Wet chemical oxidation of silicon surfaces prior to the deposition of all-PECVD AlO_x/a-SiN_x passivation stacks for silicon solar cells

摘要

The work has demonstrated that wet chemical oxides with low manufacturing costs can be used to improve the passivation quality of PECVD deposited AlO_x/a-SiN_x:H stacks. An important contribution to the high level of passivation of the SiO_x/AlO_x/a-SiN_x:H stacks after post-deposition thermal steps is attributed to improved interface properties controlled by the Si-O-Si bonding structure and saturation of recombination centers by hydrogen. The second contribution is assigned to the negative charge, the origin of which could be identified to be partly due to the increase of the density of negatively charged AlO_4 tetrahedra at the AlO_x/SiO_x interface. These findings are revealed by infrared spectroscopy.