Finnegan, Henderson, Farabow, Garrett & Dunner, L.L.P.
Method of forming top corner rounding of shallow trenches in semiconductor substrate
 A method of forming shallow trenches in a semiconductor substrate is provided. This method allows the thus-formed trenches to be shaped with a rounded top corner having a desired radius of curvature in accordance with actual requirements. From experiments, it is learned that the radius of curvature of the top corners of the trenches decreases linearly with the depth of a pre-trench formed by over-etching in the substrate. The relationship between radius of curvature and depth of pre-trench can be pre-established by experimentation. After that, the top corners of the shallow trenches in the substrate can be controlled to be shaped with a desired radius of curvature by adjusting the depth of the pre-trench based on the pre-established linear relationship. In this method, the substrate is removed to a predetermined depth corresponding to the desired radius of curvature of the top corner of the to-be-formed trench; then, thermal oxidation is performed on the substrate so as to form an oxide layer on the exposed area of the substrate; and finally, the oxide layer is removed. The empty space left by the removed oxide layer serves as the desired trench. 
Winbond Electronics Corp.
Y H
Y10S H01L
additional inventional
Michael
Ho