Epitaxial Layer Composition Matching for Defect-Free Thick Growth

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Solution Overview

Problem

Thick epitaxially grown layers on engineered substrates with significant thermal expansion coefficient differences between the handle substrate and crystalline seed layer lead to strain and relaxation defects, which can propagate through the layer, deteriorating device performance.

Innovation Solution

Selecting the composition of the second crystalline semiconductor layer to match the lateral lattice constant of the strained top layer at growth temperature, ensuring the layer is essentially unstrained, thereby preventing relaxation defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thick epitaxial layers are grown on engineered substrates with large thermal expansion coefficient differences, then the substrate integration benefits are achieved, but strain and relaxation defects propagate through the layer

Engineering Contradiction:

Improvedevice performanceVSAvoidstrain and relaxation defects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the compositional parameters of the epitaxial layer to match the lateral lattice constant of the strained seed layer at growth temperature. This parameter adjustment eliminates the strain that would otherwise propagate through thick layers, allowing reliable device performance without relaxation defects.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention applies a specific compositional gradient or localized composition adjustment in the epitaxial layer to match the strained lattice constant of the seed layer. This local quality adjustment ensures that the interface region accommodates the strain while the bulk layer can grow thick without defects.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the grown layer has the same free-standing lateral lattice constant as the seed layer, then lattice matching is achieved, but the layer becomes strained at growth temperature due to thermal expansion differences

Engineering Contradiction:

Improvelattice matchingVSAvoidstrain at growth temperature

Core Design Contradiction:

Manufacturing precisionVSStress or pressure

Solution Approach 1:

The invention adjusts the compositional parameters of the epitaxial layer so that its free-standing lateral lattice constant at growth temperature matches the strained seed layer's lateral lattice constant. This compensates for thermal expansion differences and eliminates strain while maintaining lattice matching.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention considers the temperature dimension when matching lattice constants. By matching the lateral lattice constant at growth temperature rather than at room temperature, the solution accounts for thermal expansion effects and eliminates strain in the grown layer.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If the composition of subsequent layers is selected to match the previous layer's lateral lattice constant at growth temperature, then relaxation defects are prevented, but composition adjustments are required for each layer

Engineering Contradiction:

Improvedefect-free thick layersVSAvoidcomposition selection process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention establishes a systematic approach to compositional parameter selection for each epitaxial layer based on the previous layer's strained lattice constant at growth temperature. This methodical parameter adjustment ensures defect-free thick layers while providing a repeatable process for multi-layer structures.

Inventive Principle:

Principle #35Parameter changes

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

Enables growth of layers beyond critical thickness without relaxation defects, improving device performance and longevity by maintaining lattice matching.

Implementation Method 1

a second crystalline semiconductor layer is produced by epitaxial growth on said top layer

Methodology Applied

Scientific EffectEpitaxial growth: Epitaxy

Implementation Method 2

The thermal expansion coefficients of the handle substrate and the top layer are significantly different from each other, so that the top layer is strained at the growth temperature

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP4576165A1A method for growing epitaxial layers on an engineered substrate

Publication Date: 2025.06.25 INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW)

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AI summary

On an engineered substrate (1) comprising a handle substrate (2), and a crystalline semiconductor top layer (4) bonded to the handle substrate (2), a second crystalline semiconductor layer (10) is produced by epitaxial growth on said top layer (4). The thermal expansion coefficients of the handle substrate and the top layer are significantly different from each other, so that the top layer is strained at the growth temperature. The composition of the second layer (10) is selected so that at said growth temperature, the second layer is essentially unstrained. This enables growing a device stack with the second layer forming the bottom layer of said stack, and wherein said bottom layer (10) can be grown above a critical thickness without exhibiting relaxation defects. This is true also for subsequent layers (101-105;201-206) of the stack, especially for layers exceeding a critical thickness, by selecting the composition of said layers in the same way as the bottom layer.