Regional proximity effect correction for replicating 28 nm lines/spaces in HSQ as dielectric diffraction gratings with high aspect ratio

Abstract

With the rapid advances of extreme ultraviolet (EUV) lithography toward ultra-high resolution, characterization technique of EUV resists by interference lithography (IL) for 14-nm node process needs urgent upgrading because of the considerable loss of light transmission by metallic grating masks. Diffraction phase gratings in dielectric silicon dioxide as masks are a promising solution, provided that 28 nm lines/spaces with high aspect ratio as well as large grating areas are obtained. This paper reports our recent success in replicating 28 nm half-pitch gratings with the aspect ratio of 13:1 and the area up to 200 × 200 μm² by state-of-the-art electron beam lithography with regional proximity effect correction (PEC) in hydrogen silsesquioxane (HSQ) coated on a 100 nm silicon nitride membrane. To ensure well resolved lines/spaces in 350 nm thick HSQ, Monte Carlo algorithm is applied in the simulations of 3D absorbing electron energy density distributions, followed by calculations of equal energy contours of deposited energy based on the kinetic development model, which enables us to work out reliable dose windows. The process developed in this work should be feasibly extended to large area gratings in a future industrialization.