Properties of the c-Si/Al2O3 interface of ultrathin atomic layer deposited Al2O3 layers capped by SiNx for c-Si surface passivation

摘要

This work presents a detailed study of c-Si/AlO interfaces of ultrathin AlO layers deposited with atomic layer deposition (ALD), and capped with SiN layers deposited with plasma-enhanced chemical vapor deposition. A special focus was the characterization of the fixed charge density of these dielectric stacks and the interface defect density as a function of the AlO layer thickness for different ALD AlO deposition processes (plasma-assisted ALD and thermal ALD) and different thermal post-deposition treatments. Based on theoretical calculations with the extended Shockley–Read–Hall model for surface recombination, these interface properties were found to explain well the experimentally determined surface recombination. Thus, these interface properties provide fundamental insights into to the passivation mechanisms of these AlO/SiN stacks, a stack system highly relevant, particularly for high efficiency silicon solar cells. Based on these findings, it was also possible to improve the surface passivation quality of stacks with thermal ALD AlO by oxidizing the c-Si surface prior to the AlO deposition.