Elimination of phosphorus vaporizing from molten silicon at
finite reduced pressure
finite reduced pressure
(1. Department of Materials Science and Engineering, Xiamen University, Xiamen 361005, China;
2. Department of Material Science, Norwegian University of Science and Technology, Trondheim 7034, Norway;
3. Silicon Refining Research Team, Research Institute of Science and Technology, Pohang 790-600, Korea)
2. Department of Material Science, Norwegian University of Science and Technology, Trondheim 7034, Norway;
3. Silicon Refining Research Team, Research Institute of Science and Technology, Pohang 790-600, Korea)
Abstract: Elimination of phosphorus vaporizing from silicon was investigated. Si-P alloy made from electronic grade silicon was used. All the samples were analyzed by GD-MS. Theory calculation determines that phosphorus evaporates from molten silicon as gas species P and P2 at a finite reduced pressure. The experimental results show that phosphorus mass fraction can be decreased from 0.046% (460ppmw) to around 0.001% (10ppmw) under the condition of temperature 1 873 K, chamber pressure 0.6−0.8 Pa, holding time 1 h. Both experimental data and calculation results agree that at high phosphorus concentration, phosphorus removal is quite dependent on high chamber pressure while it becomes independent on low chamber pressure. The reason is that phosphorus evaporates from molten silicon as gas species P2 at a relatively high phosphorus concentration, while gas species P will be dominated in its vapour at low phosphorus content.
Key words: phosphorus concentration; molten silicon; equilibrium partial pressure; temperature; chamber pressure