EUV Condenser Mirror Protective Layer Thickness Distribution
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Solution Overview
Problem
Existing extreme ultraviolet light generation apparatuses face challenges in maintaining high EUV light reflectance due to the uniform thickness of protective layers, which leads to increased transmittance and contamination from charged particles and fine particles.
Innovation Solution
The EUV light condenser mirror features a protective layer with a thickness distribution that varies based on the distance from the magnetic field axis, magnetic flux density, distance from the plasma point, and charged particle quantity, maximizing thickness at positions where collisions are most likely to occur, thereby reducing contamination and maintaining reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a protective layer with uniform thickness is used on the condenser mirror, then the manufacturing process is simple, but the EUV light transmittance decreases and contamination from charged particles increases
Solution Approach 1:
The protective layer is designed with varying thickness across different regions of the condenser mirror. Specifically, the thickness is increased in regions where charged particle impact is more frequent (such as the central region where plasma-generated particles converge), while maintaining thinner layers in regions with lower particle flux. This local variation optimizes both contamination protection and EUV light transmittance by matching the protective layer's thickness to the actual contamination risk at each location.
2Object-affected harmful factors
If the protective layer thickness is increased to reduce contamination, then contamination resistance improves, but EUV light transmittance decreases
Solution Approach 1:
The protective layer thickness is optimized locally rather than uniformly. Regions with high charged particle flux (such as the center of the mirror where plasma particles converge) receive thicker protective layers for enhanced contamination resistance, while regions with lower particle flux maintain thinner layers to preserve EUV light transmittance. This spatially varying thickness distribution resolves the contradiction by providing contamination protection only where actually needed.
3Use of energy by moving object
If the protective layer thickness is decreased to improve EUV light transmittance, then light transmission improves, but contamination resistance decreases
Solution Approach 1:
The protective layer is designed with minimum necessary thickness at each location based on the local charged particle flux density. In regions where EUV light transmission is critical and particle contamination is less severe, the layer is kept thin to maximize transmittance. In regions where particle impact is intense, the layer is thickened to provide adequate protection. This localized optimization allows the system to achieve both good transmittance and adequate contamination resistance simultaneously.
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 configuration effectively reduces the decrease in EUV light transmittance and contamination of the reflective layer, enhancing the overall performance of the extreme ultraviolet light generation apparatus by optimizing the protective layer thickness distribution.
Implementation Method 1
a laser beam is condensed to an internal space and plasma is generated from a target substance at a condensation position of the laser beam
Implementation Method 2
a reflective layer provided on the substrate and configured to reflect the extreme ultraviolet light
Implementation Method 3
a magnetic field generation unit configured to generate a magnetic field that converges a charged particle generated by the plasma of the target substance toward a wall of the chamber
Data Source
AI summary
An extreme ultraviolet light generation apparatus includes: a chamber in which plasma is generated from a target substance at a condensation position of a laser beam; a condenser mirror configured to condense extreme ultraviolet light generated by the plasma; and a magnetic field generation unit configured to generate a magnetic field that converges a charged particle generated by the plasma toward a wall of the chamber, the condenser mirror includes a substrate, a reflective layer, and a protective layer provided on the reflective layer, the protective layer has layer thickness distribution in which a layer thickness of the protective layer from a reflective layer surface changes, and the layer thickness of the protective layer is maximum at a position on a line (CL) on which a plane passing through a magnetic field axis of the magnetic field generation unit and a central axis (CA) of the condenser mirror intersects the reflective layer surface (62F).