US Patent 9711372 Double patterning method

In some embodiments, the disclosure relates to a method of forming an integrated circuit device. The method is performed by forming a first mask layer over a substrate and a second mask layer over the first mask layer. The second mask layer is patterned to form cut regions. A mandrel is formed over the first mask layer and the cut regions, and the first mask layer is etched using the mandrel form a patterned first mask. The substrate is etched according to the patterned first mask and the cut regions to form trenches in the substrate, and the trenches are filled with conductive metal to form conductive lines.