Narrow Band Excimer Laser Line Narrowing Module
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Solution Overview
Problem
Current semiconductor exposure apparatuses face challenges in achieving high resolving power due to chromatic aberration caused by the wide spectral linewidth of KrF and ArF excimer lasers, which is exacerbated by impurities and gas quality issues within the laser chamber, leading to deterioration of optical performance.
Innovation Solution
A narrow band excimer laser apparatus is equipped with an optical resonator, a line narrowing module, and a nitrogen gas management system that includes valves and pumps to purge and maintain a controlled atmosphere, ensuring the removal of impurities and maintaining optimal gas quality within the chamber, thereby reducing spectral linewidth and enhancing optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a KrF or ArF excimer laser is used as a light source for exposure, then high power ultraviolet light output is achieved, but the spectral linewidth is wide (350-400 pm) causing chromatic aberration and reduced resolving power
Solution Approach 1:
The laser system is divided into two functional parts: a high-power excimer laser source that generates ultraviolet light, and a separate line narrowing module that reduces spectral linewidth. This segmentation allows each component to optimize its specific function without compromising the other.
Solution Approach 2:
A line narrowing module acts as an intermediary component between the excimer laser source and the projection lens. This module includes a band narrowing element that selectively narrows the spectral linewidth while maintaining the high power output, thereby reducing chromatic aberration without sacrificing power.
2Manufacturing precision
If a line narrowing module is added to narrow the spectral linewidth, then chromatic aberration is reduced and resolving power improves, but the device complexity increases
Solution Approach 1:
The line narrowing module is designed to perform multiple functions: it narrows the spectral linewidth, maintains beam quality, and can be integrated into existing excimer laser systems. The band narrowing element serves as a universal component that can be applied to both KrF and ArF excimer lasers.
Solution Approach 2:
The line narrowing module is nested within the optical path of the excimer laser system, with the band narrowing element positioned between the laser source and the projection lens. This nested configuration allows the line narrowing function to be added without requiring a complete system redesign.
3Reliability
If gas is continuously circulated in the laser chamber, then gas quality is maintained, but impurities accumulate and deteriorate optical performance over time
Solution Approach 1:
The system periodically discards a portion of the circulated gas through the exhaust unit and replaces it with fresh gas from the nitrogen gas supply apparatus. This discarding and recovering process removes accumulated impurities while maintaining overall gas quality, preventing deterioration of optical performance.
Solution Approach 2:
The gas management system uses feedback control through sensors that monitor gas quality parameters. When impurity levels reach a threshold, the control unit automatically activates the exhaust unit and nitrogen gas supply apparatus to restore gas quality, creating a closed-loop feedback system.
4Object-generated harmful factors
If nitrogen gas is supplied to purge the chamber, then impurities are removed and optical performance is protected, but the operational time and gas consumption increase
Solution Approach 1:
Instead of continuous nitrogen gas supply, the system uses periodic purging where the nitrogen gas supply apparatus and exhaust unit are activated at intervals. This periodic action maintains gas quality by removing impurities accumulations while minimizing operational time and gas consumption compared to continuous purging.
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 effectively narrows the spectral linewidth, reduces chromatic aberration, and suppresses deterioration of the line narrowing elements, leading to improved resolving power and extended operational stability of the excimer laser apparatus.
Implementation Method 1
a nitrogen gas supply apparatus; a nitrogen gas introducing unit configured to cause nitrogen gas supplied from the nitrogen gas supply apparatus to flow into the casing
Implementation Method 2
an exhaust unit configured to cause gas within the casing to flow outside the casing; an exhaust pump configured to cause gas within the casing to be exhausted outside the casing through the exhaust unit
Implementation Method 3
a line narrowing module including a casing and a line narrowing optical element housed in the casing, the line narrowing module being provided in the optical resonator and being configured to narrow a spectral line width of laser light
Data Source
AI summary
A narrow band excimer laser apparatus includes a line narrowing module that narrows the spectral line width of laser light, a nitrogen gas introducing unit, a first valve that restricts the flow of nitrogen gas from the introducing unit into a casing of the module, an exhaust unit that causes gas to flow out from the casing, an exhaust pump for exhausting the gas from the casing, a second valve that restricts the exhausting of gas from the exhaust unit, an atmosphere discharge unit that discharges the gas within the casing into the atmosphere, a third valve that restricts the discharge of gas into the atmosphere, and a control unit that closes the second valve while opening the first and third valves, supplies nitrogen gas into the casing, then closes the third valve while opening the first and second valves, drives the exhaust pump, and causes laser oscillation thereafter.