Heat stability of Mo/Si multilayers inserted with silicon oxide layers

摘要

The Mo/Si multilayers inserted with the SiO_2 layers with 2.0 nm in thickness have been proven to be thermally more stable than the conventional Mo/Si multilayer. The Mo/Si/SiO_2 multilayer inserted with the SiO_2 layers at the Mo-on-Si interfaces had a relatively high soft X-ray reflectivity even after annealing at 400℃. The Mo/SiO_2/Si/SiO_2 multilayer was structurally the most stable against annealing but the soft X-ray reflectivity of this multilayer was quite small because of the absorption of X-rays by oxygen. To minimize the deterioration of the soft X-ray reflectivity of the Mo/SiO_2/Si/SiO_2 multilayer with keeping the high heat stability, the optimum thicknesses of the inserted SiO_2 layers have been investigated. We have found that the Mo/SiO_2/Si/SiO_2 multilayer having asymmetric SiO_2 layer thicknesses at the Si-on-Mo interface (0.5 nm) and at the Mo-on-Si interface (1.5 nm) has thermally the most stable structure and maintains a high soft X-ray reflectivity after annealing.