Ultra-shallow junction formation using very low energy B and BF2 sources

Ultra-shallow junctions were formed using 0.5-8.9 keV B and BF₂ ion implantation and plasma doping (PLAD) in conjunction with rapid thermal annealing, RTA, or furnace annealing. The effect of pre-amorphization and solid phase epi (SPE) regrowth on dopant retention, sheet resistance, and junction depth was quantified. The PLAD junctions were comparable to those formed by BF₂ ion implantation. After a 550°C SPE anneal, preamorphized PLAD junctions had nearly 100% dopant activation. Using 0.5 kV PLAD, junction depths less than 40 nm deep were obtained for 10 sec annealing at 950°C. In preamorphized PLAD junctions, transient enhanced diffusion (TED) and dopant trapping at end-of-range damage was seen at very low temperature (550°C). Preamorphization eliminated channeling but enhanced diffusion such that when the boron energy was 0.5 keV or less, preamorphized junctions were deeper after annealing for 10 seconds at 850°C or higher. A 48 nm deep PLAD was successfully incorporated in a 0.18/0.25 μm PMOS technology