Nanocrystal Light Source for Semiconductor Inspection

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Solution Overview

Problem

Current broadband light sources for semiconductor inspection and metrology face limitations in radiance, particularly with conventional plasma-based sources being limited by black-body radiation and laser-based sources experiencing speckle noise and sensitivity issues due to their narrow band and coherent nature.

Innovation Solution

A broadband illumination system utilizing a pump source and an active medium containing nanocrystals that down-convert pump illumination via photoluminescence to generate broadband illumination, overcoming radiance limitations and noise issues through the selection of nanocrystal composition and size for tailored emission spectra.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional plasma-based broadband light sources are used, then broadband illumination is achieved, but radiance is limited by black-body radiation

Engineering Contradiction:

ImproveradianceVSAvoidblack-body limit

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent changes the fundamental operating parameters of the light source by using laser pumping at specific wavelengths (e.g., 355 nm, 266 nm) to excite nanocrystals, transitioning from thermal equilibrium black-body radiation to non-equilibrium photoluminescence, thereby achieving radiance beyond black-body limits

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite nanocrystal materials with specific compositions (e.g., CdSe, CdS, ZnSe, PbS) and core-shell structures to achieve both broadband emission and high radiance, combining the advantages of different semiconductor materials to overcome individual limitations

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If laser-based narrow band sources are used, then high brightness is achieved, but speckle noise and sensitivity to film thickness occur

Engineering Contradiction:

ImprovebrightnessVSAvoidspeckle noise

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the narrow-band laser output into multiple wavelength components by using multiple nanocrystal types with different emission spectra, creating a composite broadband source that maintains high brightness while eliminating speckle noise through spectral diversity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the coherence parameter of the light source by using photoluminescence emission from nanocrystals, which inherently reduces temporal and spatial coherence compared to direct laser emission, thereby eliminating speckle noise while maintaining brightness

Inventive Principle:

Principle #35Parameter changes

3Temperature

If laser-sustained plasma sources are used, then higher temperatures are achieved, but radiance is still insufficient for many inspection applications

Engineering Contradiction:

Improveplasma temperatureVSAvoidradiance

Core Design Contradiction:

TemperatureVSIllumination intensity

Solution Approach 1:

The patent replaces the thermal-mechanical plasma heating mechanism with a direct photoluminescence emission mechanism, where laser energy is converted to light emission through quantum mechanical transitions in nanocrystals, achieving higher radiance efficiency without relying on thermal equilibrium

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 achieves high radiance and reduced noise, providing improved imaging capabilities for semiconductor inspection and metrology by generating stable, broadband visible and near-infrared radiation suitable for defect detection and characterization.

Implementation Method 1

the active medium is configured to emit broadband illumination by down converting a portion of the pump illumination via photoluminescence

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Data Source

PatentUS10495287B1Nanocrystal-based light source for sample characterization

Publication Date: 2019.12.03 KLA CORP

AI summary

A broadband illumination source is disclosed. The broadband illumination source may include a pump source configured to generate pump illumination. The broadband illumination also includes an active medium containing nanocrystals. The broadband illumination source includes pump illumination optics configured to direct pump illumination into the active medium. The active medium is configured to emit broadband illumination by down-converting a portion of the pump illumination via photoluminescence.