EUV Beam Splitting Apparatus Using Reflective Diffraction Gratings
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Solution Overview
Problem
Lithographic systems using EUV radiation face challenges in maintaining the stability of beam power and pointing direction due to variations in wavelength and pointing direction, particularly when using free electron lasers as radiation sources.
Innovation Solution
A beam-splitting apparatus comprising multiple reflective diffraction gratings that split the input radiation beam into output beams with only one instance of a diffraction order that is not the 0th order in each optical path, ensuring stability by configuring the gratings to prioritize the 0th diffraction order for power and pointing direction stability, and using directing optics to maintain consistent polarization across output beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple diffraction orders are used in the beam splitting apparatus, then the beam can be split into multiple output beams, but the stability of power and pointing direction deteriorates due to wavelength and pointing direction variations
Solution Approach 1:
The beam splitting apparatus is divided into multiple independent diffraction grating modules, each handling a specific diffraction order. This segmentation allows each module to be optimized for stability while collectively providing multiple output beams, resolving the contradiction between versatility and reliability.
Solution Approach 2:
The patent changes the diffraction order parameter to always use the 0th order for subsequent gratings in the optical path. This parameter constraint ensures that only wavelengths and angles within a stable range are processed, eliminating the instability caused by higher diffraction orders while maintaining beam splitting capability through multiple gratings.
2Productivity
If higher diffraction orders are used to increase beam splitting efficiency, then more output beams can be obtained, but the sensitivity to wavelength and pointing direction variations increases
Solution Approach 1:
The patent extracts and eliminates higher diffraction orders from the optical path, retaining only the 0th order for subsequent gratings. This extraction removes the source of wavelength and angle sensitivity while preserving beam splitting efficiency through the use of multiple gratings operating in the stable 0th order regime.
3Adaptability or versatility
If the beam splitting apparatus is designed to handle wavelength variations, then adaptability improves, but the stability of output beam parameters deteriorates
Solution Approach 1:
The apparatus is designed with preliminary anti-action by pre-configuring all subsequent gratings to operate in the 0th diffraction order, which inherently resists wavelength and pointing direction variations. This preemptive design choice counteracts potential instability before it occurs, maintaining output stability while handling wavelength variations through the systematic use of 0th order diffraction throughout the beam path.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the stability of beam power and pointing direction across lithographic apparatuses, improving the reliability and precision of EUV lithography by minimizing the impact of wavelength and pointing direction variations in the input radiation.
Implementation Method 1
comprising a plurality of reflective diffraction gratings arranged to receive a radiation beam and configured to form a diffraction pattern comprising a plurality of diffraction orders
Implementation Method 2
reflective diffraction gratings arranged to receive a radiation beam and configured to form a diffraction pattern
Data Source
AI summary
A beam-splitting apparatus arranged to receive an input radiation beam and split the input radiation beam into a plurality of output radiation beams. The beam-splitting apparatus comprising a plurality of reflective diffraction gratings arranged to receive a radiation beam and configured to form a diffraction pattern comprising a plurality of diffraction orders, at least some of the reflective diffraction gratings being arranged to receive a 0th diffraction order formed at another of the reflective diffraction gratings. The reflective diffraction gratings are arranged such that the optical path of each output radiation beam includes no more than one instance of a diffraction order which is not a 0th diffraction order.