Master Oscillator Timing in Excimer Lasers for Stable Linewidth
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Solution Overview
Problem
Chromatic aberration occurs in semiconductor exposure apparatuses due to the large spectral line width of KrF and ArF excimer laser devices, leading to decreased resolution, which is not adequately addressed by existing line narrowing modules.
Innovation Solution
A laser device with a master oscillator and power oscillator configuration, controlled by a processor to adjust discharge timings and delay times to stabilize spectral line width and pulse energy during changes in repetition frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a line narrowing module is provided in the laser resonator to narrow the spectral line width, then chromatic aberration is reduced, but the device complexity increases
Solution Approach 1:
The patent extracts the line narrowing function from a separate optical module and integrates it directly into the resonator structure by forming a distributed feedback mechanism using grating structures written directly into the laser medium or gain guide. This eliminates the need for separate etalons or gratings, thereby narrowing spectral line width while reducing device complexity.
Solution Approach 2:
The patent merges the laser gain medium and the wavelength selection function into a single integrated structure. The grating pattern is written directly into the laser medium, combining the amplification and spectral filtering functions in one component, which simplifies the overall device architecture while achieving narrow spectral line width.
2Adaptability or versatility
If the repetition frequency is changed to adjust exposure conditions, then adaptability is improved, but the spectral line width and pulse energy stability deteriorate
Solution Approach 1:
The patent implements dynamic control of the delay time between master oscillator and power oscillator discharges based on the repetition frequency. The control unit adjusts the delay time dynamically according to the selected repetition frequency, ensuring that spectral line width and pulse energy remain stable across different operating conditions while maintaining frequency adaptability.
Solution Approach 2:
The patent employs a control unit that monitors the repetition frequency and automatically adjusts the delay time parameter to maintain optimal spectral line width and pulse energy. This feedback mechanism ensures stability of laser characteristics when adaptability requirements demand frequency changes.
3Stability of the object's composition
If the delay time between master oscillator and power oscillator is adjusted to optimize pulse energy, then energy stability is improved, but the control complexity increases
Solution Approach 1:
The patent implements self-service control where the control unit automatically determines and adjusts the delay time based on the repetition frequency without requiring manual intervention. The system stores predetermined delay time values for different repetition frequencies and automatically selects the appropriate value, simplifying operation while maintaining pulse energy stability.
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
Stabilizes spectral line width and pulse energy, preventing deviations from target ranges and improving energy and dose stability during frequency changes.
Implementation Method 1
a master oscillator configured to output pulse laser light at a first discharge timing synchronized with a repetition frequency
Implementation Method 2
an amplifier configured to amplify the pulse laser light by exciting, at a second discharge timing, a laser medium through which the pulse laser light passes
Data Source
AI summary
A laser device includes a master oscillator outputting pulse laser light at a first discharge timing synchronized with a repetition frequency; an amplifier amplifying the pulse laser light by exciting, at a second discharge timing, a laser medium through which the pulse laser light passes; and a processor setting the second discharge timing by adding a delay time to the first discharge timing, holding a first value as a command value of the delay time corresponding to a first repetition frequency, holding a second value as the command value of the delay time corresponding to a second repetition frequency, and outputting the command value of the second value after outputting the command value of a third value between the first value and the second value when the repetition frequency is changed from the first repetition frequency to the second repetition frequency after outputting the command value of the first value.