Excimer Laser Spectral Linewidth Control via Gas Pressure
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Solution Overview
Problem
Chromatic aberrations in KrF and ArF excimer laser apparatuses due to wide spectral linewidths lead to decreased resolution in semiconductor exposure, necessitating a solution to narrow the spectral linewidth for improved performance.
Innovation Solution
An excimer laser apparatus with a controller that adjusts gas pressure based on voltage corrections to maintain a target spectral linewidth, using specific functions to control the gas pressure and stage positions within the laser resonator, thereby optimizing the spectral linewidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the spectral linewidth is narrowed to reduce chromatic aberrations, then the resolution is improved, but the device complexity increases due to the need for line narrowing modules and precise gas pressure control
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting gas pressure based on the relationship between gas pressure and spectral linewidth. The controller modifies operating parameters (gas pressure, voltage) to achieve the desired spectral linewidth without adding complex hardware, thereby resolving the contradiction between improving resolution and reducing device complexity
Solution Approach 2:
The patent implements feedback control where the controller receives target spectral linewidth values, calculates required gas pressure adjustments using stored functions, and applies corrected voltage to the power supply. This closed-loop feedback mechanism enables precise spectral linewidth control while avoiding the need for complex mechanical line narrowing modules
2Object-affected harmful factors
If the spectral linewidth is narrowed using a line narrowing module, then the chromatic aberrations are reduced, but the device complexity and control difficulty increase
Solution Approach 1:
The patent extracts the line narrowing function from traditional hardware modules (etalons, gratings) and implements it through gas pressure control. By removing the physical line narrowing module and replacing it with a control system that adjusts gas pressure based on stored functional relationships, the patent eliminates chromatic aberrations while reducing device complexity
Solution Approach 2:
The patent replaces the mechanical/optical line narrowing system with an electrical control system. Instead of using physical components like etalons or gratings to narrow the spectral linewidth, the system uses electrical voltage control to adjust gas pressure, which in turn controls the spectral linewidth. This substitution simplifies the device structure while achieving the same optical effect
3Manufacturing precision
If the gas pressure is controlled to maintain spectral linewidth, then the resolution is improved, but the controllability becomes more difficult without precise voltage correction
Solution Approach 1:
The patent applies preliminary action by pre-storing the functional relationship between voltage and spectral linewidth in the controller's memory. Before actual operation, the system has the characteristic curve or function data ready, allowing the controller to directly calculate the required voltage correction for any target spectral linewidth without real-time measurement or iteration, thereby improving controllability
Solution Approach 2:
The patent implements feedback control where the controller calculates the difference between the current and target spectral linewidth, retrieves the appropriate correction from stored functions, and applies voltage adjustment to the power supply. This feedback mechanism makes the system easy to operate while maintaining precise spectral linewidth control
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 allows for precise control of spectral linewidth, enhancing the resolution and performance of the excimer laser apparatus, reducing unnecessary gas operations and improving controllability.
Implementation Method 1
a chamber configured to accommodate a laser gas and a pair of electrodes and generate pulse-oscillating laser light when gas pressure of the laser gas is controlled in accordance with voltage applied between the pair of electrodes
Data Source
AI summary
An excimer laser apparatus according to the present disclosure includes a chamber configured to accommodate a laser gas and a pair of electrodes and generate pulse-oscillating laser light when the gas pressure of the laser gas is controlled in accordance with voltage applied between the pair of electrodes, a power supply configured to apply the voltage between the pair of electrodes, and a controller to which a target value of the spectral linewidth of the laser light is inputted, the controller configured to correct the voltage used to control the gas pressure, when the target value changes from a first target value to a second target value, based on a first function having the second target value as a parameter and control the gas pressure in accordance with the corrected voltage.