Layer Transfer Process Using Localized Electromagnetic Irradiation

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Solution Overview

Problem

The existing SmartCut process for transferring a layer generates high stresses due to differential thermal expansion coefficients, leading to defects and delamination in the structure, particularly during heat treatment steps.

Innovation Solution

A localized heat treatment using electromagnetic irradiations is applied to the embrittlement region, with a bonding layer thermally decoupling the support substrate, preventing excessive temperature increase and stress generation, allowing for controlled fracturing and annealing at lower temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If blanket heat treatment is applied to the entire structure during fracturing and annealing, then the embrittlement region can be effectively treated, but high stresses are generated due to differential thermal expansion coefficients causing defects and delamination

Engineering Contradiction:

Improveintegrity of transferred structureVSAvoidthermal stress and defects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies localized heat treatment only to the embrittlement region rather than the entire structure. The electromagnetic radiation (e.g., laser) is focused on the specific area requiring treatment, creating a localized temperature increase that avoids generating high thermal stresses in the bulk structure while still achieving the desired embrittlement effect in the target region.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The heat treatment process is segmented into localized zones rather than applied uniformly. The bonding layer acts as a thermal barrier that segments the thermal field, confining the heat to the donor substrate side and preventing thermal propagation to the support substrate, thereby treating only the necessary region without affecting the entire structure.

Inventive Principle:

Principle #1Segmentation

2Use of energy by moving object

If the support substrate is thermally coupled to the donor substrate, then heat can be efficiently transferred, but the support substrate temperature increases leading to stress generation and potential defects

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoidthermal stress and defects

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The bonding layer serves as a thermal intermediary or barrier between the donor substrate and support substrate. It allows mechanical bonding while providing thermal isolation, preventing heat from the donor substrate from propagating to the support substrate during localized heat treatment, thus avoiding thermal stress generation in the support substrate.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The bonding layer creates a localized thermal environment where heat is confined to specific regions. By having different thermal properties at different locations (coupled mechanically but isolated thermally), the system achieves efficient localized heat treatment without unwanted thermal propagation to adjacent components.

Inventive Principle:

Principle #3Local quality

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 minimizes the risk of defects and delamination by maintaining the support substrate temperature below threshold levels, enabling efficient transfer of the layer with reduced thermal stress, thus improving the integrity of the transferred structure.

Implementation Method 1

The electromagnetic irradiations belong to a spectral domain in which the support substrate, the bonding layer and the donor substrate are transparent, transparent and absorbent, respectively

Methodology Applied

Scientific EffectAbsorption of electromagnetic radiation: Absorption (EM radiation)

Implementation Method 2

exposing, in succession, portions of the embrittlement region to electromagnetic irradiations for an exposure time at a given power density

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 3

the presence of the bonding layer is essential as it allows the support substrate to be thermally decoupled from the first part of the donor substrate

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 4

The donor substrate and the support substrate made of materials having a first and second thermal expansion coefficient

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP2865004B1Process for transferring a layer

Publication Date: 2020.07.29 SOITEC SA

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Figure 2

AI summary

This transfer process comprises the following steps: (a) providing a donor substrate (2) and a support substrate (3); (b) forming a embrittlement region (4) in the donor substrate (2); (c) forming what is called a bonding layer (5) between the first part (1) of the donor substrate (2) and the support substrate (3); and (d) assembling the donor substrate (2) to the support substrate (3), and is noteworthy in that it comprises the following step: (e) exposing, in succession, portions (40) of the embrittlement region (4) to electromagnetic irradiations (6) for an exposure time at a given power density, the exposure time being chosen depending on the thickness (E) of the bonding layer so that the support substrate (3) is thermally decoupled from the first part (1) of the donor substrate (2), the exposure time being chosen depending on the power density in order to activate kinetics that weaken the embrittlement region (4).