Excimer Laser Timing Control for Stable Pulse Energy Switching
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Solution Overview
Problem
Chromatic aberration in semiconductor exposure apparatuses due to the large spectral line width of KrF and ArF excimer laser devices leads to decreased resolution, necessitating a line narrowing module, but existing control methods result in unstable pulse energy when repetition frequency is switched.
Innovation Solution
A laser device with a master oscillator and power oscillator, controlled by a processor to adjust delay time and charge voltage based on repetition frequency changes, using correction coefficients to stabilize spectral line width and pulse energy.
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 control stability becomes poor when repetition frequency is switched
Solution Approach 1:
The patent applies dynamics by making the delay time adjustable and adaptive based on repetition frequency. The control unit dynamically changes the delay time between master oscillator discharge and power oscillator charge according to the selected repetition frequency, enabling the system to adapt to different operating conditions and maintain stable pulse energy across frequency switches.
Solution Approach 2:
The patent changes the delay time parameter in response to repetition frequency changes. By pre-storing delay time values corresponding to different repetition frequencies and selecting the appropriate delay time based on the current operating frequency, the system maintains optimal performance and control stability across different operating modes.
2Ease of operation
If the delay time is fixed between master oscillator discharge and power oscillator charge, then the system is simple to control, but the pulse energy becomes unstable when repetition frequency changes
Solution Approach 1:
The control unit dynamically adjusts the delay time based on the repetition frequency. When the repetition frequency changes, the control unit selects a corresponding delay time from pre-stored values, enabling the system to maintain stable pulse energy without requiring complex real-time calculations or manual adjustments.
Solution Approach 2:
The patent implements preliminary action by pre-storing the relationship between repetition frequencies and corresponding delay times in the control unit. This allows the system to quickly switch between operating modes by simply selecting from pre-calculated values, avoiding the need for complex real-time optimization while maintaining stability.
3Productivity
If the repetition frequency is increased to improve productivity, then the exposure speed increases, but the spectral line width becomes unstable leading to chromatic aberration
Solution Approach 1:
The system dynamically adjusts the delay time parameter in response to changes in repetition frequency. When operating at higher repetition frequencies for improved productivity, the control unit automatically selects the corresponding optimized delay time, maintaining spectral line width stability and preventing chromatic aberration even at high speeds.
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, maintaining control stability even with frequency changes, thereby enhancing resolution and reducing chromatic aberration.
Implementation Method 1
a master oscillator configured to output pulse laser light
Implementation Method 2
by exciting, with a charge voltage, a laser medium
Implementation Method 3
an amplifier configured to amplify the pulse laser light by exciting, with a charge voltage, a laser medium through which the pulse laser light passes
Data Source
AI summary
A laser device includes a master oscillator configured to output pulse laser light at a first discharge timing synchronized with a repetition frequency; an amplifier configured to amplify the pulse laser light by exciting, with a charge voltage at a second discharge timing, a laser medium through which the pulse laser light passes; and a processor configured to provide a command on the charge voltage to the amplifier based on a charge voltage command value provided from an exposure apparatus, set the second discharge timing by adding a delay time to the first discharge timing, and perform a process of changing the delay time and a process of correcting the charge voltage command value in accordance with a change of the repetition frequency.