The relationship between the oxygen impurity distribution in multicrystalline silicon and the use of top and/or side heaters in an unidirectional solidification process was investigated by numerical analysis. It was found that the oxygen concentration in the melt for the side heating system is lower than that for only the top heating system. This occurs because of the difference in flow direction of the melt near the crucible wall. The melt flows upward near the crucible wall when the side heating system is used. Oxygen is therefore dissolved from the silica crucible wall and is transported easily to the melt surface, where it evaporates. (C) 2013 Elsevier B.V. All rights reserved.