Illumination Optimization for the Beol Dtco with 45 Degree Local Interconnection

In previous work we have shown a few typical patterns containing 45-degree local interconnection in the BEOL layers under 7 nm logic design rules. Our simulation result has demonstrated that the 45-degree design can save mask area up to 20%. As illumination source optimization has been widely applied in lithography in advanced technology nodes for improving process window, in this work, we will report a study on the subject that, with source optimization, how the SO may affect the process window in the patterns containing the 45-degree design. Some typical patterns using conventional design rules will be presented first, then the 45-degree interconnection design will be fully investigated under illumination source optimization.