Raw material preparation-crucible loading-melt-growth
The initial material, which has passed the stage of thorough cleaning, is loaded into the crucible, which is placed in the furnace and heated to the melting temperature in vacuum. The molten silicon begins to cool slowly so that the growth of crystals begins in the lower part of the crucible and occurs vertically. This process of growth allows to achieve maximum efficiency of future PV module. (Method of direct crystallization)
Squaring – measurements
The grown ingot is placed into the «squaring» equipment, where it is cut into 49 identical bricks of a given size by a dimond wire. Each brick is checked for compliance with geometric dimensions and electrophysical parameters (lifetime of minor charge carriers and resistivity). According to the results of the control, the bricks are forwarded to the cutting, during which the diamond wire cuts off the low-efficient upper and lower parts in which the «harmful» impurities are segregated and are transferred to the grinding to give them the size of the final wafer.
Polished silicon bricks are glued by 1-2 pieces on a polymer beam, which in turn was previously glued to the metal table of the wire cutting machine.
Dimond wire cutting
Cutting bricks into wafers is performed using a thin steel wire with a diamond coating, wired on two rotating main rollers in the form of a web. As the feed table with the bricks moves through the wire web, the bricks are being cut into wafers.
After the cutting process is complete, the wafers remain glued to the beam. They are placed in a special basket, which is alternately lowered into the baths with different concentrations of cleaning solutions for ungluing. At the end of the set time the adhesive is softened, and the unglued wafers are removed from the ungluing bath and transferred to the final cleaning line, where they are chemically washed in special baths with the set washing modes, afterwards they are dried and go to the quality control and sorting.
Quality control and sorting
At this stage, geometric parameters (thickness, total thickness variation, bow), the quality of the surface of the wafers (cracks, chips, holes, saw marks, glue residues, spots), as well as electrical parameters of 100% of wafers are being measured.