Full silicidation process for making CoSi2 on SiO2

Applied Physics Letters (Impact Factor: 3.3). 04/2004; 84(17). DOI: 10.1063/1.1728299
Source: OAI


A silicidation process was developed to produce high-quality CoSi2 directly on SiO2, which can be used for metal gates of metal-oxide-semiconductor field-effect transistors (MOSFETs). Normally, the formation of a CoSi2 layer on SiO2 is very difficult because of the requirement for an exact Co/Si thickness ratio. In our process, an additional Si layer was deposited after the first rapid thermal processing (RTP) at 500 degreesC and selective etching of the unreacted Co. The additional Si layer provided a Si supply for the second RTP at a higher temperature. This method allows the Co layer thickness to be varied over a fairly large range, and in addition, the microstructure of the silicide layer and the CoSi2/SiO2 interface were substantially improved. (C) 2004 American Institute of Physics.

Download full-text


Available from: Qing-Tai Zhao
  • [Show abstract] [Hide abstract]
    ABSTRACT: The fully silicided (FUSI)-nickel monosilicide (NiSi) metal gate electrode on the HfSiON gate dielectric has been investigated for low-power metal-oxide-semiconductor field effect transistors (MOSFETs). We found that the FUSI-NiSi electrode on the HfSiON dielectric has a work function of 4.55 eV, which improved the threshold voltage shift of PMOSFETs by 0.15 V compared with that of the poly-Si/HfSiON MOSFETs. At the same time, full silicidation eliminated the gate depletion and thereby we achieved the capacitance equivalent thickness at inversion of 2.1 nm and a five-order-of-magnitude reduction in the gate leakage current compared with the poly-Si/SiO2 devices. Moreover, we obtained an excellent carrier mobility for the FUSI-NiSi/HfSiON transistors (PMOS: 100%, NMOS: 90% compared with the poly-Si/SiO2 reference transistors). These results show that the FUSI-NiSi/HfSiON gate stack is a promising candidate for next-generation low-power MOSFETs.
    No preview · Article · Apr 2005 · Japanese Journal of Applied Physics
  • [Show abstract] [Hide abstract]
    ABSTRACT: To investigate the origin of the threshold voltage (Vth) change by impurity segregation in a fully silicided (FUSI) NiSi/SiO2 gate stack, for the first time we directly examined the vacuum work function (phivac) of the electrodes, the electrical dipole moment (Dinter), and the chemical state of the impurity at the NiSi/SiO2 interface by backside X-ray photoelectron spectroscopy (XPS). We found that the impurity causes neither a change in the phivac nor the formation of a fixed charge in SiO2, and that the interface dipole is a dominant factor to cause the Vth change. We propose that the origin of the interface dipole is the impurity atoms with large electronegativity bonded to both NiSi and SiO2 at the NiSi/SiO2 interface.
    No preview · Article · Apr 2006 · Japanese Journal of Applied Physics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have studied the phase formation of a CoSi2 layer by solid-state reaction of ternary Co/WxTa(1−x)/Si(1 0 0) systems. The effect of cosputtered WxTa(1−x) nanometric interlayers, with different values of x (0, 0.25, 0.5, 0.75 and 1), on the degree of texturing of a CoSi2 layer and disilicide formation of the refractory metals has been investigated. The annealed samples, in a temperature range of 400–1000 °C, were analysed by x-ray diffraction, sheet resistance measurement, scanning electron microscopy, and energy-dispersive x-ray techniques. Using W0.25Ta0.75 and W interlayers, the best (1 0 0) texture of the CoSi2 layer with a thermal stability in the range of 900–1000 °C was produced. In the Co/W/Si system, a considerable amount of WSi2 is formed as a cap layer, while a nearly negligible amount of refractory metal disilicide is formed in the Co/W0.25Ta0.75/Si system. Study of the growth kinetics shows that the activation energies of CoSi2 formation in these two systems are greater than those of other thermally stable systems. The mechanism of single-texture formation of a nanothickness CoSi2 layer has been explained on the basis of controlling Co–Si interdiffusion via the intermediate layers.
    Full-text · Article · Jul 2006 · Semiconductor Science and Technology
Show more