Double patterning (DP) has now become a fixture on the development roadmaps of many device manufacturers for half pitches of and beyond. Depending on the device feature, different types of DP and double exposure (DE) are being considered. This paper focuses on the requirements of the most complex forms of DP, pitch-splitting (where line density is doubled through two exposures) and spacer processes (where a deposition process is used to achieve the final pattern). Budgets for critical dimension uniformity and overlay are presented along with tool and process requirements to achieve these budgets. Experimental results showing lines and spaces using dry ArF lithography with a factor of 0.20 are presented to highlight some of the challenges. Finally, alternatives to DP are presented.