Doped semiconductor wafer of float zone pulled semiconductor material, and process for producing the semiconductor wafer

#1. Field of The Invention

#The invention relates to a doped semiconductor wafer of float zone-pulled semiconductor material and to a process for producing the semiconductor wafer. The process comprises the production of a doped single crystal by float zone pulling (floating zone crystal growth, FZ method) and the division of the single crystal into semiconductor wafers. During the pulling of the single crystal, a molten material which has been produced using an induction coil is exposed to at least one rotating magnetic field and is solidified. The single crystal which is formed during the solidification of the molten material is rotated.

#2. The Prior Art

#Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings which disclose several embodiments of the present invention. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention.

#In the drawing, wherein similar reference characters denote similar elements throughout the several views:

#FIG. 1 shows an arrangement which is suitable for carrying out the process;

#Turning now in detail to the drawings, the arrangement illustrated in FIG. 1 comprises a single crystal 4, which is connected to a polycrystalline stock ingot 1 via a molten material 3. The molten material is produced by an induction coil 2. During the lowering of the single crystal, some of the molten material solidifies, so that the volume of the single crystal increases. At the same time, the induction coil causes material of the stock ingot to melt, and in this way the volume of the molten material is increased.

#According to the invention, a magnet system 5 with at least three poles or a multiple thereof is to be provided, such as for example the system used in a three-phase electric motor with three-pole stator. This generates a magnetic field which rotates in the opposite direction to the direction of rotation of the single crystal. The magnet system is preferably shielded from thermal radiation and water-cooled. It is also preferable for it to be possible for the field strength of the magnetic field to be varied between 0 and 100% by means of a potentiometer. The field lines 6 of the magnetic field are illustrated by arrows in FIG. 1.

#The arrangement illustrated in FIG. 2, comprises a 6-pole magnet system 5 with three-phase driving. This is formed by six individual magnets (L1a-L3b) distributed uniformly around the single crystal, with in each case two opposite poles corresponding, is particularly preferred.