Electron Beam Lithography of 15×15 nm2Pitched Nanodot Arrays with a Size of Less than 10 nm Using High Development Contrast Salty Developer

We investigated the effects of developer and hydrogen silsesquioxane (HSQ) resist thickness in the formation of dot arrays with a pitch of <18 × 18 nm 2 by using 30-keV electron beam (EB) lithography for bit patterned media (BPM). Optimum resist thickness and developer were investigated for the formation of fine dot arrays. We found that a 12-nm-thick HSQ resist was suitable to form fine dot patterns and the addition of NaCl into tetramethylammonium hydroxide (TMAH) could improve the development contrast (γ-value) of HSQ (the highest is 9.7). By using the 12-nm-thick HSQ resist film and 2.3 wt % TMAH/4 wt % NaCl developer, we successfully fabricated very fine resist dot arrays with a dot size of <10 nm and a pitch of 15 × 15 nm 2 , which corresponds to a storage density of about 3 Tbit/in. 2 in BPM.