Hybrid Excimer Laser Beam Shaping for Divergence Control
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Solution Overview
Problem
Current discharge-excited excimer laser apparatuses have lower beam quality and significant beam divergence differences between vertical and transverse directions, leading to vignetting and unnecessary light condensing in exposure apparatuses, affecting throughput and potentially damaging optical elements.
Innovation Solution
A hybrid laser system with a solid-state laser device, an excimer amplifier, a beam shaping optical system, a random phase plate, and a collimating optical system, which shapes and expands the laser beam to match the beam characteristics of existing excimer laser apparatuses, reducing beam divergence and improving beam quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a discharge-excited excimer laser apparatus is used, then the laser beam can be generated with sufficient power, but the beam quality deteriorates and beam divergence differences occur between vertical and transverse directions
Solution Approach 1:
The invention divides the laser system into two separate functional segments: a solid-state laser oscillation apparatus that generates high-quality seed beams, and a discharge-excited excimer laser amplifier that provides power amplification. This segmentation allows each component to optimize for its specific function, resolving the contradiction between power and beam quality.
Solution Approach 2:
The solid-state laser beam serves as an intermediary between the seed generation and final amplification stages. It carries the high beam quality characteristics from the oscillation stage into the amplifier, acting as a mediator that transfers quality properties through the system while enabling power amplification.
2Productivity
If a discharge-excited excimer laser apparatus is used, then the laser beam can be generated, but vignetting and unnecessary light condensing occur in the exposure apparatus
Solution Approach 1:
The invention changes the beam parameters (divergence angles, beam profile) by using a solid-state laser with inherently different beam characteristics compared to discharge-excited excimer lasers. This parameter change eliminates vignetting and light condensing issues in the exposure apparatus while maintaining productivity.
3Area of stationary object
If the beam section is expanded uniformly in both directions, then the beam coverage is improved, but the beam quality deteriorates due to increased divergence
Solution Approach 1:
The invention applies asymmetric beam expansion where the expansion ratios in the vertical and horizontal directions are deliberately made different. This asymmetric expansion optimizes beam coverage area while maintaining beam quality by matching the specific divergence characteristics of the solid-state laser beam in different directions.
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 hybrid laser system produces an amplified laser beam with higher coherence and beam quality, reducing vignetting and unnecessary light condensing, and achieving beam characteristics similar to current excimer laser apparatuses, thus enhancing exposure apparatus performance.
Implementation Method 1
a solid-state laser device SLT configured to output a laser beam
Implementation Method 2
an excimer amplifier ALM including a pair of discharge electrodes arranged to face each other with a discharge space therebetween, the laser beam passing through the discharge space, the excimer amplifier being configured to amplify the laser beam
Implementation Method 3
a beam shaping unit arranged in an optical path between the solid-state laser device and the excimer amplifier, the beam shaping unit being configured to expand a beam section of the laser beam output from the solid-state laser device
Implementation Method 4
a collimating optical system arranged in an optical path between the random phase plate and the excimer amplifier
Data Source
AI summary
A laser system includes a beam shaping unit, a random phase plate, and a collimating optical system in an optical path between a solid-state laser device and an excimer amplifier. When a traveling direction of a laser beam entering the excimer amplifier is a Z direction, a discharge direction of a pair of discharge electrodes is a V direction, a direction orthogonal to the V and Z directions is an H direction, a shaping direction of the beam shaping unit corresponding to the V direction is a first direction, a shaping direction of the beam shaping unit corresponding to the H direction is a second direction, an expansion rate in the first direction is E1, and an expansion rate in the second direction is E2, the beam shaping unit expands a beam section of the laser beam such that an expansion ratio defined by E2/E1 is lower than 1.