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Formation and Electrical Transport Properties of Nickel Silicide Synthesized by Metal Vapor Vacuum Arc Ion Implantation X. W. Zhang, S. P. Wong, W. Y. Cheung and F. Zhang1 Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, N. T., Hong Kong, P. R. China ABSTRACT Nickel disilicide layers were prepared by nickel ion implantation into silicon substrates using a metal vapor vacuum arc ion source at various beam current densities to an ion dose of 6x1017 cm-2. Characterization of the as-implanted and annealed samples was performed using Rutherford backscattering spectrometry, x-ray diffraction, electrical resistivity and Hall effect measurements. The temperature dependence of the sheet resistivity and the Hall mobility from 30 to 400 K showed peculiar peak and valley features varying from sample to sample. A twoband model was proposed to explain the observed electrical transport properties. INTRODUCTION Metal silicides have attracted widespread interest as contact and interconnect materials for silicon based microelectronic devices because of their low electrical resistivity, high chemical resistivity, good thermal stability, and compatibility to modern Si technology. Various techniques have been reported to synthesize nickel silicide [1-4], including ion beam synthesis (IBS) [4]. The advantages of the IBS method include the ease of control of the implant dose, the high reproducibility of the process, and the ability to directly form a buried layer. But the high dose requirement is a problem. However, the high dose problem is solved by using a metal vapour vacuum arc (MEVVA) ion source, which was first developed by Brown et al. in 1985 [5] and can provide very high beam current. In fact, there have been a number of reports in recent years that metal silicide layers with good crystal quality and good electrical properties can be formed by MEVVA implantation [4, 6, 7]. In this paper, we shall report the formation and electrical transport properties of NiSi2 layers synthesized by MEVVA implantation. EXPERIMENTAL DETAILS NiSi2 layers were prepared on p-Si (100) substrates of 10-20 Ω cm by nickel implantation using a MEVVA ion source. The MEVVA source was operated in a pulse mode. The implantation was performed at an extraction voltage of 65 kV to an ion dose of 6x1017 cm-2 at various mean ion current densities from 13 to 52 µA/cm2. During implantation, the vacuum level of the target chamber was 8×10-4 Pa. Rapid thermal annealing was performed in an Ar ambient at 700 oC for 40 s. Glancing incidence x-ray diffraction (XRD) was performed to identify the phases of the synthesized silicides. Rutherford backscattering spectrometry (RBS) experiments were performed at a 170° scattering angle with a 2 MeV 4He2+ ion beam. The sheet 1

Visiting from Shanghai Institute of Metallurgy, Chinese Academy of Sciences, Shanghai, China Present address: University Heidelberg, Physikalisch-Chemisches Institut/Radiochemie, Germany

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resistivity and Hall effect measurements were carried out using the van der P