Al2O3-TiO2 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.