SiC and Si3N4 inclusions in multicrystalline silicon ingots

In this study we have investigated inclusions present in certain areas of a multicrystalline silicon ingot cast in industry. The inclusions were retrieved from the matrix by dissolution in HF:HNO3, followed by filtration. We identified the inclusions as beta-SiC and beta-Si3N4 by using Electron Probe Microanalyzer and Electron Backscatter Diffraction. These inclusions appear to a great extent as large clusters consisting of both types of particles. We also obtained a particle size distribution giving the following diameter range; 75 mum < 80 mass% < 385 mum. As the carbide particles tend to grow on the nitrides, the latter seem to act as nucleating centers for carbide precipitation. Several of the analyzed parts resulted in no measurable content by this method, indicating an inhomogeneous distribution. (C) 2004 Elsevier Ltd. All rights reserved.