Below I wil introduce some production processes of Monocrystalline silicon:
Adding -→ Melting - → Necking Growth - → Shoulder Growth - → Equal Path Growth - → Tail Growth
(1) Feeding: The polycrystalline silicon raw materials and impurities are placed in a quartz crucible, and the type of impurities depends on the N or P type of the electric resistance. Impurities are boron, phosphorus, antimony and arsenic.
(2) Melting: After adding the polycrystalline silicon raw material to the quartz crucible, the crystal growth furnace must be closed and vacuumed, then filled with high-purity argon gas to maintain a certain pressure range, then the graphite heater power supply is turned on, and heated to the melting temperature. Above (1420 ° C), the polycrystalline silicon raw material is melted.
(3) Neck growth: After the temperature of the silicon melt is stabilized, the seed crystal is slowly immersed in the silicon melt. Due to the thermal stress of the seed crystal in contact with the silicon melt field, the seed crystal is dislocated, and these dislocations must be removed by necking growth. Neck growth is the rapid lifting of the seed crystal, so that the diameter of the growing seed crystal is reduced to a certain size (4-6mm). Since the dislocation line forms an angle with the growth axis, the dislocation can be long as long as the neck is long enough. Out of the crystal surface, a crystal with zero dislocations is produced.
(4) Shoulder growth: After lengthening the neck, the temperature and pulling speed must be lowered, so that the diameter of the crystal gradually increases to the required size.
(5) Equal-diameter growth: After the neck and shoulders are finished, the diameter of the ingot can be maintained between plus and minus 2mm by constant adjustment of the pulling speed and temperature. The fixed diameter portion is called the equal diameter. section. The single crystal silicon wafer is taken from the equal diameter portion.
(6) Tail growth: If the ingot is separated from the liquid surface immediately after the completion of the equal diameter portion, the thermal stress will cause dislocations and slip lines of the ingot. Therefore, in order to avoid this problem, the diameter of the ingot must be gradually reduced until it is a sharp point and separated from the liquid surface. This process is called tail growth. The long-lasting ingot is lifted to the upper chamber for a while and then taken out, that is, a growth cycle is completed.
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