Pulse Stretcher Beam Splitter Reduces Plasma Generation
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Solution Overview
Problem
In semiconductor exposure apparatuses, the large spectral line width of KrF and ArF excimer laser devices leads to chromatic aberration, reducing resolution, and existing pulse stretchers face issues with energy density and reliability due to overlapping beam concentrations, which can cause plasma generation and wavefront distortion.
Innovation Solution
A pulse stretcher design with a beam splitter and concave mirrors arranged to reduce overlapping beam concentrations from two to three, shifting mirrors to minimize energy density and prevent plasma generation, ensuring stable wavefronts and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If pulse laser light is reflected multiple times by concave mirrors in a pulse stretcher, then the pulse width is stretched, but the energy density increases and plasma generation occurs
Solution Approach 1:
The patent divides the single optical path into multiple separate optical paths by introducing a beam splitter. Instead of reflecting light multiple times along one path (which concentrates energy), the system creates several parallel paths where light is reflected different numbers of times (e.g., 2, 4, 6 times respectively). This segmentation distributes the energy across multiple paths, preventing plasma generation while still achieving pulse stretching through the cumulative effect of multiple reflections.
Solution Approach 2:
The patent transitions from a one-dimensional single optical path to a multi-dimensional structure with multiple optical paths arranged in space. By using a beam splitter to create parallel paths and positioning concave mirrors at different locations, the system adds spatial dimensions to the optical path design. This dimensional expansion allows light to be distributed across different spatial trajectories, reducing energy concentration at any single point.
2Duration of action of moving object
If the number of overlapping beams at concentration points is increased, then the pulse stretching effect is enhanced, but wavefront distortion occurs
Solution Approach 1:
The patent segments the beam path into multiple independent optical paths with different reflection counts. Each path maintains its own wavefront characteristics, and the beams are kept spatially separated throughout their propagation. This prevents the overlapping and interference that would otherwise cause wavefront distortion, while the combined effect of all paths achieves the desired pulse stretching.
3Volume of moving object
If concave mirrors are used to reflect laser light, then the pulse stretcher achieves compact design, but energy concentration at reflection points increases
Solution Approach 1:
The patent uses a beam splitter to divide the optical path into multiple segments, each with its own concave mirrors. This allows the system to maintain compact dimensions through multiple reflections while distributing the energy load across different mirror surfaces and paths. No single mirror or reflection point bears the full energy burden, preventing excessive energy concentration.
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 suppresses plasma generation and wavefront distortion, maintaining the required performance and reliability of the gas laser device, ensuring consistent and accurate semiconductor manufacturing.
Implementation Method 1
a beam splitter configured to split pulse laser light into two beams of pulse laser light
Implementation Method 2
one beam of pulse laser light split by the beam splitter travels to one first concave mirror among the plurality of first concave mirrors and is reflected alternately by the first concave mirrors and the second concave mirrors 12 times or more as even number times
Implementation Method 3
a number of overlapping of the one beam of pulse laser light at each of a plurality of concentration points where at least part of the one beam of pulse laser light overlaps at beam waists of the one beam of pulse laser light is two
Data Source
AI summary
A pulse stretcher includes a beam splitter splitting pulse laser light into two beams of pulse laser light, first concave mirrors arranged side by side in a predetermined direction, and second concave mirrors arranged side by side in the predetermined direction as having the same number as the first concave mirrors and facing the first concave mirrors, respectively. One beam of pulse laser light split by the beam splitter travels to one first concave mirror among the first concave mirrors and is reflected alternately by the first concave mirrors and the second concave mirrors 12 times or more as even number times to return to the beam splitter. A number of overlapping of the one beam at each of concentration points where at least part of the one beam of pulse laser light overlaps at beam waists of the one beam is two.