Ring Resonator Beam Shifting for Optical Element Lifespan
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-output ArF laser devices for semiconductor exposure systems face challenges in extending the life of optical elements like chamber windows and output coupling mirrors due to increased energy density, leading to shortened lifespans and issues with injection efficiency and spatial coherence.
Innovation Solution
The implementation of a narrow-band laser device with a ring-type resonator where the optical path of the laser beam shifts in each round trip within a plane perpendicular to the discharge direction, eliminating the need for beam expansion elements and optimizing mirror arrangements to reduce energy density and prevent unstable resonator formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-output ArF laser is used to achieve high dose stability and throughput, then productivity is improved, but the energy density on optical elements increases which shortens their lifespan
Solution Approach 1:
The patent introduces a longitudinal dimension to the optical path by shifting the beam position in the longitudinal direction perpendicular to the discharge direction. This dimensional change allows the laser beam to traverse different spatial locations within the resonator, distributing the energy load across multiple optical elements rather than concentrating it on a single element, thereby extending their operational lifespan while maintaining high output power
2Duration of action of stationary object
If beam expander is introduced to reduce energy density on optical elements, then lifespan of optical elements is extended, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the beam expander component from the optical system. Instead of using a separate beam expansion device, the invention achieves beam width increase through the longitudinal shift mechanism inherent to the ring resonator configuration, thereby reducing device complexity while still protecting optical elements from excessive energy density
Solution Approach 2:
The patent merges the beam expansion function with the resonator's inherent optical path structure. The longitudinal shift mechanism that defines the ring resonator's operation simultaneously accomplishes both beam circulation and effective beam width distribution, eliminating the need for a separate beam expander component
3Productivity
If ring resonator with high seed injection efficiency is used to achieve high output, then productivity is improved, but energy density on OC and windows increases which shortens their lifespan
Solution Approach 1:
The patent applies longitudinal beam shifting within the ring resonator to distribute the high-energy laser beam across multiple optical elements including the output coupling mirror and chamber windows. This dimensional approach allows efficient seed injection and high output generation while preventing excessive energy concentration on any single element, thereby extending their operational lifespan
4Duration of action of stationary object
If optical path is shifted in longitudinal direction, then energy density on optical elements is reduced extending their lifespan, but beam expansion function is eliminated which may affect injection efficiency
Solution Approach 1:
The patent merges the beam circulation function with the longitudinal shift mechanism in the ring resonator. The optical path design ensures that the longitudinal shift naturally distributes the beam across multiple elements while maintaining proper beam alignment and overlap for efficient seed injection, achieving both extended element lifespan and high injection efficiency through a unified optical architecture
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
This configuration reduces energy density on optical elements, prolongs their lifespan, enhances injection efficiency, and minimizes spatial coherence, thereby reducing speckle patterns in exposure devices.
Implementation Method 1
a laser beam emitted by an oscillation stage laser (MO) functions as a seed laser beam, while the amplification stage laser (PO) has a function of amplifying that seed laser light
Implementation Method 2
the amplification stage laser (PO) has provided therein a ring resonator comprising an OC, which is a partial reflection (PR) mirror, and high reflection mirrors (5a, 5b, 5c)
Data Source
AI summary
A narrow-band laser device for exposure apparatus that allows to reduce damage to, and to hence extend the life of, optical elements such as chamber windows, output coupling mirrors or the like. A ring resonator is provided in an amplification stage laser of the narrow-band laser device for exposure apparatus that comprises an oscillation stage laser and an amplification stage laser. An OC, a high reflection mirror and a high reflection mirror are arranged to be offset, for instance, relative to a longitudinal direction axis of discharge electrodes. As a result, the beam width of laser light injected through the OC of the amplification stage laser becomes wider as the beam shifts inside the ring resonator, in each round trip within the ring resonator. The energy density of laser light in the optical elements of the amplification stage laser becomes reduced thereby, thus prolonging the life of the optical elements.