Al 2 O 3 -TiO 2 Nanolaminates for Conductive Silicon Surface Passivation

Al 2 O 3 -TiO 2 nanolaminates are very attractive candidates for future conductive passivation layers because they are purely based on dielectric materials, which allow a simple integration in the state-of-the-art manufacturing process. In this study, Al 2 O 3 -TiO 2 double and multilayers are grown by atomic layer deposition and systematically investigated. The nanolaminates feature good silicon surface passivation and moderate electrical conductivity. The best performance is found for a double-layer stack consisting of a 5 nm Al 2 O 3 interface layer and a 15 nm TiO 2 capping layer after postdeposition annealing in N 2 or forming gas. With this stack, a surface recombination velocity of 15 cm/s and a contact resistance of 20 Ω·cm 2 are achieved. In Al 2 O 3 -TiO 2 nanolaminates, the electrical transport is strongly influenced by the interaction of TiO 2 and Al 2 O 3 during layer growth. Raman measurements reveal that high conductivity correlates with a phase transition of TiO 2 from amorphous to anatase.