In order to form practical arrays of Si nanowires narrower than 22 nm using electron beam lithography (EBL) with hydrogen silsesquioxane (HSQ) resist and reactive ion etching (RIE) process with inductively-coupled plasma, a new type of lithography/etching interaction is studied. The inter-pattern electrostatic repulsion appears to determine the patterning limit to be 28 nm while causing the RIE dummy patterns to collapse. Approaches to reduce the electrostatic force on the RIE dummies are tried from design and process perspectives. Designing additional dummy patterns next to the RIE dummies and fixing pattern-to-pattern distance to be 70 nm are tried. Another efficient approach is to use thinner HSQ resist to reduce the repulsion among patterns. Here we confirm that the nanowire patterns narrower than 20 nm can be formed by using diluted HSQ solutions.