EUV Collector Contamination Reduction via Dual-Pulse Laser and Hydrogen Gas

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Solution Overview

Problem

The collector in extreme ultraviolet lithography systems, particularly those using laser-produced plasma, faces contamination and degradation due to particle and ion impacts, leading to reduced reflectivity and shorter usable lifetime, primarily caused by tin debris deposition.

Innovation Solution

The implementation of a dual-pulse laser-produced plasma system with controlled pre-pulse and main pulse timing to generate multiply-oriented target plumes, combined with hydrogen gas flow to chemically react with tin debris, effectively spreading and removing tin deposition on the collector surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single-pulse laser system is used to generate EUV radiation, then the system structure is simple, but tin debris accumulates on the collector leading to rapid contamination and degradation

Engineering Contradiction:

Improvelaser system structureVSAvoidcollector contamination resistance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The single laser pulse is divided into two sequential pulses: a pre-pulse (first pulse) that creates a low-density plasma plume, and a main pulse (second pulse) that generates EUV radiation. This temporal segmentation of the laser pulse prevents direct interaction between the main pulse and target debris, reducing tin contamination on the collector while maintaining system feasibility

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The pre-pulse is applied before the main pulse to pre-ionize the target and create a low-density plasma plume. This preliminary action removes potential debris-forming material from the interaction zone before the main pulse arrives, preventing tin debris generation and collector contamination

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the laser pulse duration is increased to improve EUV output, then more tin debris is generated and deposited on the collector, but shorter pulses reduce EUV generation efficiency

Engineering Contradiction:

ImproveEUV radiation outputVSAvoidtin debris deposition

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The laser system uses periodic pulsed operation with two distinct pulse phases: a pre-pulse phase that prepares the target by creating low-density plasma, and a main pulse phase that generates EUV radiation. This periodic two-phase action separates the debris-generation risk from the EUV production moment, maintaining high productivity while minimizing contamination

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The dual-pulse system maintains continuous useful action by ensuring the pre-pulse always precedes the main pulse in each cycle, continuously preparing the target state optimal for EUV generation. This continuous preparatory action ensures consistent low debris generation across all EUV production cycles

Inventive Principle:

Principle #20Continuity of useful action

3Productivity

If the collector is positioned closer to the target to improve EUV collection efficiency, then more tin debris reaches and contaminates the collector surface

Engineering Contradiction:

ImproveEUV collection efficiencyVSAvoidcollector usable lifetime

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The system converts the potentially harmful direct line-of-sight path between target and collector into a beneficial arrangement by using the pre-pulse created low-density plume as a protective medium. The plume fills the space between target and collector, allowing the collector to remain close for efficient EUV collection while the low-density plume prevents tin debris from reaching the collector surface

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 significantly reduces tin contamination on the collector, enhancing its reflectivity and extending its usable lifetime by distributing debris deposition and utilizing hydrogen gas to remove tin debris efficiently.

Implementation Method 1

A first laser source produces a plurality of first laser pulses that heat a target droplet to generate a low-density target plume. A second laser source produces a plurality of second laser pulses that heat the target plume to generate plasma that emits extreme ultraviolet (EUV) radiation.

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

The stannane is reacted with a hydrogen gas flow to form stannane, and the stannane is pumped away.

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Data Source

PatentUS9625824B2Extreme ultraviolet lithography collector contamination reduction

Publication Date: 2017.04.18 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An extreme ultraviolet (EUV) radiation source module includes a target droplet generator, a first laser source, and a second laser source. The target droplet generator is configured to generate a plurality of target droplets. The first laser source is configured to generate a plurality of first laser pulses that heat the target droplets at respective excitation positions thereby generating a plurality of target plumes. At least one of the target droplets is heated at an excitation position different from that of other target droplets. The second laser source is configured to generate a plurality of second laser pulses that heat the target plumes thereby generating plasma emitting EUV radiation.