CZ semi grade pot scrap

La description

Ingots are grown through a process known as Czochralski (CZ) method. CZ ingot growth requires chunks of virgin polycrystalline silicon which are placed in a quartz crucible along with small quantities of elements called dopants - the most common of which are boron, phosphorus, arsenic and antimony. The materials are heated to a temperature above the melting point of silicon, ***0 degrees Celsius. Once the polycrystalline and dopant combination has been liquefied, a single silicon crystal, the seed, is positioned on top of the melt, barely touching the surface. The seed has the same crystal orientation required in the finished ingot. To achieve doping uniformity, the seed crystal and the crucible of molten silicon are rotated in opposite directions. Once conditions for the crystal growth have been met, the seed crystal is slowly lifted out of the melt. Growth begins with a rapid pulling of the seed crystal in order to minimize the number of crystal defects within the seed at the beginning of the growing process. The pull speed is then reduced to allow the diameter of the crystal to increase. When the desired diameter is obtained the growth conditions are stabilized to maintain the diameter. As the seed is slowly raised above the melt, the surface tension between the seed and the melt causes a thin film of the silicon to adhere to the seed and then to cool. While cooling, the atoms in the melted silicon orient themselves to the crystal structure of the seed. 
 
Once a polysilicon ingot is fully-grown, it is removed from the quartz crucible from which it was pulled. The silicon scrap that remains in the crucible after removal is called “pot scrap”. The scrap is broken into chunks, and cleaned of any residual quartz. The pot scrap can then be remelted into lower grade silicon for a variety of utilizations.