Multi-Nozzle Tin Droplet Control for Stable EUV Plasma Generation
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Solution Overview
Problem
The efficiency and stability of laser-produced plasma (LPP) based extreme ultraviolet (EUV) radiation sources in semiconductor lithography are limited by the synchronization of high-powered laser pulses with the movement and formation of tin droplets, which affects the intensity and consistency of EUV radiation produced.
Innovation Solution
A method is introduced to control and synchronize the generation of elongated droplets using a nozzle assembly with multiple nozzles, where small drops are aggregated to form elongated droplets that are precisely timed and positioned to optimize heating and ionization by the laser pulse, enhancing the EUV radiation source's efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional droplet generation methods are used, then the system is simpler, but the synchronization between laser pulses and droplet movement is poor, reducing EUV radiation intensity and stability
Solution Approach 1:
The nozzle assembly is divided into multiple independent nozzles (first nozzle, second nozzle, third nozzle) arranged in specific patterns. Each nozzle can be independently controlled to generate droplets at precise timing, enabling better synchronization with laser pulses while maintaining modular simplicity
Solution Approach 2:
The system dynamically controls the timing and positioning of droplet generation from multiple nozzles based on laser pulse timing. The nozzle assembly can adjust droplet ejection timing and spatial arrangement to optimize synchronization with incoming laser pulses, improving reliability through adaptive control
2Use of energy by moving object
If droplet aggregation is not used, then the processing is simpler, but the energy conversion efficiency is lower
Solution Approach 1:
Multiple small droplets from different nozzles are merged to form aggregated droplet structures. This combining of multiple droplets increases the target mass for laser interaction, improving energy conversion efficiency while the modular nozzle design keeps the control system manageable
Solution Approach 2:
Droplets are pre-positioned and pre-aggregated in space before laser pulse arrival. The nozzle assembly generates and positions droplets in advance, ensuring optimal targeting when laser pulses arrive, thereby improving energy conversion efficiency through preparatory spatial arrangement
3Temperature
If pre-pulse lasers are used, then droplet heating is improved, but manufacturing costs increase
Solution Approach 1:
The main laser pulse itself performs the heating function that would otherwise require a separate pre-pulse laser. By optimizing droplet positioning, size, and timing through the multi-nozzle assembly, the system uses the primary laser energy efficiently for both heating and EUV generation, eliminating the need for additional pre-pulse laser equipment and reducing manufacturing costs
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 energy conversion efficiency and stability of the EUV radiation source, reducing the need for pre-pulse lasers and lowering manufacturing costs, while maintaining high EUV energy production.
Implementation Method 1
a high-power laser pulse is focused on small tin droplets to form highly ionized plasma that emits EUV radiation
Implementation Method 2
highly ionized plasma that emits EUV radiation with a peak maximum emission at 13.5 nm
Data Source
AI summary
A lithography method in semiconductor fabrication is provided. The method includes generating a plurality of first drops of a target material through a first nozzle group selected from a plurality of nozzles to form a first elongated droplet; generating a first laser pulse to convert the first elongated droplet into plasma that generates a first extreme ultraviolet (EUV) radiation; reflecting the first EUV radiation by a collector mirror having an optical axis; generating a plurality of second drops of the target material through a second nozzle group selected from the plurality of nozzles to form a second elongated droplet, the second elongated droplet being oblique with the optical axis of the collector mirror at a different angle than the first elongated droplet.