Solid-State Laser Spectral Linewidth Control
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Solution Overview
Problem
Existing laser systems for semiconductor manufacturing struggle to produce laser light with a spectral form that effectively suppresses speckle and chromatic aberration, as they often lack the ability to adjust the spectral linewidth and longitudinal mode spacing to achieve the desired spectral purity for exposure applications.
Innovation Solution
A solid-state laser apparatus and laser system that includes a master oscillator capable of changing its spectral linewidth, an amplifier, a wavelength converter, and a controller to feedback-control the spectral characteristics of the laser light, using a combination of optical elements such as Ti:sapphire crystals, etalons, and nonlinear optical crystals to generate laser light with multiple longitudinal modes and specific spectral properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gas gain medium is used in master oscillator and amplifier, then laser light can be generated and amplified, but the spectral linewidth cannot be adjusted to suppress speckle and chromatic aberration
Solution Approach 1:
The patent changes the gain medium from gas to solid-state (Ti:sapphire crystal), enabling continuous spectral linewidth adjustment from 0.1nm to 10nm. This parameter change in the medium type allows the spectral characteristics to be tuned to suppress speckle and chromatic aberration while maintaining laser generation capability
Solution Approach 2:
The patent introduces dynamic control of spectral linewidth through the solid-state gain medium, allowing the spectral characteristics to be continuously adjusted during operation. The controller dynamically modifies the spectral linewidth based on process requirements, providing adaptability for different exposure conditions while maintaining high spectral purity
2Manufacturing precision
If multiple optical elements are added to control spectral characteristics, then spectral purity is improved, but device complexity increases
Solution Approach 1:
The solid-state gain medium (Ti:sapphire crystal) performs multiple functions simultaneously: it generates laser light, amplifies the signal, and enables spectral linewidth control. This multi-functionality eliminates the need for separate spectral control elements, reducing system complexity while achieving high spectral purity
Solution Approach 2:
The patent combines the gain medium function with the spectral control function into a single solid-state laser apparatus. The Ti:sapphire crystal serves both as the amplification medium and as the element that enables spectral linewidth adjustment, merging what would traditionally be separate components into one integrated system
3Manufacturing precision
If spectral linewidth is narrowed to suppress speckle, then exposure quality improves, but longitudinal mode spacing control becomes more difficult
Solution Approach 1:
The patent changes to a solid-state gain medium with broad emission bandwidth, enabling independent control of spectral linewidth and longitudinal mode spacing. This parameter change in the medium allows simultaneous optimization of both speckle suppression (through linewidth control) and mode spacing adjustment without the constraints of gas medium systems
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 achieves laser light with a spectral form that suppresses speckle and chromatic aberration, improving the throughput and resolving power of semiconductor exposure processes while reducing the complexity and size of the laser system.
Implementation Method 1
a master oscillator configured to output laser light having at least one longitudinal mode
Implementation Method 2
using a combination of optical elements such as Ti:sapphire crystals, etalons
Implementation Method 3
a wavelength converter located downstream of the amplifier on the optical path
Data Source
AI summary
A solid-state laser apparatus may include: a master oscillator configured to output laser light having at least one longitudinal mode, the master oscillator being capable of changing the spectral linewidth of the laser light output therefrom; at least one amplifier located downstream of the master oscillator on an optical path; a wavelength converter located downstream of the amplifier on the optical path; a detector configured to detect the spectrum of the laser light; and a controller configured to control the spectral linewidth of the laser light output from the master oscillator based on a detection result of the detector.