US 6,143,627 A · Method for electrochemical oxidation of silicon

Abstract

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 non-conductive 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.

Claims40

Dependent claims

A method for forming a patterned oxide region on a silicon substrate of a semiconductor wafer, the method comprising:

masking the silicon substrate with a generally non-conductive layer to leave an unmasked region of the silicon substrate;
exposing at least a portion of the silicon substrate to a liquid electrolyte, the portion of the silicon substrate exposed to the liquid electrolyte containing therein the unmasked region of the silicon substrate;
and
applying a voltage to the silicon substrate across the liquid electrolyte thereby causing the silicon substrate to react with the liquid electrolyte to form a patterned oxide region in the silicon substrate at the unmasked region of the silicon substrate.

1 more element

A method for forming a patterned silicon dioxide region on a silicon substrate, the method comprising:

masking the silicon substrate with a patterned layer of silicon nitride to leave an unmasked region of the silicon substrate;
immersing the silicon substrate in an ammonium compound selected from the group consisting NH.sub.4 OH, TMAH, and TEOH;
applying a selected voltage between the silicon substrate and a cathode that is in electrical contact with the ammonium compound so as to create an electrical field between the cathode and the silicon substrate, thereby causing the silicon substrate to react with the ammonium compound to form a silicon dioxide region having a selected depth within the silicon substrate at the unmasked region of the silicon substrate;
and
removing the silicon substrate from the ammonium compound, removing the patterned layer of silicon nitride from the silicon substrate, and annealing the silicon substrate to densify and remove liquid from the silicon dioxide region.

2 more elements

Dependencies are inferred from the claim text.

Method for electrochemical oxidation of silicon

Life of this patent

Method for electrochemical oxidation of silicon

Life of this patent

Abstract

Claims40