Collector Mirror Substrate with Integrated Cooling Channels
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Solution Overview
Problem
Plasma-based radiation sources for semiconductor lithography face challenges in managing the high thermal loads caused by short-wavelength radiation, leading to degradation of collector mirrors and reduced reflectivity due to insufficient cooling, especially with pulsed operation causing transient temperature spikes.
Innovation Solution
Incorporating flow channels with a high thermal conductivity substrate, such as silicon, directly into the collector mirror substrate for efficient heat management, allowing a heat transport medium to flow through and stabilize the optically active mirror surface, thereby dissipating heat from transient temperature spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If glass is used as substrate material for collector mirror, then surface quality is excellent, but thermal conductivity is too low to manage thermal load
Solution Approach 1:
The patent uses a composite substrate structure combining silicon (high thermal conductivity) with a reflective coating layer. The silicon substrate provides excellent thermal management with conductivity >100 W/mK, while the deposited reflective coating maintains optical performance. This composite approach resolves the contradiction between glass's excellent surface quality and poor thermal conductivity.
2Temperature
If external thermostat system is used for cooling, then temperature management is achieved, but space requirements and precision manufacturing requirements increase
Solution Approach 1:
The patent merges the cooling function directly into the mirror substrate by incorporating flow channels within the silicon substrate itself. This integration eliminates the need for separate external thermostat systems and contact foils, reducing both space requirements and manufacturing complexity while maintaining effective temperature management.
Solution Approach 2:
The mirror substrate serves its own cooling needs through integrated flow channels that allow heat transport medium to flow directly through the substrate. This self-service approach eliminates dependence on external cooling systems, reducing system complexity and space requirements.
3Temperature
If contact foils are used for cooling connection, then thermal connection is established, but cooling efficiency is insufficient for high power outputs
Solution Approach 1:
The patent removes the intermediate contact foil layer from the cooling system. Instead of using foils to connect the mirror to the cooling system, the design extracts this intermediate layer and replaces it with direct integration of flow channels into the silicon substrate, enabling more efficient thermal management for high power outputs.
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 enables reliable cooling and temperature management of collector mirrors, maintaining high reflectivity and extending their lifetime by preventing thermal degradation, while avoiding the space and precision manufacturing issues associated with external thermostat systems.
Implementation Method 1
flow channels for cooling and temperature management are incorporated directly in the substrate so that a heat transport medium can flow through directly for rapidly stabilizing the temperature of the optically active mirror surface
Implementation Method 2
heat from transient temperature spikes which occur in pulsed operation for plasma generation and which temporarily exceed the temperature average prevailing at the mirror surface by a multiple is quickly dissipated
Data Source
AI summary
The invention is directed to a collector mirror for short-wavelength radiation based on a plasma. It is the object of the invention to find a novel possibility for managing the temperature of a collector mirror for focusing short-wavelength radiation generated from a plasma which allows an efficient thermal connection to be produced between the optically active mirror surface and a thermostat system without the disadvantages relating to space requirements or high-precision manufacture of the collector mirror. This object is met, according to the invention, in that the collector mirror has a solid, rotationally symmetric substrate which comprises a material with high thermal conductivity of more than 50 W/mK and in which channels for cooling and temperature management are incorporated in the substrate so that a heat transport medium can flow through directly and for rapidly stabilizing the temperature of the optically active mirror surface. Heat of transient temperature spikes which occur in pulsed operation for plasma generation at the mirror surface and which temporarily exceed the temperature average by a multiple is quickly dissipated.