Requirements and strategies of High-NA EUV mask using MBMW

High-resolution EUV mask patterning capability has been one of the key factors to enable sub-10nm nanofabrication. Especially, the emergence of the Multi-Beam Mask writer (MBMW) in photomask lithography was a breakthrough for achieving the write time independent of pattern complexity with fine resolution, opening the EUV era. However, as the transition towards high-NA EUV technology is ongoing to extend Moore's law beyond 2nm-node and over, the novel exposure system challenges photomask manufacturing for higher resolution, accurate patterning fidelity and higher overlay due to 40% reduced resolution limit. Therefore, development of photomask lithography technologies including improved mask writer, photoresist, new materials of the substrate, and optimized EUV process is necessary to meet the desired minimum feature size and local fidelity such as local CDU, line edge roughness (LER) etc. In this paper, we aim to establish the evaluation method for optimized photomask process in upcoming high-NA EUV era. We analyze the budget of each factor contributing to EUV mask patterning performance including locality and resolution, and evaluate the total process window using MBMW. Finally, we discuss the comprehensive requirements and strategies on MBMW technology and relevant process to satisfy the mask patterning in the next generations from EUV mask maker's point of view.