Lithium-Alloy Vacuum Purification for EUV Contaminant Control
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Solution Overview
Problem
Current methods for maintaining ultraclean vacuum environments in EUV inspection systems are inadequate, as they fail to effectively control contaminant levels, leading to rapid degradation due to oxide formation and carbonaceous layer accumulation, and existing techniques like high-temperature baking damage critical components, while alkali metal getters have uncontrolled evaporation rates and purity issues.
Innovation Solution
A lithium-aluminum alloy is sublimated within a vacuum chamber using a feedback control system, with a collection plate to condense contaminants, enhancing the purification process by dynamically controlling lithium sublimation based on chamber conditions and reacting with contaminants to form non-volatile compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional ultra-high vacuum approaches such as multi-stage pumping and high temperature baking are used, then the partial pressures of O2, H2O and hydrocarbons are reduced, but key components in the UCV/EUV inspection system are damaged by the elevated temperature
Solution Approach 1:
The patent changes the temperature parameter by using room temperature or moderately heated conditions instead of high temperature baking, while achieving contaminant removal through lithium sublimation and chemical reaction mechanisms
Solution Approach 2:
The patent replaces the thermal-mechanical high temperature baking process with a chemical-physical process involving lithium sublimation and contaminant reaction, eliminating the need for elevated temperatures while maintaining purification effectiveness
2Quantity of substance
If alkali metal getters are used for contaminant removal, then contaminant levels are reduced, but the evaporation rate is difficult to control and the liquid alkali metal is highly corrosive and mobile
Solution Approach 1:
The patent uses a lithium-aluminum alloy instead of pure alkali metal, combining lithium's high reactivity with aluminum's structural stability and lower reactivity, creating a composite material that maintains gettering effectiveness while improving controllability and reducing corrosiveness
Solution Approach 2:
The patent changes the physical state parameter by using sublimation instead of evaporation, and changes the compositional parameter by using a alloy instead of pure metal, thereby controlling the release rate and improving operational safety
3Quantity of substance
If direct evaporation of alkali metal on chamber surface is used, then a getter film is formed to react with impurities, but the evaporation rate is difficult to control and the metal film has low purity
Solution Approach 1:
The patent uses a lithium-aluminum alloy target instead of pure alkali metal, where the alloy composition enables controlled sublimation and produces a higher purity getter film with improved stoichiometry
Solution Approach 2:
The patent replaces direct evaporation with sublimation process, and replaces simple physical deposition with a controlled chemical reaction process, thereby achieving better control over film formation and purity
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 effectively maintains a clean environment by dynamically controlling lithium sublimation and condensing contaminants, extending component life and reducing maintenance downtime, while avoiding component damage from high temperatures and improving contaminant removal efficiency.
Implementation Method 1
an activation element arranged to impart energy to the piece of lithium-aluminum alloy to sublimate lithium from the piece of lithium-aluminum alloy
Implementation Method 2
a collection plate located in the chamber and arranged to form a layer of the sublimated lithium on a surface of the collection plate
Implementation Method 3
reacting with contaminants to form non-volatile compounds
Data Source
AI summary
An apparatus for purifying a controlled-pressure environment in a chamber, including: a piece of lithium-aluminum alloy located in the chamber; an activation element arranged to impart energy to the piece of lithium-aluminum alloy to sublimate lithium from the piece of lithium-aluminum alloy; a feedback control system including a sensor system arranged to measure a condition within the chamber, and a controller in communication with the sensor and configured to control operation of the activation element according to an evaluation of the condition; and a collection plate located in the chamber and arranged to form a layer of the sublimated lithium on a surface of the collection plate.