Excimer Laser Spectral Control Using Multiline Seed Lasers
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Solution Overview
Problem
Current semiconductor exposure technologies face challenges in achieving precise control over the spectral line width and center wavelength of excimer laser beams, which are crucial for high-resolution imaging, due to limitations in semiconductor laser oscillation modes and the occurrence of stimulated Brillouin scattering (SBS) in fiber amplifiers.
Innovation Solution
A laser system comprising multiple semiconductor lasers operating in single longitudinal modes, with a beam combiner and spectrum monitor, allows for precise control of the spectral line width and center wavelength of the excimer laser beam by adjusting the oscillation wavelengths and light intensities of individual semiconductor lasers, thereby suppressing SBS and achieving target spectral characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single semiconductor laser operating in single longitudinal mode is used, then the spectral line width is narrow, but stimulated Brillouin scattering (SBS) occurs in fiber amplifiers limiting pulse energy increase
Solution Approach 1:
The invention divides a single laser source into multiple semiconductor lasers (e.g., three lasers) operating at different wavelengths. Each laser operates in single longitudinal mode to maintain narrow spectral width, while the combined multi-line spectrum suppresses SBS in fiber amplifiers. The beam combiner merges these separate laser beams into a single composite beam with multiple spectral lines.
2Reliability
If multiple semiconductor lasers with different wavelengths are combined, then SBS is suppressed, but precise control of spectral line width and center wavelength becomes difficult
Solution Approach 1:
The invention incorporates a spectrum monitor that measures the actual spectral characteristics of the combined laser beam. This spectral information is fed back to the control unit, which adjusts the oscillation wavelengths and light intensities of individual semiconductor lasers to achieve the target spectral line width and center wavelength. This closed-loop feedback system enables precise spectral control despite using multiple lasers.
3Power
If conventional excimer laser systems are used, then high pulse energy is achieved, but chromatic aberration reduces resolution due to large spectral line width
Solution Approach 1:
The invention fundamentally changes the spectral parameter of the laser system by using multiple discrete wavelength lines instead of a broad continuous spectrum. Each semiconductor laser operates in single longitudinal mode with narrow spectral width, and their combination maintains a narrow overall spectral width while providing sufficient pulse energy. This parameter change eliminates chromatic aberration and improves resolution.
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 approach enables accurate control of the excimer laser beam's spectral properties, enhancing the resolution and reliability of semiconductor exposure processes while minimizing SBS, thus improving the precision and efficiency of semiconductor manufacturing.
Implementation Method 1
a plurality of first semiconductor lasers configured to perform continuous wave oscillation in a single longitudinal mode with different wavelengths
Implementation Method 2
a first beam combiner configured to combine laser beams output from the first semiconductor lasers and output a laser beam having a first multiline spectrum including a plurality of peak wavelengths
Implementation Method 3
a first semiconductor optical amplifier configured to pulse-amplify a laser beam output from the first multiple semiconductor laser system
Implementation Method 4
a first fiber amplifier including a first optical fiber configured to amplify the pulse laser beam output from the first semiconductor optical amplifier
Implementation Method 5
a wavelength conversion system configured to wavelength-convert the first pulse laser beam output from the first solid-state laser device
Implementation Method 6
an excimer amplifier configured to amplify a second pulse laser beam wavelength-converted by the wavelength conversion system
Implementation Method 7
a first spectrum monitor configured to receive part of the continuous wave laser beams output from the first semiconductor lasers and measure a wavelength and light intensity of each of the laser beams output from the first semiconductor lasers
Data Source
AI summary
A laser system according to one aspect of the present disclosure includes a first solid-state laser device, a wavelength conversion system, an excimer amplifier, and a control unit. The first solid-state laser device includes a first multiple semiconductor laser system, a first semiconductor optical amplifier, and a first fiber amplifier. The first multiple semiconductor laser system includes a plurality of first semiconductor lasers configured to perform continuous wave oscillation in a single longitudinal mode with different wavelengths, a first spectrum monitor, and a first beam combiner. The control unit controls an oscillation wavelength and light intensity of each line of a first multiline spectrum generated by the first semiconductor lasers to obtain an excimer laser beam having at least a target center wavelength or a target spectral line width instructed by an external device.