On eliminating deposition-induced amorphization of interfaces in refractory metal multilayer systems

Multilayer thin films with refractory metal components are susceptible to solid state amorphization. It is an objective to minimize this interfacial reaction in order to ensure smooth layering and compositionally abrupt interfaces. These features are desirable for maximum reflectivity in X-ray optic applications such as projection lithography as well as neutron supermirror applications. This goal is achievable when the deposition process is optimized to thermalize the sputtered neutrals. Low working gas pressures (below 5 m Torr) and large source-to-substrate distances (more than 12 cm) typically provide the proper conditions to form dense sputter deposits without adatom-induced, interfacial amorphization. The interfaces of Mo/Si and Ni/Ti multilayers are examined with high resolution electron microscopy for samples sputter deposited under thermalized conditions. It is shown to be possible to produce crystalline, refractory metal layers in the as-deposited structure without amorphous interfacial regions.