Laser Device Burst Oscillation Voltage Control
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Solution Overview
Problem
Current semiconductor exposure systems face challenges with chromatic aberration due to the large spectral line width of KrF and ArF excimer laser devices, which affects resolution and requires line narrowing modules, leading to unstable pulse energy output during burst oscillation.
Innovation Solution
A laser device configured to output pulse laser light through multiple burst oscillations with adjustable voltage settings based on stored values and offset calculations, using a data table and offset values to maintain stable pulse energy by adjusting application voltages during burst oscillations.
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 and resolution is improved, but the pulse energy becomes unstable during burst oscillation
Solution Approach 1:
The patent applies dynamics by making the application voltage adjustable and variable during burst oscillation. The control unit dynamically changes the voltage applied to the electrodes based on the pulse number, allowing the laser device to adapt its operating conditions during operation. This dynamic voltage adjustment stabilizes pulse energy while maintaining the line narrowing effect for high resolution.
Solution Approach 2:
The patent changes the electrical parameter (application voltage) to control and stabilize pulse energy. By varying the voltage applied to the electrodes during burst oscillation based on pulse number, the system maintains consistent pulse energy output. This parameter change approach allows simultaneous achievement of stable pulse energy and high resolution through the line narrowing module.
2Manufacturing precision
If the spectral line width is narrowed using a line narrowing element, then chromatic aberration can be ignored, but the device complexity increases due to additional components
Solution Approach 1:
The patent uses a line narrowing module that provides sufficient line narrowing capability to make chromatic aberration negligible, without over-engineering the system. The voltage adjustment mechanism is applied partially during burst oscillation (based on pulse number ranges) rather than continuously, achieving the necessary chromatic aberration control with moderate complexity.
3Ease of operation
If a constant voltage command value is used during burst oscillation, then the control is simple, but the pulse energy fluctuates and becomes unstable
Solution Approach 1:
The patent segments the burst oscillation into different pulse number ranges (first range: 1 to i-1, second range: i to j). Different voltage control strategies are applied to each segment: a first voltage command value for the initial pulses and a second voltage command value for subsequent pulses. This segmentation allows stable pulse energy while maintaining relatively simple control through discrete voltage levels.
Solution Approach 2:
The control unit is pre-programmed with the knowledge that pulse energy tends to be higher in the initial pulses of burst oscillation. Therefore, it preliminarily applies a lower voltage command value for pulses 1 to i-1, and then switches to a higher voltage command value for pulses i to j. This preliminary voltage adjustment compensates for the natural pulse energy variation and achieves 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
The solution stabilizes pulse energy output and reduces chromatic aberration, enhancing the resolution and performance of semiconductor exposure systems by finely controlling application voltages and offset values.
Implementation Method 1
a power source configured to apply a voltage to the electrodes
Implementation Method 2
output pulse laser light by performing plural times of burst oscillation
Data Source
AI summary
A laser device may include a laser resonator; a chamber arranged on an optical path of the laser resonator; a pair of electrodes arranged in the chamber; a power source applying a voltage to the electrodes; a storage unit storing a voltage value; and a control unit configured to set an application voltage value of the voltage applied to the electrodes as setting the application voltage value for outputting a pulse whose pulse number is equal to or larger than 1 and smaller than i based on the voltage command value and the voltage value stored in the storage unit, and setting the application voltage for outputting a pulse whose pulse number is equal to or larger than i and smaller than j based on the voltage command value and an offset value corresponding to the voltage command value, where i>1 and j>i.