EUV Lithography Mirror With Laminar Flow Microchannel Cooling
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Solution Overview
Problem
EUV lithography mirrors experience heat-induced distortion and vibrations due to inadequate cooling methods, particularly when radiant cooling is insufficient and internal cooling with turbulent flow causes vibrations that compromise the accuracy of the lithography process.
Innovation Solution
An internally cooled mirror using a fluid with laminar flow properties through microchannels, which absorbs heat without inducing vibratory motion, minimizing curvature distortion and undulation errors, and maintaining a stable temperature rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If radiant cooling methods are used to cool mirrors, then mirror distortion is minimized, but cooling effectiveness is insufficient under high heat loads
Solution Approach 1:
The mirror is segmented into multiple functional layers: an optical surface layer for light reflection and a separate cooling structure with microchannels for heat removal. This segmentation allows the optical surface to maintain its integrity while the cooling system independently manages thermal loads through internal fluid circulation.
Solution Approach 2:
A cooling fluid acts as an intermediary medium, circulating through microchannels within the mirror structure to absorb heat from the optical surface and transport it to external heat exchangers. This intermediary mechanism enables efficient heat removal without direct contact between the cooling system and the optical surface.
2Reliability
If turbulent flow internal cooling is used to cool mirrors, then cooling effectiveness is improved, but mirror vibrations increase compromising lithography accuracy
Solution Approach 1:
The flow regime parameter is changed from turbulent to laminar flow by controlling the Reynolds number through appropriate channel dimensions and flow rates. This parameter change maintains sufficient cooling effectiveness while eliminating the vibrations associated with turbulent flow that would compromise lithography accuracy.
Solution Approach 2:
The cooling approach transitions from external radiant cooling to internal cooling through microchannels, adding a dimensional aspect of internal fluid circulation. This internal cooling pathway enables effective heat removal while maintaining external surface stability by containing the cooling mechanism within the mirror structure.
3Temperature
If internal cooling methods are used to cool mirrors, then cooling effectiveness is improved, but vibrations are induced affecting lithography process accuracy
Solution Approach 1:
The cooling system is localized within the mirror structure through integrated microchannels, providing targeted cooling where heat generation occurs. This localized approach ensures effective temperature control of the optical surface while minimizing disturbances to the overall mirror stability and surrounding lithography components.
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 cools EUV lithography mirrors under high heat loads, reducing vibrations and maintaining optical performance, thereby enhancing the accuracy and reliability of the EUV lithography process.
Implementation Method 1
The fluid is subjected to a laminar flow and absorbs heat associated with the absorbed light
Implementation Method 2
The fluid is subjected to a laminar flow and absorbs heat associated with the absorbed light
Data Source
AI summary
Methods and apparatus for internally or directly cooling a mirror using a fluid with laminar flow properties are disclosed. According to one aspect of the present invention, an internally cooled mirror includes an optical surface that absorbs light, and at least one microchannel formed beneath the optical surface. The mirror also includes a port that supplied a fluid to the microchannel. The fluid is subjected to a laminar flow and absorbs heat associated with the absorbed light.