High Purity Tin Vacuum Heating Oxygen Removal
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Solution Overview
Problem
Highly purified tin produced by conventional electrolytic methods contains high oxygen and sulfur content, leading to clogging issues in EUV light source devices when used as a tin target material, as these contaminants are difficult to remove effectively.
Innovation Solution
Vacuum heating of electrolytically refined tin with a controlled carbon presence to react with oxygen and sulfur, reducing their concentrations to extremely low levels, achieving high purity tin with oxygen below 10 ppb and sulfur below 0.01 ppm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electrolytic methods are used to produce high purity tin, then metal impurities are removed effectively, but oxygen and sulfur content remains high
Solution Approach 1:
The patent applies vacuum heating treatment to create an inert vacuum environment that prevents re-oxidation while enabling selective removal of oxygen and sulfur through reaction with carbon. The vacuum atmosphere allows volatile products (CO, CO2, SO2) to escape while preventing external contamination, thereby reducing oxygen and sulfur content to extremely low levels without introducing new impurities.
Solution Approach 2:
The patent introduces carbon as an intermediary substance that reacts with oxygen and sulfur to form volatile compounds (CO, CO2, SO2). This intermediary approach allows indirect removal of harmful elements through chemical transformation, where carbon acts as a sacrificial reagent that converts non-volatile impurities into volatile products that can be easily removed under vacuum conditions.
2Ease of manufacture
If tin is used as EUV light source target material with high oxygen content, then production cost is reduced, but nozzle clogging occurs and droplet formation becomes unstable
Solution Approach 1:
The patent changes the purity parameters of tin by applying vacuum heating treatment at specific temperatures (400-1000°C) for controlled durations. This parameter change approach selectively removes oxygen and sulfur to achieve ultra-low levels (oxygen <10 ppb, sulfur <0.01 ppm) while maintaining cost-effectiveness through optimized processing conditions that balance treatment intensity with production efficiency.
3Manufacturing precision
If vacuum heating treatment is applied to reduce oxygen and sulfur content, then purity is improved, but processing time and energy consumption increase
Solution Approach 1:
The patent performs preliminary electrolytic refining to remove metal impurities before applying vacuum heating treatment. This preliminary action reduces the overall impurity burden, allowing the subsequent vacuum heating step to focus specifically on oxygen and sulfur removal. This two-stage approach optimizes total processing time by dividing the purification task into efficient specialized steps rather than attempting single-step removal of all impurities.
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 method effectively reduces oxygen and sulfur content in tin, preventing nozzle clogging and ensuring stable droplet formation, making the high purity tin suitable for EUV light source applications.
Implementation Method 1
when electrolytically refined tin is heated under vacuum in a state where a certain amount of carbon is contained in the tin
Implementation Method 2
oxygen in the form of free oxygen or oxide in the tin will react with carbon to form carbon monoxide or carbon dioxide which is removed by volatilization
Implementation Method 3
by such operation, a sulfur content in tin is significantly reduced
Implementation Method 4
Since sulfur has a high vapor pressure, it is removed as elementary sulfur by vacuum heating, as well the sulfur is also removed as a compound such as sulfur oxide
Data Source
AI summary
Provided is a high purity tin (Sn) having an extremely low oxygen content. A high purity tin having a tin purity of 5N (99.999% by mass, provided that carbon, nitrogen, oxygen and hydrogen are excluded) or more, wherein the high purity tin has an oxygen content of less than 10 ppb by mass, as measured by elemental analysis using Dynamic-SIMS.