Effects of electric field on the oxide growth with plasma anodization of silicon

In this work, a new theory is proposed to rectify the apparently inconsistent results reported by others. The new kinetics of constant current plasma anodization kinetics is developed based on the ionic transport of oxidizing species. Using the experimental observations that the oxide electric field can either remain unchanged or increase linearly with the oxide growth, both logarithm and power laws for oxide thickness growth are obtained. The theoretical model correlates very well with the experiments reported by others. Space charge built-up in the oxide film, which depends on the current density of the oxidizing species and the reaction rate, is proposed to be origin for oxide field variations and different growth laws of the anodization. At very high current densities (e.g. 30 mA/cm2), the oxygen ion density in the oxide film reaches its saturated value, the space charge distribution and then the oxide electric field remains unchanged and the oxide growth is governed by a logarithm law. When the supply of ions is greater than the ion consumption in reaction, the electric field increases and the oxide growth can be precisely described by a power law.