Electron Beam Polysilicon Refining for High Purity Production
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Solution Overview
Problem
Current silicon production processes for semiconductor-level silicon, particularly for photovoltaic cells, face challenges in achieving high purity at low cost due to contamination and low production efficiency, especially when using raw silicon with lower purity levels.
Innovation Solution
The use of electron-beam melting in a vacuum chamber with a unidirectional solidification unit to refine silicon, where electron beams are applied to melt and solidify silicon, segregating impurities and enhancing refining efficiency through controlled cooling and electron beam patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical gasification processes are used to produce semiconductor level silicon, then high purity (11N) silicon can be achieved, but production cost increases and production efficiency decreases
Solution Approach 1:
The invention changes the purification parameter from chemical gasification to metallurgical refining using electron beam melting. By controlling the electron beam energy and vacuum conditions, the process achieves 6N purity (99.9999%) through physical melting and segregation rather than chemical reactions, thereby improving production efficiency while maintaining high purity standards suitable for photovoltaic applications
Solution Approach 2:
The invention utilizes phase transition from solid to liquid and back to solid during electron beam melting. The raw silicon is melted by electron beam irradiation, allowing impurities to segregate during the liquid phase, and then solidifies upon cooling. This phase transition mechanism enables effective impurity removal without requiring complex chemical gasification processes
2Productivity
If metallurgical refining processes are used to reduce production cost, then production efficiency improves, but achieving high purity (6N to 11N) becomes more difficult
Solution Approach 1:
The invention replaces conventional thermal or chemical refining mechanisms with electron beam irradiation. The high-energy electron beam directly melts the silicon and generates sufficient heat for impurity segregation without requiring complex mechanical or chemical systems. This substitution maintains the simplicity of metallurgical refining while achieving high purity levels through controlled electron beam parameters
Solution Approach 2:
The invention employs a vacuum environment during electron beam melting to prevent oxidation and contamination of the molten silicon. The vacuum atmosphere serves as an inert environment that protects the silicon from reacting with atmospheric gases, thereby maintaining high purity levels while using simple metallurgical refining without complex chemical protection systems
3Object-generated harmful factors
If vacuum refining or unidirectional solidification refining is used, then contamination during operation is reduced, but the process complexity increases
Solution Approach 1:
The invention merges vacuum refining and unidirectional solidification refining into a single integrated electron beam melting process. The electron beam simultaneously provides heating for melting, maintains vacuum conditions to prevent contamination, and enables controlled solidification. This merging eliminates the need for separate vacuum systems and solidification apparatus, reducing overall process complexity while maintaining low contamination levels
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 method effectively produces high purity polysilicon with a purity of 5N to 7N, suitable for photovoltaic cells, by efficiently removing volatile and metal impurities, thereby improving production efficiency and reducing costs.
Implementation Method 1
melting the fed raw silicon by irradiating a first electron beam to the raw silicon using a first electron gun
Implementation Method 2
molten silicon fed from the silicon melting unit is transferred in the downward direction by the start block while being kept in a molten state by the second electron beam
Implementation Method 3
solidified from a lower portion thereof to an upper portion thereof through the cooling channel
Implementation Method 4
a vacuum chamber maintaining a vacuum atmosphere
Data Source
AI summary
Apparatus and method for manufacturing high purity polysilicon. The apparatus includes a vacuum chamber maintaining a vacuum atmosphere; first and second electron guns disposed at an upper side of the vacuum chamber to irradiate electron beams into the vacuum chamber; a silicon melting unit placed on a first electron beam-irradiating region corresponding to the first electron gun and in which powdery raw silicon is placed and melted by the first electron beam; and a unidirectional solidification unit placed on a second electron beam-irradiating region corresponding to the second electron gun and connected to the silicon melting unit via a runner. The unidirectional solidification unit is formed at a lower part thereof with a cooling channel and is provided therein with a start block driven in a downward direction.