Microstructures of Polycrystalline Silicon Wafer Directly Grown on Si3N4 Substrate from Liquid Silicon

Abstract

Polycrystalline silicon (Si) wafers were directly grown on Si3N4 substrate using a horizontal growth process and the their microstructures were observed. Si wafer with a dimension of 50×80 mm2 was successively achieved and typical growth velocity was 315–926 cm/min. From the investigations of process, microstructures were mainly determined by the substrate movement velocity, which was equal to the growth velocity. When the movement velocity increased, the wafer thickness and grain sizes decreased, but, the number of twins increased. When the movement velocity was 315.6 cm/min, wafer thickness was 312 µm and mean grain size was 82 µm. When the graphite substrate was used, there was severe carbon contamination and SiC was even formed near the rear side of wafer. Substitution of the substrate material with Si3N4 instead of graphite reduced the amount of carbon from about 1×1020 to 5.87×1018 atoms/min.