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Double patterning is essentially an "edge patterning" process with critical dimension of a line, or space pattern, being defined by the independent position of its left and right edges. [2] Figure 2287b shows process flow of pitch doubling of sidewall spacer type. In this techonique, variations of lines and spaces depends on various parameters. Variations of L₁ depend on spacer film thickness variation and etching variation of left sidewall shown by a red arrow. Variations of L₂ depend on spacer film thickness variation and etching variation of right sidewall shown by a red arrow. Variations of S₁ depend on variations in lithography process and etching variation. Variations of S₂ is depend on variations in lithography process, spacer film thickness variation and etching variation.

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[1] Shinji Okazaki, High resolution optical lithography or high throughput electron beam lithography: The technical struggle from the micro to the nano-fabrication evolution, Microelectronic Engineering 133(8):23-35, DOI: 10.1016/j.mee.2014.11.015, 2015.
[2] Mircea Dusa, John Quaedackers, Olaf F. A. Larsen, Jeroen Meessen, Eddy van der Heijden, Gerald Dicker, Onno Wismans, Paul de Haas, Koen van Ingen Schenau, Jo Finders, Bert Vleemingb, Geert Storms, Patrick Jaenen, Shaunee Cheng, Mireille Maenhoudt, Pitch Doubling Through Dual Patterning Lithography Challenges in Integration and Litho Budgets, Proceedings of SPIE - The International Society for Optical Engineering 6520, DOI: 10.1117/12.714278, 2007.