Feasibility of EUVL thin absorber mask for minimization of mask shadowing effect

Conventional EVUL mask has 80nm absorber height which brings considerable shadowing effect. H-V CD bias of 40nm line and space by shadowing effect is more than 4nm, and that is expected to increase much more for narrower patterns by simulation. However various reports have been presented on mask shadowing bias correction, experimental results are not reliable to derive required mask bias correctly. Even more difficulty will arise when complex 2D structures are taken into account. Therefore minimization of shadowing effect by reducing absorber thickness is desirable. To transfer EUV lithography from experimental stage to HVM era, we need to find optimum absorber height of EUVL mask which allows us less shadowing effect with minimum loss of process window. In this paper, we present optimal absorber height of EUV mask which has been found in terms of shadowing effect and process window by simulation and exposure. To find minimized absorber height experimentally, we will compare the printing result of conventional and thin mask stack using simple 1:1 line and space and island patterns. Simulated H-V CD bias and process window will be presented.