Litho-etch-litho-etch (LELE) is the double patterning (DP) technology of choice for 20 nm contact, via, and lower metal
layers. We discuss the unique design and process characteristics of LELE DP, the challenges they present, and various
○ We examine DP design methodologies, current DP conflict feedback mechanisms, and how they can help
designers identify and resolve conflicts.
○ In place and route (P&R), the placement engine must now be aware of the assumptions made during IP cell
design, and use placement directives provide by the library designer. We examine the new effects DP
introduces in detail routing, discuss how multiple choices of LELE and the cut allowances can lead to different
solutions, and describe new capabilities required by detail routers and P&R engines.
○ We discuss why LELE DP cuts and overlaps are critical to optical process correction (OPC), and how a hybrid
mechanism of rule and model-based overlap generation can provide a fast and effective solution.
○ With two litho-etch steps, mask misalignment and image rounding are now verification considerations. We
present enhancements to the OPCVerify engine that check for pinching and bridging in the presence of DP
overlay errors and acute angles.