EUV Optical Elements with Nanoscale Features
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Solution Overview
Problem
Current EUV lithography systems face inefficiencies due to high absorption and scattering of EUV radiation by materials used in optical elements, leading to the need for high-power light sources and susceptibility to thermal damage, with limited reflectivity and short lifetimes.
Innovation Solution
The development of optical elements with integrated nanoscale features that enhance reflectivity beyond bulk materials, using materials like Molybdenum and Ruthenium, and fabrication techniques such as atomic layer deposition to achieve reflectivities greater than 70% at EUV wavelengths, reducing absorption and scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional EUV optical elements are used, then the lithography system can operate, but the reflectivity is limited to around 67% and absorption is high
Solution Approach 1:
The patent changes the physical parameters of the optical element surface by introducing nanoscale features (ripples, gratings, or textured patterns) with specific dimensions (e.g., 1-100 nm period) and geometries. These parameter changes modify the optical interaction at the nanoscale, enabling enhanced reflectivity through plasmonic resonances or photonic crystal effects while reducing absorption losses in the bulk material.
Solution Approach 2:
The patent creates composite optical elements combining conventional bulk materials (like Mo/Si multilayers) with nanoscale surface structures. This composite approach integrates the bulk material's inherent EUV reflectivity with the nanoscale features' ability to trap and resonate EUV photons, achieving synergistic effects that improve overall reflectivity beyond what either component could achieve alone.
2Illumination intensity
If high power EUV light sources are used to compensate for absorption, then sufficient light reaches the wafer, but the optical components suffer thermal damage and have limited lifetime
Solution Approach 1:
The patent converts the harmful effect of high light intensity (which causes thermal damage) into a benefit by using nanoscale features to enhance reflectivity. This reduces the amount of light absorbed as heat, allowing high illumination intensity at the wafer while keeping optical component temperatures manageable through improved optical efficiency.
3Measurement precision
If more mirrors are added to the scanner tool to manage and focus light, then the desired resolution is achieved, but less than 1% of light energy is transferred through the system
Solution Approach 1:
The patent applies nanoscale surface feature parameters (period, amplitude, geometry) to mirror surfaces to enhance their reflectivity specifically at EUV wavelengths. This parameter optimization allows each mirror in the multi-mirror system to reflect more light, compensating for the cumulative losses across 12 or more interfaces and improving overall energy transmission while maintaining the necessary focusing capability for sub-20 nm resolution.
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 increases the efficiency of EUV lithography systems by allowing the use of lower power light sources, reducing thermal issues, and extending the lifetime of optical components, while improving reflectivity and transmission efficiency.
Implementation Method 1
The plurality of structural features can increase the reflectivity of the material to greater than 70% for a wavelength between 0.1 nanometer and 250 nanometer
Implementation Method 2
Most materials tend to absorb EUV radiation, consequently there are limited selection of materials available for optical elements used in photolithography systems
Data Source
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AI summary
Nanostructured photonic materials, and associated components for use in devices and systems operating at ultraviolet (UV), extreme ultraviolet (EUV), and/or soft Xray wavelengths are described. Such a material may be fabricated with nanoscale features tailored for a selected wavelength range, such as at particular UV, EUV, or soft Xray wavelengths or wavelength ranges. Such a material may be used to make components such as mirrors, lenses or other optics, panels, lightsources, masks, photoresists, or other components for use in applications such as lithography, wafer patterning, astronomical and space applications, biomedical applications, biotech or other applications.