EUV Mirror Carrier Cooling for Thermal Deformation Control
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Solution Overview
Problem
EUV projection exposure apparatuses for semiconductor lithography face challenges in maintaining imaging quality due to thermally induced deformations caused by uneven thermal loads on mirror arrangements, which are exacerbated by changes in illumination settings and electrical power loss.
Innovation Solution
An integrated cooling system within the mirror carrier that uses a cooling fluid circulating through cooling lines to dissipate thermal loads from the optically active surfaces into a rear region, with a throttling action achieved by connecting lines designed to create uniform backpressure, ensuring symmetric heating and minimizing temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single cooling circuit is used for the mirror carrier, then the device complexity is reduced, but the ability to compensate for asymmetric energy input and reduce thermal deformations is insufficient
Solution Approach 1:
The cooling system is segmented into multiple independent cooling circuits, each responsible for cooling specific regions of the mirror carrier. This segmentation allows differential cooling rates to be applied to different areas, enabling compensation for asymmetric thermal loads while maintaining manageable system complexity through modular design
Solution Approach 2:
Different regions of the mirror carrier are provided with customized cooling characteristics through the segmented cooling circuits. Each cooling circuit can be independently controlled to provide the appropriate cooling rate for its specific region, addressing local thermal requirements and preventing uniform overheating that would cause deformation
2Temperature
If the cooling fluid flow rate is increased to remove thermal load more effectively, then the thermal load dissipation improves, but the temperature uniformity across the mirror carrier deteriorates due to excessive cooling in certain regions
Solution Approach 1:
The cooling system employs dynamic control of cooling fluid flow rates in each cooling circuit, allowing the cooling intensity to be adjusted in real-time based on the actual thermal conditions. This dynamic adjustment enables effective thermal load removal while maintaining temperature uniformity by preventing over-cooling in any single region
Solution Approach 2:
Temperature sensors are integrated into the cooling system to provide feedback on the thermal state of the mirror carrier. This feedback information is used to automatically adjust the cooling fluid flow rates in each circuit, ensuring that thermal loads are removed effectively while maintaining uniform temperature distribution across the mirror surface
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 effectively distributes thermal loads across the mirror carrier, preventing thermally induced deformations and maintaining good imaging quality even under varying thermal conditions.
Implementation Method 1
dissipate a thermal load which is introduced into the mirror carrier via the optically active surfaces
Implementation Method 2
cooling fluid circulating through cooling lines
Implementation Method 3
connecting lines are designed to create uniform backpressure, ensuring symmetric heating and minimizing temperature gradients
Data Source
AI summary
A projection exposure apparatus for semiconductor lithography has a mirror arrangement that is exposed to thermal loads in operation. The mirror arrangement includes a mirror carrier having an optically active surface arranged on a top surface of the mirror carrier. A cooling system is integrated into the mirror carrier. The cooling system has cooling lines through which a cooling fluid circulates. The cooling system is designed so that the thermal load introduced into the mirror carrier via the optically active surface is dissipated at least partially into a rear region remote from the top surface of the mirror carrier.