Structural control of dendrite crystals in practical size silicon ingots grown by floating cast method

We report on successful control of the growth of dendrite crystals to suppress dislocation generation in practical size multicrystalline silicon ingots by modifying the growth condition. Local temperature distributions and gas flow above silicon melt surface were controlled by utilizing additional heat insulators and carbon components in a furnace. The size, positions and shapes of the insulators and the components were optimized by the aid of numerical calculations on heat transfer and radiation. As a result, we succeeded in controlling the nucleation of dendrite crystals and realized directional growth on the melt surface to form multicrystalline structure. This structural control leads to suppression of dislocation generation around grain boundaries which are formed by contacts of dendrite crystals. This shows that the structural control by manipulating dendrite crystal growth by the floating cast method is one of the promising approaches to realize high quality Si ingot based on a casting method.