High Harmonic Generation Pre-Pulse Plasma Wavefront Conditioning

Solution Overview

Problem

Current high harmonic radiation sources face limitations in power scaling and beam quality due to plasma defocusing effects, which impair efficiency and output power, especially in metrology applications requiring high-resolution imaging for shrinking semiconductor features.

Innovation Solution

A method involving a pre-pulse with a customized spatial distribution is used to condition the gas target, creating a pre-pulse plasma distribution that counteracts subsequent plasma defocusing, thereby improving the phase matching condition and beam quality of the high harmonic radiation generated by the main pulse.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If high harmonic generation is used to generate EUV radiation for metrology applications, then spatial resolution is improved, but power scaling and beam quality are limited due to plasma defocusing effects

Engineering Contradiction:

Improvespatial resolutionVSAvoidoutput power

Core Design Contradiction:

Measurement precisionVSPower

Solution Approach 1:

A pre-pulse is applied before the main high harmonic generation pulse to condition the gas medium and create a plasma distribution that counteracts plasma defocusing effects during the main pulse interaction, thereby improving beam quality and power scaling

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The spatial distribution of plasma density is modified by controlling the pre-pulse parameters (intensity, duration, focal position) to optimize the phase matching condition and reduce defocusing effects during the main pulse interaction

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If high harmonic generation is used to generate EUV radiation for metrology applications, then spatial resolution is improved, but beam quality deteriorates due to plasma defocusing effects

Engineering Contradiction:

Improvespatial resolutionVSAvoidbeam quality

Core Design Contradiction:

Measurement precisionVSShape

Solution Approach 1:

A pre-pulse is applied before the main high harmonic generation pulse to condition the gas medium and create a plasma distribution that counteracts plasma defocusing effects during the main pulse interaction, thereby improving beam quality and power scaling

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The spatial distribution of plasma density is modified by controlling the pre-pulse parameters (intensity, duration, focal position) to optimize the phase matching condition and reduce defocusing effects during the main pulse interaction

Inventive Principle:

Principle #35Parameter changes

3Power

If plasma defocusing effects are present in high harmonic generation, then efficiency is reduced, but power scaling is limited

Engineering Contradiction:

Improveoutput powerVSAvoidgeneration efficiency

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

A pre-pulse is applied before the main high harmonic generation pulse to condition the gas medium and create a plasma distribution that counteracts plasma defocusing effects during the main pulse interaction, thereby improving beam quality and power scaling

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The spatial distribution of plasma density is modified by controlling the pre-pulse parameters (intensity, duration, focal position) to optimize the phase matching condition and reduce defocusing effects during the main pulse interaction

Inventive Principle:

Principle #35Parameter changes

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 power and beam quality of high harmonic radiation, enabling higher throughput and better optical resolution in metrology systems, particularly for EUV and SXR regions, thus addressing the limitations of existing high harmonic radiation sources.

Implementation Method 1

an intense laser pulse of visible or infrared (IR) radiation is focused into a gas target, leading to emission of radiation in the desired range by the gas atoms due to their interaction with the laser light

Methodology Applied

Scientific EffectHigh harmonic generation:

Implementation Method 2

the plasma comprising a pre-pulse plasma distribution acts to configure a wavefront of said main pulse to improve one or both of: the efficiency of the high harmonic generation process and the beam quality

Methodology Applied

Scientific EffectPhase matching:

Data Source

PatentUS12196688B2Method and apparatus for efficient high harmonic generation

Publication Date: 2025.01.14 ASML NETHERLANDS BV

AI summary

A high harmonic radiation source and associated method of generating high harmonic radiation is disclosed. The high harmonic radiation source is configured to condition a gas medium by irradiating the gas medium with a pre-pulse of radiation, thereby generating a plasma comprising a pre-pulse plasma distribution; and irradiate the gas medium with a main pulse of radiation to generate said high harmonic radiation. The conditioning step is such that the plasma comprising a pre-pulse plasma distribution acts to configure a wavefront of said main pulse to improve one or both of: the efficiency of the high harmonic generation process and the beam quality of the high harmonic radiation. The high harmonic radiation source further may comprise a beam shaping device configured to shape said customized pre-pulse prior to said conditioning.