Optical Shutter Controls EUV Light Energy Stability

Solution Overview

Problem

Current extreme ultraviolet (EUV) light generating systems face challenges in achieving stable energy and pointing stability during the initial bursts of pulsed laser light, leading to unstable EUV light generation and reduced ionization rates, particularly in the first few tens of pulses.

Innovation Solution

The system incorporates a light emission control system with an optical shutter or optical isolators that control the pulsed laser light based on a burst signal, ensuring stable energy and pointing by opening or closing the optical components in synchronization with the laser emission, thereby stabilizing the EUV light generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If pulsed laser light is applied continuously to generate EUV light, then EUV light production continues, but energy stability and pointing stability deteriorate during initial pulses

Engineering Contradiction:

ImproveEUV light production continuityVSAvoidenergy stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system performs preliminary actions by continuously applying pulsed laser light to the target substance before actual EUV exposure begins. This pre-ionization process creates a stable plasma environment that ensures subsequent EUV light generation maintains consistent energy and pointing stability from the first pulse.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The laser pulsing is divided into two distinct phases: a preliminary phase for plasma generation and stabilization, followed by an operational phase for actual EUV production. This segmentation allows the system to establish stable plasma conditions before beginning the measurement or exposure process.

Inventive Principle:

Principle #1Segmentation

2Productivity

If pulsed laser light is applied continuously to generate EUV light, then EUV light production continues, but ionization rate stability deteriorates during initial pulses

Engineering Contradiction:

ImproveEUV light production continuityVSAvoidionization rate stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system performs preliminary actions by continuously applying pulsed laser light to the target substance before actual EUV exposure begins. This pre-ionization process creates a stable plasma environment that ensures subsequent EUV light generation maintains consistent energy and pointing stability from the first pulse.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system monitors plasma generation effectiveness during the preliminary pulsing phase and adjusts laser parameters accordingly to optimize ionization rates. This feedback mechanism ensures stable plasma conditions are established before operational EUV production begins.

Inventive Principle:

Principle #23Feedback

3Productivity

If pulsed laser light is applied continuously to generate EUV light, then EUV light production continues, but neutral debris formation increases during initial pulses

Engineering Contradiction:

ImproveEUV light production continuityVSAvoidneutral debris

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The system performs preliminary actions by continuously applying pulsed laser light to the target substance before actual EUV exposure begins. This pre-ionization process creates a stable plasma environment that ensures subsequent EUV light generation maintains consistent energy and pointing stability from the first pulse.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system converts the potentially harmful neutral debris generated during initial pulsing into beneficial pre-ionized plasma. By continuously pulsing before operation, the neutral material is transformed into ionized plasma that enhances EUV generation efficiency and reduces harmful debris during actual production.

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 enhances the stability of EUV light energy and pointing, improving the ionization rate and reducing neutral debris formation, leading to more consistent and efficient EUV light production.

Implementation Method 1

a laser apparatus (3) configured to provide pulsed laser light (31) inside a chamber (2) in which extreme ultraviolet (EUV) light (251) is generated

Methodology Applied

Scientific EffectLaser: Laser

Implementation Method 2

an optical shutter (310) disposed on an optical path of the pulsed laser light (31)

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Implementation Method 3

The Pockels cell (394) may include a high-voltage power source (393), a first electrode (395a), a second electrode (395b), and an electrooptical crystal (395c)

Methodology Applied

Scientific EffectPockels effect: Pockels Effect

Implementation Method 4

plasma generated by application of a laser beam to a target substance

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 5

extreme ultraviolet (EUV) light (251) is generated

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Data Source

PatentUS9439276B2Extreme ultraviolet light generating system

Publication Date: 2016.09.06 GIGAPHOTON INC

AI summary

There is provided an extreme ultraviolet light generating system. The extreme ultraviolet light generating system may include: a laser apparatus configured to provide pulsed laser light inside a chamber in which EUV light is generated; an optical shutter disposed on an optical path of the pulsed laser light; and a controller configured to open or close the optical shutter, based on a generation signal supplied from an external unit, the generation signal instructing generation of the EUV light.