Laser System Top Hat Beam Conversion for Window Durability
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Solution Overview
Problem
Current semiconductor exposure systems face challenges with chromatic aberration due to the wide spectrum line width of KrF and ArF excimer laser apparatuses, leading to decreased resolving power, which is exacerbated by the degradation of windows due to high energy density Gaussian light intensity distributions.
Innovation Solution
A laser system that converts the Gaussian light intensity distribution of a pulse laser beam into a top hat shape using a conversion optical system, comprising axicon lenses or aspherical lenses, to reduce energy density and enhance durability, and incorporates expansion and contraction optical systems to improve conversion efficiency and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a Gaussian light intensity distribution is used in the laser beam, then the laser beam can be easily generated, but the energy density becomes concentrated causing window degradation and reduced durability
Solution Approach 1:
The patent changes the light intensity distribution parameter from Gaussian to top hat shape using a conversion optical system. This transformation redistributes the energy uniformly across the beam cross-section, preventing concentration at the center and thereby reducing window degradation while maintaining laser generation feasibility
Solution Approach 2:
The patent converts the harmful concentrated energy distribution into a beneficial uniform distribution. By using the conversion optical system to transform the Gaussian profile into a top hat profile, the previously harmful energy concentration that caused window degradation is converted into a uniform energy distribution that protects the windows while still delivering effective laser energy
2Adaptability or versatility
If a wide spectrum line width is used in the excimer laser apparatus, then the laser can be generated at required wavelengths, but chromatic aberration occurs leading to decreased resolving power
Solution Approach 1:
The patent changes the spectral parameter by introducing a line narrowing module with a grating into the laser resonator. This module selectively transmits a narrow wavelength band while blocking other wavelengths, thereby narrowing the spectrum line width and reducing chromatic aberration without preventing laser generation at the required wavelengths
3Manufacturing precision
If a line narrowing module is added to narrow the spectrum line width, then chromatic aberration is reduced, but the device complexity increases
Solution Approach 1:
The patent integrates the line narrowing function into the existing laser resonator structure by positioning a grating within the resonator. This allows the same optical component to serve both as a resonator element and a wavelength-selective element, achieving chromatic aberration control without proportionally increasing device complexity
4Manufacturing precision
If expansion and contraction optical systems are added to improve conversion efficiency, then the light intensity distribution conversion accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent divides the optical conversion function into separate expansion and contraction optical systems. The expansion system prepares the beam for optimal conversion, while the contraction system delivers the final transformed beam. This segmentation allows each subsystem to be optimized independently for its specific function, improving overall conversion accuracy
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 conversion of light intensity distribution to a top hat shape decreases window degradation, improves durability, and enhances the resolving power of the semiconductor exposure system by maintaining uniform energy distribution, thereby improving the overall performance of the laser system.
Implementation Method 1
a conversion optical system configured to convert the light intensity distribution of the pulse laser beam output from the amplifier into a top hat shape
Implementation Method 2
an amplifier including a pair of discharge electrodes and configured to amplify the pulse laser beam in a discharge space between the pair of discharge electrodes
Data Source
AI summary
A laser system includes: A. a solid-state laser apparatus configured to output a pulse laser beam having light intensity distribution in a Gaussian shape that is rotationally symmetric about an optical path axis; B. an amplifier including a pair of discharge electrodes and configured to amplify the pulse laser beam in a discharge space between the pair of discharge electrodes; and C. a conversion optical system configured to convert the light intensity distribution of the pulse laser beam output from the amplifier into a top hat shape in each of a discharge direction of the pair of discharge electrodes and a direction orthogonal to the discharge direction.