ELECTRICAL-PROPERTIES OF COPPER SILICON SCHOTTKY BARRIERS

The electrical properties of Cu-Si(100) Schottky barriers formed by the deposition of Cu on lightly doped (10(14)-10(15) cm-3) n-type and p-type Si(100) have been studied in the temperature range 80-295 K using current-voltage and capacitance-voltage techniques. Deep-level transient spectroscopy was used to determine Cu-related energy levels in Si and x-ray photoemission spectroscopy to monitor the reaction between Cu and Si. In both n-type and p-type Si(100), no Cu-related levels deeper than approximately 0.1 eV below (above) the conduction-band edge (the valence-band edge) and with concentrations above 10(11) cm-3 were observed after copper deposition or after silicide formation. Silicide formation was found to have very little or no effect on the barrier height and its temperature dependence. For both the as-deposited Cu and the reacted Cu3Si silicide phase, the temperature coefficient of the n-type barrier height was found to be almost equal to that of the indirect band gap in Si. The p-type barrier height did not exhibit a temperature dependence. These results suggest that the Fermi level at the interface is pinned relative to the valence-band edge. These results deviate significantly from the predictions of models of Schottky-barrier formation based on Fermi-level pinning in the centre of the semiconductor indirect band gap.