Sub-50 nm stencil mask for low-energy electron-beam projection lithography

Abstract

Low-energy electron-beam-proximity projection lithography using a stencil mask is proposed for sub-70 nm node lithography. In this study, the anisotropic nature of Si wet etching is utilized for the fabrication of sub-50 nm stencil masks. A 20-nm-width aperture with a right angle and a 90-nm-width crossbeam with a smooth edge are obtained using silicon-on-insulator (SOI) wafers. 20-nm-thick Pt is calculated to be thick enough to block 2 keV electrons and it is shown that the evaporation of 10-nm-thick Pt from both sides of a membrane causes no significant degradation of sub-50 nm holes. It is estimated that a 25-nm-width aperture with a 100 nm pitch is feasible using an SOI wafer with an 18-nm-thick surface Si layer and a mask writer with a 50 nm resolution.