Optical Material Testing for Lithography
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Solution Overview
Problem
Current methods are unable to quickly and efficiently determine irreversible radiation damage in optical materials, which is crucial for selecting suitable materials for long-term lithographic applications, as existing procedures are time-consuming and only assess short-term, reversible damage.
Innovation Solution
A method involving three tests: irradiating with ultraviolet radiation below 250 nm to measure non-intrinsic fluorescence, high energy density laser light to assess absorption changes, and forming color centers to compare absorption spectra before and after irradiation, which indicates both short-term and long-term radiation damage mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing testing methods are used to determine radiation damage in optical materials, then short-term reversible damage can be assessed, but long-term irreversible radiation damage cannot be determined quickly
Solution Approach 1:
The patent applies preliminary action by pre-irradiating the optical material with high-energy radiation (such as X-rays or gamma rays) to create color centers and simulate long-term radiation damage effects before the actual measurement. This preliminary treatment accelerates the damage process that would normally occur over extended periods of operational use, allowing irreversible damage to be detected in a short testing timeframe rather than waiting for natural degradation during actual device operation.
Solution Approach 2:
The patent employs parameter changes by utilizing high-energy radiation with sufficient energy to create color centers in the optical material. By changing the energy parameter of the irradiation (using high-energy photons instead of normal operational wavelengths), the testing method can induce and detect irreversible structural changes and absorption changes that simulate long-term damage, thereby enabling rapid assessment of long-term stability without requiring prolonged exposure to operational conditions.
2Loss of energy
If optical materials with high transmission are selected for lithographic systems, then absorption and heating are reduced, but irreversible radiation damage accumulates over long-term use
Solution Approach 1:
The patent applies preliminary action by pre-irradiating the optical material with high-energy radiation to create color centers and simulate long-term radiation damage effects before the actual measurement. This preliminary treatment accelerates the damage process that would normally occur over extended periods of operational use, allowing irreversible damage to be detected in a short testing timeframe rather than waiting for natural degradation during actual device operation.
Solution Approach 2:
The patent converts the harmful effect of radiation-induced color center formation into a beneficial testing mechanism. By deliberately creating color centers through high-energy pre-irradiation, the method transforms the normally detrimental long-term accumulation of radiation damage into an immediate, measurable effect that reveals the material's long-term stability characteristics during a short test, thereby turning a reliability concern into a diagnostic advantage.
3Manufacturing precision
If high energy density radiation is used for lithography, then smaller circuit structures can be produced, but absorption and heating of optical materials increase
Solution Approach 1:
The patent employs parameter changes by utilizing high-energy radiation with sufficient energy to create color centers in the optical material. By changing the energy parameter of the irradiation (using high-energy photons instead of normal operational wavelengths), the testing method can induce and detect irreversible structural changes and absorption changes that simulate long-term damage, thereby enabling rapid assessment of long-term stability without requiring prolonged exposure to operational conditions.
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 method allows for the rapid determination of optical materials' suitability for long-term use by identifying irreversible absorption changes, ensuring materials meet predetermined standards for stability and reducing waste and costs in lens system production.
Implementation Method 1
irradiating with ultraviolet radiation below 250 nm to measure non-intrinsic fluorescence
Implementation Method 2
high energy density laser light to assess absorption changes
Implementation Method 3
forming color centers to compare absorption spectra before and after irradiation
Data Source
AI summary
An optical material for lithographic applications is selected from crystal materials by a testing method. The crystal materials are preferably quartz and/or alkali or alkaline earth halides, especially fluorides, or mixed crystals. The testing method includes three tests to measure irreversible radiation damage: 1) the optical material is irradiated with ultraviolet radiation at 193 nm and the non-intrinsic fluorescence intensity at 740 nm is measured; 2) the optical material is irradiated with high energy density laser light and a change in respective absorptions before and after irradiation at 385 nm is measured; and 3) the optical material is irradiated with an X-ray or radioactive source to form all possible color centers and a difference of respective surface integrals of corresponding absorption spectra in ultraviolet spectral and/or visible spectral regions is measured before and after irradiation.