Raman scattering study of nanoscale Mo/Si and Mo/Be periodic multilayer structures

Investigation of the microstructure and phase analysis of the periodic Mo/Si and Mo/Be multilayers are essential for depositing high reflective multilayers that operate at soft x-ray to extreme ultraviolet radiations. Raman spectroscopy revealed the presence of an amorphous phase of silicon (Si) in the Mo/Si multilayers. Furthermore, the disorder of the amorphous Si phase was increased with decreasing the periodic thickness of the Si layers in the nanoscale Mo/Si multilayers. The polycrystalline Mo periodic layers coexisted with the amorphous silicon layers in the Mo/Si multilayers. In contrast, both the Mo and Be layers in the Mo/Be periodic multilayers were condensed into the polycrystalline phases. At higher annealing temperatures, the polycrystalline and amorphous phases in both the Mo/Si and Mo/Be multilayers were destroyed due to the extensive interdiffusion process. However, the amorphous Si phase was partially preserved due to the formation of crystalline intermetallic h-MoSi2 and t-MoSi2 phases, for critically thicker Si layers in periodic Mo/Si multilayers.