Single-crystal semiconductor growth technique - using Czochralski method with applied magnetic field, provides equalised axial oxygen concn. of crystal blank

摘要

The Czochralski crystal growth process is operated in a magnetic field, and a single crystal semiconductor blank is grown from a molten semiconductor material. A device is used which has; a closed chamber (2) with a quartz crucible arrangement (5) surrounded by a graphite container (4), a heating element (6) for heating the crucible, a drive shaft (3) for rotating the crucible at a predetermn. angular velocity, and a crystal pulling device (8) for pulling a seed crystal; a magnetic field generator (7) for directing a magnetic field around the melt. The generator has at least two parts disposed on an outer face of the chamber, opposite each other transverse to the crucible arrangement. The process has the following steps: (1) coating the crucible with a predetermn. amt. of semiconductor material and evacuating the closed chamber; (2) filling the chamber with an inert gas, and then rotating the crucible at a predetermn. velocity via the shaft; (3) heating the rotating crucible to melt the semiconductor material at a temp. above the single crystal growth temp., to give a molten semiconductor material; (4) immersing a seed crystal in the melt and withdrawing it upwards from the melt to grow a semiconductor crystal, with a magnetic field being directed on to the melt; the magnetic field strength at the melt is reduced in proportion to the crystal growth, in order to equalise the oxygen concn. in the axial direction of the crystal blank, the surface temp. of the melt being maintained at the single crystal growth temp.; and (5) rotating the seed crystal about its vertical path of movement as the axis and pulling the melt upwards to grow a single crystal rod. ADVANTAGE - The method claims to equalise the axial oxygen concn. of the crystal blank at low mfg. cost.