Multiline ArF Excimer Laser Reducing Speckle
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in semiconductor exposure systems is the wide spectral linewidth of KrF and ArF excimer laser beams, which leads to chromatic aberrations and decreased resolution due to oxygen absorption lines, requiring a narrow spectral linewidth that increases temporal coherence and causes speckle issues during laser processing.
Innovation Solution
A wavelength-tunable multiline ArF excimer laser apparatus using multiple semiconductor lasers and optical switches, with a wavelength conversion system that generates a multiline pulsed laser beam with a wide effective spectral linewidth, avoiding oxygen absorption lines to reduce temporal coherence and speckle formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the spectral linewidth of the laser beam is narrowed to avoid chromatic aberrations, then the resolution of the projection lens is improved, but the temporal coherence increases causing speckle issues during laser processing
Solution Approach 1:
The patent segments the laser beam into multiple wavelength components using a diffraction grating, creating a multiline spectrum. This segmentation approach allows the system to achieve a wide effective spectral linewidth (sum of individual linewidths) while each individual component remains narrow enough to avoid chromatic aberrations, thereby resolving the contradiction between resolution and speckle reduction
Solution Approach 2:
The patent combines multiple wavelength components from different semiconductor lasers through optical switching and wavelength conversion. By merging these multiple narrow linewidth components into a single multiline beam, the system achieves an effective wide spectral linewidth that reduces temporal coherence and speckle, while maintaining the resolution benefits of narrow individual components
2Manufacturing precision
If a line narrowing module is provided in the laser resonator to narrow the spectral linewidth, then chromatic aberrations are reduced, but the device complexity increases
Solution Approach 1:
The patent replaces traditional mechanical line narrowing modules (etalons, gratings in resonator) with a semiconductor laser-based wavelength selection system. Multiple semiconductor lasers with different wavelengths are used directly, and optical switching replaces the need for mechanical tuning mechanisms, thereby reducing device complexity while maintaining chromatic aberration control
Solution Approach 2:
The patent changes the fundamental parameter approach from actively narrowing a single wavelength to utilizing multiple discrete wavelengths from the start. By changing the wavelength parameter selection method and using direct wavelength conversion, the system avoids the complexity of line narrowing modules while achieving the desired spectral characteristics
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 solution effectively reduces temporal coherence, allowing for smaller optical elements and improved laser processing by maintaining the spectral linewidth wide enough to avoid oxygen absorption while minimizing speckle issues, enhancing processing precision and efficiency.
Implementation Method 1
a wavelength conversion system configured to convert pulsed beams outputted from the plurality of optical switches in terms of wavelength to generate wavelength-converted beams
Implementation Method 2
an ArF excimer laser amplifier configured to amplify the wavelength-converted beams outputted from the wavelength conversion system
Implementation Method 3
a plurality of optical switches disposed in optical paths of the plurality of respective semiconductor lasers
Data Source
AI summary
A laser apparatus according to an aspect of the present disclosure includes a plurality of semiconductor lasers, a plurality of optical switches disposed in the optical paths of the plurality of respective semiconductor lasers, a wavelength conversion system configured to convert pulsed beams outputted from the plurality of optical switches in terms of wavelength to generate wavelength-converted beams, an ArF excimer laser amplifier configured to amplify the wavelength-converted beams, and a controller configured to control the operations of the plurality of semiconductor lasers and the plurality of optical switches, and the plurality of semiconductor lasers are each configured to output a laser beam so produced that wavelengths of the wavelength-converted beams are wavelengths at which the ArF excimer laser amplifier performs amplification and differ from the optical absorption lines of oxygen.