Smoothing, passivation and re-passivation of silicon surfaces by anodic oxidation: a low thermal budget process

Abstract

The anodic oxidation of silicon surfaces as a low thermal budget process was investigated. The anodic oxidation leads to a smoothing effect of the surface due to the electric field enhanced growth process. This behavior leads to an increase of the breakdown voltage with respect to the thermally grown oxides. The rate of oxide formation depends on the amount of water in the solution, the temperature of the solution and the current density. The electronic properties (oxide charge and interface state density) depend only slightly on the temperature and current density, but they are strongly influenced by the amount of water. The oxidation rate is strongly increased by the water content of the electrolyte, which then leads to a higher defect concentration at the interface. The final oxide thickness depends on the applied potential and the amount of water in the electrolyte. The liquid contact allows the passivation and re-passivation of highly structured Si surfaces.