Unitized Crucible Assembly for Silicon Ingot Growth
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Solution Overview
Problem
Conventional crucible assemblies for continuous Czochralski silicon ingot growth deform and lose tolerances due to connection degradation, requiring alignment tools and complex fabrication processes.
Innovation Solution
A unitized crucible assembly is formed using a crucible mold with a channel network filled with a slip slurry containing silica and a liquid carrier, which is then sintered to create a seamless, one-piece construction with central and inner weirs, eliminating seams and the need for alignment tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nested crucibles with connected weirs are used, then the crucible assembly can be formed with multiple melt zones, but the connections degrade causing deformation and loss of tolerances
Solution Approach 1:
The patent merges the crucible body and weirs into a single unitized structure formed by sintering silica sand in a mold cavity. This eliminates separate connections between crucible and weirs, preventing connection degradation and maintaining tolerances throughout the assembly during continuous Czochralski operation.
Solution Approach 2:
The mold cavity is segmented into multiple zones including outer sidewall cavity, central weir cavity, and inner weir cavity, which are filled with silica sand to form the unitized crucible assembly with distinct functional regions while maintaining structural integrity as one piece.
2Ease of operation
If nested crucibles with alignment tools are used, then uniform gas flow can be achieved, but the fabrication process becomes complex requiring alignment tools
Solution Approach 1:
The patent combines the crucible and weirs into a single pre-formed unitized assembly with integrated geometry. The mold cavity design incorporates all structural features including outer sidewall, central weir, and inner weir in one piece, eliminating the need for alignment tools and complex assembly procedures while ensuring uniform gas flow characteristics.
Solution Approach 2:
The crucible assembly is pre-formed in the mold cavity with all geometric features and tolerances established before use. The sintering process creates the final geometry in advance, eliminating the need for alignment tools during operation and simplifying the fabrication process.
3Ease of manufacture
If connections are formed at the bottom of crucible assembly, then nested crucibles can be assembled, but the connections degrade causing deformation
Solution Approach 1:
The patent eliminates separate connections by forming the crucible body and weirs as a single unitized structure. The silica sand compacted in the mold cavity creates monolithic bonds during sintering, removing weak connection points at the bottom where degradation previously occurred.
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 unitized crucible assembly resists deformation, simplifies fabrication, and maintains tolerances, enabling continuous ingot growth with reduced alignment tool usage and processing complexity, while ensuring improved thermal response and purity.
Implementation Method 1
The slip slurry is introduced into the channel network to fill the bottom channel, outer sidewall channel, central weir channel, and inner weir channel with the slip slurry
Implementation Method 2
The liquid carrier is at least partially removed from the channel network to form a green body
Implementation Method 3
The green body is sintered to dry and densify the green body to form the unitized crucible assembly
Data Source
AI summary
Methods for forming a unitized crucible assembly for holding a melt of silicon for forming a silicon ingot are disclosed. In some embodiments, the methods involve a porous crucible mold having a channel network with a bottom channel, an outer sidewall channel that extends from the bottom channel, and a central weir channel that extends from the bottom channel. A slip slurry may be added to the channel network and the liquid carrier of the slip slurry may be drawn into the mold. The resulting green body may be sintered to form the crucible assembly.