Thermodynamic Modeling and Experimental Study on Interaction of Fe to P in Silicon Solution

The studies on the thermodynamics of P in silicon solution are significant for phosphorus removal in silicon purification technology. The activity interaction coefficient of Fe to P (\( \varepsilon_{\text{P}}^{\text{Fe}} \)) in a ternary system of Si-P-Fe at temperatures of 1623 K, 1673 K, and 1693 K was determined experimentally by the same activity method. The dissolution of P and Fe in the ternary Si-P-Fe alloy solution was investigated, and the possible phases in Si-P-Fe alloy were identified. Meanwhile, the activities of P and Fe (a_Fe and a_P) and the activity interaction coefficient \( \varepsilon_{\text{P}}^{\text{Fe}} \) in Si solution at 1693 K to 1873 K were calculated by a molecular interaction volume model (MIVM). The relationship between the activity interaction coefficient and temperature was achieved. The experimental results demonstrate that the presence of Fe in Si solution can improve the solubility of phosphorous, which is consistent with the calculation results by MIVM. In theory, it is beneficial for the removal of P from silicon by reducing the Fe concentration in Si.