Coherent Fourier scatterometry using orbital angular momentum beams for defect detection

Abstract

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.

Super-resolved time–frequency measurements of coupled phonon dynamics in a 2D quantum material

“…The term "super-resolution" in this context is slightly different from the well-known optical super-resolution imaging-however, a common feature is the use of either structured frequency pulses (akin to structured illumination in imaging 12 ) or by oversampling and averaging (akin to techniques such as STORM 13 ). New approaches for metrology and scatterometry can also harness structured light 14 . Specifically, a superlet analysis uses a "structured" estimator in the time-frequency domain to better detect localized time-frequency signal components 11 .…”

Material-specific high-resolution table-top extreme ultraviolet microscopy

“…This approach offers significantly higher flexibility and lowers experimental complexity compared to state-of-the-art table-top implementations 49 – 52 . Since OAM beams have already shown a wide variety of advantages in other spectral regions 53 we foresee a plethora of future applications of functional beams in the EUV, including actinic defect inspection via scatterometry with tailored beams 54 and OAM-induced dichroic spectroscopy 55 .…”

Single-Frame Characterization of Ultrafast Pulses with Spatiotemporal Orbital Angular Momentum

“…The OAM of light also inspires new physics concepts, such as classical entanglement and self-torque, where the former relates to inseparable states of spin angular momentum and OAM (different from direct spin-orbit conversion or coupling) and the latter relates to the recently discovered ability to create pulses with a time-varying OAM. Conventional OAM of light has been employed in applications such as optical trapping, optical tweezers, super-resolution imaging, quantum and classic communication, and scatterometry-based surface metrology. − …”