Epitaxial Silicon Wafer Nitrogen Diffusion for Dislocation Locking

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Solution Overview

Problem

The increased stress in epitaxial films due to three-dimensional device structures makes it challenging to achieve sufficient strength and reduce dislocation occurrence, as previously methods like increasing oxygen concentration are insufficient.

Innovation Solution

Increasing the nitrogen concentration of the epitaxial film surface to 5.0×10^13 atoms/cm^3 or more, achieved through inward diffusion from a nitride film formed on the silicon wafer, helps lock dislocations and prevent their extension, while maintaining sufficient film strength and reducing defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a strain layer is formed on an epitaxial film to enhance carrier mobility, then device performance is improved, but film stress increases causing dislocation occurrence

Engineering Contradiction:

Improvecarrier mobilityVSAvoiddislocation occurrence

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

Nitrogen atoms are introduced as an intermediary substance between the strain layer and the epitaxial film. These nitrogen atoms lock to small dislocations at the interface, preventing their extension into the epitaxial film while allowing the strain layer to maintain its stress-induced carrier mobility enhancement

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If heat treatment is conducted to increase oxygen concentration for enhancing film strength, then film strength is improved, but it becomes insufficient for three-dimensional device structures with increased stress

Engineering Contradiction:

Improvefilm strengthVSAvoidsufficiency for 3D device structure

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention changes the chemical composition parameter by introducing nitrogen atoms into the epitaxial film at a concentration of 5.0×10^13 atoms/cm³ or more. This parameter change fundamentally alters the dislocation locking mechanism, providing sufficient reliability for three-dimensional device structures where oxygen concentration alone is inadequate

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 effectively reduces dislocation occurrence and maintains carrier mobility enhancement, even under strain, by ensuring a nitrogen concentration that withstands heat treatment and device processing without compromising film integrity.

Implementation Method 1

setting a nitrogen concentration of the epitaxial film through inward diffusion from a nitride film on the epitaxial film

Methodology Applied

Scientific EffectInward diffusion: Diffusion

Implementation Method 2

heat treatment for setting oxygen concentration is conducted after epitaxial growth to enhance strength of the epitaxial film

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS11888036B2Method for setting a nitrogen concentration of a silicon epitaxial film in manufacturing an epitaxial silicon wafer

Publication Date: 2024.01.30 SUMCO CORP

AI summary

A manufacturing method of an epitaxial silicon wafer includes forming an epitaxial film made of silicon on a surface of a silicon wafer in a trichlorosilane gas atmosphere; and setting the nitrogen concentration of the surface of the epitaxial film through inward diffusion from a nitride film on the epitaxial film, the nitride film being formed by subjecting the silicon wafer provided with the epitaxial film to heat treatment in a nitrogen atmosphere.