22nm node ArF lithography performance improvement by utilizing mask 3D topography: controlled sidewall angle

To improve lithography performance, resolution enhancement technique (RET) such as source mask optimization (SMO) will be applied to 22 nm node and beyond. We examine if lithography performance is improved by altering mask 3D topography. In this paper, we report that we have confirmed what topography is effective for lithography performance improvement in the dense region of 22nm technology node. Since shadowing effect is strong at the dense region, we focus on sidewall angle that decreases shadowing effect. As a basic analysis, we evaluate maximum exposure latitude (EL) and mask error enhancement factor (MEEF) of mask 3D topographic patterns that have various sidewall angles by 3D rigorous simulator. This result shows the increasing of maximum exposure latitude when changing sidewall angle. As a next step, we fabricate a test mask which has optimized sidewall angle and the exposure is performed on NA1.30 immersion scanner (Nikon NSR-S610C). Then we compare wafer printing results and simulation results. These results induce that the optimization of mask 3D topography has a potential to improve lithographic performance.