Fabrication of X-ray mask for nanolithography by EBL

Abstract

This paper investigate the manufacturing aspects of x-ray masks with sub-100 nm resolution obtained by medium voltage EBL and gold electroplating. To accomplish this task, commercial EBL systems, Leica Cambridge EBMF 10 /cs 120 and EBPG 5-HR were used. Although, it was demonstrated that at accelerating voltages as high as 100 KV resolution down to 75 nm is achievable in 0.75 μm thick resist, we found that similar results at sub-100 nm resolution can be obtained even at 40–50 KV in a single resist layer. Since the requirements of resolution and absorbers aspect ratio are challenging, an in-depth process study of the variables affecting the process behavior is needed. Therefore, we focus our investigation on some critical points, namely the reproducibility of the results, the effects on the ultimate resolution of the electron beam diameter and the exposure latitude. The extensive use of Monte Carlo simulation (MC) allowed the study of the scattering processes (and thus the energy deposition mechanism) occurring in the resist. In particular, the contributes from the forward and from the backscattering, could be separately computed. Dense and reproducible 65 nm gold line-width resolution x-ray mask have been fabricated at 50 kV in a 0.55 nm thick PMMA.