New design of anodic oxidation reactor for high-quality gate oxide preparation

This work reports a new structure of anodic oxidation apparatus which can be used for high quality oxide preparation. By implanting an additional anode, the current flux in the silicon is redistributed and a uniformity of 1.2% on an area of 4 cm³ is achieved. On the other hand, as the oxide thickness is a linear function of time and the growth rate is governed by anode current, the reproducible thickness of oxide film is well defined. When pure D.L. water is used as the electrolyte, the interface state density and the oxide charge density of the anodic oxides are extremely low. In addition, the breakdown field can be as high as 13 MV/cm for 400 A pure water anodic oxide (WAO). Although the refractive index of the WAO is smaller than the conventional growth thermal oxide, the parameter can be upgraded to the thermal oxide levels when the samples are annealed in nitrogen at 700°C for 1 h.