(1) Thickness (T) 200-1200um
Total thickness variation (TTV) <10um
Bending (BOW) <35um
Warp (WARP) <35um
Monocrystalline silicon polishing surface quality: positive requirements no scribe, no pit, no fog, no regional contamination, no collapse, no cracks, no pits, no ditch, no hillock, no marks and so on. The back requires no area contamination, no chipping, no cracks, and no marks.
(2) Processing process knowledge
Polycrystalline silicon is processed into monocrystalline silicon rods:
There are two kinds of polycrystalline silicon crystal growth methods:
CZ (Czochralski) method
FZ (Float-Zone Technique) method
At present, more than 98% of electronic component materials use monocrystalline silicon. Among them, the CZ method accounts for about 85%, and the other part is the FZ growth method by the floatation method. Single crystal silicon grown by the CZ method is used to produce low power integrated circuit components. Monocrystalline silicon grown by the FZ method is mainly used for high-power electronic components. The CZ method is therefore more commonly adopted by the semiconductor industry than the FZ method, mainly because its high oxygen content provides the advantages of wafer hardening. Another reason is that the CZ method makes it easier to produce large-sized single crystal silicon rods than the FZ method.
At present, China mainly adopts the CZ method.
The main equipment of CZ method: CZ growth furnace
The components of the CZ furnace can be divided into four parts
(1) Furnace body: including quartz crucible, graphite crucible, heating and insulation element, furnace wall
(2) Crystal rod and rod lift rotating mechanism: including seed chuck, hanging wire and pull-up rotating element
(3) Atmospheric pressure control: including gas flow control, vacuum system and pressure control valve
(4) Control system: including sensor and computer control system
Processing technology:
Feeding → melting → necking growth → shoulder growth → equal diameter growth → tail growth
(1) Feeding: Polysilicon raw materials and impurities are placed in quartz crucibles, and the type of impurities depends on the N or P type of resistance. Impurities include boron, phosphorus, antimony and arsenic.
(2) Melting: After the polycrystalline silicon material is added to the quartz crucible, the crystal growth furnace must be turned off and evacuated and then filled with high-purity argon gas to maintain a certain pressure range. Then, the graphite heater is turned on and heated to the melting temperature. Above (1420°C), the polycrystalline silicon raw material is melted.
(3) Constriction 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 crystals in contact with the silicon melt field, dislocations are generated in the seed crystals, and these dislocations must be eliminated by shrinkage growth. Constriction necking is to raise the seed crystal upwards quickly, so that the diameter of the growing seed crystal is reduced to a certain size (4-6mm). Because the dislocation line forms a cross angle with the growth axis, the dislocation can be long as long as the necking is long enough. Crystal surface is produced, producing a dislocation crystal.
(4) Shoulder growth: After the neck is finished, the temperature and the pulling speed must be reduced so that the diameter of the crystal gradually increases to the required size.
(5) Equal diameter growth: After finishing the neck and shoulders, the diameter of the crystal rod can be maintained between plus and minus 2mm by constant adjustment of the pulling speed and temperature. This fixed diameter part is called equal diameter. section. Single crystal silicon wafers are taken from equal diameter sections.
(6) Tail growth: If the crystal rod is separated from the liquid surface immediately after the equal diameter part is completed, the effect force will cause the crystal rod to have dislocations and slip lines. Therefore, in order to avoid this problem, the diameter of the crystal rod must be gradually reduced until it becomes a sharp point and is separated from the liquid surface. This process is called tail growth. The long finished crystal rod is lifted to the upper furnace chamber and cooled for a period of time to complete the growth cycle.
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