Excimer laser enhanced nitridation of silicon substrates

Abstract

Silicon direct nitridation has been successfully done using purified ammonia gas and an ArF excimer laser (λ=193 nm). Direct nitride films were grown at a substrate temperature of 400 °C and a laser pulse energy of 15 mJ/pulse cm2. As far as Auger signal intensities are concerned, there is little difference between the excimer laser enhanced nitrided films grown at 400 °C and thermally nitrided films grown at 1000 °C. The maximum film thickness grown is limited to 2.5 nm at 400 °C by diffusion of nitridation species across the grown film. The temperature rise on the substrate surfaceirradiated by the laser was calculated and found to be around 50 °C. Therefore, the thermal effect of the laser irradiation is of little significance in this experiment. The photochemically dissociated products of ammonia molecules were investigated by a quadrupole mass analyzer. The photochemically generated NH2 radicals seem to enhance the nitridation.