Process-Induced Degradation Resistant n-Cz Wafers through Tabula Rasa Defect Engineering

We explore a simple annealing technique tabula rasa that allows monocrystalline n-type Czochralski silicon (n-Cz) wafers to avoid the oxygen precipitation that occurs during solar cell processing at high thermal budget. With this technique, the deep B emitter formation used in n-FZ based record efficiency Si cells, now becomes possible in n-Cz wafers. Wafers of both low and high O
_i
are subject to different tabula rasa processes that inject either vacancies or interstitials. As a result, we see strong variations in the carrier lifetime immediately after tabula rasa treatments in various ambients. However, after a thermal budget of the deep boron emitter formation, these variations disappear and we see significant lifetime improvement after tabula rasa, especially in wafers with high O
_i
content. This suggests that tabula rasa, an industrially relevant batch technique, could be successfully implemented for n-Cz wafers to remain oxygen precipitation-free during high efficiency n-type Cz solar cell processing and greatly improving fabrication yield.