Wavefront Adjusters Stabilize EUV Laser Beam Against Thermal Distortion
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Solution Overview
Problem
In EUV light generation systems, particularly for semiconductor production, the stability of the laser beam is compromised due to heat-induced deformation of optical elements in the beam delivery unit, leading to fluctuations in wavefront and focus position, which affects the output of extreme ultraviolet light.
Innovation Solution
The implementation of a device with first and second wavefront adjusters, along with a beam monitor and controller, to detect and adjust the wavefront of the laser beam before and after the beam delivery unit, ensuring the beam width and wavefront curvature meet predetermined ranges, thereby stabilizing the EUV light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical elements in the beam delivery unit are used to transmit the laser beam, then the laser beam can be delivered to the chamber, but heat-induced deformation occurs causing wavefront and focus position fluctuations
Solution Approach 1:
The first wavefront adjuster is positioned before the beam delivery unit to pre-compensate for expected thermal distortions. By adjusting the wavefront in advance, the system counteracts the heat-induced deformations that will occur during beam delivery, maintaining stable EUV light output despite thermal effects in the optical path
Solution Approach 2:
The beam monitor detects actual wavefront deviations caused by thermal distortion in real-time, and the controller uses this feedback to dynamically adjust the second wavefront adjuster. This closed-loop control compensates for focus position fluctuations and wavefront distortions occurring during operation, stabilizing the EUV light generation process
2Reliability
If optical elements are placed in the beam path for delivery, then beam transmission is enabled, but heat-induced deformation affects focus position
Solution Approach 1:
The first wavefront adjuster pre-compensates for thermal focus shifts by adjusting the wavefront curvature before the beam enters the heated beam delivery unit. This preliminary adjustment ensures that even as optical elements heat up and expand, the focus position remains stable at the target
Solution Approach 2:
The beam monitor continuously measures focus position deviations caused by thermal effects, and the controller adjusts the second wavefront adjuster in real-time to maintain the correct focus position, compensating for temperature-induced changes in the optical path
3Reliability
If wavefront adjusters are added before and after the beam delivery unit, then beam control is improved, but device complexity increases
Solution Approach 1:
The beam control system is divided into two independent wavefront adjusters positioned at different locations in the optical path. The first adjuster handles pre-compensation before the beam delivery unit, while the second adjuster handles real-time correction after the unit. This segmentation allows each component to address specific aspects of beam instability, making the overall system more manageable and effective despite the added complexity
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 solution effectively stabilizes the EUV light output by compensating for heat-induced distortions in the beam delivery unit, maintaining consistent beam width and wavefront, thus enhancing the precision and reliability of microfabrication processes for feature sizes below 32 nm.
Implementation Method 1
a first wavefront adjuster provided in a beam path of a laser beam outputted from a laser apparatus, a beam delivery unit provided in a beam path of the laser beam from the first wavefront adjuster, a second wavefront adjuster provided in a beam path of the laser beam from the beam delivery unit
Implementation Method 2
a beam monitor provided in a beam path of the laser beam from the second wavefront adjuster, and a controller configured to control the first and second wavefront adjusters based on a detection result of the beam monitor
Implementation Method 3
a laser beam focusing optical system for focusing the laser beam in the chamber
Implementation Method 4
a Laser Produced Plasma (LPP) type system in which plasma is generated by irradiating a target material with a laser beam
Data Source
AI summary
A device is provided for controlling a laser beam. The device may include a first wavefront adjuster provided in a beam path of a laser beam outputted from a laser apparatus, a beam delivery unit provided in a beam path of the laser beam from the first wavefront adjuster, a second wavefront adjuster provided in a beam path of the laser beam from the beam delivery unit, a beam monitor provided in a beam path of the laser beam from the second wavefront adjuster, and a controller configured to control the first and second wavefront adjusters based on a detection result of the beam monitor. An extreme ultraviolet light apparatus including the device is also provided.