Transmission Grating Fabrication for Replicating Resist Patterns of 20 nm and Below

Abstract

We proceed to develop the extreme ultraviolet (EUV) interference lithographic exposure tool to determine whether the obtained resist could satisfy the requirement for the 20 nm node and below down to the 11 nm node. Transmission grating fabrication is a key technology in EUV interference lithography (EUV-IL). To replicate a 20 nm line and space resist pattern, a 40 nm line and space (L/S) pattern is required for the transmission grating. In the hard mask process, by optimizing the resist thickness to 60 nm and the dry etching conditions, and improving the alignment procedure for back-side etching, the 40 and 35 nm L/S patterns of the transmission grating were successfully fabricated. In addition, by applying a chemically amplified resist to adopt the center stop process in the transmission fabrication process and optimizing the resist thickness to attenuate completely the 0th order light, which was transmitted through the absorber and membrane, we succeeded in increasing the light intensity of the interference fringes and in replicating the 20 nm L/S resist pattern on a wafer. Furthermore, the chemically amplified molecular resist in the positive tone was confirmed to have a 20 nm resolution.