EUV Light Source Droplet Spacing via Modulated Waveforms

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Solution Overview

Problem

Current laser-produced plasma EUV light sources face challenges in producing a stable stream of droplets with sufficient spacing to reduce the impact of plasma debris, leading to lower EUV output and increased source material consumption, due to limitations in droplet spacing caused by single frequency non-modulated disturbance waveforms.

Innovation Solution

A plasma generating system using a nozzle with an electro-actuable element producing a modulated disturbance waveform, optimized to match resonance frequencies with the modulation frequency, allowing droplets to coalesce and form larger droplets with increased spacing, reducing the effect of plasma debris and improving EUV output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If single frequency non-modulated disturbance waveforms are used to eject droplets, then the droplet generation process is simple, but the droplet spacing is insufficient and timing jitter is high, leading to lower EUV output and increased source material consumption

Engineering Contradiction:

Improvedroplet generation processVSAvoiddroplet spacing and timing

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent applies dynamics by transitioning from a static single-frequency disturbance waveform to a dynamic modulated disturbance waveform. The modulation frequency is specifically tuned to match the resonance frequency of the droplet stream, creating time-varying disturbances that enhance droplet spacing control and reduce timing jitter, thereby resolving the contradiction between process simplicity and precision.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameters of the disturbance waveform by introducing modulation frequency as an additional control parameter. By adjusting the modulation frequency to match the resonance frequency of the droplet stream, the system achieves improved droplet spacing and timing precision without fundamentally changing the droplet generation mechanism, thus maintaining relative simplicity while enhancing precision.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If droplet spacing is increased to reduce plasma debris impact, then debris effect is minimized, but droplet stream stability decreases and EUV output is reduced

Engineering Contradiction:

Improveplasma debris impactVSAvoiddroplet stream stability

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The patent utilizes mechanical vibration principles by applying resonant vibrations to the droplet stream through modulated disturbance waveforms. The modulation frequency matches the natural resonance frequency of the droplet stream, creating controlled vibrations that enhance droplet spacing and reduce plasma debris impact while maintaining stream stability through resonant coupling.

Inventive Principle:

Principle #18Mechanical vibration

3Object-affected harmful factors

If modulated disturbance waveform is used to increase droplet spacing, then plasma debris impact is reduced, but the system complexity increases

Engineering Contradiction:

Improveplasma debris impactVSAvoiddisturbance waveform generation

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies periodic action by using modulated disturbance waveforms with specific modulation frequencies that match the resonance frequency of the droplet stream. This periodic modulation creates regular, predictable droplet spacing patterns that reduce plasma debris impact while maintaining system controllability and avoiding excessive complexity.

Inventive Principle:

Principle #19Periodic action

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 modulated disturbance waveform enables a stable stream of coalesced droplets with reduced timing jitter and increased spacing, enhancing EUV output while minimizing source material consumption and debris impact, thus improving the efficiency and accuracy of the EUV light source.

Implementation Method 1

A plasma generating system using a nozzle with an electro-actuable element producing a modulated disturbance waveform, optimized to match resonance frequencies with the modulation frequency

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 2

laser producing a beam irradiating target material droplets at an irradiation region

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 3

The irradiated droplets form a plasma that produces extreme ultraviolet (EUV) radiation

Methodology Applied

Scientific EffectPlasma: Plasma

Data Source

PatentUS8969839B2Laser produced plasma EUV light source

Publication Date: 2015.03.03 ASML NETHERLANDS BV

AI summary

Methods and apparatus for producing irradiation targets in an extreme ultraviolet (EUV) light source having an irradiation target generating system that includes a nozzle configured for ejecting droplets of a target material, and a subsystem having an electro-actuable element producing a modulation waveform to cause disturbance to the droplets thereby causing at least some of the droplets to coalesce into irradiation targets. There is included a laser producing a beam for irradiating the irradiation targets to generate an EUV-producing plasma, wherein the electro-actuable element is biased against the nozzle to enable transfer of the disturbance to the droplets while permitting relative movement between the electro-actuable element and the nozzle.