HSQ application for sub-10 nm scale lithography
An application of hydrogen silsesquioxane (HSQ) negative tone elctron beam resist for a sub-10 nanometer scale fabrication is reported. Flowable Oxide resist solutions in methyl isobutyl ketone (MIBK) (FOx-12, Dow Corning) was further diluted with MIBK and spun over silicon wafers. Spin-coated films were prebaked for 5 min at 180°C. Characterisation of the resist was carried out. The resist surface roughness after the prebake process was better than 2nm over a 20µm square area measured by an atomic fofce microscopy (AFM). After e-beam irradiation resist was developed in MF322 (Shipley) for 60 s, and then rinse in deionized water for 15 s and blown dry with N2. The measurements of the sensitivity, contrast and etching durability follow. The threshold of the sensitivity about 600 µC/cm2 was found, whereas the dose needed for proper generation of 40 nm lines is about 1300 µC/cm2. We have found that about 13 fC is sufficient to develop properly dots with diameter of 20 nm. The influence of the e-beam source fluctuation on the control of the electron beam exposure is reported.