Activation of Silicon Implanted with Phosphorus Atoms by Infrared Semiconductor Laser Annealing

Abstract

We activated silicon implanted with phosphorus atoms by infrared semiconductor laser annealing with a diamond-like carbon (DLC) optical absorption layer. The silicon samples implanted with phosphorus atoms at 10 and 70 keV with concentrations of 5×1014, 1×1015, and 2×1015 cm-2 were coated with 200-nm-thick DLC films. The samples were annealed by irradiation with a 940 nm continuous wave laser at 70 kW/cm2 with a beam diameter of 180 µm. The laser beam was scanned using a moving stage at 3–20 cm/s, which gave an effective dwell time of 0.9–6.0 ms. The amorphized surface regions were recrystallized by laser annealing longer than 1.2 ms. The in-depth profile of phosphorus concentration hardly changed within 5 nm for laser annealing for 2.6 ms. The sheet resistance markedly decreased to 106 and 46 Ω/sq for the samples implanted with phosphorus atoms at 10 and 70 keV by laser annealing at a dwell time of 2.6 ms, respectively. Phosphorus atoms were effectively activated with a carrier density near the phosphorus concentration for implantation at 70 keV. A low carrier generation rate was observed for implantation at 2×1015 cm-2 and 10 keV. An intermediate SiO2 layer effectively blocked carbon incorporation to a level below 1017 cm-3.