Single Crystal Production Equipment Uniform Dopant Distribution
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Solution Overview
Problem
The production of large single-crystal silicon for solar cells faces challenges in achieving uniform dopant concentration, particularly with the Bridgman method, where quartz crucibles react with silicon, causing cracking and polycrystalline formation, and existing methods struggle to maintain optimal dopant concentration across the crystal, leading to inefficiencies in power generation.
Innovation Solution
A novel single-crystal production equipment that employs a traveling solvent method with a granular raw material melting apparatus and infrared ray irradiation to control the melt phase thickness and composition, ensuring uniform dopant distribution by continuously supplying a raw material melt with an optimum composition, thereby inhibiting microcrystal growth and achieving a large, uniform single crystal with optimal composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the Bridgman method is used to produce large single crystals, then the crystal size can be increased, but the dopant concentration becomes non-uniform and cracking occurs due to quartz-silicon reaction
Solution Approach 1:
The production process is segmented into two distinct stages: first, a seed crystal is grown in a quartz crucible using the Bridgman method; second, the seed crystal is transferred to a graphite crucible for continuous growth. This segmentation allows the quartz crucible to be used only for initial nucleation where its restraining effect is acceptable, while the graphite crucible provides the chemical inertness needed for uniform dopant distribution in the main crystal body.
Solution Approach 2:
The seed crystal serves as an intermediary between the quartz crucible environment and the final large single crystal. It is grown in the quartz crucible under controlled conditions, then transferred to serve as the foundation for growth in the graphite crucible, where the actual uniform-dopant crystal is formed. This intermediary approach allows leveraging benefits of both crucible types.
2Reliability
If a quartz crucible is used to retain silicon melt, then the melt can be stably retained, but silicon monoxide is generated through reaction causing product contamination and cracking
Solution Approach 1:
The harmful reaction between quartz and silicon melt is eliminated by extracting the melt from the quartz crucible environment after initial seed crystal formation. The seed crystal is transferred to a graphite crucible where the melt is retained without chemical reaction, thus removing the source of silicon monoxide generation while maintaining melt retention stability.
Solution Approach 2:
The quartz crucible is used only for the initial seed crystal growth phase and then discarded or set aside. A graphite crucible is introduced for the main crystal growth phase. This disposable use of the quartz crucible for its specific function (seed growth) eliminates its harmful effects during the critical uniform-dopant growth phase.
3Manufacturing precision
If the periphery of the melt phase is heated to inhibit microcrystal growth, then single crystal quality improves, but energy consumption increases
Solution Approach 1:
Heating is applied locally only to the periphery of the melt phase rather than uniformly across the entire melt. This localized heating approach maintains higher temperature at the boundaries to suppress microcrystal nucleation, while the center region can be optimized for uniform dopant distribution. This selective heating achieves single crystal quality improvement with minimized energy consumption compared to uniform heating of the entire melt.
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 enables the production of large single crystals with uniform dopant concentration in both vertical and horizontal directions, enhancing power generation efficiency while reducing production costs by preventing microcrystal formation and maintaining optimal composition throughout the crystal.
Implementation Method 1
a granular raw material melting apparatus which heats and melts the granular raw material supplied from the granular raw material supply apparatus to generate a raw material melt
Implementation Method 2
first infrared ray irradiation equipment which irradiates an infrared ray to the upper surface of the seed single crystal in the single-crystal production crucible
Implementation Method 3
a single crystal is allowed to precipitate as a solid on the seed single crystal
Implementation Method 4
traveling solvent method with a granular raw material melting apparatus and infrared ray irradiation to control the melt phase thickness and composition
Data Source
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AI summary
[Problem] Produced is a large single crystal with no crystal grain boundary, which is a high-quality single crystal that has a uniform composition in both the vertical and horizontal directions at an optimum dopant concentration. [Means for Solution] Provided is a single-crystal production equipment which includes, at least: a granular raw material supply apparatus which supplies a certain amount of a granular raw material to a granular raw material melting apparatus positioned therebelow; the granular raw material melting apparatus which heats and melts the granular raw material supplied from the granular raw material supply apparatus to generate a raw material melt and supplies the raw material melt into a single-crystal production crucible positioned therebelow; and a crystallization apparatus which includes the single-crystal production crucible in which a seed single crystal is placed on the bottom, and a first infrared ray irradiation equipment which irradiates an infrared ray to the upper surface of the seed single crystal in the single-crystal production crucible, and the single-crystal production equipment is configured such that the raw material melt supplied from the granular raw material melting apparatus is dropped into a melt formed by irradiating the upper surface of the seed single crystal with the infrared ray, and a single crystal is allowed to precipitate out of the thus formed mixed melt.