Etch selectivity inversion for etching along crystallographic directions in silicon

摘要

Methods for expanding trenches are disclosed. A trench is formed in a substrate having side walls including at least two crystallographic planes. One crystallographic plane is etchable at a faster rate than a second crystallographic plane. A dielectric layer is selectively grown on surfaces of the crystallographic planes such that the dielectric layer includes a greater thickness on one of the crystallographic plane than on the other. The dielectric layer and the substrate are etched such that an etch rate inversion is achieved. That is, the second crystallographic plane is effectively etched at a faster rate than the first crystallographic plane.