Optimazation of the parameters involved in the photochemical doping of Si with a pulsed ArF excimer laser

The use of lasers in the doping of semiconductors has been investigated extensively during the last years, both for photovoltaic and microelectronic applications. By contrast with conventional thermal treatment, pulsed lasers offer the possibility to confine high temperature processing to the near-surface region of solids (< 0.5 μm), within well defined regions of good spatial resolution during very short periods of time, not exceeding a few tens of nanoseconds. The use of pulsed excimer lasers, working at UV wavelengths, appears especially attractive, since they are able to obtain by a one-step process, the photo-dissociation of the dopant gas and the subsequent incorporation, by liquid phase diffusion, of the dopant into the molten irradiated surface layer. We examine, in this work, the ability of a repetitive pulsed ArF excimer laser, working at 193 nm, for the p⁺-type doping of silicon, using BCl₃ as the active gas. The different parameters involved in the process (laser energy density, pulse repetition, BCl₃ gas pressure) will be optimized in order to achieve very sharp and shallow p⁺ junctions (∼ 0.1 μm).