Production of the silicon feedstock for the semiconductor industry cannot meet the requirement for the solar cell industry because the production volume is too small and production cost is too high. This situation stimulates the solar cell industry to...
Production of the silicon feedstock for the semiconductor industry cannot meet the requirement for the solar cell industry because the production volume is too small and production cost is too high. This situation stimulates the solar cell industry to try the lower grade silicon feedstock like UMG (Upgraded Metallurgical Grade) silicon of 5$\sim$6 N in purity. However, this material contains around 1 ppma of dopant atoms like boron or phosphorous. Calculation of the composition profile of these impurities using segregation coefficient during crystal growth makes us expect the change of the type from p to n : boron rich area in the early solidified part and phosphorous rich area in the later solidified part of the silicon ingot. It was expected that the change of the growth speed during the silicon crystal growth is effective in controlling the amount of the metal impurities but not effective in reducing the amount of dopants.