EUV Reflective Optical Element Correction via Electron Irradiation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
EUV lithography devices require high reflectivity in their reflective optical elements to ensure optimal imaging properties, but existing methods struggle to achieve uniform reflectivity across the surface, leading to intensity fluctuations and optical aberrations.
Innovation Solution
A method involving irradiation of the multilayer system with electrons to locally alter the structure and reduce reflectivity, ensuring that the reflectivity distribution matches a target distribution, thereby compensating for intensity fluctuations and maintaining optical homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the multilayer system is designed to achieve high reflectivity, then the overall reflectivity is improved, but the homogeneity of reflectivity distribution across the surface deteriorates
Solution Approach 1:
The patent applies local electron beam irradiation to specific regions of the multilayer system where reflectivity needs correction. By selectively irradiating partial surfaces with electrons, the layer structure is locally modified to reduce reflectivity in those specific areas, thereby achieving homogeneous reflectivity distribution across the entire surface while maintaining high overall reflectivity
Solution Approach 2:
The patent changes the physical and chemical parameters of the multilayer system through electron beam irradiation. The electron irradiation induces local structural changes in the alternating layers, modifying the real parts of the refractive index and thereby adjusting the reflectivity parameter locally to achieve the desired homogeneity
2Manufacturing precision
If electron beam irradiation is applied to correct reflectivity, then the homogeneity of reflectivity distribution is improved, but the structural integrity of the multilayer system may deteriorate
Solution Approach 1:
The electron beam is applied locally only to specific partial surfaces where reflectivity correction is needed, rather than irradiating the entire multilayer system. This localized approach minimizes the total volume of material exposed to high-energy electrons, thereby reducing the risk of widespread structural damage while achieving the desired reflectivity homogeneity
Solution Approach 2:
The patent applies electron beam irradiation with controlled dosage and duration, using just enough energy to achieve the required structural modification for reflectivity correction without excessive irradiation that would cause damage. The irradiation parameters are optimized to achieve partial action sufficient for correction while avoiding excessive action that would compromise structural integrity
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 method allows for precise correction of reflective optical elements, ensuring that the reflectivity remains within 1% of the average, reducing scattered radiation and maintaining optical homogeneity, even in areas of high incident intensity, thus improving the uniformity of illumination in EUV lithography devices.
Implementation Method 1
the multi-layer system is irradiated with electrons on this or these partial surface(s), so that the structure of the multilayer system changes locally and the reflectivity becomes lower
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a method for correcting a reflective optical element for the wavelength range between 5 nm and 20 nm, comprising a multilayer system on a substrate, the multilayer system comprising layers consisting of at least two alternately arranged different materials with a different real component of the refractive index for a wavelength in the extreme ultraviolet wavelength range. Said method comprises the following steps: measuring the reflectivity distribution over the surface of the multilayer system; comparing the measured reflectivity distribution with a nominal distribution of the reflectivity over the surface of the multilayer system and determining at least one partial surface having a measured reflectivity above the nominal reflectivity; and irradiating the at least one partial surface with ions or electrons.