In this process, the primary polysilicon will be produced into polycrystalline silicon with single crystal orientation, no grain boundaries, no dislocation defects and very low impurity density in a single crystal furnace.
The growth process of polycrystal itself determines that it cannot grow large-area single crystals (single crystals), and the essence of polycrystal is a large number of small single crystals.
1. The so-called single crystal (single crystal, single crystal) means that the particles in the crystal are regularly and periodically arranged in the three-dimensional space, or the whole crystal is composed of the same spatial lattice in the three-dimensional direction, and the arrangement of particles in the whole crystal in the space is long-range and orderly. The whole lattice of single crystal is continuous, which has important industrial applications. Due to the entropy effect, the microstructure of solids is not ideal, such as impurities, uneven strain and crystal defects. Ideal single crystals with a certain size are extremely rare in nature and difficult to produce in the laboratory. On the other hand, in nature, imperfect single crystals can be very huge. For example, some minerals, such as emeralds, gypsum and feldspar, are known to form crystals up to several meters.
Baidu Encyclopedia _ Single Crystal
2. Polycrystalline is a collection of single crystals with many oriented grains. Polycrystalline and single crystal are based on lattice periodic structure, which is essentially the same for the same kind of crystal. The difference between them is that single crystal is anisotropic, while polycrystalline is isotropic. Polycrystalline samples also have their own characteristics when shooting polycrystalline diffraction patterns or counting diffraction.
Baidu encyclopedia _ polycrystal