Facile and Thermally-Stable Al2O3 Passivation by Using In-Situ TiO2 as a Capping Layer for Boron Emitter of N-Type Silicon

초록

Al2O3/TiO2 stacks formed by atomic layer deposition are known to provide a high level of passivation for boron-doped silicon. In previous works, the TiO2 layer was deposited on a pre-annealed Al2O3 layer, however this stack showed passivation degradation after post-deposition annealing. This work presents an alternative to using the as-deposited Al2O3 for the Al2O3/TiO2 stack, which shows no degradation of passivation after post-deposition annealing up to 400 degrees C. This approach simplifies the processing, allowing continuous layer deposition, and eliminates the undesirable vacuum breaking. This simplified processing leads to better thermal stability of the Al2O3/TiO2 stacks and a low emitter saturation current density. In order to understand the underlying mechanism of surface passivation, an investigation on the effect of thermal SiO2 on the passivation of the Al2O3/(T)iO(2) stack was performed, which indicates that the TiO2 capping layer enhances the field-effect passivation for both the Si/Al2O3 and SiO2/Al2O3 structures.

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