EUV Target Control Using Reflection Aberration Feedback
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Solution Overview
Problem
Existing EUV lithography systems using laser-produced plasma (LPP) sources face inefficiencies due to the lack of precise control over the excitation laser's shape, angle of incidence, and beam profile, leading to reduced EUV energy output, as these factors are not adequately considered in current methods.
Innovation Solution
The system controls the relative position and direction of the excitation laser in relation to the target droplet based on the angle of incidence and beam profile, using Zernike polynomials to analyze and correct aberrations, thereby optimizing the interaction between the laser and droplets to enhance EUV energy generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If laser-produced plasma (LPP) sources are used for EUV lithography, then EUV radiation can be generated, but the conversion efficiency is reduced due to lack of precise control over excitation laser parameters
Solution Approach 1:
The system employs a feedback mechanism where a wavefront sensor measures the actual beam profile and angle of incidence of the excitation laser, and this measurement is fed back to a control system that adjusts the laser parameters. This closed-loop feedback enables precise control over the excitation laser, maximizing EUV energy conversion efficiency by ensuring optimal laser-target interaction.
Solution Approach 2:
The patent replaces mechanical adjustment methods with optical measurement and control systems. Instead of physically adjusting laser parameters through mechanical means, the system uses wavefront sensing and optical feedback to precisely control the excitation laser parameters, thereby improving EUV energy efficiency without complex mechanical adjustments.
2Power
If the excitation laser parameters are not precisely controlled, then the system operation is simpler, but the EUV energy output is reduced
Solution Approach 1:
A wavefront sensor provides real-time feedback on the excitation laser beam profile and angle of incidence, enabling the control system to maintain optimal EUV energy output. This feedback mechanism ensures high power efficiency by continuously monitoring and adjusting laser parameters based on actual beam characteristics.
Solution Approach 2:
The system performs self-diagnosis and self-adjustment through the wavefront sensor that automatically measures beam parameters and feeds this information back to the control system. This self-service capability allows the system to maintain optimal EUV energy output without requiring external intervention or complex manual adjustments.
3Productivity
If precise synchronization of laser pulses with droplet targets is achieved, then EUV radiation efficiency improves, but the control system becomes more complex
Solution Approach 1:
The wavefront sensor provides feedback on the actual laser beam characteristics, enabling precise synchronization control between laser pulses and droplet targets. This feedback mechanism ensures that the excitation laser consistently achieves optimal angle of incidence and beam profile on each droplet, maximizing EUV radiation efficiency through precise temporal and spatial synchronization.
Solution Approach 2:
The system replaces complex mechanical synchronization mechanisms with optical feedback and electronic control. The wavefront sensor measures beam parameters and the control system electronically adjusts timing and positioning, achieving precise laser-droplet synchronization without complex mechanical linkages or physical adjustment mechanisms.
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 approach improves the conversion efficiency of the EUV energy by precisely adjusting the laser-target interaction, stabilizing EUV output and minimizing fluctuations, leading to increased EUV energy production.
Implementation Method 1
detecting laser radiation reflected by the target droplet
Implementation Method 2
a high-power laser beam is focused on small droplet targets of metal, such as tin, to form a highly ionized plasma that emits EUV radiation
Implementation Method 3
a high-power laser beam is focused on small droplet targets
Data Source
AI summary
A method of controlling an extreme ultraviolet (EUV) lithography system is disclosed. The method includes irradiating a target droplet with EUV radiation, detecting EUV radiation reflected by the target droplet, determining aberration of the detected EUV radiation, determining a Zernike polynomial corresponding to the aberration, and performing a corrective action to reduce a shift in Zernike coefficients of the Zernike polynomial.