Carbon impurity in crystalline silicon

Carbon impurity contamination during growth of crystalline silicon has been systematically studied in a representative unidirectional furnace. Mechanism of carbon incorporation into silicon has been illuminated. To better understand the carbon contamination process, a global simulation in a unidirectional solidification furnace was implemented. The effects of flow rate and pressure on impurities were examined. To reduce carbon contamination, an improved unidirectional solidification furnace with a crucible cover was designed. Results show that this improvement enables the production of a high-purity multicrystalline silicon crystal in a unidirectional solidification furnace. In addition, the material of crucible cover has a great influence on carbon contamination. Another possible contamination mechanism due to the reaction between silica crucible and the graphite susceptor has also been given. Results show that the crucible reaction with graphite susceptor has a marked effect on carbon impurity in the crystal.