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The Effect of the Growth Rate on the Microstructure of multi-crystalline Silicon
Schmid, E.; Würzner, S.; Funke, C.; Galindo, V.; Pätzold, O.; Stelter, M.;
This paper presents an experimental study of the influence of the growth rate on the microstructure of multi-crystalline silicon (mc-Si). Crystals with a diameter of 105 mm were grown from an inductively heated, well-mixed melt by the conventional vertical Bridgman technique. Axial and vertical samples were prepared from the crystals to analyze the grain structure as well as the distribution of dislocations and precipitates. The results show that the growth rate influences the microstructure of the crystals mainly at the beginning of the solidification process. Growth with a low growth rate, for instance, favors the formation of radially elongated grains near the bottom of the crystal and suppresses the heterogeneous nucleation of SiC precipitates at the inner crucible wall. The effect of the grain shape is restricted to the bottom region of the crystals, whereas the precipitates are identified to be the origin of dislocations or dislocation clusters propagating throughout the crystal during growth. As a consequence, the dislocation density in a slowly grown crystal is found to be significantly lower than in a fast grown crystal.
Keywords: A1. Directional solidification, A2. Bridgman technique, B2. Semiconducting silicon, A1. Crystal structure, A1. Defects

Publ.-Id: 17410 - Permalink