Study On The Orientation Relationship Between Si₃N₄/Si,SiC/Si In Polysilicon

Si₃N₄ and SiC particles are often used as seed crystals of heterogeneous nucleation to assist the growth of polycrystalline silicon ingots in the photovoltaic industry.The Si₃N₄ coating can prevent the adhesion of crucible wall and silicon ingot.It is inevitable to be contaminated by N and C elements,and and the inclusion of Si₃N₄ and SiC particles is formed in the process,which will cause great harm to the electrical properties and yield of the ingots.How to use the heterogeneous nucleation of Si₃N₄and SiC particles to assist the growth of high-performance polycrystalline silicon,and fully remove the hard particle inclusion in the subsequent process,is an important research subject.This paper studies the orientation relationship between Si₃N₄/Si,SiC/Si in polycrystalline silicon during the directional solidification process and its influence on the electrical properties of ingots.The effect of electromagnetic field on the segregation of Si₃N₄ and SiC hard particles was also studied.The main conclusions are as follows:?1??-Si₃N₄ particles are pale yellow needle-like transparent crystal on the macro level and rod-like structure on the micro level.SiC granule is black granule macroscopically and massive structure microscopically.The presence of hard particles in silicon will lead to the enrichment of metal impurities,which will reduce the life of silicon ingots.Induction melting has a good elimination effect on hard particles.Hard particles deposit on the bottom of liquid silicon,and the hard particles gradually reduce to disappear within the range of 50mm-100mm from the bottom.?2?The edge-to-edge model was used to calculate the mismatching degree between<112^<sub>0>?_-Si3N4 and Si?<110>orientations,which was 0.92%.The spacing mismatch between{01^<sub>1^<sub>3}?_-Si3N4 and{110}_Si crystal planes was only 0.1%.Through transmission electron microscopy,the crystal plane?1^—10?_Si and the crystal plane?01^<sub>1^<sub>3??_-Si3N4 have diffraction spots superposition.Based on the calculation of the edge-to-edge model and the characterization of transmission electron microscopy,there is potential matching relationship between Si and?-Si₃N₄,and?-Si₃N₄ can be used as the heterogeneous nucleated seed crystal of Si.?-Si₃N₄ phase was observed between?-Si₃N₄ and Si,and?-Si₃N₄ appears as a transition phase in a certain sense.?3?HRTEM observed that the interface between SiC and Si was relatively flat,the crystal plane?011^—?_Si was well matched with the crystal plane?1^—13?_SiC,and the crystal plane?101^—?_Si was well matched with the crystal plane?12^—1?_SiC..Turnbull-Vonnegut formula was used to calculate the lattice mismatch between SiC and Si,and the mismatching degree of crystal plane spacing between?011^—?_Si and?1^—13?_SiC,and between?101^—?_Si and?12^—1?_SiC are all less than 5%,.SiC has potential nucleation ability for Si and can be used as seed crystal to assist the growth of high-performance polycrystalline silicon.