EUV Lithography Vacuum Surface Pore Structure Particle Adhesion
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Solution Overview
Problem
In EUV lithography systems, contaminating particles adhere strongly to surfaces due to high vacuum pressures, leading to surface contamination and reduced cleaning efficiency, especially on surfaces with high roughness.
Innovation Solution
A surface structure with pore-shaped depressions separated by webs is implemented, reducing particle adhesion by minimizing the contact area and interaction forces, with pore diameters smaller than the particles to prevent adhesion, and a periodic pore structure with varying period lengths to address different particle sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If surfaces with high roughness are used in vacuum environment, then particle adhesion is reduced, but cleaning efficiency deteriorates and surface contamination increases
Solution Approach 1:
The patent applies a porous coating layer with controlled pore structures on the optical element surface. The pores have specific size distributions that create reduced adhesion zones for particles while maintaining surface cleanliness. The porous structure allows particles to rest in pore cavities rather than adhering to the surface, and enables cleaning gases to access and remove particles effectively.
Solution Approach 2:
The patent uses composite material structures combining different layers with specific properties. The coating comprises multiple layers including porous layers and dense layers, where each layer contributes different functions - porous layers for particle trapping and reduced adhesion, and dense layers for protection and controlled gas permeability. This composite structure resolves the contradiction between particle adhesion reduction and cleaning efficiency.
2Productivity
If smooth surfaces are used in vacuum environment, then cleaning efficiency is improved, but particle adhesion increases leading to surface contamination
Solution Approach 1:
The patent introduces a porous coating layer on smooth optical surfaces to create controlled adhesion zones. The porous structure provides cavities where particles can rest without strong adhesion to the underlying smooth surface, while the overall surface remains clean and accessible to cleaning gases. This resolves the contradiction by adding porosity to otherwise smooth surfaces.
Solution Approach 2:
The patent applies local quality changes by creating porous structures only in specific regions or at controlled depths within the coating layers. The pore size, distribution, and depth are locally optimized to provide reduced adhesion zones while maintaining overall surface integrity and cleaning accessibility. Different regions of the coating may have different pore characteristics tailored to specific functional requirements.
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 surface structure effectively reduces particle adhesion, allowing for the removal of contaminating particles from EUV lithography systems without impairing the reflectivity of multilayer coatings, enhancing the cleaning efficiency in vacuum environments.
Implementation Method 1
The efficiency of such cleaning depends on how strongly the contaminating particles adhere to the surface to be cleaned, i.e. the strength of the adhesion of the particles to the surface
Implementation Method 2
an optical element, comprising: a substrate, and also a multilayer coating for reflecting EUV radiation
Data Source
AI summary
A vacuum system, in particular an EUV lithography system, includes: a vacuum housing (2), in which a vacuum environment (16) is formed. A surface (2a) of the vacuum housing is subjected to contaminating particles (17) in the vacuum environment. A surface structure (18) at the surface reduces adhesion of the contaminating particles and has pore-shaped depressions (24) separated from one another by webs (25).