Pedestal procedure

The pedestal process is a process for the production of high-purity monocrystalline materials ( crystal growing ).

technology

An already prepared, cleaned rod (or column) with a still polycrystalline crystal structure is in a protective atmosphere. By means of induction heating above the supply rod, material is melted on its end face. The rod rotates slowly so that the zone melts evenly. The melted zone is brought into contact with a seed crystal and grows onto it, assuming its crystal structure. In contrast to the zone melting process , the crystal is pulled upwards out of the melt, similar to the Czochralski process , except that no crucible is used here, which means that it is as pure as with the zone melting process. However, so far only small diameters (up to about 50 mm) have been possible. The supply rod is tracked while maintaining the distance to the induction coil. Foreign atoms remain largely in the melting zone and are finally deposited at the end of the supply rod.

A dopant can be obtained by addition of gaseous materials, which then penetrate into the melt and / or be achieved by incorporating metal pieces.

application

With this method, the production of high-purity silicon and other materials is possible, but it is associated with very high costs. You can pull thin, high-purity crystals from thick supply rods.