Reclaimable SOI Donor Substrates With Deep Denuded Zones

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Solution Overview

Problem

Existing silicon wafers used in silicon-on-insulator (SOI) structures face challenges due to the growth of defects, such as oxygen precipitates and surface imperfections during SOI processing, limiting the number of times donor wafers can be reclaimed for producing defect-free device layers, which increases costs and material waste.

Innovation Solution

The use of perfect silicon wafers with a denuded zone extending at least 25 μm, created through an ultra-high temperature rapid thermal process (UHT RTP), maintains a low concentration of interstitial oxygen and dominant intrinsic point defects, ensuring the wafers remain defect-free throughout multiple SOI processing cycles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional silicon wafers are reused for multiple SOI processing cycles, then material cost increases and productivity decreases, but defect growth (oxygen precipitates and surface imperfections) limits the number of reclaims

Engineering Contradiction:

Improvenumber of wafer reclaimsVSAvoiddefect-free quality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by performing an ultra-high temperature rapid thermal process (UHT RTP) on the silicon wafer before it enters the SOI processing cycles. This pre-treatment creates a denuded zone that prevents oxygen precipitates from forming during subsequent processing, thereby enabling multiple reclaims while maintaining defect-free quality. The preliminary action of UHT RTP modifies the wafer's internal structure in advance to resist future defect formation.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If conventional silicon wafers undergo SOI processing, then device layers are produced, but oxygen precipitates and surface defects grow during processing

Engineering Contradiction:

Improvedevice layer productionVSAvoidoxygen precipitates and surface defects

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by using UHT RTP to create a denuded zone that actively prevents oxygen precipitates from forming during SOI processing. The rapid thermal process drives oxygen out of the near-surface region before processing begins, creating a protective zone that resists defect formation. This counter-action occurs in advance to offset the harmful effect of oxygen precipitate growth that would otherwise occur during device layer production.

Inventive Principle:

Principle #9Preliminary anti-action

3Loss of substance

If donor wafers are reclaimed multiple times, then material waste reduces and costs decrease, but defect accumulation limits reuse capability

Engineering Contradiction:

Improvematerial wasteVSAvoidwafer quality consistency

Core Design Contradiction:

Loss of substanceVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by fundamentally altering the thermal history and oxygen distribution parameters of the silicon wafer through UHT RTP treatment. This process changes the concentration and distribution of interstitial oxygen, creating a denuded zone with suppressed oxygen content. By changing these material parameters in advance, the wafer can withstand multiple processing cycles without accumulating defects, thereby enabling repeated reuse while maintaining consistent manufacturing precision.

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

This approach allows for multiple reclaims of silicon wafers, reducing material losses and costs while maintaining high device performance by preventing the growth of defects, thus enhancing productivity and widening the control window for wafer specifications.

Implementation Method 1

created through an ultra-high temperature rapid thermal process (UHT RTP)

Methodology Applied

Scientific EffectRapid thermal processing: Heating

Implementation Method 2

maintains a low concentration of interstitial oxygen

Methodology Applied

Scientific EffectOxygen diffusion: Diffusion

Implementation Method 3

characterized by non-detectable oxygen precipitates

Methodology Applied

Scientific EffectPrecipitation suppression: Precipitation

Data Source

PatentUS20250293073A1Reclaimable donor substrates for use in preparing multiple silicon-on-insulator structures

Publication Date: 2025.09.18 GLOBALWAFERS CO LTD

AI summary

A donor structure for use in preparing silicon-on-insulator structures includes a donor substrate made of single crystal silicon and a dielectric layer formed on a front surface of the donor substrate. The donor substrate has an interstitial oxygen concentration of less than 7.5×1017 atoms/cm3 and includes a denuded zone extending from the front surface of the donor substrate a denuded zone depth of at least 25 μm. The denuded zone is characterized by non-detectable oxygen precipitates measured by light scattering tomography. The denuded zone depth enables the donor structure to be reclaimed for preparing multiple silicon-on-insulator structures.