Source Selection Module for Spectral Shaping in Lithography

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Solution Overview

Problem

Metrology applications in lithographic processes face challenges with wavelength/polarization-dependent variations in measured values due to imperfections in metrology targets, requiring improved switching and selection of spectral components for accurate measurements.

Innovation Solution

A source selection module comprising a beam dispersing element, a grating light valve module for spatial modulation of the broadband illumination beam, and a beam combining element to produce a spectrally shaped illumination beam, allowing for precise control of spectral components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple different wavelengths and/or polarizations are used for measurement, then measurement accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvemeasurement accuracyVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The illumination system dynamically switches between different spectral components and polarization states using a grating light valve module. This allows the system to adapt illumination conditions based on measurement requirements without requiring multiple fixed illumination sources, thereby improving measurement accuracy while controlling device complexity through a single reconfigurable source.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes physical parameters of the illumination beam (wavelength, polarization state) by using a tunable broadband source combined with a grating light valve. This enables multiple measurement conditions to be achieved by modifying beam parameters rather than using multiple separate illumination systems, resolving the contradiction between measurement precision and device complexity.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If spectral components are switched and selected for metrology applications, then measurement accuracy is improved, but switching speed may be reduced

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidswitching speed

Core Design Contradiction:

Measurement precisionVSSpeed

Solution Approach 1:

The system replaces mechanical wavelength selection methods (such as rotating filter wheels) with a grating light valve module that uses electro-optic or acousto-optic effects to switch between spectral components. This substitution of mechanical switching with field-controlled modulation significantly improves switching speed while maintaining the ability to select different spectral components for accurate measurements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If broadband illumination is used, then measurement versatility is improved, but intensity fluctuations and noise increase

Engineering Contradiction:

Improvemeasurement versatilityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system extracts only the necessary spectral components from the broadband illumination using a grating light valve module. By selecting specific wavelength ranges and polarization states relevant to the measurement task, the system maintains measurement versatility while eliminating unnecessary spectral components that contribute to noise and intensity fluctuations, thereby improving signal-to-noise ratio.

Inventive Principle:

Principle #2Taking out (Extraction)

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 solution enhances measurement accuracy by enabling tunable transmission and control of spectral components, reducing noise and improving signal-to-noise ratios, and extends the lifespan of broadband sources by compensating for intensity fluctuations.

Implementation Method 1

a beam dispersing element for dispersing the broadband illumination beam

Methodology Applied

Scientific EffectDispersion: Dispersion (of waves)

Implementation Method 2

a grating light valve module for spatially modulating the broadband illumination beam subsequent to being dispersed

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 3

a beam combining element to recombine the spatially modulated broadband illumination beam to obtain an output source beam

Methodology Applied

Scientific EffectInterference: Interference

Data Source

PatentUS20240402620A1Source selection module and associated metrology and lithographic apparatuses

Publication Date: 2024.12.05 ASML NETHERLANDS BV

AI summary

A source selection module for spectrally shaping a broadband illumination beam to obtain a spectrally shaped illumination beam. The source selection module includes a beam dispersing element for dispersing the broadband illumination beam; a grating light valve module for spatially modulating the broadband illumination beam subsequent to being dispersed; and a beam combining element to recombine the spatially modulated broadband illumination beam to obtain an output source beam.