Float-Zone silicon crystal growth at reduced RF frequencies

Abstract

The growth of Float-Zone silicon crystals of larger crystal diameter requires increasing power, e.g. increasing voltage at the inductor, which is limited by the breakdown voltage. Reduced working frequencies could help to solve this problem. However, the smooth melting of the feed rod is at risk for this case. The aim of this work is to investigate how a stable FZ-growth at reduced RF frequencies can be achieved and how the crystal parameters are influenced. Dislocation-free crystals of 4 inch diameter were grown at RF frequencies of 2.0 and 1.7MHz. It was confirmed that lower frequencies reduce the risk of arcing and silicon “nose” formation can be suppressed. Therefore, reduced RF frequencies can help to enable the growth of silicon FZ-crystals with bigger diameters.