Importance

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Abstract

A method for forming a trench having upper rounded corners comprising the following steps. A substrate having an oxide layer formed thereover is provided. A hard mask layer is formed over the oxide layer. A patterned patterning layer is formed over the hard mask layer leaving one or more portions of the hard mask layer exposed. The hard mask layer is patterned using the patterned patterning layer as a mask to form a patterned hard mask layer having one or more openings exposing one or more portions of the oxide layer. The patterned patterning layer is removed. The oxide layer is patterned using the patterned hard mask layer as a mask using a first trench etching process to etch through the oxide layer at the one or more exposed portions of the oxide layer and into the substrate to form one or more shallow trenches within the substrate having upper rounded corners at the respective interfaces between substrate and patterned oxide layer. The substrate is further etched at the one or more shallow trenches using a second trench etching process to form one or more completed trenches having the upper rounded corners at the respective interfaces between substrate and patterned oxide layer.

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First Claim