EFG Die Slit Orientation for Impurity Uniformity

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Solution Overview

Problem

The existing EFG-based single crystal growth methods using dies with parallel slits on the upper surface result in insufficient uniformity of impurity concentration in the grown single crystals, leading to fluctuations in semiconductor and fluorescence properties.

Innovation Solution

A die design with a rectangular upper surface having a long side and a short side, where the slit sections extend from the lower to the upper surface with longitudinal directions parallel to each other but non-parallel to the long side, reducing the interval between neighboring slits and enhancing impurity concentration uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the respective longitudinal directions of openings of the slit sections on the upper surface are made parallel to the long side of the rectangular upper surface, then the interval between neighboring slits can be reduced, but impurity segregation occurs between the slits resulting in insufficient uniformity of impurity concentration

Engineering Contradiction:

Improveuniformity of impurity concentrationVSAvoidslit configuration complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by making the longitudinal directions of the slit sections non-parallel to the long side of the rectangular upper surface. Specifically, the slits are oriented at an angle relative to the long side, creating an asymmetric configuration that prevents impurity segregation while maintaining uniform impurity concentration distribution in the grown single crystal.

Inventive Principle:

Principle #4Asymmetry

2Manufacturing precision

If the distance between neighboring slits is shortened to improve impurity concentration uniformity, then the interval between slits decreases, but the device structure becomes more complex

Engineering Contradiction:

Improveimpurity concentration uniformityVSAvoidinterval between slits

Core Design Contradiction:

Manufacturing precisionVSLength of moving object

Solution Approach 1:

The patent changes the orientation parameter of the slits by making their longitudinal directions non-parallel to the long side of the rectangular upper surface. This parameter change allows for an optimized balance between the interval between slits and the uniformity of impurity concentration, achieving good uniformity without excessively reducing the slit interval or complicating the device structure.

Inventive Principle:

Principle #35Parameter changes

3Loss of substance

If a rectangular upper surface with long side and short side is used to define the cross section shape, then processing loss is suppressed, but controlling impurity distribution becomes more difficult

Engineering Contradiction:

Improveprocessing lossVSAvoidimpurity distribution uniformity

Core Design Contradiction:

Loss of substanceVSManufacturing precision

Solution Approach 1:

The patent applies local quality by making the longitudinal directions of different slit sections non-parallel to the long side, creating localized variations in slit orientation that are optimized for impurity distribution control. This local optimization within the rectangular upper surface structure allows simultaneous achievement of reduced processing loss and improved impurity uniformity.

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 configuration improves the uniformity of impurity concentration in the grown single crystals, reducing segregation and maintaining high impurity uniformity across the crystal, with an impurity concentration fluctuation coefficient of 30% or less, excluding a 1 mm distance range from the outer edge.

Implementation Method 1

a plurality of slit sections extending from the lower surface to the upper surface and causing the raw material melt to ascend from the lower surface to the upper surface

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

impurity segregation is less likely to occur between the slit sections, and so it is possible to improve uniformity of an impurity concentration of the grown single crystal

Methodology Applied

Scientific EffectImpurity segregation reduction: Diffusion

Data Source

PatentUS11492724B2Die for EFG-based single crystal growth, EFG-based single crystal growth method, and EFG single crystal

Publication Date: 2022.11.08 TDK CORP

AI summary

A die for EFG-based single crystal growth includes a lower surface to be immersed into a raw material melt with an impurity added, a rectangular upper surface facing a seed crystal and having a long side and a short side, and a plurality of slit sections extending from the lower surface to the upper surface and causing the raw material melt to ascend from the lower surface to the upper surface. Respective longitudinal directions of openings of the plurality of slit sections on the upper surface are parallel to one another and non-parallel to the long side of the upper surface.