SiC Single Crystal Composite Defect Segmentation

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Solution Overview

Problem

The existing methods for growing larger SiC wafers face issues with defects, polytype inclusions, and cracks due to contact between single crystals and polycrystals, which deteriorate the quality of the SiC ingot, and require complex treatments like heating the guide member.

Innovation Solution

A SiC single crystal composite is designed with a central portion and an outer circumferential portion where the crystal planes are inclined or different, creating a boundary that prevents defect intrusion, allowing for high-quality SiC wafer production by directing crystal growth and preventing integration of defective crystals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If a single crystal and a polycrystal are grown on a guide member to increase the diameter of SiC ingot, then the diameter of SiC wafer can be increased, but defects, polytype inclusions, and cracks occur due to contact between single crystal and polycrystal

Engineering Contradiction:

Improvediameter of SiC waferVSAvoidquality of SiC ingot

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The guide member is divided into a first guide member for growing the single crystal and a second guide member for growing the polycrystal. This segmentation prevents direct contact between the single crystal and polycrystal, eliminating the generation of defects, polytype inclusions, and cracks while still enabling increased wafer diameter through the combined structure.

Inventive Principle:

Principle #1Segmentation

2Area of stationary object

If a tapered guide member is used to increase the diameter of SiC single crystal, then the diameter of SiC ingot can be increased, but heating treatment is required to suppress crystal growth of polycrystalline SiC

Engineering Contradiction:

Improvediameter of SiC ingotVSAvoidcomplexity of heating treatment

Core Design Contradiction:

Area of stationary objectVSDevice complexity

Solution Approach 1:

The guide member is segmented into two distinct parts: a first guide member with a first tapered angle for single crystal growth and a second guide member with a second tapered angle for polycrystal growth. This structural segmentation eliminates the need for heating treatment to suppress polycrystal formation, as the second guide member is specifically designed to accommodate and control polycrystal growth.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the guide member structure are assigned different functional properties. The first guide member has properties optimized for single crystal growth (first tapered angle), while the second guide member has properties optimized for polycrystal growth (second tapered angle). This local differentiation allows each region to perform its specific function without interfering with the other, eliminating the need for heating treatment.

Inventive Principle:

Principle #3Local quality

3Reliability

If the guide member is heated to suppress polycrystal growth, then crystal quality can be maintained, but the process becomes more complex and requires additional energy

Engineering Contradiction:

Improvecrystal qualityVSAvoidenergy for heating guide member

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The guide member structure incorporates localized functional zones where the first guide member is designed for single crystal growth and the second guide member is designed for polycrystal growth with appropriate tapered angles. This local quality differentiation allows polycrystals to be contained and controlled in the second guide member without requiring heating treatment, thereby maintaining crystal quality in the first guide member without additional energy input.

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 enables the production of high-quality SiC ingots and wafers by preventing defect propagation from the outer circumferential portion to the central portion, maintaining the integrity and quality of the SiC ingot during growth and processing.

Implementation Method 1

a single crystal growth apparatus for growing a SiC single crystal, the single crystal growth apparatus comprising: a central portion positioned at a center in plan view; and an outer circumferential portion surrounding an outer circumference of the central portion, in which crystal planes of the central portion and the outer circumferential portion are inclined to each other or different from each other

Methodology Applied

Scientific EffectCrystal growth: Crystallisation

Data Source

PatentUS11618969B2SiC single crystal composite and SiC ingot

Publication Date: 2023.04.04 DENSO CORP

AI summary

A SiC single crystal composite includes: a central portion positioned at a center in plan view; and an outer circumferential portion surrounding an outer circumference of the central portion, in which crystal planes of the central portion and the outer circumferential portion are inclined to each other or different from each other, a boundary is present between the central portion and the outer circumferential portion, and a direction of a crystal constituting the central portion and a direction of a crystal constituting the outer circumferential portion are different from each other via the boundary.