Vitreous Silica Crucible Reference Point for Silicon Crystal Yield
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Solution Overview
Problem
Existing vitreous silica crucibles face challenges in accurately detecting defect locations and determining their impact during the silicon single crystal pulling process, leading to decreased yield due to defects like bubbles and impurities, especially with larger crucible diameters and increased growing temperatures.
Innovation Solution
A vitreous silica crucible with a fixed reference point on its inner or outer walls, formed using a carbon mold or laser marking, allows for precise detection of defect positions and distances, enabling the setting of optimal immersion times to prevent defect exposure during crystal pulling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a vitreous silica crucible is used to pull silicon single crystals, then oxygen supply to the silicon wafer is improved, but defects such as bubbles and impurities are introduced into the silicon melt
Solution Approach 1:
The patent applies local quality by creating a specific structural feature (protrusion) at a localized position on the crucible inner wall. This protrusion is positioned at a specific height from the bottom to prevent bubble exposure while maintaining oxygen supply benefits elsewhere in the crucible.
Solution Approach 2:
The patent implements preliminary action by pre-positioning the protrusion structure on the crucible before the crystal pulling process begins. This protrusion is designed to preemptively prevent bubble exposure and impurity introduction during the melting and crystal growth process.
2Productivity
If the crucible diameter is increased to 700 mm or more, then production capacity is improved, but vitreous silica melts faster and defects increase
Solution Approach 1:
The patent addresses the reliability issue in large-diameter crucibles by introducing a localized structural modification (protrusion) at a specific position. This protrusion creates a barrier that prevents bubble exposure and impurity introduction, thereby maintaining crystal quality even in large 700mm+ diameter crucibles where melting is more rapid.
3Speed
If the single crystal growing temperature is increased, then pulling speed is improved, but vitreous silica melts faster and defects are introduced
Solution Approach 1:
The patent implements preliminary action by pre-positioning the protrusion structure on the crucible inner wall before the high-temperature pulling process. This protrusion is designed to preemptively prevent bubble exposure and impurity introduction that would otherwise occur at elevated temperatures, enabling faster pulling speeds without compromising crystal quality.
4Quantity of substance
If bubbles are exposed or burst during pulling, then oxygen supply is enhanced, but broken silica pieces and gases are introduced into the silicon melt
Solution Approach 1:
The patent implements preliminary action by pre-positioning the protrusion structure on the crucible inner wall. This protrusion serves as a barrier that prevents bubbles from reaching the melt surface and bursting, thereby preventing the introduction of broken silica pieces and gases into the silicon melt while still allowing controlled oxygen supply.
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 solution enables accurate detection and prevention of defective products by establishing a numeric representation of defect locations, thereby enhancing the yield of single crystal silicon ingots by avoiding defect-related issues.
Implementation Method 1
formed using a carbon mold or laser marking
Implementation Method 2
formed using a carbon mold or laser marking
Implementation Method 3
Vitreous silica is progressively molten into the silicon melt
Implementation Method 4
the seed crystal or the vitreous silica crucible is rotated to make the seed crystal thin
Implementation Method 5
The pieces of vitreous silica move by the heat convection of the silicon melt
Data Source
AI summary
Provided is a vitreous silica crucible having a reference point, which is capable of accurately detecting the location of a defect in the vitreous silica crucible used for pulling silicon single crystal, determining a defect generating site of silicon single crystal, and investigating the cause of the defect. The reference point used for specifying the position relationship with respect to a particular part is formed in at least one site of an end portion, an inner wall and an outer wall of the crucible.