SiC Monocrystalline Layer Transfer via Polycrystalline Intermediate

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Solution Overview

Problem

Achieving high-quality direct bonding between single-crystal SiC and polycrystalline SiC substrates is challenging due to surface finish and roughness complexities, leading to bonding defects and impaired thermal and electrical conduction in composite structures for power electronics.

Innovation Solution

A process involving the formation of a polycrystalline SiC layer on a donor substrate, followed by ionic species implantation to create a plane of weakness, and direct bonding with a polycrystalline SiC carrier substrate, using a bonding layer with a melting point below the annealing temperature to facilitate stable interface formation and transfer of a thin single-crystal SiC layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If direct bonding is performed between single-crystal SiC and polycrystalline SiC substrates, then thermal and electrical conduction is improved, but bonding defects occur due to surface finish and roughness complexities

Engineering Contradiction:

Improvethermal and electrical conductionVSAvoidbonding quality

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

A polycrystalline SiC intermediate layer is introduced at the bonding interface between the single-crystal SiC thin layer and the polycrystalline SiC carrier substrate. This intermediate layer acts as a mediator that facilitates bonding while maintaining good thermal and electrical conduction, resolving the contradiction between achieving reliable conduction and avoiding bonding defects caused by direct bonding between mismatched crystal structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If surface activation methods (argon bombardment or sputter deposition) are used to achieve bonding, then bonding between single-crystal SiC and polycrystalline SiC is achieved, but an unstable layer is generated at the bonding interface

Engineering Contradiction:

Improvebonding capabilityVSAvoidbonding interface stability

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The polycrystalline SiC intermediate layer is deliberately designed as a sacrificial or stable intermediary that can be formed through standard deposition processes. Rather than using unstable activated surfaces, this intermediate layer provides a stable, reproducible bonding interface that maintains composition stability while enabling manufacturing of the composite structure.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If bonding defects are present at the joining interface, then adhesion is lost, but the thin layer detaches locally during transfer

Engineering Contradiction:

Improveadhesion qualityVSAvoidlayer attachment strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The polycrystalline SiC intermediate layer is formed in advance on the single-crystal SiC substrate before bonding to the carrier substrate. This pre-formed intermediate layer acts as a cushioning buffer that prevents direct adhesion failures between the thin single-crystal layer and the carrier, thereby preventing local detachment during the transfer process and maintaining both adhesion quality and layer strength.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 enhances the quality and reliability of composite structures by avoiding conduction barriers and surface defects, ensuring improved thermal and electrical performance in power devices.

Implementation Method 1

implanting ionic species in the surface portion of the donor substrate, so as to form a plane of weakness delimiting a thin single-crystal SiC layer to be transferred

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Implementation Method 2

bonding the donor substrate and the polycrystalline SiC carrier substrate, the polycrystalline SiC layer being at the bonding interface

Methodology Applied

Scientific EffectDirect bonding: Diffusion Welding

Data Source

PatentUS20240392476A1Method for transferring a monocrystalline sic layer onto a polycrystalline sic carrier using a poly crystalline sic intermediate layer

Publication Date: 2024.11.28 SOITEC SA

AI summary

A method of fabricating a composite structure including a thin layer of single-crystal silicon carbide on a polycrystalline SiC carrier substrate includes: forming a polycrystalline SiC layer on a donor substrate, at least a surface portion of which is made of single-crystal SiC; before or after forming the polycrystalline SiC layer, implanting ionic species into the surface portion of the donor substrate, so as to form a plane of weakness delimiting a thin single-crystal SiC layer to be transferred; after the implanting of the ionic species and the forming of the polycrystalline SiC layer, bonding the donor substrate and the polycrystalline SiC carrier substrate, the polycrystalline SiC layer being at the bonding interface; and detaching the donor substrate along the plane of weakness, so as to transfer the polycrystalline SiC layer and the thin single-crystal SiC layer onto the polycrystalline SiC carrier substrate.