Uniform spike anneals of ultra low energy boron implants using xR LEAP and RTP Centura XEplus: ramp rate effects up to 150°C/sec

In order to form junctions shallower than 0.1 μm required for the source/drain extensions for 0.18 μm technology and beyond, boron ions have been implanted in pre-amorphised Si at 1 keV and doses of 1E14-1E15 cm^-2 using an Applied Materials xR LEAP ion implanter. Implanted wafers were subsequently annealed in an RTP Centura to ~1 sec soak time and to temperatures between 1000-1100°C. Ramp up rates between 75°C/s and 150°C/s were examined. Junctions with depths between 40-80 nm (taken at 1E17 cm^-3 SIMS B concentration) can be formed routinely with sheet resistance tuneable between 300-900 Ω/□ using Ge pre-amorphisation, and subsequent spike annealing at ramp up rates of 150°C/sec in nitrogen atmosphere. It was found that sheet resistance (Rs) is most dependent on the spike anneal temperature, while the ramp up rate appear to have a minimal effect on reducing Rs or controlling junction depth (χ_j ). The oxygen content in the RTA ambient is an important parameter in controlling both Rs and χ_j. The crystallinity of the spike annealed wafers has been evaluated using high resolution transmission electron microscopy (HRTEM)