Interface roughening and effect of tensile WSi _x laer on srain rlaxation of eitaxial SiGe lyer in CVD-WSi _x/Si _0.83Ge _0.17/Si(001)

In this study, we investigated and compared the strain relaxation behaviors of the SiGe layers and interface roughening in Si _0.83Ge _0.17/Si(001) and CVD-WSi _x/Si _0.83Ge _0.17/Si(001) structures. The samples with and without the WSi _x layers grown by chemical vapor deposition were annealed at elevated temperatures, TA = 650 - 950°C. X-ray reflectivity (XRR) and high-resolution X-ray diffraction (HR-XRD) measurements showed a very smooth interface between SiGe and Si(001) substrate up to T _A = 900°C from the samples with and without the WSi _x layers but at T _A = 950°C a greater increase in the roughness of the SiGe/Si(001) interface for the sample without the WSi _x layer compared to the case of the sample with the WSi _x layer. High-resolution ω-2θ scans and reciprocal space mapping (RSM) by HR-XRD showed that the samples with and without the WSi _x layer annealed up to T _A = 900°C showed a negligible strain relaxation of the SiGe layers. However, thermal annealing at T _A = 950°C resulted in the strain relaxation of the SiGe layer without WSi _x layer but no strain relaxation of the SiGe layer with WSi _x, layer. These data indicate that tensile WSi _x layer effectively suppresses the strain relaxation of the compressive SiGe layers and roughening of the SiGe/Si interface in CVD-WSi _x/Si _0.83Ge _0.17/Si.