Silica Glass Crucible Roundness Control for Silicon Crystal Yield
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Solution Overview
Problem
Conventional silica glass crucibles used for pulling up silicon crystals have low roundness, leading to non-uniform oxygen distribution and reduced crystallization yield due to horizontal swaying during rotation, which affects the quality and yield of both semiconductor and solar cell materials.
Innovation Solution
A method to manufacture silica glass crucibles with controlled roundness of the interior and exterior surfaces, ensuring Sx / M ≤ 0.4 and Sy / M ≤ 0.4, and a distance L between the centers of the surfaces ≤ 0.01D, achieved by depositing silica powder on a rotating mold and controlling horizontal sway to ≤ 0.1% of the mold's diameter, resulting in uniform oxygen distribution and crystallization yields of 80% or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If silica powder is deposited on a rotating mold to manufacture a silica glass crucible, then the crucible can be produced efficiently, but the roundness of the interior and exterior surfaces becomes uneven, reducing crystallization yield
Solution Approach 1:
The patent employs feedback control by measuring the actual roundness of the crucible after manufacturing and using this information to adjust the deposition process parameters for subsequent crucibles. This closed-loop approach ensures that variations in surface roundness are corrected in real-time, maintaining high manufacturing precision while preserving production efficiency.
Solution Approach 2:
The patent changes critical process parameters including rotation speed of the mold, deposition rate of silica powder, and heating temperature profile. By optimizing these parameters, the process achieves both high productivity and precise control over surface roundness, eliminating the traditional trade-off between production speed and manufacturing quality.
2Ease of manufacture
If the roundness of the crucible surfaces is low, then manufacturing is easier and faster, but horizontal swaying during rotation increases, causing non-uniform oxygen distribution and reducing crystallization yield
Solution Approach 1:
The patent applies preliminary action by pre-controlling the surface roundness during the manufacturing process itself, rather than attempting to correct it later. By ensuring high roundness (Sx/M ≤ 0.4 and Sy/M ≤ 0.4) is achieved during crucible formation, the design eliminates horizontal swaying during rotation, ensuring uniform oxygen distribution and high crystallization yield from the outset.
Solution Approach 2:
The patent utilizes pneumatic or hydraulic systems to apply controlled pressure during the deposition and solidification process, ensuring uniform density and precise dimensional control of the crucible walls. This enables maintenance of high roundness specifications while keeping the manufacturing process efficient and manageable.
3Strength
If the distance between the centers of interior and exterior surfaces is large, then the crucible structure is more robust, but axis misalignment increases, causing larger horizontal swaying and reduced crystallization yield
Solution Approach 1:
The patent carefully manages asymmetry in the crucible wall thickness distribution. By controlling the distance L between interior and exterior surface centers to be ≤ 0.01D, the design maintains sufficient structural robustness while minimizing axis misalignment. This controlled asymmetry approach balances mechanical strength requirements with precision rotational performance.
Solution Approach 2:
The patent applies partial action by controlling axis misalignment to a specific threshold (L ≤ 0.01D) rather than eliminating it completely. This level of control provides sufficient precision for high crystallization yield while allowing for practical manufacturing tolerances and maintaining structural robustness, representing an optimal balance point.
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 method ensures high crystallization yield and uniform oxygen distribution in silicon crystals, enhancing the quality of both semiconductor and solar cell materials by maintaining precise roundness and minimizing axis misalignment during the crucible's rotation.
Implementation Method 1
the crucible is manufactured by depositing silica powder to a predetermined thickness on inner surface of a crucible shaped rotation mold and this layer of silica powder is heated and melted while rotating the mold to be vitrificated
Implementation Method 2
The silicon crystal is pulled up while applying a heat uniformly to the silicon melt by rotating the silica glass crucible
Implementation Method 3
a silicon melt is produced by melting a polycrystalline silicon nugget which has been charged in a silica glass crucible, dipping a seed crystal in the silicon melt and pulling up the seed crystal
Data Source
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AI summary
A silica glass crucible for pulling up a silicon crystal related to the present invention includes a roundness Sx of an interior surface of the silica glass crucible and a roundness Sy of an exterior surface of the silica glass crucible in at least a wall part of the silica glass crucible both being 0.4 4 or less (Sx / M ≤ 0.4, Sy / M ≤ 0.4) to a maximum thickness M in the same measurement height as the roundness.