Microstructure of multicrystalline silicon seeded by polysilicon chips and fluidized bed reactor granules

• Published in: Journal of crystal growth 2016-05, Vol.441, p.95-100
• Main Authors: Ekstrøm, K.E., Stokkan, G., Autruffe, A., Søndenå, R., Dalaker, H., Arnberg, L., Di Sabatino, M.
• Format: Article
• Language: English
• Subjects: A1. Characterization; A1. Crystal structure; A1. Solidification; A2. Seed crystals; B1. Silicon; Chips; Dislocations; Fluidized beds; Granular materials; Granules; Reactors; Silicon; Texture
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2016.02.017

Multicrystalline silicon displays a considerable smaller average grain size and reduced dislocation generation when being seeded by polycrystalline silicon chips or fluidized bed reactor silicon granules. A simple texture analysis shows how the initially random grain structure of the seeds develops a weak preference for near-〈111〉 and near-〈112〉 oriented grains upwards in the ingot. Closer investigations reveal a considerable coarsening of the initial microstructure of the seeds during the directional solidification process, especially for small fluidized bed reactor granules. The irregular shape of polysilicon chips allows for melt penetration into the seeding structure and potential indentation effects that may account for the increased dislocation generation observed in this case. The increased generation may, however, also be related to a higher ratio of ∑27 grain boundaries. •An increasing preference for near-〈111〉 and near-〈112〉 grains.•Coarsening of the as-grown microstructure of the seeds.•The irregular shape of polysilicon chips enables indentation and melt penetration.•Large and uniformly shaped seeds are preferred for seeding applications.