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

Abstract

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 (ta) from 1.2 ms to 340 µs, the sheet resistance (RS) of the As2+-implanted Si wafer decreased from 1520 to 1287 Ω/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 ∼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.