Crystallization of a Mono-Ingot at Fraunhofer CSP with high-end polysilicon produced by Schmid Polysilicon Production SPP

First, an 8” mono ingot was grown with a body length of 400 mm and a total weight of 41 kg. After harvesting the ingot (the remaining silicon was kept liquid and the chamber was separated by a gate valve), a second ingot with a diameter of 4” and a length (body) of 790mm was crystallized. As much material as possible was crystallized in order to analyze whether the crystal keeps the single crystalline orientation or is loosing the structure towards the end of the run. The ingot grew completely mono-crystalline, down to a residual melt level of 1.7 kg, which is a good indication that we had no accumulation of residual impurities, in particular metals with low segregation coefficient, which would stay in the melt and result in supersaturation, defect generation and finally multicrystalline structure.  

Summary

On February 7th, the Fraunhofer CSP in Halle produced an 8“ Czochralski mono ingot using 100% Schmid-silicon. The polysilicon was produced by the proprietary Schmid process based on the CVD refinement of monosilane. It was the first crystallization test with this kind of material and we had no problem to achieve single-crystalline structure for the whole ingot, down to a residual melt level of less than 2 kg. In fact, no difference was seen between the Schmid material and other high quality polysilicon. Crystallization went very smoothly without any difficulties or peculiarities.