US Patent 11682558 Fabrication of back-end-of-line interconnects

A semiconductor structure includes a set of mandrel lines and a set of non-mandrel lines disposed on a hardmask in an alternating pattern. Spacers are disposed between adjacent mandrel lines and non-mandrel lines. The spacers include a composition which exhibits an etch rate greater than an etch rate of the mandrel lines and the non-mandrel lines.