Deformable Mirror Feedback for EUV Laser Pulse Synchronization
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Solution Overview
Problem
The synchronization and positioning of laser pulses in laser-produced plasma (LPP) based EUV radiation sources for extreme ultraviolet lithography are challenging due to mechanical and electrical drift, leading to inefficient EUV radiation generation and contamination, resulting in dose errors and reduced throughput.
Innovation Solution
A selectively detachable deformable mirror is introduced in the excitation laser path to control beam size, wavefront aberration, and spatial separation, enabling inline feedback and optimization to synchronize the pre-pulse and main pulse with target droplets, thereby stabilizing plasma generation and improving EUV radiation quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser pulses are used to heat target droplets in LPP based EUV source, then EUV radiation is generated, but mechanical and electrical drift cause desynchronization between laser pulses and target droplets, leading to reduced efficiency and contamination
Solution Approach 1:
The patent implements a feedback control system that uses wavefront sensors to detect drift in the laser beam path and adjusts the deformable mirror in real-time to maintain proper synchronization between laser pulses and target droplets, thereby resolving the reliability-productivity contradiction
Solution Approach 2:
The patent employs a dynamically adjustable deformable mirror that can change its shape in response to detected wavefront aberrations, allowing the system to adapt to mechanical and electrical drift conditions and maintain optimal laser pulse targeting throughout operation
2Stability of the object's composition
If laser pulses are not synchronized with target droplets, then plasma generation becomes unstable, but synchronization requires precise positioning control which is difficult to maintain
Solution Approach 1:
The feedback control system continuously monitors the laser beam wavefront and automatically adjusts the deformable mirror to compensate for positioning drift, reducing the complexity of manual positioning control while achieving stable plasma generation
Solution Approach 2:
The patent replaces complex mechanical positioning adjustment mechanisms with an optical solution using a deformable mirror that corrects wavefront aberrations through controlled deformation, simplifying the overall positioning control system
3Object-generated harmful factors
If pre-pulse and main pulse are not optimally synchronized, then heating efficiency decreases and contamination increases, but synchronization requires precise timing control
Solution Approach 1:
The feedback system detects timing deviations between pre-pulse and main pulse relative to target droplet arrival and automatically adjusts pulse timing through the deformable mirror, reducing contamination while simplifying timing control operations
Solution Approach 2:
The pre-pulse is used to pre-heat and prepare the target droplet before the main pulse arrives, with the deformable mirror ensuring both pulses are precisely synchronized with the droplet's position and velocity, thereby reducing contamination without complex timing adjustments
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 enhances the stability of EUV radiation generation, reduces contamination, minimizes dose errors, and improves the overall throughput of the lithography system by ensuring optimal heating and synchronization of target droplets with the laser pulses.
Implementation Method 1
The excitation laser is configured to heat the target droplets using excitation pulses to convert the target droplets to plasma
Implementation Method 2
heat the target droplets using excitation pulses to convert the target droplets to plasma
Implementation Method 3
control beam size, wavefront aberration, and spatial separation
Implementation Method 4
control beam size, wavefront aberration, and spatial separation
Implementation Method 5
enabling inline feedback and optimization to synchronize the pre-pulse and main pulse with target droplets
Implementation Method 6
One method for producing EUV radiation is laser-produced plasma (LPP). In an LPP based EUV source a high-power laser beam is focused on small tin droplet targets to form highly ionized plasma that emits EUV radiation
Data Source
AI summary
An apparatus for generating extreme ultraviolet (EUV) radiation includes a droplet generator configured to generate target droplets. An excitation laser is configured to heat the target droplets using excitation pulses to convert the target droplets to plasma. A deformable mirror is disposed in a path of the excitation laser. A controller is configured to adjust parameters of the excitation laser by controlling the deformable mirror based on a feedback parameter.