EUV Reflective Optical Element Edge Geometry
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Solution Overview
Problem
EUV lithography apparatuses face defects such as sputtering and delamination in reflective optical elements due to hydrogen plasma interactions, leading to reduced reflectivity and throughput, primarily at the edges of electrically conductive materials exposed to plasma.
Innovation Solution
A reflective optical element with a chamfered or rounded edge design is used to mitigate the effects of hydrogen plasma, featuring a substrate body made from conductive materials like aluminum, with a coating system acting as an interference layer, and an edge geometry adapted based on plasma-dependent parameters to reduce electric field overshoot and ion flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reflective optical elements are used in EUV lithography, then the ability to work at EUV wavelengths is achieved, but defects such as sputtering and delamination occur due to hydrogen plasma interactions
Solution Approach 1:
The patent applies different geometric treatments to different regions of the optical element. Specifically, the edges are chamfered or rounded while the central optically effective region maintains its original surface quality. This local differentiation protects the vulnerable edge regions from plasma-induced defects while preserving the optical performance of the central region.
Solution Approach 2:
The chamfering or rounding of edges is performed as a preliminary manufacturing step before the optical element is exposed to hydrogen plasma during EUV lithography operations. This pre-treatment creates a geometric configuration that prevents plasma accumulation and reduces electric field concentration at edges, thereby preventing defects before they can occur during operation.
2Productivity
If edge regions of reflective optical elements are exposed to hydrogen plasma, then EUV lithography operation is enabled, but electric field overshoot and ion flux increase leading to sputtering and delamination
Solution Approach 1:
The patent applies curvature to the edges of the reflective optical element by rounding or chamfering them. This geometric modification eliminates sharp edges that would otherwise concentrate electric fields and create regions of high ion flux. The curved or angled surfaces distribute the electric field more uniformly, reducing plasma-induced damage while maintaining operational productivity.
3Ease of manufacture
If conventional edge geometry is used, then manufacturing is simpler, but defects occur at edge sections exposed to plasma
Solution Approach 1:
The manufacturing process applies a localized treatment only to the edge regions of the optical element, leaving the central optically effective region unchanged. This approach maintains relatively simple manufacturing while achieving the reliability needed for defect-free operation. The chamfering or rounding is confined to peripheral zones where plasma exposure creates the highest risk of defects.
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 effectively prevents or suppresses defects like sputtering and delamination, ensuring long-lasting and reliable operation of EUV lithography systems by minimizing hydrogen plasma-induced damage through optimized edge geometry and coating configurations.
Implementation Method 1
with a coating system acting as an interference layer
Implementation Method 2
configured to reflect light incident on a surface (illuminated region) of the optically effective region
Implementation Method 3
defects such as sputtering and delamination in reflective optical elements due to hydrogen plasma interactions
Data Source
AI summary
A reflective optical element (1) for reflecting light having at least one wavelength in an EUV wavelength range has an optically effective region configured for reflecting the light incident on a surface (2) of the optically effective region. The reflective optical element (1) has an edge (4) forming at least part of a boundary of an edge-free surface (3) of the reflective optical element (1), wherein the edge-free surface (3) includes the surface (2) of the optically effective region. The edge (4) has a chamfer and/or a rounding. Also disclosed is a method for adapting a geometry of at least one surface region of a component of an optical arrangement, for example of a reflective optical element (1).