Asymmetric interface and growth mechanism in sputtered W/Si and WSi2/Si multilayers

Abstract

This paper presents a comparative study on W/Si and WSi2/Si multilayers for analyzing the asymmetric interfacial effect in Si-based multilayers. The interfacial characteristic, crystallization and growth mechanism of W/Si and WSi2/Si multilayers were investigated using grazing incidence X-ray reflectivity, X-ray diffraction, X-ray diffuse scattering, total external reflection X-ray diffuse scattering and Transmission Electron Microscopy. Roughness characteristics including frequency response, conformity and replication were quantitatively determined from the simulation of diffuse scattering profiles and the calculation of resonant diffuse scattering sheets. The intrinsic power spectral density of W/Si and WSi2/Si multilayers was fitted to demonstrate the related growth mechanism of the interfacial roughness. The experimental results exhibit the diffusion-dominant interfaces of the W/Si multilayer are obvious asymmetric for the wider interfacial region of 0.37 nm in the W-on-Si interface than that of 0.28 nm in the Si-on-W interface. Interfaces of the WSi2/Si multilayer without the distinguishable interdiffusion present the roughness-dominant property with the asymmetric transverse relaxation. The asymmetric interfaces of W/Si and WSi2/Si multilayers were further interpreted by a modified ballistic argument with the interfacial relaxation and reaction analysis.