Formation of metal silicide and metal germanosilicide contacts to silicon germanium alloys

The goals of this research were to study the phase stability and formation of Ti-Si1-xGex and Co-Si1-xGe x thin film reactions. The Ti-Si1-xGex and Co-Si1-xGex solid phase reactions result in the formation of precipitates within the grain boundaries of the films thus formed. The precipitates are either Ge or a Si-Ge compound, depending on the type of metal used in the reaction.; The formation of Ti(Si1-yGey)2 thin films on Si1-xGex has been examined. It has been found that the generation of Ge-rich Si-Ge precipitates which form in the Ti-Si1-xGex solid phase reaction could be reduced or eliminated by the insertion of an amorphous Si layer before the metallization step. A Gibbs free energy model, which was parameterized in terms of Ge concentration by atomic percentage was used to determine stability between the Ti(Si1-yGey)2 layer and the Si1-xGex substrate. The films in this study were characterized using x-ray diffraction (XRD) to investigate phase formation, stability, and the composition of the Ti(Si1-yGey) 2 layer. Scanning electron microscopy (SEM) was used to determine the surface morphology and phase stability. It was found that amorphous Si layers of a certain thickness could prevent precipitate formation, depending on the composition of the underlying Si1-xGex layer.; The formation of CoSi2 on Si1-xGex was also examined. The solid phase reaction of Co and Si1-xGe x results in the formation of a poly-crystalline CoSi2 layer, and the occurrence of a Ge precipitate. The TIME (Titanium Interlayer Mediated Epitaxy) process has been used in the formation of epitaxial CoSi2 on Si (100). A Ti layer of varying thicknesses, which serves as a barrier to retard the diffusion of Co atoms was deposited on a c-Si/Si1-x Gex substrate pseudomorphically strained to Si (100), before the final Co metallization step. The films in this study were characterized using x-ray absorption fine structure (XAFS) to determine the short-range crystalline order, XRD to determine phase formation and long-range crystalline order, Auger electron spectroscopy (AES) to determine surface chemistry, and SEM to determine the surface morphology. This work shows that the formation of epitaxial CoSi2 on Si1-xGex can be achieved, depending on the thickness of the diffusion barrier. In addition, the optimal diffusion barrier thickness has been determined for the Co layer thickness used in these studies.