Pulse Stretcher Optical Layout for Excimer Laser Line Narrowing
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Solution Overview
Problem
Chromatic aberration occurs in KrF and ArF excimer laser devices due to their large spectral line widths, leading to decreased resolution in semiconductor exposure processes, necessitating a solution to narrow the spectral line width to ignore chromatic aberration.
Innovation Solution
A gas laser device with a chamber device and a pulse stretcher that includes a looped optical path and light guide system, where pulse laser light is caused to overlap within the system, effectively narrowing the spectral line width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a line narrowing module (LNM) including a line narrowing element (etalon, grating, and the like) is provided in a laser resonator to narrow spectral line width, then chromatic aberration is reduced, but device complexity increases
Solution Approach 1:
The patent extracts the line narrowing function from the traditional resonator configuration and implements it through a separate pulse stretcher module. This module uses a looped optical path with beam splitters and mirrors to achieve spectral line narrowing without requiring complex line narrowing elements like etalons or gratings within the resonator itself.
Solution Approach 2:
The patent introduces a pulse stretcher as an intermediary component between the laser resonator and the exposure system. This pulse stretcher uses a looped optical path to temporarily store and reshape the laser pulse, achieving line narrowing through the optical path design rather than through complex filtering elements.
2Manufacturing precision
If a looped optical path with multiple mirrors is used to narrow spectral line width, then chromatic aberration is reduced, but the optical path becomes more complex and harder to align
Solution Approach 1:
The patent combines multiple optical functions into a single integrated pulse stretcher module. The looped optical path with beam splitters and mirrors is configured to perform both pulse stretching and line narrowing in one compact unit, reducing the number of separate alignment-critical interfaces.
Solution Approach 2:
The patent uses a looped optical path that folds the light path in three-dimensional space, allowing the optical components to be arranged in a compact configuration. This spatial arrangement reduces sensitivity to alignment errors by distributing the optical path across multiple dimensions rather than requiring precise linear alignment.
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 significantly reduces chromatic aberration, enhancing the resolution of semiconductor exposure processes by ensuring precise alignment and focus of laser light.
Implementation Method 1
the looped optical path is configured to return a part of the pulse laser light having entered the beam splitter to the beam splitter via the plurality of mirrors to cause the part of the pulse laser light to overlap another part of the pulse laser light
Data Source
AI summary
A gas laser device includes a chamber device; and a pulse stretcher which includes a looped optical path including a beam splitter and a plurality of mirrors, and a light guide optical system, and which the pulse laser light output from the chamber device enters. The light guide system causes the pulse laser light having entered the pulse stretcher to be output from the pulse stretcher via the beam splitter. The looped optical path returns a part of the pulse laser light having entered the beam splitter to the beam splitter via the plurality of mirrors to cause the part of the pulse laser light to overlap another part thereof, and is sandwiched between a first straight line along an optical path of the pulse laser light entering the pulse stretcher and a second straight line along an optical path of the pulse laser light output from the pulse stretcher.