Multi-Layer Quartz Crucible for Heat Deformation and Devitrification
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Solution Overview
Problem
Quartz glass crucibles used in the Czochralski method for single crystal silicon production face issues with deformation due to prolonged heating, and excessive devitrification leads to cracking, necessitating a balance between crystallization promotion and suppression.
Innovation Solution
A quartz glass crucible with multiple layers, including an easily devitrifiable layer and a low devitrification layer, defined by devitrification spot numbers, to enhance strength and prevent excessive devitrification progression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a crystallization promoting layer is provided in the outer layer of the quartz glass crucible to prevent deformation due to prolonged heating, then the deformation problem is solved, but excessive devitrification occurs leading to cracking and breakage
Solution Approach 1:
The outer layer is divided into multiple sub-layers with different devitrification characteristics. The first sub-layer (closest to the melt) has high devitrification resistance to prevent cracking, while the second sub-layer has moderate devitrification resistance to provide structural support. This segmentation allows each layer to perform its specific function without causing harmful effects.
Solution Approach 2:
Different regions of the outer layer are given different devitrification resistance properties. The inner portion (first sub-layer) has high devitrification resistance to prevent cracking from excessive devitrification, while the outer portion (second sub-layer) has moderate devitrification resistance to provide mechanical strength and prevent deformation. This local differentiation resolves the contradiction between preventing deformation and avoiding excessive devitrification.
2Stability of the object's composition
If the impurity concentration (Al, Ba, Ca, K) is increased to promote crystallization and prevent deformation, then deformation resistance is improved, but the correlation with devitrification control becomes insufficient
Solution Approach 1:
The invention changes the control parameter from impurity concentration to devitrification spot number. Instead of controlling devitrification through Al, Ba, Ca, or K concentrations, the patent uses the devitrification spot number (visual count of devitrification nuclei per unit area) as the precise measurement parameter. This allows accurate control and evaluation of devitrification resistance, directly addressing the insufficient correlation between impurity concentration and devitrification control.
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
The crucible maintains strength and prevents excessive devitrification, ensuring durability and reliability during prolonged heating processes.
Implementation Method 1
an easily devitrifiable layer which has a devitrification spot number of 50/cm³ or more when heated
Implementation Method 2
a low devitrification layer which has a devitrification spot number of less than 5/cm³ when heated
Data Source
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AI summary
The present invention is a quartz glass crucible including a bottom portion, a curved portion, and a straight body portion, where the quartz glass crucible includes an outer layer including opaque quartz glass containing bubbles therein, and an inner layer including transparent quartz glass, the outer layer includes a plurality of layers in at least a part of the straight body portion, out of the plurality of layers, at least one layer is an easily devitrifiable layer having a devitrification spot number of 50/cm3 or more and 70/cm3 or less when the quartz glass crucible is heated at 1600°C for 24 hours, and out of the plurality of layers, a layer positioned inwards of the easily devitrifiable layer in a thickness direction of the quartz glass crucible is a low devitrification layer having a devitrification spot number of 2/cm3 or less when the quartz glass crucible is heated at 1600°C for 24 hours. This provides a quartz glass crucible that can be suppressed from deformation due to heating, and at the same time, can be suppressed from excessive progression of devitrification.