EUV Illumination System Polarization Control via Rotatable Subunit
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Solution Overview
Problem
Current EUV lithography systems face challenges in achieving optimal polarization control for illumination optics and projection systems, leading to reduced light throughput and contrast ratios due to polarization-dependent effects, especially as the numerical aperture increases.
Innovation Solution
An adaptable illumination system with a rotatable EUV light source and polarization setting device allows for precise adjustment of the EUV emission beam's polarization, using rotational and translational movements to align with the optics' requirements, enabling optimized high EUV illumination and fulfilling contrast demands through linear, elliptical, or circular polarization settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Bragg mirrors with individual layer coatings are used for EUV illumination, then the illumination system can guide the EUV light, but the polarization-dependent effects reduce the light throughput and contrast ratio
Solution Approach 1:
The patent applies the dynamics principle by making the illumination subunit rotatable about the optical axis, allowing the polarization direction of the EUV light to be dynamically adjusted. This rotational degree of freedom enables the system to adapt to different polarization requirements of downstream components, resolving the contradiction between maintaining high light throughput and achieving polarization versatility.
2Productivity
If the numerical aperture of the illumination system is increased, then the resolution and productivity improve, but the polarization sensitivity of optical components increases
Solution Approach 1:
The patent applies parameter changes by enabling continuous adjustment of the polarization state parameter through rotation of the illumination subunit. This allows the system to optimize performance for high numerical aperture operations by adapting the polarization parameter to match the specific requirements of each optical component in the projection path, thereby maintaining high productivity while mitigating polarization sensitivity issues.
3Adaptability or versatility
If fixed polarization settings are used in the illumination system, then the system structure is simpler, but the system cannot adapt to different polarization requirements of components
Solution Approach 1:
The patent implements a relatively simple dynamic structure by rotating the entire illumination subunit about the optical axis, rather than incorporating complex polarization control components within the illumination path. This approach achieves polarization adaptability through a single rotational degree of freedom, maintaining system simplicity while providing the needed versatility.
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
This solution enhances EUV light throughput and maintains consistent polarization, reducing downstream component demands and achieving high contrast ratios in microstructured component production, with adjustable polarization settings ensuring optimal performance across various applications.
Implementation Method 1
Currently light sources for systems of this type include plasma sources
Implementation Method 2
Synchrotron radiation is an interesting alternative thereto
Implementation Method 3
The known EUV lithography systems are usually equipped with Bragg mirrors as bundle-guiding components
Implementation Method 4
a polarization setting device for setting a defined polarization of the EUV emission beam of the illumination subunit by a rotational and/or translational movement of the illumination subunit
Data Source
AI summary
An illumination system for a microlithographic projection exposure apparatus includes an EUV light source which generates an emission beam of linearly polarized EUV illumination light. An illumination optics guides the emission beam along an optical axis which causes an illumination field in a reticle plane to be illuminated by the emission beam. The illumination system also includes an illumination subunit of the illumination system. The illumination subunit includes at least the EUV light source and a polarization setting device for setting a defined polarization of the EUV emission beam of the illumination subunit.