On the growth mechanism of multicrystalline silicon ingots with small grains fabricated using single-layer silicon beads

摘要

The growth mechanism of multicrystalline silicon ingots in directional solidification using single-layer silicon beads (SLSB) coated with Si3N4 was investigated. The grains in the SLSB-seeded ingot were smaller than those in a nonseeded ingot, but still larger than those in a polycrystalline Si (poly-Si)-seeded ingot. The dislocation density in the SLSB-seeded ingot was lower than that in the nonseeded ingot, but higher than that in the poly-Si-seeded ingot. The minority carrier lifetime mapping showed that a higher production yield was obtained in the SLSB-seeded ingot than in the poly-Si-seeded ingot. Grain refinement by the SLSB-seeding method was associated with the increase in nucleation rate. The increase in the surface area of the bottom of the crucible cannot quantitatively explain the grain refinement. Therefore, it is considered that SLSB may supply many nucleation sites because of their uneven structure. (C) 2017 The Japan Society of Applied Physics