Radiation Analysis System Using Thermal Expansion

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Solution Overview

Problem

Current radiation power measurement techniques in lithographic apparatuses, such as photodetectors, suffer from high uncertainties due to inherent calibration issues, temperature variations, and contamination, leading to inaccurate power readings which can damage pellicles and affect throughput.

Innovation Solution

A radiation analysis system comprising a thermally isolated target with two marks that undergo thermal expansion when illuminated, allowing for accurate measurement of radiation power through a position measurement system, which can be easily retrofitted into existing lithographic apparatuses, and utilizing multiple targets with different absorption properties to analyze various wavelengths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If photodetectors are used for radiation power measurement, then measurement capability is provided, but measurement precision deteriorates due to calibration issues, temperature variations, and contamination

Engineering Contradiction:

Improveradiation power measurement accuracyVSAvoidmeasurement reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces photodetector-based electromagnetic measurement with a mechanical measurement system. A target with marks is illuminated by radiation, causing thermal expansion that changes the separation between marks. This mechanical change is then measured by a position measurement system, providing a more reliable and calibration-free measurement method.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent directly utilizes thermal expansion as the measurement mechanism. When the target is illuminated with radiation, it absorbs energy and expands thermally. The separation between marks on the target changes proportionally to the radiation power, providing a direct physical correlation between radiation intensity and measurable mechanical displacement.

Inventive Principle:

Principle #37Thermal expansion

2Productivity

If radiation power is increased to maintain throughput, then productivity is improved, but harmful factors increase causing pellicle damage

Engineering Contradiction:

Improvelithographic throughputVSAvoidpellicle damage risk

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback control system where the radiation power measurement obtained through thermal expansion provides real-time information about actual radiation intensity. This feedback enables dynamic adjustment of radiation power to maintain optimal throughput while preventing excessive power levels that would damage the pellicle, thus resolving the contradiction between productivity and harmful effects.

Inventive Principle:

Principle #23Feedback

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 system provides accurate, in-situ, passive measurements of radiation power with reduced uncertainties, preventing pellicle damage and optimizing lithographic apparatus performance by ensuring precise power control.

Implementation Method 1

a target comprising two marks which are separated from each other, the target being configured to undergo thermal expansion when illuminated with radiation

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

a position measurement system configured to measure a change in the separation of the marks

Methodology Applied

Scientific EffectPosition measurement:

Data Source

PatentUS10935673B2Radiation analysis system

Publication Date: 2021.03.02 ASML NETHERLANDS BV

AI summary

A radiation analysis system comprising a target comprising two marks which are separated from each other, the target being configured to undergo thermal expansion when illuminated with radiation; a position measurement system configured to measure a change in the separation of the marks; and a processor configured to determine a power of the radiation using the measured change in separation of the marks.