Activation of As Atoms in Ultrashallow Junction during Milli- and Microsecond Annealing Induced by Thermal-Plasma-Jet Irradiation

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We irradiated a micro-thermal-plasma-jet (μ-TPJ) to an As-implanted Si wafer surface to form an ultrashallow junction (USJ). A high-power-density TPJ for microsecond rapid thermal annealing (RTA) was generated by using a small orifice of 0.8 mm diameter instead of 2.0 mm to concentrate the TPJ. The μ-TPJ could anneal the Si wafer surface at a temperature as high as 920 K for 340 μs. By reducing the annealing duration ($t_{\text{a}}$) from 1.2 ms to 340 μs, the sheet resistance ($R_{\text{S}}$) of the As2+-implanted Si wafer decreased from 1520 to 1287 $\Omega$/sq. In addition, the chemical bond states of As at the very surface were measured by X-ray photoelectron spectroscopy (XPS) and the fraction of activated As was estimated to be ${\sim}15$% larger than that in the case of millisecond annealing. Surface As atoms in Si wafers were more efficiently activated by a microsecond annealing than a millisecond annealing owing to the suppression of diffusion and clustering.
2011-04-25