EUV Laser Beam Size Control via Dual-Algorithm Actuation
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Solution Overview
Problem
Current extreme ultraviolet light generation systems face challenges in controlling the beam size of pulse laser beams, leading to vignetting and reduced EUV energy due to thermal deformation of optical elements, which existing control methods like threshold control and PID control struggle to manage effectively.
Innovation Solution
The system employs a dual-control method approach, initially applying a large control amount to minimize the beam size when it exceeds a threshold, then switching to a smaller control amount to adjust the beam size closer to a target value, using a combination of threshold control and feedback control based on the beam size's drift rate, and incorporating adaptive settings for the drive amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single threshold control or PID control method is used to manage beam size, then the control system is simple to implement, but the beam size cannot be effectively controlled when thermal deformation occurs, leading to vignetting and reduced EUV energy
Solution Approach 1:
The control system is segmented into two distinct algorithms: a first algorithm that applies large control amounts when beam size exceeds a first threshold (addressing thermal deformation and vignetting), and a second algorithm that applies small control amounts when beam size is within the threshold (maintaining precision and avoiding overshoot). This segmentation resolves the contradiction by making the control system adaptable to different operational conditions without requiring a completely complex system architecture.
Solution Approach 2:
The control system dynamically switches between different control algorithms based on the beam size conditions. When thermal deformation causes the beam size to exceed the first threshold, the first algorithm with large control amounts is activated to quickly correct the issue. When the beam size returns within the threshold, the second algorithm with small control amounts takes over for precise maintenance. This dynamic adaptation improves reliability without permanently increasing system complexity.
2Reliability
If a large control amount is continuously applied to minimize beam size, then vignetting is prevented, but the beam size oscillates excessively and overshoots the target value
Solution Approach 1:
The first algorithm applies an excessive control amount (larger than needed for precise control) specifically when the beam size exceeds the first threshold, which is necessary to quickly prevent vignetting caused by thermal deformation. However, this excessive action is only applied partially - when needed - and switches to the second algorithm with appropriate control amounts when the beam size is within the threshold, thereby preventing continuous oscillation and overshoot.
Solution Approach 2:
The control system continuously monitors beam size and provides feedback to determine which algorithm to apply. When feedback indicates the beam size has exceeded the first threshold (suggesting thermal deformation), the first algorithm with large control amounts is activated to prevent vignetting. When feedback shows the beam size is within the threshold, the second algorithm with small control amounts is used to maintain precision and avoid oscillation.
3Manufacturing precision
If a small control amount is used to avoid oscillation, then beam size stability is improved, but the system cannot quickly respond to thermal deformation and vignetting occurs
Solution Approach 1:
The system applies a small control amount (appropriate action) as the default to maintain beam size stability and avoid oscillation. However, when thermal deformation occurs and the beam size exceeds the first threshold, the system partially switches to applying a large control amount (excessive action) through the first algorithm to quickly prevent vignetting. This partial application of excessive action only when necessary resolves the contradiction between stability and responsiveness.
Solution Approach 2:
The control system prepares for potential thermal deformation by having the first algorithm with large control amounts ready to be activated. When the beam size approaches or exceeds the first threshold, the system preemptively applies the first algorithm to counteract the thermal deformation before it causes severe vignetting. This preliminary anti-action ensures rapid response capability while maintaining stability during normal operation through the second algorithm.
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 method effectively reduces beam size variation and minimizes EUV energy loss and optical element damage by dynamically adjusting the beam size within predetermined limits, improving control accuracy and reducing overshoot.
Implementation Method 1
a laser produced plasma (LPP) device that uses plasma generated by irradiating a target material with a pulse laser beam
Implementation Method 2
a sensor configured to detect a beam size of the pulse laser beam
Implementation Method 3
an actuator configured to change the beam size
Data Source
AI summary
An extreme ultraviolet light generation system according to one aspect of the present disclosure includes: a pulse laser apparatus configured to output a pulse laser beam, the pulse laser beam being supplied to a predetermined region in a chamber in which plasma containing extreme ultraviolet light is to be generated; a sensor configured to detect a beam size of the pulse laser beam; an actuator configured to change the beam size; and a controller. The controller performs, based on a first algorithm, first control that controls the actuator by a first control amount in a beam size minifying direction when the beam size has exceeded a first upper limit threshold in one burst duration, and then performs, based on a second algorithm, second control that controls the actuator by a second control amount smaller than the first control amount so that the beam size becomes closer to a target value.