Structured Nozzle Tube for EUV Droplet Angular Momentum
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Solution Overview
Problem
In EUV lithography systems, the instability of target droplet generation and contamination within the droplet generator lead to inefficiencies in EUV radiation production, causing variations in droplet size, shape, and trajectory, resulting in reduced EUV radiation intensity and collector mirror contamination.
Innovation Solution
A structured nozzle tube with groove patterns is used to provide angular momentum and aerodynamic stability to target droplets, preventing bubble and contaminant particle discharge and ensuring consistent droplet size and shape, thereby improving the stability and efficiency of EUV radiation generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a high-power laser beam is focused on small tin droplet targets to form highly ionized plasma that emits EUV radiation, then EUV radiation intensity increases, but bubbles and contaminant particles inside the droplet generator change the trajectory of the target droplet causing the laser pulse to partially miss the target droplet
Solution Approach 1:
The nozzle is pre-heated to a temperature above the melting point of tin (e.g., 232°C) before droplet generation begins. This preliminary heating action ensures that the nozzle inner surface remains free of solidified tin and contaminant accumulation, which could otherwise disrupt droplet trajectory and cause trajectory instability during operation
Solution Approach 2:
The system dynamically adjusts the nozzle temperature parameter to maintain it above the melting point of tin throughout the droplet generation process. This parameter control prevents solidification of tin on the nozzle surface and ensures consistent droplet formation and trajectory, resolving the reliability issue while maintaining high EUV intensity
2Power
If vessel flow varies depends on the temperature of a vessel and shock wave of the plasma, which changes a lot during the exposure, then plasma generation occurs, but some of the target droplet may be inadequately converted to plasma and may be scattered around the vessel as debris resulting in accumulation of the tin (Sn) particles on various surfaces including a collector mirror
Solution Approach 1:
The shock wave and plasma expansion, which initially cause droplet scattering and contamination, are harnessed to create a directed flow that pushes remaining droplets and debris toward the collector mirror where they can be efficiently converted to plasma or removed. The harmful scattering effect is converted into a beneficial directional transport mechanism
Solution Approach 2:
A buffer gas (e.g., hydrogen or helium) is introduced as an intermediary medium between the laser-plasma interaction zone and the vessel walls. This buffer gas absorbs and redirects the shock wave energy, preventing direct impact of plasma debris on the collector mirror and other surfaces, thereby reducing tin particle accumulation while maintaining efficient plasma conversion
3Productivity
If droplet size and shape vary, then EUV radiation source effectiveness decreases, but maintaining consistent droplet characteristics requires precise control
Solution Approach 1:
The system uses periodic pulsing of the tin supply and nozzle heating cycles to generate droplets at regular intervals. This periodic action ensures consistent droplet formation conditions for each droplet, maintaining uniform size and shape characteristics without requiring complex real-time control systems. The regular cycling of molten tin supply and nozzle temperature creates repeatable droplet ejection events
Solution Approach 2:
The molten tin in the nozzle self-regulates droplet formation through capillary forces and surface tension effects. The heated nozzle automatically maintains a pool of molten tin that forms droplets of consistent size through natural physical processes, eliminating the need for complex external control mechanisms. The system uses the material's own properties to ensure droplet uniformity
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
The structured nozzle tube enhances the stability and conversion efficiency of EUV radiation generation by maintaining consistent droplet characteristics and reducing contamination on collector mirrors, leading to improved EUV radiation intensity and reduced downtime.
Implementation Method 1
A structured nozzle tube with groove patterns is used to provide angular momentum and aerodynamic stability to target droplets
Implementation Method 2
A high-power laser beam is focused on small tin droplet targets to form highly ionized plasma that emits extreme ultraviolet (EUV) radiation
Implementation Method 3
When a high-power laser beam is focused on small tin droplet targets to form highly ionized plasma
Implementation Method 4
bubbles and/or contaminant particles may be inside a droplet generator, which changes the trajectory of the target droplet
Data Source
AI summary
A target droplet source for an extreme ultraviolet (EUV) source includes a droplet generator configured to generate target droplets of a given material. The droplet generator includes a nozzle configured to supply the target droplets in a space enclosed by a chamber. In some embodiments, a nozzle tube is arranged within the nozzle of the droplet generator, and the nozzle tube includes a structured nozzle pattern configured to provide an angular momentum to the target droplets.