Dislocation Filtering in Epitaxial Layer Growth

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Solution Overview

Problem

The formation of dislocations in germanium-tin and silicon-germanium-tin epitaxial layers during growth on lattice-mismatched substrates degrades their electronic and optical properties, making it challenging to achieve thick, strain-free layers for optoelectronic applications.

Innovation Solution

A process involving the formation of a sacrificial layer with dislocations due to interfacial strain, followed by a bulk layer grown using epitaxial chemical vapor deposition, where the bulk layer is substantially free from dislocations, achieved by using a reaction system like Epsilon® 2000 Plus, with specific precursor gases and temperature/pressure conditions to create a strain-relaxed structure that inhibits dislocation propagation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If epitaxial layers are grown on lattice-mismatched substrates, then thick layers can be formed, but dislocations are generated that degrade electronic and optical properties

Engineering Contradiction:

Improvethickness of epitaxial layerVSAvoidquality of electronic and optical properties

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

A sacrificial layer is introduced as an intermediary between the substrate and the bulk epitaxial layer. This sacrificial layer absorbs the lattice mismatch strain and generates dislocations within itself, preventing dislocation propagation into the bulk layer. The sacrificial layer is later removed, leaving a dislocation-free bulk epitaxial layer on the substrate.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The dislocation-generating sacrificial layer is extracted and removed after serving its purpose of filtering dislocations. This extraction leaves behind a high-quality bulk epitaxial layer free from dislocations, resolving the contradiction between achieving thick layers and maintaining material quality.

Inventive Principle:

Principle #2Taking out (Extraction)

2Volume of moving object

If strain relaxation occurs via dislocation formation, then thick epitaxial layers can be achieved, but the presence of dislocations degrades layer properties

Engineering Contradiction:

Improvethickness of epitaxial layerVSAvoiddislocation impact on layer properties

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The harmful dislocations are converted into a beneficial filtering mechanism. The sacrificial layer is deliberately designed to generate dislocations through strain relaxation, but these dislocations are confined to the sacrificial layer and serve to block dislocation propagation into the bulk epitaxial layer, ultimately improving the quality of the final structure.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The sacrificial layer acts as a mediator that undergoes strain relaxation and dislocation formation, protecting the bulk epitaxial layer from these harmful effects. This intermediary layer absorbs the mechanical stress and prevents it from propagating to the functional layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a sacrificial layer is used to filter dislocations, then dislocation-free bulk layers can be formed, but the process complexity increases

Engineering Contradiction:

Improvedislocation-free quality of bulk layerVSAvoidnumber of layers and process steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The sacrificial layer is discarded after serving its temporary purpose of filtering dislocations. This temporary structure is removed via selective etching, simplifying the final structure to just the substrate and the high-quality bulk epitaxial layer, while the benefits of dislocation filtering are retained.

Inventive Principle:

Principle #34Discarding and recovering

Solution Approach 2:

The sacrificial layer is prepared in advance before growing the bulk epitaxial layer. This preliminary action of creating a dislocation-filtering structure enables the subsequent growth of high-quality thick layers without dislocation contamination, even though it adds an initial process step.

Inventive Principle:

Principle #10Preliminary action

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 allows for the formation of thick, dislocation-free epitaxial layers, enhancing the operational performance of optoelectronic devices by preventing dislocation propagation and improving the incorporation of tin, resulting in improved electronic and optical properties.

Implementation Method 1

forming a bulk layer on top of the sacrificial layer, wherein the bulk layer comprises a same material as the sacrificial layer

Methodology Applied

Scientific EffectChemical vapor deposition: Chemical Vapour Deposition

Implementation Method 2

the sacrificial layer comprises at least one dislocation caused by an interfacial strain; and wherein the bulk layer is substantially free from dislocations caused by an interfacial strain

Methodology Applied

Scientific EffectStrain relaxation: Stress Relaxation

Data Source

PatentUS10388509B2Formation of epitaxial layers via dislocation filtering

Publication Date: 2019.08.20 ASM IP HLDG BV

AI summary

A process for forming a thick defect-free epitaxial layer is disclosed. The process may comprise forming a buffer layer and a sacrificial layer prior to forming the thick defect-free epitaxial layer. The sacrificial layer and the thick defect-free epitaxial layer may be formed of the same material and at the same process conditions.