| dc.description.abstract | Strain engineering is commonly used for improving the performance of metal-oxide-semiconductor (MOS) devices. For example, n-channel MOS (NMOS) devices with silicon-carbon (Si1-yCy) grown in the source and drain (S/D) regions as uniaxial compressive stressors for the channel can achieve significant drive current improvements. However, successfully integrating Si1-yCy epilayers into a standard device process flow requires reliable metal-silicide contacts in the Si1-yCy S/D regions. Pt silicide formed on p-type silicon has a low Schottky barrier height, which useful as Schottky transistors. However, Pt silicide has poor thermal stability. In this study, the reaction between Pt and Si1-yCy epilayers with an interfacial oxide layer was investigated. Pt silicide has inevitable oxide layer, which as a diffusion barrier layer. During the silicidation, Pt atoms diffused to react with Si through the oxide pinholes. C atoms play a critical role in Pt silicide microstructure and reaction. The presence of C atoms retards the growth kinetics of PtSi and significantly enhances the thermal stability of PtSi thin films. In addition, C atoms suppressed PtSi agglomeration and widened the process window of low-resistivity PtSi silicides. On the other hand, the thermal stability of Pt silicides in the Pt/Si1-yCy samples was found to be significantly improved, even after long-time annealing at 800 ℃.
In recently years, channel strain has been becoming a promise technique. Strain distribution with different depth of annealed Si1-yCy epilayers using lattice strain analysis were investigated in this study. At the initial stage of annealing, the strain of Si1-yCy epilayers increased. The Cs increased 0.001 in the Si1-y2Cy2 epilayers sample annealed at 800 ℃. Lattice strain analysis was performed using high-resolution transmission electron microscopy (HRTEM) and diffractograms obtained by fast Fourier transform of HRTEM images. The magnitude of compressive strain was larger towards Si1-y2Cy2 epilayers sample surface. It speculates that C atoms at interstitial sites were incorporated into substitutional sites after annealing, resulting in Cs and strain increment. In addition, no strain relief by the introduction of misfit dislocations was detectible in the Si1-y2Cy2 epilayers sample after annealing 900℃, possibility due to the formation of carbon-containing interstitial complexes.
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