Raw material preparation — crucible loading — melt — growth
The initial material that has passed the stage of thorough cleaning, sorting and preparation is loaded into a crucible, which is placed in a furnace and heated to the melting temperature in a vacuum. The seed crystal, which serves as the embryo of the future ingot, is introduced into the melt. With a constant rotation of the crucible, a gradual extension of the ingot occurs, which allows to obtain a single crystal with minimal defects in the structure. After completion of the growth and exhaustion of the melt residues, the ingot is separated from the melt and gradually cooled to a set temperature. (Czochralski method)
Extraction – measurements
After cooling the ingot, the control of its geometric dimensions and electrophysical parameters is carried out and its marking for subsequent processing is performed.
The marked ingot is cut into cylinders, which are then «squared». During the squaring the side sectors are cut off from the cylindrical workpiece and it takes the form of a pseudosquare (brick). The produced brick is gridded to 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.