Abstract This study investigates the formation and accumulation of α-SiC in the low-temperature zone of two industrial silicon furnaces, a region typically considered too cold for such material to form. The accumulation of SiC and Si at such a high position in the furnace was considered an abnormal condition that affected the furnace's electrical behavior. This phenomenon occurred periodically for > 1 year and is shown to decrease process stability by reducing resistance in the low-temperature zone. By investigating industrial samples using a scanning electron microscope (SEM), X-ray diffraction (XRD), computed tomography (CT) scanning, and chemical analysis, the material was found to consist primarily of α-SiC with 1 to 13 wt.% silicon, while oxygen and free carbon contents were below 1.5 wt.%. This is similar to material previously excavated from the crater crust in the high-temperature furnace zone and challenges the assumption that such material cannot form in the low-temperature zone. Although the exact formation mechanism remains uncertain, we believe that the material originates from condensation of gas-phase species such as SiC x , Si, SiO and CO. This means that the material has most likely been exposed to temperatures > 2000°C.
Sindland et al. (Fri,) studied this question.