Silicon Wafer Slip Dislocation Prediction via Oxygen Concentration

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Solution Overview

Problem

Existing methods for evaluating silicon wafers are insufficient in preventing the formation of slip dislocations during device fabrication processes, especially under severe thermal stress conditions, as they fail to accurately determine the critical shear stress related to BMD size and residual oxygen concentration.

Innovation Solution

A quality evaluation method for silicon wafers that measures the precipitated oxygen concentration instead of BMD size, using the formula τcri=24.6×(1/ΔOi)+7.0×10−5×CO×exp(0.91 eV/kT) to determine the critical shear stress, allowing for accurate assessment of slip dislocation formation by comparing thermal stress with the calculated critical shear stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If oxygen precipitation is controlled to form small-sized BMDs, then the mechanical strength of silicon wafer is improved, but the ability to suppress slip dislocation formation under severe thermal stress is insufficient

Engineering Contradiction:

Improvemechanical strengthVSAvoidresistance to slip dislocation formation

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention changes the evaluation parameter from BMD size to precipitated oxygen concentration (ΔOi). By using the formula τcri=24.6×(1/ΔOi)+7.0×10−5×CO×exp(0.91 eV/kT), the critical shear stress is calculated based on precipitated oxygen concentration and residual oxygen concentration, allowing accurate prediction of slip dislocation formation under severe thermal stress while maintaining mechanical strength through controlled oxygen precipitation.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If existing evaluation methods based on BMD size are used, then manufacturing simplicity is maintained, but measurement precision and accuracy in predicting slip dislocation formation are insufficient

Engineering Contradiction:

Improveevaluation process simplicityVSAvoidaccuracy of slip dislocation prediction

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The invention replaces the mechanical measurement approach (BMD size measurement) with a chemical composition approach (precipitated oxygen concentration measurement). This substitution enables more accurate prediction of slip dislocation formation by directly measuring the oxygen concentration that causes the defect, rather than measuring the resulting defect size.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

3Productivity

If rapid heating and cooling processes are used in device fabrication, then productivity is improved, but severe thermal stress causes slip dislocations to form easily

Engineering Contradiction:

Improvefabrication process efficiencyVSAvoidthermal stress-induced slip dislocations

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The invention performs preliminary evaluation of the silicon wafer's resistance to slip dislocation formation by calculating the critical shear stress using the formula τcri=24.6×(1/ΔOi)+7.0×10−5×CO×exp(0.91 eV/kT). This allows selection or optimization of wafers before rapid heating and cooling processes, ensuring they can withstand the severe thermal stress without forming slip dislocations, thereby maintaining both productivity and product quality.

Inventive Principle:

Principle #10Preliminary action

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 method enables high-accuracy determination of slip dislocation formation, ensuring the production of silicon wafers that do not form slip dislocations during device fabrication, thereby improving yield and mechanical strength.

Implementation Method 1

when heat treatment is performed on a silicon wafer, oxygen contained in the wafer reacts with silicon to form oxygen precipitates (bulk micro defects, BMDs)

Methodology Applied

Scientific EffectOxygen precipitation: Precipitation

Implementation Method 2

silicon wafers are subjected to more severe thermal stress than conventional ones, which results in an environment in which slip dislocations are easily formed

Methodology Applied

Scientific EffectThermal stress: Thermal Expansion

Data Source

PatentUS9995693B2Quality evaluation method for silicon wafer, and silicon wafer and method of producing silicon wafer using the method

Publication Date: 2018.06.12 SUMCO CORP

AI summary

After determining the precipitated oxygen concentration and the residual oxygen concentration in a silicon wafer after heat treatment performed in a device fabrication process; the critical shear stress τcri at which slip dislocations are formed in the silicon wafer in the device fabrication process is determined based on the obtained precipitated oxygen concentration and residual oxygen concentration; and the obtained critical shear stress τcri and the thermal stress τ applied to the silicon wafer in the heat treatment of the device fabrication process are compared, thereby determining that slip dislocations are formed in the silicon wafer in the device fabrication process when the thermal stress τ is equal to or more than the critical shear stress τcri, or determining that slip dislocations are not formed in the silicon wafer in the device fabrication process when the thermal stress τ is less than the critical shear stress τcri.