Line-Narrowing Laser Wavefront Control for Stable Spectral Width
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Solution Overview
Problem
Existing KrF and ArF excimer laser devices used in semiconductor exposure apparatuses suffer from large spectral line widths, leading to chromatic aberration and decreased resolution in projection lenses.
Innovation Solution
A line narrowing laser device is developed, featuring a laser resonator with an output coupling mirror and a line narrowing module comprising a prism and a grating with a concave reflection surface, along with a processor to control the wavefront adjuster based on measured spectral line widths.
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, but the spectral line width varies when the repetition frequency is changed
Solution Approach 1:
A feedback control system is implemented where a spectrum detector measures the spectral line width of the laser light, and a processor adjusts the wavefront adjuster based on the measured value to maintain the spectral line width within a predetermined range even when repetition frequency changes
Solution Approach 2:
The wavefront adjuster is made dynamically adjustable to change its wavefront adjustment amount based on measured spectral line width, allowing the system to adapt and maintain stable spectral characteristics across different operating conditions
2Productivity
If the repetition frequency of pulse laser light is changed to improve productivity, then exposure efficiency is improved, but the spectral line width varies causing resolution degradation
Solution Approach 1:
The feedback control system continuously monitors spectral line width and adjusts the wavefront adjuster in real-time to compensate for frequency-induced variations, enabling high-speed exposure while maintaining resolution quality
Solution Approach 2:
The system dynamically changes the wavefront adjustment parameter based on the measured spectral line width to optimize both exposure efficiency and resolution across different repetition frequencies
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 line width of pulse laser light, reducing chromatic aberration and stabilizing the spectral line width even when the repetition frequency of the pulse laser light is changed.
Implementation Method 1
a line narrowing module that includes a prism and a grating that has a reflection surface having a concave shape
Implementation Method 2
a line narrowing module that includes a prism and a grating
Implementation Method 3
a spectrum detector configured to measure a spectral line width of pulse laser light output from the output coupling mirror
Data Source
AI summary
A line narrowing laser device includes a laser resonator including an output coupling mirror and a line narrowing module that includes a prism and a grating that has a reflection surface having a concave shape; a laser chamber including a pair of discharge electrodes, and arranged on an optical path of the laser resonator; a power source configured to apply, to the discharge electrodes, a high voltage pulse whose repetition frequency is variable; a wavefront adjuster including the output coupling mirror; a spectrum detector configured to measure a spectral line width of pulse laser light output from the output coupling mirror; and a processor configured to control the wavefront adjuster based on the measured spectral line width.