Fin-like field effect transistor patterning methods for achieving fin width uniformity

Abstract

FinFET patterning methods are disclosed for achieving fin width uniformity. An exemplary method includes forming a mandrel layer over a substrate. A first cut removes a portion of the mandrel layer, leaving a mandrel feature disposed directly adjacent to a dummy mandrel feature. The substrate is etched using the mandrel feature and the dummy mandrel feature as an etch mask, forming a dummy fin feature and an active fin feature separated by a first spacing along a first direction. A second cut removes a portion of the dummy fin feature and a portion of the active fin feature, forming dummy fins separated by a second spacing and active fins separated by the second spacing. The second spacing is along a second direction substantially perpendicular to the first direction. A third cut removes the dummy fins, forming fin openings, which are filled with a dielectric material to form dielectric fins.