EUV Optic Cleaning via Hydrogen Radical Pressure Control
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Solution Overview
Problem
Current EUV lithographic apparatuses face challenges in efficiently removing contamination from mirror elements, particularly tin contamination, which leads to reduced reflectivity and system malfunctions, despite existing cleaning techniques having limited protection efficiency.
Innovation Solution
A cleaning arrangement that supplies hydrogen radicals and halogen molecules at a partial pressure of 0.1-10 Pa to effectively clean EUV optics, including pulsed radical delivery to manage temperature and prevent damage, and utilizing palladium to interdiffuse remaining tin for reflectivity restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cleaning techniques (foil traps, collectors) are used to prevent tin contamination, then some protection is provided, but the protection efficiency is limited and contamination still occurs on mirror elements
Solution Approach 1:
The invention converts the harmful tin contamination into a removable state by reacting it with hydrogen radicals to form gaseous tin-hydrides (SnH4). The tin that would otherwise permanently degrade mirror reflectivity is transformed into a volatile compound that can be evacuated, turning the harmful deposition process into a reversible cleaning mechanism.
Solution Approach 2:
The invention changes the chemical state of tin from solid deposited contamination to gaseous tin-hydride through controlled chemical reactions. By adjusting parameters such as hydrogen radical density, temperature, and pressure in the vacuum chamber, the tin is transformed from a harmful solid deposit into a removable gas phase species.
2Productivity
If hydrogen radicals are supplied at high concentration to clean tin contamination, then cleaning efficiency increases, but the optic may be damaged due to excessive temperature or radical intensity
Solution Approach 1:
The invention applies periodic or pulsed hydrogen radical supply rather than continuous exposure. This allows cleaning cycles to be interspersed with rest periods, preventing cumulative thermal damage while maintaining effective tin removal during active cleaning phases. The periodic action enables high cleaning efficiency during treatment intervals without causing damage from sustained exposure.
Solution Approach 2:
The invention uses controlled excess of hydrogen radicals temporarily to ensure complete tin removal, then stops the supply. The excessive radical concentration is applied only during brief cleaning intervals rather than continuously, achieving thorough cleaning while limiting total exposure dose to prevent optic damage.
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 significantly enhances the cleaning efficiency of EUV optics by maintaining high reflectivity and preventing damage, ensuring reliable operation of the lithographic apparatus by effectively removing contamination and restoring reflectivity through controlled radical exposure and interdiffusion processes.
Implementation Method 1
hydrogen radicals react with tin to form gaseous tin-hydrides (SnH4)
Implementation Method 2
halogen molecules, wherein a partial pressure of the radicals/molecules ranges between 0.1-10 Pa
Implementation Method 3
utilizing palladium to interdiffuse remaining tin for reflectivity restoration
Data Source
AI summary
A cleaning arrangement is configured to clean an EUV optic of an EUV lithographic apparatus. The partial radical pressure ranges between 0.1-10 Pa. The cleaning arrangement can be configured inside a cleaning cocoon of the lithographic apparatus for offline cleaning. It can also be configured at particular positions inside the apparatus to clean nearby optics during production. In the pressure range of 0.1-10 Pa the penetration of atomic hydrogen into the optical devices is high, while the recombination to molecular hydrogen and hydrogen consumption is limited.