Boron doping of silicon by ArF excimer laser irradiation in B2H6

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Abstract
Boron doping of silicon using a pulsed ArF excimer laser (λ=193 nm, FWHM=17 ns) with B2H6 has been investigated. Doping atoms are supplied mainly from both thermal and photochemical decomposition of the adsorbed layers on the surface. UV laser irradiation realizes both high surface carrier concentration (1×1021 cm−3) and a very shallow junction (0.1 μm). Diodes fabricated by laser doping show good electrical characteristics (n factor=1.10, reverse current density=1×10−7 A/cm2 at −5 V). Thermal annealing improves the reverse current density (3×10−9 A/cm2 at −5 V). A numerical calculation of boron concentration profiles has been performed by solving the diffusion equation in the melted region, which is evaluated by the heat conduction equation. From this calculation the diffusion coefficient of boron in liquid phase silicon (3×10−4 cm2/s) is obtained.