Coherent Radiation Beam Processing Using Waveguide Mode Segmentation
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Solution Overview
Problem
Current lithographic systems face challenges in providing a radiation beam with high spatial uniformity and stability over time, particularly for metrology targets, due to interference effects and fluctuations in spatial coherence.
Innovation Solution
A device comprising an optical system and a waveguide that directs components of a coherent radiation beam with different frequencies onto various waveguide spatial modes, increasing the étendue and reducing interference effects, thereby achieving spatial uniformity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a laser beam with high spatial coherence is used to provide high intensity radiation, then the intensity is high, but spatial uniformity deteriorates due to speckle and fringes
Solution Approach 1:
The patent segments the coherent radiation beam into multiple spatial modes using a mode scrambler, which divides the single-mode laser output into multiple transverse modes. This segmentation reduces the coherence length and eliminates speckle patterns while maintaining high intensity, thereby resolving the contradiction between intensity and spatial uniformity.
Solution Approach 2:
The patent introduces temporal dimension by modulating the laser output and uses spatial-temporal mode mixing in the waveguide to transform the beam characteristics. By operating in multiple transverse modes simultaneously and mixing them temporally, the system achieves spatial uniformity without sacrificing intensity.
2Illumination intensity
If a laser beam with high spatial coherence is used, then high intensity is achieved, but stability over time deteriorates due to fluctuations in spatial coherence
Solution Approach 1:
The mode scrambler segments the laser output into multiple spatial modes that are less sensitive to fluctuations in spatial coherence. By distributing the intensity across multiple modes, the system achieves temporal stability while maintaining high overall intensity, resolving the contradiction between intensity and reliability.
Solution Approach 2:
The patent changes the spatial mode parameters of the laser beam by coupling it into a waveguide that supports multiple transverse modes. This parameter transformation from a single spatial mode to multiple spatial modes reduces sensitivity to coherence fluctuations, thereby improving temporal stability while preserving intensity.
3Stability of the object's composition
If broadband radiation is used to improve spatial uniformity, then intensity uniformity improves, but the harmful effect of reduced signal strength increases
Solution Approach 1:
The patent uses periodic modulation of the laser output combined with temporal mode mixing in the waveguide to achieve spatial uniformity. By modulating the laser at specific frequencies and allowing temporal evolution of the modes, the system maintains high signal strength while achieving uniformity, resolving the contradiction between uniformity and signal strength.
Solution Approach 2:
The patent changes the temporal and spatial parameters of the radiation beam by coupling it into a waveguide with multiple modes. This parameter transformation allows the beam to maintain high intensity while achieving spatial uniformity through mode mixing, counteracting the harmful effect of reduced signal strength that would normally accompany broadband radiation.
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 provides a radiation beam with improved spatial uniformity and stability, reducing interference effects like speckle and fluctuations, enhancing the accuracy of metrology measurements in lithographic processes.
Implementation Method 1
the optical system is configured to direct a plurality of the components of the radiation beam belonging to a common radiation beam spatial mode and having different frequencies onto the waveguide in such a way that each of the plurality of components couples to a different set of the waveguide spatial modes
Implementation Method 2
a waveguide configured to support a plurality of waveguide spatial modes
Data Source
AI summary
Devices and methods for processing a radiation beam with coherence are disclosed. In one arrangement, an optical system receives a radiation beam with coherence. The radiation beam comprises components distributed over one or more radiation beam spatial modes. A waveguide supports a plurality of waveguide spatial modes. The optical system directs a plurality of the components of the radiation beam belonging to a common radiation beam spatial mode and having different frequencies onto the waveguide in such a way that each of the plurality of components couples to a different set of the waveguide spatial modes, each set comprising one or more of the waveguide spatial modes.