Bulk and Surface Related Degradation Phenomena in Monocrystalline Silicon at Elevated Temperature and Illumination

Abstract

This work investigates the stability of lifetime samples made of monocrystalline silicon at elevated temperature and illumination. It is shown that samples made of Czochralski (Cz-Si) and float-zone silicon (FZ-Si) are affected by significant bulk related degradation (BRD) and surface related degradation (SRD) phenomena. SRD is observed in samples passivated with SiNx:H, SiO2/SiNx:H, SiOx:H/SiNx:H, SiOxNy:H/SiNx:H, and AlOx/SiNx:H. SRD furthermore occurs after variation of wet-chemical and most other processing steps and thus appears to present a general phenomenon in samples made of crystalline silicon. However, SRD is much weaker on highly doped silicon surfaces, and different degrees of changes in chemical passivation and field effect passivation are observed depending on choice of passivation layers. Frequently, SRD is followed by a recovery of surface passivation quality. A large number of samples is furthermore affected by BRD and subsequent regeneration phenomena. While BRD is expected in Cz-Si samples due to boron oxygen related degradation, even samples made of FZ-Si may show severe BRD. An in-depth analysis of degradation properties leads to the conclusion that BRD in FZ-Si is very likely related to light and elevated temperature induced degradation (LeTID) as originally observed in multicrystalline silicon. It is furthermore shown that samples made of Cz-Si may likely suffer from LeTID in addition to boron oxygen related degradation. Finally, the long-term stability of samples is investigated after a regeneration process. It is shown that regeneration of boron oxygen defects is very stable whereas samples affected by strong LeTID may suffer from a bulk related long-term instability.