| 摘要 |
A method for electrochemical local oxidation of silicon of selected regions of a silicon substrate of a semiconductor wafer avoids the formation of bird's beak structures of the prior art. The method involves the initial formation of a patterned generally nonconductive layer such as silicon nitride on a silicon substrate of a semiconductor wafer. The semiconductor wafer is then immersed in a bath of oxidizing electrolyte solutions such as pure water, acid, or ammonium. While immersed, the semiconductor wafer is subjected to an electrical field. The electrical field is created by connecting a power source both to a cathode located within the bath and to the semiconductor wafer, thereby employing the semiconductor wafer as an anode. The electrical field causes the oxygen of the bath to react with the silicon substrate and form patterned oxide regions in the locations where the silicon substrate was left unmasked by the patterned generally non-conductive layer. The directionality of the electrical field causes the patterned oxide regions to be formed with substantially anisotropic sidewalls. The anisotropic sidewalls enable the patterned oxide regions to be more densely packed and to have high dielectric properties. The semiconductor wafer is annealed after the bath to densify and remove moisture from the patterned regions of silicon dioxide.
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