Decomposition difficulty analysis for double patterning and the impact on photomask manufacturability

Double patterning technology (DPT) is one of the most practical candidate technologies for 45nm half-pitch or beyond while conventional single exposure (SE) is still dominant with hyper NA avoiding DPT difficulties such as split-conflict or overlay issue. However small target dimension with hyper NA and strong illumination causes OPC difficulty and small latitude of lithography and photomask fabricated with much tight specification are required for SE. Then there must be double patterning (DP) approach even for SE available resolution. In this paper DP for SE available resolution is evaluated on lithography performance, pattern decomposition, photomask fabrication and inspection load. DP includes pattern pitch doubled of SE, then lithography condition such as mask error enhancement factor (MEEF) is less impacted and the lower MEEF means less tight specification for photomask fabrication. By using Synopsys DPT software, there are no software-induced conflicts and stitching is treated to be less impact. And also this software detects split-conflicts such as triangle or square placement from contact spacing. For estimating photomask inspection load, programmed defect pattern and circuit pattern on binary mask are prepared. Smaller MEEF leads less impact to defect printing which is confirmed with AIMS evaluation. As an inspection result, there are few differences of defect sensitivity for only dense features and also few differences of false defect counts between SE and DP with less NA. But if higher NA used, DP's inspection sensitivity is able to be lowered Then inspection load for DP would be lighter than SE.