Formation of steep, low Schottky-barrier contacts by dopant segregation during nickel silicidation

We present a systematic analysis of arsenic dopant segregation during nickel silicide formation. The slopes and concentrations of the arsenic dopant profiles at the NiSi∕Si interface have been studied as a function of implantation energy, implantation dose, and NiSi thickness. Silicidation induced dopant segregation conserves the dopant slope at the silicide/silicon interface up to NiSi thicknesses of three times the as-implanted peak depth before degrading. Best slopes and highest dopant concentrations are obtained for low implantation energies and thin NiSi layers. We also demonstrate that the steepness of the dopant profile at the NiSi∕Si interface can be significantly improved through a two-step annealing process for NiSi formation. For As, 1keV, 1×1015cm−2, and a 17nm NiSi layer, a NiSi∕Si junction with a dopant slope of 3.2nm/decade has been obtained. An effective Schottky barrier of ΦSB=0.12eV was determined by low temperature measurements of Schottky diodes with 20nm NiSi formed by an optimized an...

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