Suppression of high-resistance phases of Ni silicide by Se passivation of Si(100)

High-resistance phases of Ni-rich Ni silicide are formed on Si(100) below 400°C, while high-resistance phases of Si-rich Ni silicide are formed above 600°C. The desired low-resistance NiSi is formed between 400°C and 600°C. In this paper, the authors report the suppression of high-resistance phases of Ni silicide by passivating the Si(100) surface with a monolayer of Se. A 500-Å Ni on n-type low 10¹⁵ cm^-3 doped Si(100) wafers, passivated with Se, shows a sheet resistance of ∼2.55 Ω/square upon annealing between 200°C and 500°C, while the sheet resistance of the 500-Å Ni on identical wafers without Se-passivation jumps to ∼7.92 Ω/square between 300°C and 350°C. Between 600°C and 700°C, the sheet resistance of the Se-passivated samples is ∼ 10% lower than that of the control samples. Transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy all confirm that the suppression of high-resistance Ni silicides below 500°C is attributed to the suppression of silicidation and above 600°C to the delay in Si-rich Ni silicide formation at the Ni/Se-passivated Si(100) interface.