Pulse Laser Linewidth Control for Chromatic Aberration Reduction
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Solution Overview
Problem
The narrow spectral linewidth of laser light output from gas laser apparatuses used in semiconductor exposure leads to chromatic aberrations in projection lenses, reducing resolution, and the existing mechanisms to widen the linewidth can cause stimulated Brillouin scattering and damage to optical components, while maintaining optimal phase matching conditions across multiple nonlinear crystals is challenging.
Innovation Solution
A laser system comprising a first laser, optical intensity changer, modulator, optical fiber amplifier, center-wavelength-variable second laser, optical parametric amplifier, and wavelength converter with multiple nonlinear crystals, controlled by a processor to generate pulse laser light with a target spectral linewidth and center wavelength, using optical frequency and intensity modulation to widen the linewidth and adjust phase matching conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the spectral linewidth of laser light is narrowed to reduce chromatic aberrations, then the resolution is improved, but the projection lens still produces chromatic aberrations due to the wide spectral linewidth of gas laser apparatuses
Solution Approach 1:
The patent applies parameter changes by using a modulator to dynamically adjust the spectral linewidth of the laser light. Instead of relying on fixed narrow-linewidth gas lasers, the system takes broadband laser light and actively modulates it to achieve the desired narrow spectral linewidth, thereby reducing chromatic aberrations while maintaining resolution.
Solution Approach 2:
The patent introduces a modulator as an intermediary device between the laser source and the projection lens. This modulator acts as a mediator that shapes the spectral characteristics of the light, enabling precise control over the spectral linewidth to minimize chromatic aberrations without requiring specialized narrow-linewidth laser sources.
2Object-generated harmful factors
If mechanisms are introduced to widen the spectral linewidth, then chromatic aberrations are reduced, but stimulated Brillouin scattering occurs and optical components may be damaged
Solution Approach 1:
The patent employs dynamic control of the spectral linewidth through modulation techniques. Rather than using fixed broadband light sources that risk optical damage, the system dynamically adjusts the spectral characteristics in real-time, allowing the linewidth to be optimized for each exposure condition while maintaining safety margins against optical component damage.
Solution Approach 2:
The modulation process inherently involves periodic action, where the spectral linewidth is periodically adjusted according to the exposure requirements. This periodic modulation allows the system to achieve broadband characteristics only when necessary, minimizing the risk of optical damage while still effectively reducing chromatic aberrations during exposure.
3Use of energy by moving object
If multiple nonlinear crystals are used for wavelength conversion, then the desired wavelength is achieved, but maintaining optimal phase matching conditions across all crystals becomes challenging
Solution Approach 1:
The patent divides the wavelength conversion process into multiple stages, each handled by a separate nonlinear crystal. This segmentation allows each crystal to be independently optimized for its specific conversion task, simplifying the phase matching requirements for each individual crystal while achieving the overall desired wavelength through the cascade of conversions.
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 system effectively generates pulse laser light with controlled spectral linewidth and center wavelength, reducing chromatic aberrations and preventing damage, enabling high-resolution semiconductor manufacturing.
Implementation Method 1
a modulator configured to widen a spectral linewidth of the first laser light or the first pulse laser light in accordance with a modulation signal
Implementation Method 2
the first nonlinear crystal outputting first harmonic light
Implementation Method 3
the second nonlinear crystal outputting second harmonic light
Implementation Method 4
the third nonlinear crystal outputting first sum-frequency light and the third pulse laser light
Implementation Method 5
the fourth nonlinear crystal outputting fourth pulse laser light that is second sum-frequency light
Implementation Method 6
an optical fiber amplifier configured to amplify the first pulse laser light and output second pulse laser light
Implementation Method 7
an optical parametric amplifier configured to pulse and amplify the second laser light and output third pulse laser light
Data Source
AI summary
A laser system includes a first laser outputting first laser light, an optical intensity changer outputting first pulse laser light, a modulator widening spectral linewidth of the first laser light or the first pulse laser light, an optical fiber amplifier amplifying the first pulse laser light and outputting second pulse laser light, a second laser outputting second laser light, an optical parametric amplifier amplifying the second laser light and outputting third pulse laser light, a wavelength converter outputting fourth pulse laser light using the second and third pulse laser light, an amplification section amplifying the fourth pulse laser light and outputting fifth pulse laser light, and a processor controlling a modulation signal such that the fifth pulse laser light having target spectral linewidth is generated, and controlling the center wavelength of the second laser light such that the fifth pulse laser light having a target center wavelength is generated.