Directional Silicon Solidification via Induction Susceptor Heating
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Solution Overview
Problem
Existing methods for purifying silicon face challenges in heating and melting silicon ore due to its non-electrical conductivity in the solid state and require controlled environments to enhance outgassing and sedimentation of impurities, while ensuring efficient directional solidification.
Innovation Solution
The method involves using a controlled environment with a susceptor vessel and induction coils to heat and melt impure silicon, employing alternating current to induce directional solidification, and a cooling medium to enhance the process, allowing for directional solidification of purified silicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional heating methods are used to melt silicon ore, then heating can be achieved, but the process is inefficient due to silicon's non-electrical conductivity in solid state
Solution Approach 1:
The patent changes the electrical conductivity parameter of silicon by transitioning it from solid to molten state. Once silicon melts, it becomes electrically conductive, enabling efficient induction heating. This parameter change resolves the heating efficiency problem by allowing the use of electromagnetic induction heating method which is much more efficient than traditional resistance or flame heating.
Solution Approach 2:
The patent introduces a susceptor material as an intermediary between the induction heating system and the silicon charge. The susceptor becomes conductive when heated and transfers thermal energy to the silicon, enabling efficient heating during the melting phase while protecting the induction system from direct contact with molten silicon.
2Manufacturing precision
If a controlled environment is used to enhance outgassing and sedimentation, then impurity removal is improved, but the device complexity increases
Solution Approach 1:
The patent employs an inert gas atmosphere (such as argon or nitrogen) in the processing chamber to prevent oxidation of silicon during heating and melting. This inert environment facilitates efficient outgassing of volatile impurities and allows sedimentation of heavier impurities without contamination, achieving high silicon purity while using a relatively simple chamber design.
Solution Approach 2:
The patent segments the impurity removal process into distinct phases: outgassing phase where volatile impurities are removed through heating, and sedimentation phase where heavier impurities settle. This segmentation allows each purification mechanism to operate optimally, improving overall silicon purity while maintaining manageable system complexity.
3Productivity
If rapid cooling is applied to solidify molten silicon, then productivity increases, but directional solidification control becomes difficult
Solution Approach 1:
The patent applies local quality control by using differential cooling - the crucible walls are cooled to promote solidification from the boundaries inward, while the center remains hotter longer. This creates a controlled directional solidification pattern where pure silicon crystallizes from the walls toward the center, maintaining high purity while achieving reasonable solidification speed.
Solution Approach 2:
The patent employs dynamic control of the solidification process by adjusting cooling rates at different stages. Initially, rapid cooling establishes directional solidification patterns, then cooling rate is modulated to maintain control as solidification progresses. This dynamic adjustment allows both directional control and improved productivity.
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 purifies silicon by separating impurities through controlled heating and melting, achieving directional solidification and maintaining a high level of purity in a controlled vacuum or inert gas environment.
Implementation Method 1
Alternating current selectively applied to induction coils associated with the upper and lower susceptor heating systems, and the induction coils making up the surrounding induction coil system, result in melting of the silicon charge in the vessel
Implementation Method 2
heating and melting a charge of impure silicon in a controlled environment by inductively heating multiple susceptor elements surrounding a crucible containing solid silicon
Implementation Method 3
Some methods involve heating and melting the silicon so that impurities are driven out of the molten silicon by outgassing or sedimentation. Outgassing is enhanced in a controlled vacuum environment.
Implementation Method 4
heating and melting the silicon so that impurities are driven out of the molten silicon by outgassing or sedimentation
Implementation Method 5
directional solidification of the molten silicon
Data Source
AI summary
An apparatus and process are provided for directional solidification of silicon by electric induction susceptor heating in a controlled environment. A susceptor vessel is positioned between upper and lower susceptor induction heating systems and a surrounding induction coil system in the controlled environment. Alternating current selectively applied to induction coils associated with the upper and lower susceptor heating systems, and the induction coils making up the surrounding induction coil system, result in melting of the silicon charge in the vessel and subsequent directional solidification of the molten silicon. A fluid medium can be directed from below the vessel towards the bottom, and then up the exterior sides of the vessel to enhance the directional solidification process.