High resolution and high density ion beam lithography employing HSQ resist

In the early stages of focused ion beam (FIB) development, ion beam lithography (IBL) employing organic resists showed potential advantages over electron beam lithography (EBL) (most notably less proximity effects and higher sensitivity [1,2]). However, EBL has always been more popular for various reasons (e.g., instrument capabilities, well known process technology, higher resolution, absence of potential shot noise effects, no unintended doping of the irradiated substrate area [3]). We will present and detail our results obtained with a gallium (Ga) liquid metal ion source (LMIS) nanofabrication system studying the resolution limits related to this kind of IBL. We will show that minimum feature sizes below 10nm and periodicity of 30nm are possible in a 6nm hydrogen silsesquioxane (HSQ) layer. Our experiments have revealed that the minimum reachable feature sizes are limited by a phenomenon called ''discontinued lines''[2,4]. Our results indicate that statistical dose fluctuations do not dominate this effect.