Helium ion beam lithography (HIBL) using HafSOx as the resist

Abstract

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.