THE INFLUENCES OF CARBON, HYDROGEN AND NITROGEN ON THE FLOATING-ZONE GROWTH OF 4-INCH SILICON-CRYSTALS

Dislocation-free silicon crystals, grown without a crucible by the flo ating zone (FZ) technique, were developed and are produced for manufac turing high voltage and high power devices. These crystals grow under extremely complicated thermal conditions, so that the advantage of hig h purity may be offset by the origin of new structural defects, which do not exist with the Czochralski method. With increasing crystal diam eters microdefects may act as sources for dislocation formation. Attem pts were made to suppress the microdefect formation by decreasing the carbon concentration in the starting material. To suppress arcing betw een the inductor electrodes and/or the inductor and the growing crysta l, extinguishing gases such as hydrogen and nitrogen were added to the argon ambient. While hydrogen gives rise to the origin of anomalous d efects, nitrogen even has beneficial effects on the crystal quality.