, and wafers. New metrology techniques that enable high-throughput, high-sensitivity, and in-line inspection are critically in need for next-generation high-volume manufacturing including those based on extreme ultraviolet (EUV) lithography. Here, a set of novel defect inspection techniques are proposed and investigated numerically [Wang et al., Opt. Express 29, 3342 (2021)], which are based on bright-field CFS using coherent beams that carry orbital angular momentum (OAM). One of our proposed methods, the differential OAM CFS, is particularly unique because it does not require a pre-established database for comparison in the case of regularly patterned structures with reflection symmetry such as 1D and 2D grating structures. We studied the performance of these metrology techniques on both amplitude and phase defects. We demonstrated their superior advantages, which shows up to an order of magnitude higher in signal-to-noise ratio over the conventional Gaussian beam CFS. These metrology techniques will enable higher sensitivity and robustness for in-line nanoscale defect inspection. In general, our concept could benefit EUV and x-ray scatterometry as well.

Coherent Fourier scatterometry (CFS) using laser beams with a Gaussian spatial profile is routinely used as an in-line inspection tool in semiconductor industry. Here, a set of novel defect inspection techniques are proposed and investigated numerically, which are based on bright-field CFS using coherent beams that carry orbital angular momentum (OAM). Through numerical simulations, we demonstrated that it shows up to an order of magnitude higher in signal-to-noise ratio over the conventional Gaussian beam CFS.

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.

A new imaging technique enables nondestructive, 3D characterization of nanostructures, their composition, and interfaces., Next-generation nano- and quantum devices have increasingly complex 3D structure. As the dimensions of these devices shrink to the nanoscale, their performance is often governed by interface quality or precise chemical or dopant composition. Here, we present the first phase-sensitive extreme ultraviolet imaging reflectometer. It combines the excellent phase stability of coherent high-harmonic sources, the unique chemical sensitivity of extreme ultraviolet reflectometry, and state-of-the-art ptychography imaging algorithms. This tabletop microscope can nondestructively probe surface topography, layer thicknesses, and interface quality, as well as dopant concentrations and profiles. High-fidelity imaging was achieved by implementing variable-angle ptychographic imaging, by using total variation regularization to mitigate noise and artifacts in the reconstructed image, and by using a high-brightness, high-harmonic source with excellent intensity and wavefront stability. We validate our measurements through multiscale, multimodal imaging to show that this technique has unique advantages compared with other techniques based on electron and scanning probe microscopies.

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.

The influence of surface and interface roughness on X-ray and extreme ultraviolet (EUV) reflectometry is becoming increasingly important as layer thicknesses decrease to a few nanometers in next-generation nanodevices and multilayer optics. Here we simulate two different approaches for numerically modeling roughness, the Névot–Croce factor and the graded-interface method, in the Parratt formalism of calculating the complex reflectance of multilayer systems. The simulations were carried out at wavelengths relevant to widely used metrology techniques, including 0.154 nm for X-ray reflectometry and 13.5 nm for EUV lithography. A large discrepancy is observed between the two approaches in several situations: when the roughness is large with respect to the wavelength, for interfaces with large changes in refractive index across the boundary, as well as around reflectance peaks due to interference effects. Caution is thus required when using either approach to model roughness in these situations.

We present a tabletop-scale complex-imaging EUV reflectometer that uses grazing- incidence ptychographic imaging to non-destructively determine depth-dependent, spatially-resolved composition with high sensitivity to chemical makeup, thin film layer thickness, interface quality and dopant profiles.

Defect inspection on lithographic substrates, masks, reticles, and wafers is an important quality assurance process in semiconductor manufacturing. Coherent Fourier scatterometry (CFS) using laser beams with a Gaussian spatial profile is the standard workhorse routinely used as an in-line inspection tool to achieve high throughput. As the semiconductor industry advances toward shrinking critical dimensions in high volume manufacturing using extreme ultraviolet lithography, new techniques that enable high-sensitivity, high-throughput, and in-line inspection are critically needed. Here we introduce a set of novel defect inspection techniques based on bright-field CFS using coherent beams that carry orbital angular momentum (OAM). One of these techniques, the differential OAM CFS, is particularly unique because it does not rely on referencing to a pre-established database in the case of regularly patterned structures with reflection symmetry. The differential OAM CFS exploits OAM beams with opposite wavefront or phase helicity to provide contrast in the presence of detects. We numerically investigated the performance of these techniques on both amplitude and phase defects and demonstrated their superior advantages—up to an order of magnitude higher in signal-to-noise ratio—over the conventional Gaussian beam CFS. These new techniques will enable increased sensitivity and robustness for in-line nanoscale defect inspection and the concept could also benefit x-ray scattering and scatterometry in general.

With increasingly 3D devices becoming the norm, there is a growing need in the semiconductor industry and in materials science for high spatial resolution, non-destructive metrology techniques capable of determining depth-dependent composition information on devices. We present a solution to this problem using ptychographic coherent diffractive imaging (CDI) implemented using a commercially available, tabletop 13 nm source. We present the design, simulations, and preliminary results from our new complex EUV imaging reflectometer, which uses coherent 13 nm light produced by tabletop high harmonic generation. This tool is capable of determining spatially-resolved composition vs. depth profiles for samples by recording ptychographic images at multiple incidence angles. By harnessing phase measurements, we can locally and nondestructively determine quantities such as device and thin film layer thicknesses, surface roughness, interface quality, and dopant concentration profiles. Using this advanced imaging reflectometer, we can quantitatively characterize materials-sciencerelevant and industry-relevant nanostructures for a wide variety of applications, spanning from defect and overlay metrology to the development and optimization of nano-enhanced thermoelectric or spintronic devices.

We present high-resolution, simultaneous two-color phase-and-amplitude characterization of 2nd harmonic up-conversion in OAM beams by ptychography. We measure topological charge conservation during 2nd harmonic generation process, which can be extended to high-order harmonic upconversion.

We demonstrate high-resolution and wide field-of-view imaging using tabletop 13nm HHG sources in transmission and reflection geometries. Additionally, we present preliminary simulations and results of complex 13nm imaging reflectometry allowing highly-sensitive, non-destructive 3D composition determination.

We experimentally demonstrate that ptychographic coherent diffractive imaging can be used to simultaneously characterize the amplitude and phase of bichromatic orbital angular momenta-shaped vortex beams, which consist of a fundamental field, together with its copropagating second-harmonic field. In contrast to most other orbital angular momentum characterization methods, this approach solves for the complex field of a hyperspectral beam. This technique can also be used to characterize other phase-structured illumination beams, and, in the future, will be able to be extended to other complex fields in the extreme ultraviolet or X-ray spectral regions, as well as to matter waves., The NSF STROBE STC (DMR-1548924); DOE BES AMOS grant (DE-FG02-99ER14982); the NSF GRFP (DGE 1650115); 2017 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation; Junta de Castilla y León (SA046U16); Ministerio de Economía y Competitividad (FIS2016-75652-P).