Characterization of NbSi2 thin films

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Abstract
The physical and electrical properties of niobium silicide thin films are studied. These films were rf sputtered from an alloy target of stoichiometric proportion onto oxidized silicon substrates at 350 °C to improve film adhesion. Structural and compositional properties of as‐sputtered and heat‐treated films were studied by x‐ray diffraction, Auger electron spectroscopy, Rutherford backscattering spectroscopy, and secondary ion mass spectrometry. Films annealed in H2 or N2 were found to consist of mainly NbSi2 with Nb5Si3 as a significant component. The resistivity of these films decreases by a factor of 2 upon annealing to ∼1×10−4 Ω cm. Heat treatment in O2 resulted in insulating films. The composition of the oxidized films was shown by both x‐ray and RBS analysis to consist of Nb2O5 and SiOx. NbSi2‐gate metal‐oxide‐semiconductor capacitors were fabricated on both n‐type and p‐type Si substrates. The work function of NbSi2, determined from C‐V measurements, was found to be 4.5 and 4.3 V for n‐type and p‐type substrates, respectively. Temperature‐bias stress measurements resulted only in minor shifts in the flatband voltage, typically 0.1 V.

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