Acceptable Atmosphere for CZ/Float-zone Refining

[Patrick Underwood]

Both the cz (Czochralski Process), and Float-zone refining of silicon require an inert atmosphere, usually argon. How pure does the argon atmosphere have to be? How high of a vacuum has to be pulled before releasing argon into the tank?

 

[BPHH85]

Hi

As always, it depends. The purer the inert gas the the lower might be the density of impurities that can diffuse in the crystal. Also the pressure depens. Higher pressure might be helpful to prohibit the separation of the volatile component from the melt and prevent stoichiometry changes.