Sub-10 nm structures written in ultra-thin HSQ resist layers, using Electron Beam Lithography

Isolated dots and lines with 6 nm width were written in 20 nm thick Hydrogen silsesquioxane (HSQ) layers on silicon substrates, using 100 keV electron beam lithography. The main factors that might limit the resolution, i.e. beam size, writing strategy, resist material, electron dose, development process, are discussed. We demonstrate that, by adjusting the development process, a very high resolution can be obtained. We report the achievement of 7 nm lines at a 20 nm pitch written in a 10 nm thick HSQ layer, using a KOH-based developer instead of a classical TMAH developer. This is the smallest pitch achieved to date using HSQ resist. We think that the resolution can be improved further, and is presently limited by either the beam diameter (which was not measured separately) or by the not fully optimized development process.