EUV Collector Reflective Shell Cooling via Thin-Wall Convection
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Solution Overview
Problem
EUV collector optics face thermally induced deformations due to non-uniform heat loads and temperature gradients, which compromise the focusing quality of extreme ultraviolet radiation sources.
Innovation Solution
A thin, axisymmetric reflective shell with a cooling channel on its back side, utilizing convective heat transfer and a controlled cooling circuit to manage temperature distribution and compensate for deformations through adjustable coolant pressure, mass flow, and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the collector surface is made rigid to reduce deformations, then the structural stability is improved, but the heat dissipation capability deteriorates due to reduced convective cooling efficiency
Solution Approach 1:
The patent employs a thin-walled reflective shell (thickness 0.5-5 mm) that is thin enough to allow efficient heat dissipation through the wall thickness, yet maintains sufficient structural integrity. The shell is supported by a rigid support structure that provides necessary stability while allowing the thin shell to flex thermally without compromising overall structural stability.
Solution Approach 2:
The collector is divided into functional segments: a thin reflective shell for heat dissipation and a separate rigid support structure for structural stability. This segmentation allows each component to optimize its specific function - the thin shell prioritizes thermal management while the support structure provides mechanical stability.
2Temperature
If the reflective shell thickness is reduced to enhance convective cooling, then the heat dissipation is improved, but the mechanical strength deteriorates
Solution Approach 1:
The patent specifies a thin reflective shell with thickness between 0.5-5 mm, which is thin enough to enable efficient convective cooling through the wall, yet maintains sufficient mechanical strength for the application. The thin wall allows heat to reach the outer surface quickly for effective heat transfer to the cooling medium.
Solution Approach 2:
A cooling medium (gas or liquid) is circulated through the thin wall structure to enhance heat dissipation. The cooling system compensates for the reduced mechanical strength of the thin shell by providing active thermal management, allowing the shell to remain thin for cooling efficiency while maintaining operational integrity.
3Temperature
If active cooling is applied to the collector, then the temperature control is improved, but the system complexity increases due to additional cooling infrastructure
Solution Approach 1:
The patent employs a relatively simple cooling system where a cooling medium (gas or liquid) is circulated through or along the thin-walled collector structure. This active cooling approach provides effective temperature control without requiring complex cooling infrastructure, leveraging the thin wall design to minimize the complexity of the cooling system while maintaining good temperature control.
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
Achieves a uniform temperature distribution across the reflective shell, minimizing deformations and maintaining high focusing quality by locally enhancing heat transfer and controlling thermal stresses, thereby ensuring a small spot size for the focused radiation.
Implementation Method 1
the thickness of the reflective shell is substantially reduced, such that the convective heat transfer between the back side of the reflective shell and a cooling medium flowing through the cooling channel dominates the process of removing heat from the reflective shell
Implementation Method 2
a cooling circuit is connected to the cooling channel to supply a cooling medium to the cooling channel with a controlled coolant pressure and/or mass flow and/or temperature
Data Source
AI summary
An optical collector (15) for collecting extreme ultraviolet radiation or EUV light generated at a central EUV production site comprises a reflective shell (25). To cope with thermal loading of the collector and avoid deformations, the reflective shell (25) is mounted on a support structure (24), such that a cooling channel (29) is established between the back side of the reflective shell (25) and the support structure (24), the thickness of the reflective shell (25) is substantially reduced, such that the convective heat transfer between the back side of the reflective shell (25) and a cooling medium (26) flowing through the cooling channel (29) dominates the process of removing heat from the reflective shell (25) with respect to heat conduction, and a cooling circuit (33) is connected to the cooling channel (29); to supply a cooling medium (26) to the cooling channel (29) with a controlled coolant pressure and/or mass flow.