The slit position dependence is particularly difficult for the tilted patterns encountered in DRAM. Besides the more complicated effects due to shadowing and pupil rotation, tilted edges are converted to stair shape, which may be distorted by OPC. In fact, the 32 nm pitch DRAM by EUV will lengthen up to at least 9F2 cell area, where F=active area half-pitch (traditionally, it had been 6F2). With a 2-D self-aligned double patterning active area cut, the cell area is still lower at 8.9F2.