Design and fabrication of densely integrated silicon quantum dots using a VLSI compatible hydrogen silsesquioxane electron beam lithography process

Abstract

► Fabricated smallest high density Si double quantum dot transistors using HSQ resist. ► E-Beam lithography gave reproducible device dimensions down to 25 nm. ► Eighty percent of the fabricated devices had dimensional variations of less than 5 nm. ► Our fabrication process can realise up to 144 scalable devices in parallel. ► This approach is compatible with very large scale integration. Hydrogen silsesquioxane (HSQ) is a high resolution negative-tone electron beam resist allowing for direct transfer of nanostructures into silicon-on-insulator. Using this resist for electron beam lithography, we fabricate high density lithographically defined Silicon double quantum dot (QD) transistors. We show that our approach is compatible with very large scale integration, allowing for parallel fabrication of up to 144 scalable devices. HSQ process optimisation allowed for realisation of reproducible QD dimensions of 50 nm and tunnel junction down to 25 nm. We observed that 80% of the fabricated devices had dimensional variations of less than 5 nm. These are the smallest high density double QD transistors achieved to date. Single electron simulations combined with preliminary electrical characterisations justify the reliability of our device and process.