Double Patterning Lithography Alignment and OVL-Control Strategy for 20nm Technology

Double patterning using 193 nm immersion lithography has been adapted as the solution to enable 20 nm technology nodes. In the Back end, Litho Etch Litho Etch (LELE) is considered as the most suitable process for this technology. The overlay control is one of the key figures for the successful realization of this technology. This paper presents a method called indirect alignment and indirect overlay measurement comparing with the common method (so called direct alignment and overlay the overlay (OVL) measurement) based on process complexity. While doing LELE, the common method need two or more films to get enough signal intensity for alignment measurement while the present method need only one film. In this paper, we will compare with the two overlay control methods and we also evaluate the risks for the present method and try to design a new APC control system to reduce the risks.