Multipatterning. With cleverly designed masks, you can use the etching of a coarser layer to create finer patterns out of essentially "residuals" left behind. Repeat this process for finer and finer patterns, with error being compounded on each step. This is what the article means when they say a wafer makes 15 trips to the litho machine. With EUV, you would still need multipatterning, but less steps, which is cheaper and less error prone.