Double Crucible Structure to Prevent Silica Crucible Inward Falling

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Solution Overview

Problem

The Czochralski method for producing silicon single crystals faces issues with buckling and inward falling of the silica crucible due to thermal expansion, leading to disruptions in crystal pulling, as existing solutions inadequately control the inward falling of the silica crucible's body portion.

Innovation Solution

A double-structured crucible with a silica crucible and a graphite crucible, where the silica crucible's opening end is equipped with an inward falling prevention means that imparts a radially outward force, featuring a diameter-expanded portion with a taperingly inclined part, preventing buckling and directing the silica crucible's body portion to fall outwardly, thus controlling inward falling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the upper end of the silica crucible is made higher than the graphite crucible to accommodate thermal expansion, then the crucible can withstand higher temperatures, but the upper portion of the silica crucible falls down inward and buckling occurs due to its own weight

Engineering Contradiction:

Improvetemperature resistanceVSAvoidcrucible shape stability

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The silica crucible is designed with different shapes for different portions: the lower portion has a larger diameter to provide structural support and prevent buckling, while the upper portion has a smaller diameter to reduce weight and prevent inward falling. This local differentiation of structural properties resolves the contradiction between temperature resistance and shape stability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of making the entire crucible uniformly tall to withstand temperature, the invention inverts the conventional design by making the lower portion larger and the upper portion smaller. This inverted shape distribution of diameter along the height direction prevents both buckling (by strengthening the lower portion) and inward falling (by reducing weight at the upper portion).

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of manufacture

If the silica crucible is made with a uniform cylindrical shape, then the manufacturing is simple, but the body portion falls down inward during crystal pulling

Engineering Contradiction:

Improvecrucible manufacturing simplicityVSAvoidinward falling of body portion

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The crucible employs local quality differentiation where the diameter varies along the height direction, with the lower portion having a larger diameter and the upper portion having a smaller diameter. This non-uniform shape design prevents inward falling of the body portion during crystal pulling while remaining manufacturable through conventional forming processes.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If the upper portion of the silica crucible is expanded upwardly to prevent buckling, then buckling control is improved, but the inward falling of the body portion is not sufficiently controlled

Engineering Contradiction:

Improvebuckling controlVSAvoidinward falling control

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The invention inverts the conventional approach by making the lower portion larger and the upper portion smaller, rather than expanding the upper portion. This inverted diameter distribution simultaneously achieves buckling prevention (through the larger lower portion providing structural support) and inward falling control (through the smaller upper portion reducing weight and stress on the body portion).

Inventive Principle:

Principle #13The other way round (Inversion)

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

Effectively suppresses buckling and inward falling of the silica crucible, ensuring continuous silicon single crystal pulling by rationalizing the silica crucible's shape and using a radially outward force mechanism.

Implementation Method 1

an inward falling prevention means for imparting a radially outward force to a body portion of the silica crucible

Methodology Applied

Scientific EffectRadially outward force: Mechanical Force

Implementation Method 2

when the silica crucible is softened at a higher temperature by heating the melt

Methodology Applied

Scientific EffectThermal softening: Heating

Implementation Method 3

the occurrence of buckling can be controlled effectively by disposing an inward falling prevention means on an opening end portion of the silica crucible for imparting a radially outward force to the body portion of the silica crucible

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8980004B2Crucible and method for pulling a single crystal

Publication Date: 2015.03.17 SUMCO CORP

AI summary

A crucible for pulling a silicon single crystal has a double structure comprising a silica crucible and a graphite crucible covering an outside of the silica crucible, wherein the silica crucible is provided at its opening end portion with an inward falling prevention means for imparting a radially outward force to a body portion of the silica crucible.