Investigation of the interface structure in sputtered WSi$_{2}$/Si multilayers by in-situ synchrotron X-ray scattering.

Multilayer X-ray optics have many applications such as X-ray microscopy, X-ray lithography, and X-ray microanalysis. The interface imperfections are critical to the optical performance of the multilayer structures. We report on the growth of WSi$_{2}$ and Si amorphous thin films by dc magnetron sputtering in a vacuum chamber with 10$^{-9}$ Torr base pressure. In-situ synchrotron X-ray scattering with high temporal resolution has been employed to probe the surface and interface roughness evolution during film deposition. X-ray reflectivity simulations were performed using the IMD software package. It is found that the structure of WSi$_{2}$/Si multilayers is with an alternately smooth and rough interface. While Si layer roughens, WSi$_{2}$ layer is observed to smooth out an initially rough surface. The ion energy and flux assisting the growth may play a role in inducing this asymmetry in the interface roughness.