US Patent 7883829 Lithography for pitch reduction

In one embodiment, a photoresist is lithographically patterned to form an array of patterned photoresist portions having a pitch near twice a minimum feature size. Fluorine-containing polymer spacers are formed on sidewalls of the patterned photoresist portions. The pattern of the fluorine-containing polymer spacers is transferred into an underlying layer to form a pattern having a sublithographic pitch. In another embodiment, a first pattern in a first photoresist is transferred into a first ARC layer underneath to form first ARC portions. A planarizing second optically dense layer, a second ARC layer, and a second photoresist are applied over the first ARC portions. A second pattern in the second photoresist is transferred into the second ARC layer to form second ARC portions. The combination of the first ARC portions and second ARC portions function as an etch mask to pattern an underlying layer with a composite pattern having a sublithographic pitch.