Emergence of assist feature OPC era in sub-130-nm DRAM devices

In this paper, application of assist feature(AF)-OPC for 120nm DRAM device was investigated. For full chip level gate- poly patterning of DRAM device with 120nm design rule, attenuated PSM and OAI(annular type) were used to improve process margin for cell pattern and assist feature(AF) which is a type of OPC for sub-resolution was applied to isolated line in order to reduce iso-dense bias in peripheral area. From simulation and experimental results, the design rule of AF such as AF width, space to main pattern, and main pattern bias was extracted. And manufacturing attenuated PSM with AF, pattern fidelity and defect inspection for mask patterns were considered. Considering the experimental results, we can achieve good iso-dense bias and enlarge the common DOF of 120nm gate pattern with 248nm KrF lithography.