A Two-Mirror Faceted Projection System for EUV Lithography
Abstract
We propose an all-reflective two-mirror projection system for extreme ultraviolet (EUV) lithography operating at exposure wavelengths of $13.5$~nm (Mo/Si) and $11.2$~nm (Ru/Be), delivering a fourfold (4×) demagnification of the periodic mask pattern at a numerical aperture approaching unity (NAmax ≈ 0.993). In contrast to conventional EUV projection objectives that incorporate 6--10 aspheric mirrors with an overall optical throughput of less than 15%, the proposed design redirects each accepted discrete spatial diffraction order scattered by the mask onto the wafer via a dedicated pair of planar mirror facets. The number of reflections is strictly fixed at two for all accepted orders, retaining $50−−60\%$ of the power leaving the mask in each accepted order. We derive a spatial geometry providing rigorous optical path length equalization across all diffraction orders, thereby removing order-dependent propagation phase shifts. Individually optimized 30-bilayer Bragg multilayer coatings are designed for each facet using the transfer matrix method combined with global evolutionary optimization algorithms. The architecture is generalized to a three-dimensional vector formulation with a two-dimensionally periodic mask. Utilizing inverse lithography technology, Fourier parameterization, and a differentiable electromagnetic modal waveguide solver, we solve the synthesis problem for binary absorber masks (La absorber on a Ru/Be/Sr multilayer mirror). We demonstrate simulated aerial images of sub-10-nm features on the wafer (isolated peaks with a full width at half maximum (FWHM) of approximately $5.4$~nm and line pairs with a critical dimension of $6$~nm) and find that the two peaks remain resolved for the tested wafer defocus values from $0$ to $5$~nm along the z-axis.
Related
- Real-time beaconless MEMS mirror-based beam steering and tracking system for mobile underwater optical wireless communication
- Systematic opto-mechanical design approach for meter-long Nano-AKB mirror system at HEPS
- In situ observation of faceted and branched eutectic growth patterns during directional solidification of thin Al–Si samples
- Origins of Faceted Anomalous Scaling
- Passive axial confinement in two-photon lithography with a 3D-printed pupil filter
BibTeX
@misc{eskin2026twomirror,
title = {{A Two-Mirror Faceted Projection System for EUV Lithography}},
author = {Vasiliy A. Es'kin and Egor V. Ivanov and Olga V. Martynova},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.11299},
eprint = {2609.11299},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.11299},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A Two-Mirror Faceted Projection System for EUV Lithography
AU - Vasiliy A. Es'kin
AU - Egor V. Ivanov
AU - Olga V. Martynova
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.11299
UR - https://arxiv.org/abs/2609.11299
AB - We propose an all-reflective two-mirror projection system for extreme ultraviolet (EUV) lithography operating at exposure wavelengths of $13.5$~nm (Mo/Si) and $11.2$~nm (Ru/Be), delivering a fourfold (4×) demagnification of the periodic mask pattern at a numerical aperture approaching unity (NA_max ≈ 0.993). In contrast to conventional EUV projection objectives that incorporate 6--10 aspheric mirrors with an overall optical throughput of less than 15%, the proposed design redirects each accepted discrete spatial diffraction order scattered by the mask onto the wafer via a dedicated pair of planar mirror facets. The number of reflections is strictly fixed at two for all accepted orders, retaining $50−−60\%$ of the power leaving the mask in each accepted order. We derive a spatial geometry providing rigorous optical path length equalization across all diffraction orders, thereby removing order-dependent propagation phase shifts. Individually optimized 30-bilayer Bragg multilayer coatings are designed for each facet using the transfer matrix method combined with global evolutionary optimization algorithms. The architecture is generalized to a three-dimensional vector formulation with a two-dimensionally periodic mask. Utilizing inverse lithography technology, Fourier parameterization, and a differentiable electromagnetic modal waveguide solver, we solve the synthesis problem for binary absorber masks (La absorber on a Ru/Be/Sr multilayer mirror). We demonstrate simulated aerial images of sub-10-nm features on the wafer (isolated peaks with a full width at half maximum (FWHM) of approximately $5.4$~nm and line pairs with a critical dimension of $6$~nm) and find that the two peaks remain resolved for the tested wafer defocus values from $0$ to $5$~nm along the z-axis.
ER -