US Patent 9153478 Spacer etching process for integrated circuit design

A method of forming a target pattern includes forming a first material layer on a substrate; performing a first patterning process using a first layout to form a first plurality of trenches in the first material layer; performing a second patterning process using a second layout to form a second plurality of trenches in the first material layer; forming spacer features on sidewalls of both the first plurality of trenches and the second plurality of trenches, the spacer features having a thickness; removing the first material layer; etching the substrate using the spacer features as an etch mask; and thereafter removing the spacer features. The target pattern is to be formed with the first layout and the second layout.