'Mask Enhancer' Technology on ArF Immersion Tool for 45-nm-Node Complementary Metal Oxide Semiconductor with 0.249 μm~2 Static Random Access Memory Contact Layer Fabrication

摘要

One of the most challenging issues for 45-nm-node contact hole printing is to ensure a sufficient process window required for day-to-day manufacturing, and to reduce large mask error enhancement factor (MEEF) to keep the critical dimension (CD) controllable. In this study, we propose a new phase-shifting mask for random layout contact hole printing, named Mask Enhancer. By applying the Mask Enhancer, we can enhance image contrast for both isolated and dense contact holes at the same time. In addition, the Mask Enhancer is extendable for a random layout including diagonally placed or non-square contact hole. In this paper, we show the principle of the Mask Enhancer for improving image contrast and we discuss the lithographic performance of the Mask Enhancer comparing it with that of the attenuated phase-shifting mask (Att-PSM). Furthermore, we demonstrate 0.249 μm~2 static random access memory (SRAM) contact layer printing which is a 45-nm-node requirement, combining it with the immersion exposure technology on a 0.85 numerical aperture (NA) ArF immersion tool.