Supercontinuum Light Source for Lithography Metrology

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Solution Overview

Problem

Current metrology devices in lithographic processes are limited by the sensitivity and speed of their radiation sources, particularly Xe lamps and SLED lasers, which have poor bandwidth and limited wavelength capabilities.

Innovation Solution

A metrology apparatus utilizing a supercontinuum light source with a non-linear fibre to generate a broadband measurement beam, enabling increased signal-to-noise ratios and measurement speed, and allowing for measurements on latent marks in undeveloped resist, integrated into the lithographic apparatus for in-line metrology.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If Xe lamps are used as radiation sources, then a wide bandwidth is achieved, but luminance and spatial coherence are poor

Engineering Contradiction:

ImprovebandwidthVSAvoidluminance

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

The radiation source is segmented into multiple independent laser sources, each operating at a specific wavelength. This allows the system to combine the advantages of narrow-line lasers (high luminance and spatial coherence) while achieving broadband coverage through wavelength multiplexing, thereby resolving the contradiction between bandwidth and luminance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system uses a composite light source configuration combining multiple laser sources with different wavelength characteristics. This composite approach enables the system to achieve both wide bandwidth (through wavelength diversity) and high luminance (through laser coherence), simultaneously addressing both requirements that were previously contradictory.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If SLED lasers are used as radiation sources, then good luminance and spatial coherence are achieved, but bandwidth is limited and wavelengths below 400nm cannot be generated

Engineering Contradiction:

ImproveluminanceVSAvoidbandwidth

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system creates a universal radiation source that can operate across multiple wavelength ranges (including UV below 400nm) by combining multiple laser sources. This multi-functional source replaces the need for different specialized sources, achieving both high luminance and wide bandwidth adaptability simultaneously.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If conventional radiation sources are used, then device complexity is low, but measurement sensitivity and speed are limited

Engineering Contradiction:

Improvemeasurement sensitivityVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

A beam combining unit acts as an intermediary component that merges multiple laser beams into a single broadband measurement beam. This intermediary element enables the system to achieve high measurement sensitivity through coherent combination while maintaining relatively simple device architecture, as the beam combining unit integrates multiple functions in a single component.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Multiple laser sources are merged into a single broadband radiation source through the beam combining unit. This merging approach increases measurement sensitivity by combining the coherent properties of multiple lasers while achieving broadband coverage, thereby improving measurement performance without proportionally increasing device complexity.

Inventive Principle:

Principle #5Merging (Combining)

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 supercontinuum light source enhances measurement sensitivity and speed, enabling accurate and rapid metrology, including the detection of latent marks, and facilitating real-time adjustments during the manufacturing process.

Implementation Method 1

a non-linear fibre to generate a broadband measurement beam

Methodology Applied

Scientific EffectNon-linear optical effect:

Implementation Method 2

One such method is scatterometry, in particular angle-resolved scatterometry in which the spectrum of the radiation reflected by the structure under inspection is measured at different angles

Methodology Applied

Scientific EffectScattering: Scattering

Data Source

PatentEP3483657B1Metrology apparatus for lithography and corresponding metrology method

Publication Date: 2021.01.13 ASML NETHERLANDS BV

Figure 1
Figure 2
Figure 3~5

AI summary

A metrology apparatus for measuring a parameter of a microscopic structure on a substrate (W), the apparatus comprising a supercontinuum light source (2) arranged to generate a measurement beam, an optical system (202) arranged to direct the measurement beam onto the substrate and a sensor (205) for detecting radiation reflected and/or diffracted by the structure.