Pulse Laser Wavelength Switching for Precise Spectral Linewidth Measurement
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Solution Overview
Problem
The challenge is to maintain the resolution of semiconductor exposure apparatuses as they miniaturize, where the wide spectral linewidth of KrF and ArF excimer laser light causes chromatic aberrations in projection lenses, leading to decreased resolution, and existing solutions like line narrowing modules may not accurately measure spectral linewidths when the target wavelength changes periodically.
Innovation Solution
A laser apparatus with a wavelength adjuster, spectrum monitor, and processor that adjusts the center wavelength periodically between multiple values, allowing for the calculation of spectral linewidths from data on spectra of pulses with different target wavelengths, enabling accurate measurement and control of spectral linewidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the spectral linewidth is narrowed using a line narrowing module, then chromatic aberrations are reduced, but measurement precision deteriorates when target wavelength changes periodically
Solution Approach 1:
The patent applies periodic action by periodically changing the target wavelength to multiple values (including first and second wavelengths) and performing spectral linewidth calculations at each wavelength point. This periodic wavelength modulation enables accurate measurement of spectral linewidth characteristics that would otherwise be difficult to obtain when the wavelength is fixed, thereby resolving the measurement precision issue while maintaining the chromatic aberration reduction benefit
Solution Approach 2:
The patent changes the wavelength parameter periodically to multiple values and calculates spectral linewidth at each wavelength point. This parameter change approach allows the system to accurately capture spectral characteristics across different wavelengths, solving the measurement precision problem without compromising the chromatic aberration reduction achieved through line narrowing
2Measurement precision
If the center wavelength is adjusted to multiple values, then spectral linewidth measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The processor is designed to perform multiple functions: it controls the wavelength adjuster to change the center wavelength, generates the periodic wavelength modulation, acquires spectral data at multiple wavelength points, and calculates spectral linewidth at each point. This multi-functionality approach improves measurement accuracy without requiring separate dedicated devices for each function, thereby managing device complexity
Solution Approach 2:
The patent merges the wavelength control function and the spectral measurement function into an integrated system where the processor simultaneously manages wavelength adjustment and spectral linewidth calculation. This combination approach achieves accurate spectral linewidth measurement across multiple wavelengths while avoiding the complexity of having separate independent 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
This approach effectively maintains resolution by accurately calculating and controlling spectral linewidths, even when the target wavelength changes, thereby reducing chromatic aberrations and improving the performance of semiconductor exposure apparatuses.
Implementation Method 1
a laser oscillator including a wavelength adjuster and configured to output pulse laser light having a center wavelength adjusted by the wavelength adjuster
Implementation Method 2
a spectrum monitor configured to generate data on a spectrum of the pulse laser light
Data Source
AI summary
A laser apparatus includes: a laser oscillator including a wavelength adjuster and configured to output pulse laser light having a center wavelength adjusted by the wavelength adjuster; a spectrum monitor configured to generate data on a spectrum of the pulse laser light; and a processor configured to control the wavelength adjuster in such a way that the center wavelength of the pulse laser light changes in accordance with a target wavelength that periodically changes to each of multiple values including first and second wavelengths, calculate a first spectral linewidth from data on spectra of multiple pulses each having the first wavelength as the target wavelength, and calculate a second spectral linewidth from data on spectra of multiple pulses each having the second wavelength as the target wavelength.