Excimer Laser Pulse Energy Control via Partial Gas Exchange
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Solution Overview
Problem
Excimer laser apparatuses face challenges in maintaining desired pulse laser beam energy over time due to impurity generation in the laser gas, leading to chromatic distortion and reduced resolution, especially in semiconductor exposure applications where precise control of gas composition and pressure is crucial.
Innovation Solution
A method for controlling the laser apparatus involves measuring pulse energy and gas pressure, calculating relationships between pulse energy, charge voltage, and gas composition, and conducting partial gas exchanges to maintain optimal conditions, using a system with a laser chamber, charger, and gas control system to adjust gas composition and pressure dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a line narrow module with line narrowing element is mounted in the laser resonator to narrow the spectrum line width, then chromatic distortion is reduced and resolution is improved, but device complexity increases
Solution Approach 1:
The patent applies partial gas exchange instead of complete gas exchange, exchanging only a portion of the laser gas to remove impurities while maintaining stable operating conditions. This partial action approach achieves the necessary purification effect without the excessive complexity and interruption of complete gas exchange systems
Solution Approach 2:
The patent dynamically adjusts gas pressure parameters during operation to compensate for impurity accumulation. By changing pressure parameters and conducting controlled partial gas exchanges, the system maintains optimal laser beam quality and narrows spectrum line width without requiring complex additional optical elements
2Reliability
If complete gas exchange is conducted to remove impurities, then laser beam quality is improved, but operation time is lost and productivity decreases
Solution Approach 1:
The patent implements partial gas exchange, replacing only a portion of the laser gas rather than performing complete gas exchange. This approach removes sufficient impurities to maintain beam quality while minimizing operation time loss and maintaining higher productivity
Solution Approach 2:
The patent enables continuous or near-continuous operation by performing brief partial gas exchanges instead of long complete gas exchanges. This maintains the continuity of useful laser action while periodically removing impurities to sustain beam quality
3Manufacturing precision
If gas pressure and composition are tightly controlled to maintain pulse energy, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent implements a control system that automatically monitors pulse energy and triggers partial gas exchanges based on measured energy degradation. This self-service approach maintains precise pulse energy control without requiring complex continuous manual adjustment of gas pressure and composition
Solution Approach 2:
The patent uses feedback from pulse energy measurements to control gas exchange timing and amount. The system measures pulse energy, compares it to reference values, and automatically initiates partial gas exchanges when degradation is detected, maintaining precision while simplifying overall 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 stable and precise control of pulse energy, reducing impurity effects and maintaining desired energy levels, even during extended operation, thereby enhancing the resolution and reliability of the excimer laser apparatus.
Implementation Method 1
a charger (12) configured to apply a charge voltage for generating discharge in the laser chamber (10)
Implementation Method 2
laser oscillation to output a pulse laser beam by exciting the laser gas
Data Source
AI summary
A method of controlling a laser apparatus may include: exchanging a gain medium in a chamber configured to output a laser beam by exciting the gain medium; first measuring, after the exchanging, pulse energy of a laser beam which is oscillated in the chamber under a specific gas pressure and a specific charge voltage; calculating an approximate expression indicating a relationship between the pulse energy of the laser beam and the gas pressure in the chamber and the charge voltage, or a table representing a correlationship between the pulse energy, the gas pressure and the charge voltage, based on the specific pressure, the specific charge voltage and the pulse energy in the first measuring; storing the approximate expression or the table; second measuring, after the first measuring, pulse energy Er of a laser beam oscillated in the chamber; calculating pulse energy Eec which is supposed to be obtained directly after the exchanging under the gas pressure and the charge voltage in the second measuring based on the approximate expression or the table; calculating a reduction amount ΔEd of pulse energy based on the pulse energy Eec and the pulse energy Er using ΔEd=Eec−Er; and calculating a partial gas exchange amount Q for partial gas exchange in the chamber based on the reduction amount ΔEd of pulse energy.