Apparatus and method of forming self-aligned cuts in mandrel and a non-mandrel lines of an array of metal lines

A method includes providing a structure having a first, second and third hardmask layer and a mandrel layer disposed respectively over a dielectric stack. An array of mandrels, a beta trench and a gamma trench are patterned into the structure. First inner spacers are formed on sidewalls of the beta trench and second inner spacers are formed on sidewalls of the gamma trench. The first and second inner spacers form a portion of a pattern. The pattern is etched into the dielectric stack to form an array of mandrel and non-mandrel metal lines extending in a Y direction and being self-aligned in an X direction. The portion of the pattern formed by the first and second inner spacers forms a first pair of cuts in a mandrel line and a second pair of cuts in a non-mandrel line respectively. The cuts are self-aligned in the Y direction.