EUV Collector Mirror Heating and Drainage for Tin Debris Removal
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Solution Overview
Problem
EUV collector mirrors in EUV lithography systems suffer from contamination and degradation due to tin debris deposition, leading to reduced reflectivity and increased maintenance frequency, which affects exposure power and throughput.
Innovation Solution
The implementation of an EUV collector mirror with a heating mechanism to melt tin debris, combined with a drain structure and recycling system to remove and reuse the debris, thereby maintaining reflectivity and reducing maintenance needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a laser-produced plasma source is used to generate EUV light, then high exposure power and throughput are achieved, but tin debris deposits on the collector mirror causing reflectivity degradation
Solution Approach 1:
The patent applies the principle of converting harm into benefit by utilizing the heat generated from laser-produced plasma to melt tin debris on the collector mirror. The harmful tin deposition is transformed into a beneficial process where the same plasma heat that causes deposition also enables controlled melting and removal of the debris through drain holes, thereby maintaining mirror reflectivity while preserving the high power EUV generation capability.
Solution Approach 2:
The patent employs phase transitions by heating the tin debris from solid to liquid state through the plasma-induced temperature rise. The melted tin is then drained through gravity-driven flow through drain holes in the collector mirror, effectively removing the debris. This phase change approach allows continuous operation without frequent mirror replacements, resolving the contradiction between maintaining high exposure power and preserving mirror reflectivity.
2Power
If tin droplet targets are used for EUV generation, then high-power EUV radiation is produced, but the collector mirror degrades due to particle and ion impact
Solution Approach 1:
The patent implements self-service by enabling the collector mirror to clean itself through the drain hole mechanism. The mirror structure incorporates features (drain holes, heating zones) that allow it to automatically melt and drain tin debris without external intervention. This self-cleaning capability extends mirror durability and reduces maintenance frequency while maintaining the high-power EUV radiation generation function.
Solution Approach 2:
The patent applies preliminary action by pre-heating the collector mirror surface and drain pathways before tin debris accumulation becomes problematic. The heating mechanism is activated in advance to maintain temperatures that prevent tin solidification and facilitate continuous draining. This preventive approach protects mirror strength from degradation and ensures sustained high-power operation.
3Productivity
If the collector mirror operates continuously to maintain throughput, then production efficiency increases, but tin deposition accumulates reducing operational lifetime
Solution Approach 1:
The patent ensures continuity of useful action by implementing a continuous self-cleaning mechanism that operates alongside the EUV generation process. The drain holes remain open and functional throughout operation, allowing tin debris to be continuously melted and removed. This eliminates interruptions for mirror replacement, maintaining both high throughput and extended operational lifetime simultaneously.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the temperature parameter of the collector mirror through plasma heating. By maintaining the mirror temperature above the melting point of tin, the system prevents debris accumulation. This parameter control enables continuous operation without degradation, resolving the contradiction between productivity and operational lifetime.
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 approach extends the usable lifetime of the EUV collector mirror, maintains high exposure power and throughput, and reduces the frequency of mirror swaps, thus optimizing operational efficiency and cost-effectiveness.
Implementation Method 1
a heating mechanism to melt tin debris
Implementation Method 2
a drain structure to drain melted metal from the reflective surface of the EUV collector mirror body to a back side of the EUV collector mirror body
Data Source
AI summary
An EUV collector mirror for an extreme ultra violet (EUV) radiation source apparatus includes an EUV collector mirror body on which a reflective layer as a reflective surface is disposed, a heater attached to or embedded in the EUV collector mirror body and a drain structure to drain melted metal from the reflective surface of the EUV collector mirror body to a back side of the EUV collector mirror body.