EUV Optical Cleaning via Reactive Gas and Off-Path Getter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current cleaning methods for optical systems in EUV lithography, such as oxygen feed and reactive discharges with fluorine, are inadequate for removing metallic contaminants and maintaining reflectivity, as they either fail to effectively detach or permanently bind these contaminants, leading to absorption losses and reduced radiation throughput.
Innovation Solution
A cleaning arrangement with a reactive-gas inlet and a getter surface positioned off the beam path, where the reactive gas reacts with contaminants to detach them from optical elements, and a getter surface absorbs these contaminants through chemical reactions or coatings, ensuring permanent binding and reduced heating from EUV radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen is fed into the lithography unit to clean contaminants, then organic contaminants are removed through oxidation, but metallic contaminants cannot be effectively removed
Solution Approach 1:
The invention changes the chemical parameter of the cleaning gas from oxygen (which only removes organic contaminants) to a mixture containing fluorine or chlorine (which can remove both organic and metallic contaminants). This parameter change enables the cleaning system to handle multiple contaminant types effectively.
Solution Approach 2:
The invention uses a composite cleaning gas mixture containing fluorine and chlorine components. This composite approach combines the benefits of different reactive gases: fluorine for removing organic contaminants and carbon-based deposits, and chlorine for removing metallic contaminants, thereby achieving versatile contaminant removal capability.
2Reliability
If reactive discharges with fluorine are used to clean the collector, then contaminants are removed, but materials resistant to fluorine radicals must be used and plasma generation is required
Solution Approach 1:
The invention extracts the plasma generation step from the cleaning process. Instead of using complex plasma discharges, it introduces reactive gases (fluorine and chlorine) in molecular form that can directly react with contaminants under EUV irradiation, simplifying the system while maintaining effective contaminant removal.
Solution Approach 2:
The invention uses EUV radiation as an intermediary to activate the reactive gases. The EUV photons serve as a mediator that provides the activation energy needed for fluorine and chlorine to react with contaminants, replacing the need for complex plasma generation equipment while achieving similar or better cleaning effectiveness.
3Reliability
If getter surfaces are placed on the beam path to absorb contaminants, then contaminants are captured, but the surfaces are severely heated by EUV radiation reducing binding efficiency
Solution Approach 1:
The invention inverts the traditional approach by placing getter surfaces off the beam path instead of on it. This spatial inversion allows the getter surfaces to capture contaminants that have been detached from optical components and transported by gas flow, avoiding direct EUV heating while maintaining binding effectiveness through chemical reactions with the getter gas or coating.
4Reliability
If conventional cleaning methods are used, then some contaminants are removed, but reflectivity is not maintained and radiation throughput decreases
Solution Approach 1:
The invention implements continuous cleaning action by continuously introducing reactive gases (fluorine and chlorine) into the lithography unit during operation. This continuous process ensures that contaminants are constantly removed from optical surfaces, maintaining high reflectivity and radiation throughput without interruption to the lithography process.
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 solution effectively prevents contamination by converting contaminants into a gas phase, allowing them to be absorbed by the getter surface, maintaining reflectivity and ensuring consistent EUV illumination by preventing deposition on optical components, thus enhancing the throughput and quality of wafers in EUV lithography.
Implementation Method 1
The contaminants present on the optical surface are detached therefrom by the incident radiation as a result of the latter co-operating with the reactive gas
Implementation Method 2
a getter gas, which causes the contaminants to be absorbed by the getter surface as a result of a chemical reaction
Implementation Method 3
The contaminants present on the optical surface are detached therefrom by the incident radiation as a result of the latter co-operating with the reactive gas
Implementation Method 4
The absorption of the contaminants by the getter surface may be assisted by a getter surface designed to be of a porous form. The getter surface thus has a large surface area available for the absorption of contaminants
Data Source
AI summary
A cleaning arrangement for an optical system and in particular for an optical system designed for EUV radiation. The cleaning arrangement has a gas inlet (28) for a reactive gas (29). Contaminants (23) that have deposited on the surface of optical elements (110) are detached by the reactive gas. Also provided are getter surfaces (32) that are preferably arranged opposite the surfaces to be clean and by which the contaminants detached from these surfaces are absorbed. This absorption may take place as a result of condensation on the getter surface and also by chemical reaction.