Crystal Growing with Induction Heating

Induction heating has been used extensively in the manufacture of semiconductor crystals for use as LEDs, integrated circuits, solar panels, etc. Advantages include the strict control over the highly critical temperature of the molten mass, a clean, non-contact method of heating the crucible, and the ability to perform within varying atmospheres.

The process by which a crucible containing metallurgical-grade material is inductively heated using a graphite susceptor until the contents melt and then become a good electrical conductor. Induction sustains the melt.

While holding the melt at a specific temperature, a single crystal seed of the material on the end of a rod is inserted into the molten mass. Carefully controlling the rotation and withdrawal of the seed crystal from the crucible results in the growth of a relatively large single-crystal boule of a semiconductor material such as silicon, germanium and gallium arsenide.

Semiconductor material is refined through this process as impurities in the crystal are more soluble in the melt than in the crystal. Using induction heat to draw a zone of molten material along a rod of the material, impurities along the rod are collected at one end. Float zone refining reduces impurity levels with each pass of the molten zone along the rod.

In this process, the melt crucible is fitted with holes or micro-channels at the base, allowing the molten mass to flow out in a desired diameter. Induction sustains the melt in the crucible and controls the temperature of the semiconductor fibers extruded.

This process begins with the molten semiconductor material and controls the cooling of the polycrystalline mass to form a single crystal. This can be conducted over a vertical ampoule or along a horizontal vessel. Typically used for Gallium arsenide.