Relationship of Free Surface Area with Oxygen Concentration in Silicon Ingot Grown by Czochralski Method for High Efficiency Solar Cells

Abstract

The relationship of free surface area with temperature, power, and oxygen concentration in a silicon ingot grown by Czochralski method for solar cells was investigated by simulating the growing process of 4-, 6-, and 8-inch diameter ingots with a 24-inch quartz crucible. It was confirmed that the temperature at auto-temperature-control (ATC) sensor of 4-inch diameter ingot was higher than 6- and 8-inch diameter ingot due to the longer distance between triple point and ATC sensor, i.e., larger area of the free surface. In addition, it was observed that the power consumption for growing 4-inch diameter ingot was greater than 6-and 8-inch diameter ingot because of its smaller heat capacity resulted from smaller charge size. In particular, it was confirmed that the oxygen concentration of 4-inch diameter ingot was lower than those of 6- and 8-inch diameter ingots since the larger free surface area and weaker melt convection led to the lower oxygen concentration in 4-inch ingot. This understanding of the relationship of free surface area with oxygen concentration in a silicon ingot can be applicable directly to control oxygen concentration in growing different diameter of silicon ingots.