Patent ID: 6972240
Filing Date: 2005-12-06
Classification: H01L

Abstract:
1. A method for forming narrow trenches in a silicon substrate comprising the steps of: etching the substrate to form first trenches separated by first silicon ribs; performing a thermal oxidation of the substrate to form a silicon oxide layer developing inside and outside of the silicon, whereby second trenches narrower than the first trenches and second silicon ribs narrower than the first silicon ribs are obtained; filling the second trenches with fingers of an etchable material; etching the silicon oxide down to the upper surface of the second ribs while keeping silicon oxide portions between said etchable material fingers and the second ribs; etching away the second silicon ribs and said etchable material fingers; etching the silicon oxide for a duration sufficient to expose the substrate at the bottom of the silicon oxide portions, while leaving in place silicon oxide fingers; and anisotropically etching the substrate between the oxide fingers to form narrow trenches in the substrate.