Indexed by:Journal Article

Date of Publication:2014-02-01

Journal:JOURNAL OF ELECTRONIC MATERIALS

Included Journals:EI、SCIE

Volume:43

Issue:2

Page Number:314-319

ISSN:0361-5235

Key Words:Vacuum refining; directional solidification; purification; phosphorus; silicon

Abstract:Silicon is widely used as a raw material for production of solar cells. As a major impurity in silicon, phosphorus must be removed to 1 x 10(-5) wt.%. In the present study, based on the distribution of phosphorus in a silicon ingot obtained by vacuum refining and directional solidification, the mechanism for removal of phosphorus from silicon is investigated. The results show that the distribution is controlled not only by segregation at the solid-liquid interface but also by evaporation at the gas-liquid interface, showing some deviation from Scheil's equation. A modified model which considers both segregation and evaporation is used to simulate the distribution, matching quite well with the experimental results. The temperature and solidification rate are two important parameters that affect the overall mass transfer coefficient and the effective segregation coefficient and thus the distribution of phosphorus. A high removal efficiency and a homogeneous distribution can be obtained by adjusting these two parameters.