2019, Sperber, David, Furtwängler, Florian, Herguth, Axel, Hahn, Giso

It is shown that a non-fired B-doped floatzone silicon sample coated with SiNx:H may show severe bulk related degradation and regeneration during illuminated treatment at elevated temperature. It is discussed that the likely cause is light and elevated temperature induced degradation (LeTID) in the silicon bulk. Firing is found to modulate the extent of LeTID so that degradation may either be weaker or stronger compared to the non-fired sample depending on firing parameters. A sample which was annealed instead of fired is found to be stable for up to 1,000 h of treatment time.

2016, Sperber, David, Furtwängler, Florian, Herguth, Axel, Hahn, Giso

Different dielectric layers were deposited onto boron doped floatzone silicon wafers and the stability of the effective lifetime was investigated at elevated temperatures ranging from 75°C to 250°C with and without illumination. It was found that samples fired in a belt furnace show an instable behavior on a timescale of minutes to months. The short term behavior of a sample is strongly influenced by the peak firing temperature whereas the long term behavior appears to be less influenced by this parameter. Different chemical cleaning procedures during sample preparation show no significant influence on stability. Via corona charging, the changes at 250°C in darkness could be associated with changes in chemical passivation quality. It could be shown that a non-fired sample shows a similar, but less pronounced instability whereas an annealed sample is stable under the given treatment conditions.