Silicon Wafer Annealing Oxygen Zone Control

Solution Overview

Problem

Silicon wafers manufactured using the Czochralski method face challenges with slip dislocations during annealing, leading to reduced mechanical strength due to oxygen diffusion and low oxygen concentration in the denuded zone, which cannot be adequately suppressed by removing the damage layer on the rear surface.

Innovation Solution

The method involves annealing silicon wafers in a non-oxidizing atmosphere at high temperatures to form a denuded zone and then removing a portion of the denuded zone or forming an oxide film on the surface to maintain a sufficient oxygen concentration, thereby exposing the bulk micro defect layer to prevent slip dislocation propagation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If annealing is performed to form a DZ layer, then crystal defects are reduced in the device formation area, but slip dislocations occur and propagate from the rear surface, reducing wafer strength

Engineering Contradiction:

Improvecrystal defect reductionVSAvoidwafer mechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies local quality by creating different oxygen concentration zones at different locations of the wafer. The front surface maintains a DZ layer with low oxygen concentration to reduce crystal defects, while the rear surface maintains high oxygen concentration to prevent slip dislocation propagation. This spatial differentiation of oxygen concentration allows simultaneous achievement of both crystal defect reduction and mechanical strength enhancement.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent inverts the conventional approach by not removing the damage layer completely from the rear surface, but rather maintaining it to preserve high oxygen concentration. Instead of following the conventional practice of removing the damage layer to improve quality, the invention retains it for its beneficial oxygen reservoir function that prevents dislocation propagation.

Inventive Principle:

Principle #13The other way round (Inversion)

2Object-affected harmful factors

If the damage layer on the rear surface is removed by etching or mechanical polishing, then contact damage is reduced, but slip dislocation propagation cannot be adequately suppressed due to low oxygen concentration

Engineering Contradiction:

Improvecontact damage reductionVSAvoidresistance to slip dislocation propagation

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The patent applies local quality by creating different oxygen concentration zones at different locations of the wafer. The front surface maintains a DZ layer with low oxygen concentration to reduce crystal defects, while the rear surface maintains high oxygen concentration to prevent slip dislocation propagation. This spatial differentiation of oxygen concentration allows simultaneous achievement of both crystal defect reduction and mechanical strength enhancement.

Inventive Principle:

Principle #3Local quality

3Strength

If oxygen concentration is maintained high throughout the wafer, then slip dislocation propagation is suppressed, but crystal defects occur in the device formation area

Engineering Contradiction:

Improveresistance to slip dislocation propagationVSAvoidcrystal defect free device area

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies local quality by creating different oxygen concentration zones at different locations of the wafer. The front surface maintains a DZ layer with low oxygen concentration to reduce crystal defects, while the rear surface maintains high oxygen concentration to prevent slip dislocation propagation. This spatial differentiation of oxygen concentration allows simultaneous achievement of both crystal defect reduction and mechanical strength enhancement.

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 effectively suppresses slip dislocation propagation by maintaining a high oxygen concentration, ensuring the silicon wafers have excellent mechanical strength and reduced defect formation, essential for device fabrication.

Implementation Method 1

a step of annealing a silicon wafer which is sliced from a silicon single crystal ingot, thereby forming a DZ layer

Methodology Applied

Scientific EffectAnnealing: Annealing

Implementation Method 2

a oxygen concentration in the DZ zone is extremely low due to outward diffusion of oxygen

Methodology Applied

Scientific EffectOxygen diffusion: Diffusion

Implementation Method 3

forming an oxide film on the surface to maintain a sufficient oxygen concentration

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS8758505B2Silicon wafer and method for manufacturing the same

Publication Date: 2014.06.24 SUMITOMO MITSUBISHI SILICON CORP

AI summary

A method for manufacturing a silicon wafer includes a step of annealing a silicon wafer which is sliced from a silicon single crystal ingot, thereby forming a DZ layer in a first surface and in a second surface of the silicon wafer and a step of removing either a portion of the DZ layer in the first surface or a portion of the DZ layer in the second surface.