An excellent barrier effect against Cu ion drift is demonstrated using self-assembled monolayer (SAM) barrier dielectrics in which phosphorous (P) atom is contained. Three kinds of SAMs, such as P-, carbon (C-), and nitrogen (N-) containing SAMs with the identical molecular structure, were wet-chemically formed on a thermal SiO2. The X-ray reflectance and infrared absorption spectroscopy revealed that nearly 1-nm-thick monolayers were successfully formed. The barrier effects of SAMs were investigated by the time-dependent dielectric breakdown measurements of Cu/SAM/SiO2/Si metal–insulator–semiconductor structures under applying a bias-temperature stress. The time-to-breakdown tBD of P-SAM was approximately 10-fold compared to SiO2 without SAM formation. The tBD of C-SAM and N-SAM were, on the other hand, well agreed with that of SiO2, indicating that the barrier effects of C- and N-SAMs are much weaker than that of P-SAM. From these results, we concluded that the existence of P atom in the SAM molecule to form Cu-P complex is the key for the barrier mechanism of the SAM studied in this report.

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Ni silicide film was deposited by chemical vapor deposition (CVD) using an Ni(PF3)4/Si3H8 gas system. Ni(PF3)4 has no carbon atoms in its molecules and has sufficiently high vapor pressure for a mass flow controller to be used. We selected Si3H8 as the silicon precursor, which was decomposed by the interaction of a metalorganic Ni precursor at a low temperature at which thermal decomposition could not occur. Using these precursors, Ni silicide film was deposited at low temperatures (∼160 °C). The deposited Ni silicide film was polycrystalline and had low crystallinity. Ni2Si and Ni5Si2 were also formed. Varying the Si3H8 flow rate and substrate temperature changed the Si/Ni ratio of the films resulting in the flat-band voltage (Vfb) for the Ni silicide electrode shifting with the Si/Ni ratio. This CVD-deposited Ni silicide should be able to be applied to the fabrication of metal gate in future metal oxide semiconductor field-effect transistors (MOSFETs).

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One of the most popular refractory metals is tungsten or W. Therefore, W chemical-vapor deposition (CVD) is expected to be useful for nanotechnology applications. In some cases, the residual atoms, such as halogen and oxygen, in films may degrade their quality. The authors therefore propose (i-C3H7C5H4)2WH2, i.e., (i-PrCp)2WH2, as a new W precursor because the authors expect some advantages from the absence in this molecule of the F and O that exist in the popular W precursors, WF6 and W(CO2)6. The melting point of (i-PrCp)2WH2 is 30°C and the precursor has a high vapor pressure of 0.1torr at 110°C. The authors conducted W CVD with the (i-PrCp)2WH2 as a precursor and obtained conformal W thin film. The deposition rate was 69nm∕min at 750°C, and the deposited film had resistivity of 2.3×10−4Ωcm. However, the deposited film included a tremendous amount of C. Therefore, investigating the possibility of reducing the C contamination is necessary.