Enhanced chip performance and miniaturization in the semiconductor industry are driven by improved lithographic capabilities, such as those of lithography systems with larger Numerical Aperture (NA). The emerging high NA Extreme Ultra Violet (EUV) lithography scanners increase the NA from 0.33 to 0.55, enabling continued shrink down to 8 nm halfpitch for lines/spaces. EUV systems with NA >= 0.75 (hyper NA) are being explored to support further cost-effective increases in device density. Our study demonstrates that hyper NA enables pattern shrink in advanced logic node designs projected in semiconductor roadmaps beyond year 2030.
High-order harmonic generation (HHG) in gases has been studied for almost 40 years under many different conditions, varying the laser wavelength, intensity, focusing geometry, target design, gas species, etc. However, no systematic investigation of the effect of the pulse duration has been performed despite its expected impact on phase-matching of the high-order harmonics. Here, we develop a compact post-compression method based on a bulk multi-pass cell enabling tunable Fourier-limited pulse durations. We examine the HHG yield as a function of the pulse duration, ranging from 42 fs to 180 fs, while maintaining identical focusing conditions and generating medium. Our findings reveal that, for a given intensity, there exists an optimum pulse duration-not necessarily the shortest-that maximizes conversion efficiency. This optimum pulse duration increases as the intensity decreases. The experimental results are corroborated by numerical simulations, which show the dependence of HHG yield on the duration and peak intensity of the driving laser and underscore the importance of the interplay between light-matter interaction and phase-matching in the non-linear medium. Our conclusion explains why HHG could be demonstrated in 1988 with pulses as long as 40 ps and intensities of just a few 1013 W/cm2.
A low pressure discharge sustained in molecular hydrogen with help of the electron cyclotron resonance heating at a frequency of 2.45 GHz is simulated using a fully electromagnetic implicit charge- and energy-conserving particle-in-cell/Monte Carlo code. The simulations show a number of kinetic effects, and the results are in good agreement with various experimentally measured data such as electron density, electron temperature and degree of dissociation. The electron energy distribution shows a tri-Maxwellian form due to a number of different electron heating mechanisms, agreeing with the experimental data in the measured electron energy interval. The simulation results are also compared with output data of a drift-diffusion model and proximity is observed between the computational results for the plasma density at the location of experimental measurement. However, the fluid approximation fails to accurately predict radical density and electron temperature because of the assumption of a single electron temperature. Special attention is paid to the characteristics of hydrogen radicals, whose production is strongly underestimated by the fluid model, whereas it is well predicted by the model considered here. The energy distribution of such radicals demonstrates the presence of a relatively large number of energetic hydrogen atoms produced by the dissociation of molecular hydrogen. The new insights are of significance for practical applications of hydrogen plasmas.
We present experimental results on the initial lofting conditions of single dust particles resting on a solid surface when exposed to a 120 eV electron beam. Lofting is characterized as a function of particle size (10-70 mu m in radii) and shape (jagged vs spherical). Similar to previous measurements of particles lofted from a dust pile, vertical launch velocities show an inverse relationship with the particle size and broad distributions for same-sized particles. Different from piled dust, the lofting velocities of single particles depend only weakly on the shape of the particles as also found in modeling. It is shown that jagged single particles have lower lofting velocities than jagged piled particles, while spherical single particles are lofted at higher velocities, compared to spherical piled particles. Based on the patched charge model (PCM) for piled particles and PCM for single particles (PCM-SP) on a solid surface, these results indicate that differences in the formation of microcavities for different scenarios play a role in determining the charging and lofting of dust particles. (C) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).https://doi.org/10.1063/5.0250511
Mask3D-induced effects, including orientation-dependent image asymmetries, non-telecentricity, pitch-dependent best focus, and image blur, are increasingly important for EUV imaging. To improve the fundamental understanding of these effects and their impact on the optical resolution limit of high NA and hyper NA EUV lithography, this paper investigates the imaging of lines/spaces (L/S) with a pitch of 9 nm using an ideal fictive diffraction-limited projection system with a NA of 0.85. The results of our simulations suggest that mask3D effects will not limit the achievable imaging performance of high NA and hyper NA EUV systems. Comparisons of rigorous mask simulations with results obtained by a Kirchhoff (flat) mask model indicate that mask3D effects do not necessarily negatively impact EUV imaging. Absorber patterns for the smallest pitches behave like volume gratings. Such volume gratings exhibit a significant dependency of the diffracted light on the illumination direction. In contrast to thin gratings, volume gratings enable a more flexible distribution of light between diffraction orders. Based on the improved understanding of the involved imaging mechanisms, one could take advantage of mask3D effects to enhance the imaging performance. The opportunities for such innovative solutions depend on the limitations of mask fabrication, which are not considered in this discussion.
