Skip to Main Content
The surface passivation of SiO2/Al 2O3 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 SiO2 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 Al2O3 capping layer, the resulting SiO2/Al2O3 stacks differ in the polarity of their fixed charge density, i.e., the PECVD SiO2 stacks had a positive and the wet chemically grown SiO2 stacks a negative fixed charge density. The PECVD SiO2/Al2O3 stacks resulted in a high surface passivation over a broad range of sheet resistances whereas the wet chemically grown SiO2 stacks were only feasible for diffused surfaces with low sheet resistances (<; 100 Ω/□). By corona charging experiments, it was established that the field effect based on a negative fixed charge density was the reason for the loss in surface passivation in the specific range of diffused surfaces.