A novel approach to reduce the oxygen content in monocrystalline silicon by Czochralski method

Abstract

High-efficiency solar cells require monocrystalline silicon wafers with lower oxygen content. This paper presents a design for an oxygen-lowering ring to decrease the oxygen content of 300 mm monocrystalline silicon, and experimentally verifies its effectiveness in reducing oxygen. Numerical simulations show that the use of the oxygen-lowering ring leads to a decrease of the crucible temperature at the bottom of the crucible and an increase of the crucible temperature at the top side of the crucible. In addition, a series of global simulations of oxygen transport were conducted to analyze how variations in the temperature distribution of the crucible wall affect the oxygen content at the m-c interface. The simulations revealed that the region of the crucible wall where dissolved oxygen is transported to the m-c interface is contained within the region of the crucible wall where the temperature decreases, implying that the addition of the oxygen-lowering ring reduces the source of oxygen transported to the m-c interface. Moreover, the addition of the oxygen-lowering ring reduces the turbulent viscosity in the melt, which weakens the ability to transport oxygen to the m-c interface.