Investigation on the Removal of B Impurity in Metallurgical Grade Si by Electron Beam Melting

Abstract

The growth in the solar energy technology caused inshortage solar grade Si. As a lowcost, environmental friendly technology, metallurgical method purity silicon is developed significantly. However, as a typical impurity in Si, B is difficult to be removed by directional refining or vacuum melting due to its large segregation coefficient and less evaporation coefficient. In this paper, the big difference of evaporation pressure between Si and B can be applied to separate B from Si, in which, B is remained in molten Si, while most of Si becomes evaporant. Electron beam is applied to scan molten Si and the Si existed in the form of the evaporant is gather on the watercooled crystallizer. The content B in the evaporant is undetectable by ICP-MS.

Research on new method of electron beam candle melting used for removal of P from molten Si

“…Compared with EBCM, the beam density was set to 200 mA and was required to be over 500 mA for melting the same size of Si ingot during EBM. 5,6 Irradiation with the electron beam caused the top surface of the ingot to melt gradually and form a molten pool, which can be seen through the observation window. The upper part of the ingot was orange red, whereas the lower part was darker.…”