Impact of molybdenum/silicon multilayer structure on extreme ultraviolet mask fabrication

Electron beam lithography (EBL) will be used to pattern an Extreme Ultraviolet (EUV) mask. Both forward scattering electrons and backscattering electrons contribute to the energy deposition in resist, which is directly related to the pattern profile. When the exposure conditions, development conditions and the thickness and material of absorber, buffer, capping, and substrate are determined, the structure of molybdenum/silicon (Mo/Si) multilayer become the exclusive factor to influent the EUV mask fabrication. Several researchers have investigated the influence of the number of repeated Mo/Si layer and their thickness on the backscattering coefficient and the deposited energy in the resist. However the secondary electron generation and tracking is not implemented. Furthermore, the characters of pattern profile were not analyzed. In this paper, EBL module of in house software MicroCruiser, which included the secondary electrons and relativistic correction of high energy electron, was used to study the impact of structure of Mo/Si multilayer on the mask fabrication by EBL. Energy distribution in resist, backscattering coefficient (BSC), and the pattern profile had been investigated. The results show that with the number of Mo/Si repeated layers increases, the BSC decrease and the line edge of pattern profile is much smoother.