Patent ID: 7465642
Filing Date: 2008-12-16
Classification: H01L

Abstract:
1. A method for forming a semiconductor structure, comprising: patterning a hardmask to define an opening; etching an area on a surface of a substrate exposed through the opening in the patterned hardmask to form a trench having sidewalls that extend from the surface to a bottom wall beneath the surface; widening the opening after the trench is formed such that the widened opening in the patterned hardmask is wider than the trench; implanting dopant ions through the widened opening to define a doped region in the substrate that extends about the sidewalls of the trench and is registered between the widened opening and the sidewalls of the trench; forming a porous region in the substrate about the sidewalls of the trench and at a depth between the surface of the substrate and the bottom wall of the trench; and converting the porous region to an insulator to define a buried isolation collar about the trench.