Defect formation induced by seed-joints during directional solidification of quasi-mono-crystalline silicon ingots

• First shown systematic and detailed investigation of various parameters like orientation, gap geometry or surface quality on the defect formation induced by seed-joints during quasi-mono silicon growth.
• The growth behavior inside the gap correlates with the gap plane orientation, the surface quality and the gap width.
• The growth behavior above the seed joints correlates with the axial seed orientation and the shape of the solid-liquid interface.

In this work, the growth behavior inside and above seed gaps during directional solidification of monocrystalline lab-scale silicon ingots was investigated. It will be shown that the silicon melt fills the gaps rapidly and monocrystalline growth starts in most cases at the seed side walls toward the gap center. During this process, dislocations were induced at the seed edges and in the gap center by the thermal shock caused by the hot melt and the coalescence of the two growth interfaces, respectively. The dislocations originating from the gap are propagating more or less parallel to the growth axis toward the top of the crystal. These dislocation bundles fan out in dependence of the growth height and axial seed orientation, respectively. It was found that <1 0 0> is the most suitable growth direction in comparison to <1 1 1> and <1 1 0> to avoid defect clusters above the seed gaps which is probably due to the orientation of the preferential glide systems.