Passivation of n ^-Type Si Surfaces by Low Temperature Processed SiO /Al O Stacks

The surface passivation of SiO 2 /Al 2 O 3 stacks prepared at low process temperatures was investigated on phosphorous diffused n + -type Si surfaces with a broad range of sheet resistances. Two kinds of SiO 2 films were prepared, the first with plasma-enhanced chemical vapor deposition (PECVD) and the second in a wet chemical process. After atomic layer deposition of the Al 2 O 3 capping layer, the resulting SiO 2 /Al 2 O 3 stacks differ in the polarity of their fixed charge density, i.e., the PECVD SiO 2 stacks had a positive and the wet chemically grown SiO 2 stacks a negative fixed charge density. The PECVD SiO 2 /Al 2 O 3 stacks resulted in a high surface passivation over a broad range of sheet resistances whereas the wet chemically grown SiO 2 stacks were only feasible for diffused surfaces with low sheet resistances (