EUV Droplet Illumination Control for Laser Synchronization
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Solution Overview
Problem
In extreme ultraviolet lithography, achieving precise synchronization of high-powered laser pulses with metal droplet targets in laser-produced plasma (LPP) sources is challenging, affecting the efficiency and stability of EUV radiation production.
Innovation Solution
The implementation of droplet illumination and detection modules to measure the speed of target droplets, allowing for accurate synchronization of excitation pulses with the arrival of droplets at the focal point, using a method that adjusts the intensity of the illumination based on detected light to ensure reliable signal detection and optimal plasma generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If droplet detection modules are implemented to measure droplet speed, then synchronization precision is improved, but device complexity increases
Solution Approach 1:
A light source is introduced as an intermediary to illuminate the droplet, and a detection module detects the reflected or scattered light to determine droplet position and speed. This intermediary lighting system enables precise synchronization without requiring direct complex measurement of the droplet itself.
Solution Approach 2:
The patent replaces mechanical measurement methods with optical detection. By using light reflection and scattering properties to detect droplet position and velocity, the system achieves high precision synchronization without mechanical contact or complex mechanical sensing systems.
2Reliability
If illumination intensity is increased to improve signal detection, then detection reliability is improved, but energy consumption increases
Solution Approach 1:
The illumination system operates dynamically by activating the light source only when a droplet is detected or expected to pass through the measurement zone. This dynamic operation maintains high detection reliability while minimizing energy consumption by avoiding continuous illumination.
Solution Approach 2:
The illumination is applied periodically or pulsed rather than continuously, synchronized with the droplet ejection frequency. This periodic illumination provides sufficient light for detection when needed while reducing overall energy consumption compared to continuous operation.
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 enhances the synchronization of laser pulses with target droplets, improving the efficiency and stability of EUV radiation production by ensuring consistent and precise timing, leading to better EUV source performance.
Implementation Method 1
A droplet illumination module is provided including a light source configured to illuminate the target droplet
Implementation Method 2
detecting light reflected and/or scattered by the target droplet
Implementation Method 3
detecting light reflected and/or scattered by the target droplet
Implementation Method 4
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 5
a high-power laser beam is focused on small droplet targets of metal, such as tin, to form a highly ionized plasma
Data Source
AI summary
A method of controlling a droplet illumination module/droplet detection module system of an extreme ultraviolet (EUV) radiation source includes irradiating a target droplet with light from a droplet illumination module and detecting light reflected and/or scattered by the target droplet. The method includes determining whether an intensity of the detected light is within an acceptable range. In response to determining that the intensity of the detected light is not within the acceptable range, a parameter of the droplet illumination module is automatically adjusted to set the intensity of the detected light within the acceptable range.