157-nm bi-layer resist: patterning and etching performance

摘要

A highly transparent (60% transmittance at 120-nm thickness: abs. = 1.85/μm), fluorine-containing, silsesquioxane-type resist for 157-nm lithography has been developed. When the resist was exposed with a 0.85-numerical-aperture (0.85-NA) microstepper and a phase-shifting mask, the high transmittance resulted in a steep profile for a 55-nm 1:1 line and space (L/S) pattern, as well as a feasible depth of focus (DOF) of 0.2 μm for a 100-nm contact hole (C/H) pattern. By using a 157-nm bHayer resist process, which employed 120 nm of silsesquioxane-type resist as the top layer and a 200-nm-thick organic film as the underlayer, a sub-100-nm C/H pattern could be successfully fabricated and transferred to a 400-nm-thick SiO_2 film by reactive ion etching (RIE). Neither pattern deformation during RIE nor residue after resist ashing was observed. The successful fabrication of a sub-100-nm C/H pattern in 400-nm-thick SiO_2 clearly demonstrated the advantage of the 157-nm bi-layer resist process for fabricating sub-65-nm-node semiconductor devices, especially for C/H fabrication or damascene processes.