Separation Annealing Cooling Profile for SOI Substrate Integrity

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Solution Overview

Problem

The existing methods for separation annealing in producing Silicon On Insulator (SOI) structures often result in 'cleavage line' defects, which prevent the recycling of substrates and can damage the positive substrate, leading to loss and defects in the final SOI structure.

Innovation Solution

Regulating the second phase of the separation annealing process to minimize temperature inhomogeneities at the surface of the substrates by controlling the duration and temperature of the cooling phase, ensuring the substrates are unloaded at a low temperature with a minimal temperature gradient, and injecting a gas stream to promote cooling, thereby reducing thermal shocks and constraints.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional separation annealing is used to detach substrates, then the detachment process is completed, but 'cleavage line' defects appear on the substrates preventing recycling and damaging the positive substrate

Engineering Contradiction:

Improvesubstrate integrityVSAvoidcleavage line defects

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by modifying the temperature profile during separation annealing. Specifically, it regulates the second phase (cooling phase) to minimize temperature inhomogeneities at the substrate surface when the furnace is opened. This involves controlling the duration and temperature of the cooling phase, and injecting a gas stream to promote uniform cooling, thereby reducing thermal shocks that cause cleavage line defects

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements preliminary action by regulating the cooling phase before the furnace is opened. The second phase is specifically designed to minimize temperature inhomogeneities at the substrate surface prior to unloading. This preliminary temperature equalization prevents thermal shocks during furnace opening that would otherwise cause cleavage line defects

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the furnace is opened immediately after annealing, then the process time is reduced, but temperature inhomogeneities cause cleavage line defects

Engineering Contradiction:

Improveprocess timeVSAvoidtemperature uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies pneumatics by injecting a gas stream during the cooling phase to promote uniform cooling of the substrates. This gas injection helps minimize temperature inhomogeneities at the substrate surface when the furnace is opened, preventing cleavage line defects while maintaining process efficiency

Inventive Principle:

Principle #29Pneumatics and hydraulics

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

Significantly reduces the occurrence of 'cleavage line' defects, improving the yield and reducing final defectivity of the SOI structures, allowing for the recycling of more substrates and minimizing manual intervention, while maintaining the overall duration of the process.

Implementation Method 1

separation annealing, the SOI surface (buried oxide layer and superficial silicon layer) is transferred from a donor substrate (previously oxidized and implanted) to a receiver substrate

Methodology Applied

Scientific EffectThermal diffusion: Diffusion

Implementation Method 2

the second phase is regulated so as to minimize temperature inhomogeneities at the surface of the detached substrates when the furnace is opened

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

minimize temperature inhomogeneities at the surface of the detached substrates

Methodology Applied

Scientific EffectThermal gradient: Temperature Gradient

Data Source

PatentUS8088671B2Defectivity of post thin layer separation by modification of its separation annealing

Publication Date: 2012.01.03 SOITEC SA

AI summary

A method of detaching two substrates at the embrittlement zone situated at a given depth of one of the two substrates. The method includes a separation annealing step implemented in a furnace, wherein the annealing includes a first phase during which the temperature changes along an upgrade allowing a high temperature to be reached and annealing at this high temperature to be stabilized, and a second phase during which the temperature changes along a downgrade, at the end of which the furnace is opened to unload the substrates from the furnace. The second phase is regulated so as to minimize temperature inhomogeneities such as cleavage defects at the detached surfaces of the substrates when the furnace is opened.