A method of forming a semiconductor structure includes forming a memorization layer over a substrate, forming a first self-aligned double patterning (SADP) stack including a first organic planarization layer (OPL), masking layer, set of mandrels, and set of spacers, and forming a patterned memorization layer by transferring a first pattern of the first set of spacers to the memorization layer. The method also includes forming a second SADP stack comprising a second OPL, masking layer, set of mandrels, and set of spacers, and forming an array of pillars by transferring a second pattern of the second set of spacers to the patterned memorization layer. The first and second OPL and the first and second sets of mandrels are a spin-on coated OPL material, and the memorization layer and first and second masking layers are a material configured for removal selective to the spin-on coated OPL material.