Enhanced density of negative fixed charges in Al2O3 layers on Si through a subsequent deposition of TiO2

Thomas Schneider; Johannes Ziegler; Kai Kaufmann; Klemens Ilse; Alexander Sprafke; Ralf B. Wehrspohn

doi:10.1117/12.2239183

29 April 2016 Enhanced density of negative fixed charges in Al₂O₃ layers on Si through a subsequent deposition of TiO₂

Thomas Schneider, Johannes Ziegler, Kai Kaufmann, Klemens Ilse, Alexander Sprafke, Ralf B. Wehrspohn

Proceedings Volume 9898, Photonics for Solar Energy Systems VI; 989816 (2016) https://doi.org/10.1117/12.2239183
Event: SPIE Photonics Europe, 2016, Brussels, Belgium

Abstract

The passivation of silicon surfaces play an important role for achieving high-efficiency crystalline silicon solar cells. In this work, a stack system comprising of 20nm Al₂O₃ with a 22nm TiO₂ topping layer was deposited on p-type Si using thermal atomic layer deposition (ALD) and was investigated regarding its passivation quality. Quasi-steady-state photo conductance (QSSPC) measurements reveal that the minority carrier lifetime at an injection density of 1015cm⁻³ increased from 1.10ms to 1.96ms after the deposition of TiO₂, which shows that the deposition of TiO₂ onto Al₂O₃ is capable of enhancing its passivation quality. Capacity voltage (CV) measurements show that the amount of negative charges in the dielectric layer has increased from -2.4·10¹²cm⁻² to -6.3·10¹²cm⁻² due to the deposition of TiO₂. The location of the additional charges was analyzed in this work by etching the dielectric layer stack in several steps. After each step CV measurements were performed. It is found that the additional negative charges are created within the Al₂O₃ layer. Additionally, ToF-SIMS measurements were performed to check for diffusion processes within the Al₂O₃ layer.

Citation Download Citation

Thomas Schneider, Johannes Ziegler, Kai Kaufmann, Klemens Ilse, Alexander Sprafke, and Ralf B. Wehrspohn "Enhanced density of negative fixed charges in Al₂O₃ layers on Si through a subsequent deposition of TiO₂", Proc. SPIE 9898, Photonics for Solar Energy Systems VI, 989816 (29 April 2016); https://doi.org/10.1117/12.2239183

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