As EUV lithography transitions to high volume manufacturing, actinic photomask inspection tools at 13.5 nm wavelength are attractive for understanding the printability of EUV mask defects, as well as for in-fab monitoring for possible defects emerging from extended use. Ptychography is a lensless imaging technique that allows for phase-and-amplitude, aberration-free, high-resolution imaging in the EUV. Moreover, sources based on high harmonic generation (HHG) of ultrafast lasers are a proven viable coherent light source for CDI, with flux sufficient for rapid large-area inspection and small-area imaging. By combining CDI and HHG, we implemented actinic EUV photomask inspection on a low-cost tabletop-scale setup. Moreover, we propose and demonstrate a solution to the decade-long challenge of ptychographic imaging of periodic structures through careful illumination engineering.
Spatiotemporal orbital angular momentum (ST-OAM) of light is an emergent, spatiotemporally sculptured light. Such spatiotemporal optical vortices carry transverse OAM and exhibit novel properties. However, the lack of a simple and straightforward characterization method substantially slows its progress and potential adaptions for future applications. Here we demonstrated a simple, stationary, single-frame method to quantitatively characterize ST-OAM pulses. Our new method can measure the presence of ST-OAM, space-time topological charge numbers, OAM helicity, pulse dispersion, and beam divergence. We also investigated the nonlinear properties of ST-OAM pulses, uncovering the conservation of space-time topological charges in a second-harmonic generation process.
As EUV lithography transitions to high volume manufacturing, actinic inspection tools at 13.5 nm wavelength are attractive for understanding the printability of EUV mask defects, as well as for in-fab monitoring for possible defects emerging from extended use. Coherent diffractive imaging (CDI) is a lensless imaging technique that allows for phaseand-amplitude, aberration-free, high-resolution imaging in the EUV. Moreover, sources based on high harmonic generation (HHG) of ultrafast lasers are a proven viable coherent light source for CDI, with flux sufficient for rapid large-area inspection and small-area imaging. By combining CDI and HHG, we implemented actinic EUV photomask inspection on a low-cost tabletop-scale setup. Moreover, we propose and demonstrate a solution to the challenge of ptychographic imaging of periodic structures through careful illumination engineering.
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.
We present preliminary through-pellicle imaging using a 30nm tabletop extreme ultraviolet (EUV) coherent diffractive imaging microscope. We show that even in a non-optimized setup, this technique enables through-pellicle imaging of a sample with no detectable impact on image fidelity or resolution.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.