Excimer Laser Spectral Line Width Calibration
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Solution Overview
Problem
In semiconductor exposure apparatuses, the wide spontaneous oscillation width of KrF and ArF excimer lasers leads to chromatic aberration and decreased resolving power due to the spectral line width of the laser beams, which is challenging to address with existing line narrow modules.
Innovation Solution
An excimer laser apparatus equipped with an etalon spectrometer and a controller that measures the fringe waveform of the laser beam, calculates the spectral line width using a first ratio in the spectral space, and calibrates it based on a correlation function with a reference meter, allowing for improved spectral line width control without the need for time-consuming deconvolution processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a line narrow module including a line narrow element is provided in a laser resonator to narrow the spectral line width, then chromatic aberration is reduced and resolving power is improved, but measurement and control of the spectral line width becomes time-consuming due to deconvolution processing
Solution Approach 1:
The patent extracts only the essential measurement information (spectral line width) from the fringe waveform without performing full deconvolution processing. By calculating the area of the first ratio in the spectral space directly from the measured fringe waveform, the system obtains the spectral line width measurement while eliminating time-consuming deconvolution steps, thus resolving the contradiction between measurement accuracy and measurement time
Solution Approach 2:
The patent performs preliminary calibration by storing a correlation function between the area of the first ratio and the spectral line width measured by a reference meter before actual measurements. This preliminary action allows the system to use the pre-established correlation for rapid measurements without repeating the full calibration process, significantly reducing measurement time while maintaining accuracy
2Measurement precision
If deconvolution processing is performed to obtain accurate spectral line width from fringe waveform measurement, then measurement accuracy is improved, but processing time increases
Solution Approach 1:
The patent extracts the spectral line width information directly from the area of the first ratio in the spectral space without performing full deconvolution. By using the correlation function that relates the area ratio to the spectral line width, the system achieves accurate measurements while avoiding the time-consuming deconvolution process
Solution Approach 2:
The patent creates a simplified measurement model by establishing a correlation function that copies the relationship between the area of the first ratio and the spectral line width from reference measurements. This copied relationship allows rapid measurements without repeating the complex deconvolution process, maintaining accuracy while reducing time
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 enhances the speed and stability of spectral line width measurement and control, maintaining accurate measurement while reducing processing time, thereby improving the resolving power of the laser apparatus.
Implementation Method 1
an etalon spectrometer configured to measure a fringe waveform of the laser beam
Data Source
AI summary
An excimer laser apparatus according to the present disclosure includes an etalon spectrometer configured to measure a fringe waveform of a laser beam; and a controller configured to obtain area of a first ratio in a spectral space obtained based on a result of the measurement by the etalon spectrometer, calculate a first spectral line width of the laser beam based on the obtained area of the first ratio, and calibrate a first spectral line width based on a correlation function representing correlation between the first spectral line width and a second spectral line width of the laser beam measured by a reference meter.