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Purified Silicon Production and Depositing System

National Renewable Energy Laboratory

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Technology Marketing Summary

Within the photovoltaic (PV) industry, the supply of the required metallurgical-grade (MG) Si feedstock at an acceptable cost is a pain point for manufacturers. One current method for the production and purification of this feedstock is the repetitive porous MG-Si etching, gettering, and surface removal of impurities. While this method is effective in the near-surface region, this process is impractical for the bulk purification of MG-Si feedstock due to the large number of process cycles required. Another method for the purification and production of MG-Si feedstock is the MG-Si gaseous melt treatment. While this MG-Si gaseous melt treatment is effective at reducing boron levels, it requires longer treatment times and adds additional costs to the production of pure feedstock. A third method is  the recrystallization of Si from MG-Si or metal solutions which, while promising for the production of pure feedstock, does not provide a viable solution due to the high cost associated with the process. Ultimately, these methods do not enable high throughput and economical production of pure feedstock and can require complicated and expensive equipment. Therefore, improvements can be made to these methods to provide manufacturers with low-cost pure feedstock.

Description

Scientists at NREL have developed a high throughput and cost-effective method and apparatus for the production of bulk Si from highly impure MG-Si source material. This method involves the reaction of Iodine (I) and MG-Si in a cold wall reactor chamber to produce SiI4 and other by-products, the isolation and purification of SiI4 within a distillation chamber, and the transference of the SiI4 back to the cold-wall reactor chamber for further reaction with MG-Si and I. This process ultimately produces SiI2 and allows for its deposition onto a substrate within the cold-wall reactor chamber. This process is scalable and low cost because it takes place at atmospheric pressure within an open system to enable the removal and replacement of substrates.

Benefits
  • High deposition rates
  • Utilizes metallurgical grade Si as source material
  • Scalable technique that takes place at atmospheric pressure
Applications and Industries
  • Semiconductor Devices
  • Photovoltaic Devices
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Patent 6,712,908
Patent
6,712,908
Purified silicon production system
Method and apparatus for producing purified bulk silicon from highly impure metallurgical-grade silicon source material at atmospheric pressure. Method involves: (1) initially reacting iodine and metallurgical-grade silicon to create silicon tetraiodide and impurity iodide byproducts in a cold-wall reactor chamber; (2) isolating silicon tetraiodide from the impurity iodide byproducts and purifying it by distillation in a distillation chamber; and (3) transferring the purified silicon tetraiodide back to the cold-wall reactor chamber, reacting it with additional iodine and metallurgical-grade silicon to produce silicon diiodide and depositing the silicon diiodide onto a substrate within the cold-wall reactor chamber. The two chambers are at atmospheric pressure and the system is open to allow the introduction of additional source material and to remove and replace finished substrates.
National Renewable Energy Laboratory 03/30/2004
Issued
Patent 6,468,886
Patent
6,468,886
Purification and deposition of silicon by an iodide disproportionation reaction
Method and apparatus for producing purified bulk silicon from highly impure metallurgical-grade silicon source material at atmospheric pressure. Method involves: (1) initially reacting iodine and metallurgical-grade silicon to create silicon tetraiodide and impurity iodide byproducts in a cold-wall reactor chamber; (2) isolating silicon tetraiodide from the impurity iodide byproducts and purifying it by distillation in a distillation chamber; and (3) transferring the purified silicon tetraiodide back to the cold-wall reactor chamber, reacting it with additional iodine and metallurgical-grade silicon to produce silicon diiodide and depositing the silicon diiodide onto a substrate within the cold-wall reactor chamber. The two chambers are at atmospheric pressure and the system is open to allow the introduction of additional source material and to remove and replace finished substrates.
National Renewable Energy Laboratory 10/22/2002
Issued
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL 01-33, 98-47Prototype - This technology is in the Prototype/Development StageAvailable08/10/201608/10/2016

Contact NREL About This Technology

To: Erin Beaumont<erin.beaumont@nrel.gov>