Silica Crucible Bottom Viscosity Control for Silicon Crystal Purity
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Solution Overview
Problem
The existing methods for manufacturing silicon single crystals using silica glass crucibles are inadequate in preventing void defects caused by gas bubbles, which significantly impact the quality and yield of semiconductor devices.
Innovation Solution
A silica glass crucible with a natural silica inner layer having a controlled concentration of Al and low alkali metals is used, where the inner surface is etched and arc-melted to create a high viscosity region that prevents damage and dent formation, thereby reducing the generation of SiO gas bubbles and void defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If synthetic silica is used for the inner layer to prevent impurity elution, then purity is improved, but heat resistance strength deteriorates
Solution Approach 1:
The patent applies composite materials by creating a two-layer structure where the inner layer uses synthetic silica for high purity and the outer layer uses natural silica for high heat resistance strength. This composite structure allows each layer to fulfill its specific functional requirement without compromising the other.
2Strength
If natural silica is used for the inner layer to improve heat resistance strength, then strength is improved, but impurity elution increases
Solution Approach 1:
The patent applies composite materials by creating a two-layer structure where the inner layer uses synthetic silica for high purity and the outer layer uses natural silica for high heat resistance strength. This composite structure allows each layer to fulfill its specific functional requirement without compromising the other.
3Productivity
If the crucible is made larger to charge more silicon, then productivity is improved, but gas bubble removal becomes more difficult
Solution Approach 1:
The patent applies local quality by creating a high viscosity region specifically at the bottom center of the crucible where gas bubbles tend to accumulate. This localized modification of viscosity allows effective gas bubble prevention in the critical growth area without requiring changes to the entire crucible structure, thus maintaining productivity while solving the gas bubble issue.
4Manufacturing precision
If the inner surface is etched deeply to remove impurities, then purity is improved, but structural integrity may deteriorate
Solution Approach 1:
The patent applies local quality by concentrating the etching treatment specifically in the bottom center region of the crucible to create a high viscosity region. This localized etching removes impurities where they are most problematic while preserving the overall structural integrity of the crucible by not over-etching other areas.
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 prevents the incorporation of gas bubbles into the silicon single crystal, enhancing the quality and yield of silicon single crystals by maintaining a low concentration of impurities and increasing the viscosity of the crucible bottom section.
Implementation Method 1
a region having a comparatively high viscosity within a certain range from a center of the crucible bottom and up to 0.5 mm deep from an inner surface
Implementation Method 2
forming a silica glass crucible by arc melting the natural silica powder
Implementation Method 3
thereby reducing the generation of SiO gas bubbles and void defects
Data Source
AI summary
A silica glass crucible used for pulling up a silicon single crystal and made from natural silica a raw material is provided with a region within a certain range from the center of a bottom section of the crucible and up to 0.5 mm deep from an inner surface and which substantially does not include gas bubbles, wherein an average value of a concentration of Al included in a region within the certain range from the center of the bottom section of the crucible and up to 0.5 mm deep from the inner surface is 30 ppm or more and 150 ppm or less. In the case where the inner layer of the crucible bottom section is formed in this way, dents in the inner surface are prevented and the generation of gas bubbles is reduced.