Excellent silicon surface passivation with 5 Å thin ALD Al2O3 layers: Influence of different thermal post-deposition treatments

Thin layers of Al2O3 always require a thermal post-deposition treatment to activate the passivation on crystalline silicon surfaces. In this work, we studied the influence of different thermal post-deposition treatments for the activation of passivating ALD Al2O3 single layers and Al2O3/SiNx stacks. For the stacks, especially with less than 5 nm Al2O3, a short high temperature process at similar to 800 degrees C results in a remarkably lower surface recombination compared to a commonly applied annealing at 425 degrees C. We observed that four ALD cycles of Al2O3 are sufficient to reach the full potential of surface passivation, and even with one atomic layer of Al2O3 (one ALD cycle) emitter saturation current densities as low as 45 fA/cm(2) can be reached on boron-diffused emitters. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim