Although lens aberrations in EUV imaging systems are very small, aberration impacts on pattern placement error and overlay error need to be carefully investigated to obtain the most robust lithography process for high volume manufacturing. Instead of focusing entirely on pattern placement errors in the context of a single lithographic process, we holistically study the interaction between two sequential lithographic layers affected by evolving aberration wavefronts, calculate aberration induced overlay error, and explore new strategies to improve overlay.
Helium ion beam lithography (HIBL) is a novel alternative lithographic technique with the capacity of fabricating highresolution and high-density features. Only limited research has been performed exploring HIBL to date. HafSOx (Hf(OH)4–2x−2y(O2)x(SO4)y·qH2O) is a negative-tone inorganic resist that is one of several candidate resist materials for extreme ultraviolet lithography (EUVL) and e-beam lithography (EBL), and has been demonstrated to show high resolution, moderate sensitivity and low line-edge roughness (LER) in both EUVL and EBL. To date, no ion beam lithography work on HafSOx has been reported. In this study, we tested HafSOx as an HIBL resist and achieved a high sensitivity compared with EBL with a turn-on dose D100 ~ 2-4 μC/cm2. We obtained sub-10 nm line widths with low LER. A simple Monte Carlo simulation suggests that ionizing excitation accounts for most of the incident He ions’ energy loss.