Narrowband Laser Spectral Linewidth Control
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Solution Overview
Problem
Current semiconductor exposure technologies face challenges in achieving narrow spectral linewidths for KrF and ArF excimer lasers, leading to color aberrations in reduced-size laser beams, which degrade resolution in semiconductor exposure apparatuses.
Innovation Solution
A narrowband laser apparatus comprising a laser resonator with optical elements for spectral linewidth narrowing, a spectrometer for detecting spectral intensity distributions, a spectral waveform producer, a device function storage, a wavelength frequency function generator, and a deconvolution processor to correct spectral waveforms and calculate accurate spectral linewidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If natural oscillation of KrF and ArF excimer laser apparatuses is used, then the laser beam can be generated, but the spectral linewidth becomes wide (350-400 pm) causing color aberration and degraded resolution
Solution Approach 1:
A line narrowing module (LNM) with a line narrowing element is introduced as an intermediary component within the laser resonator. This module acts as a mediator that selectively transmits specific wavelengths while blocking others, thereby narrowing the spectral linewidth of the laser beam without requiring changes to the fundamental laser oscillation mechanism.
Solution Approach 2:
The spectral linewidth parameter is actively changed from its natural wide state (350-400 pm) to a narrowed state through the line narrowing module. By adjusting the parameters of the line narrowing element (such as etalon thickness or grating angle), the spectral linewidth can be precisely controlled to minimize color aberration while maintaining laser performance.
2Manufacturing precision
If a line narrowing module is added to narrow the spectral linewidth, then color aberration is reduced, but the device complexity increases
Solution Approach 1:
The line narrowing module is designed to perform multiple functions within a single integrated component. The line narrowing element not only narrows the spectral linewidth but also maintains laser oscillation stability and can be adjusted to target different wavelength ranges, making it a multi-functional component that reduces the need for additional separate systems.
3Measurement precision
If spectral intensity distributions of multiple pulses are measured and processed through deconvolution, then accurate spectral linewidth can be obtained, but the measurement and processing complexity increases
Solution Approach 1:
The device function of the spectrometer is pre-measured and stored before actual spectral measurements. This preliminary characterization of the spectrometer's response function allows the deconvolution process to efficiently correct for instrumental broadening without requiring real-time complex calculations, thereby reducing measurement system complexity while maintaining high precision.
Solution Approach 2:
Instead of directly measuring the true spectral linewidth, the system measures the convolved spectrum (copy of the true spectrum distorted by the spectrometer's device function) and then mathematically reconstructs the original spectrum through deconvolution. This copying and reconstruction approach allows accurate retrieval of the true spectral linewidth while using standard, readily available spectrometer hardware.
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 narrows the spectral linewidth, reducing color aberrations and improving the resolution of semiconductor exposure apparatuses by accurately measuring and controlling the spectral characteristics of the laser beams.
Implementation Method 1
The laser resonator may include optical elements for narrowing a spectral linewidth
Implementation Method 2
The spectrometer may be configured to detect spectral intensity distributions of multiple pulses included in a pulsed laser beam
Implementation Method 3
The deconvolution processor may be configured to perform deconvolution processing on the spectral waveform with the device function and the wavelength frequency function
Data Source
AI summary
A narrowband laser apparatus may be provided with a laser resonator including optical elements for narrowing a spectral linewidth, a spectrometer configured to detect spectral intensity distributions of multiple pulses included in a pulsed laser beam output from the laser resonator, a spectral waveform producer configured to produce a spectral waveform by adding up the spectral intensity distributions of the multiple pulses, a device function storage configured to store a device function of the spectrometer, a wavelength frequency function generator configured to generate a wavelength frequency function which represents a frequency distribution of center wavelengths of the multiple pulses, and a deconvolution processor configured to perform deconvolution processing on the spectral waveform with the device function and the wavelength frequency function.