METHOD FOR THERMAL TREATMENT OF SAPPHIRE PLATES Russian patent published in 2011 - IPC H01L21/324 

FIELD: chemistry.

SUBSTANCE: in the method for thermal treatment of sapphire plates, polished and washed leucosapphire plates are placed in depressions of graphite cell-cups and the surface of the plates is covered with graphite powder, filling the cell to its top level. Cells with leucosapphire plates are placed inside a graphite container, placing them vertically one on top of the other. The container is filled with graphite powder to its top level and closed with a graphite cover. The container is placed in the chamber of a vacuum annealing furnace. A vacuum of not less than 5·10^-4 mm Hg is created inside the chamber. The container with leucosapphire plates is heated to annealing temperature 1400-1500°C while raising the temperature at a rate of not more than 30 degrees per minute and continuing to evacuate the chamber using vacuum pumps. Vacuum annealing is carried out for 2-4 hours. The container with luecosapphire plates is cooled to room temperature at a rate of not more than 2 degrees per minute. The leucosapphire plates are removed from the cells and substrates are made from said plates using existing technologies.

EFFECT: obtaining leucosapphire plates with low content of active impurities and obtaining substrates from said plates, which are resistant to annealing in air for 2 hours and UV exposure for 1 hour.

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