Soft X-ray reflectometry applied to the evaluation of surface roughness variation during the deposition of thin films

Abstract

Thin films of boron, silicon and tungsten-rhenium materials were prepared by vapor deposition in a high vacuum system. During the deposition, the reflectivity was measured using the carbon Ka line (A = 4.47 nm). The surface roughness evolution was calculated as a function of thickness from the soft X-ray reflectance of the films. It was found that the mean square deviation of the surface height is proportional to the average thickness. A statistical model is proposed to explain this behaviour ; it rests on the random condensation process of evaporated particules and takes into account the role of incident kinetic energy of adatoms in disordered thin film growth