Characteristics of shallow p+-n junctions formed by low-energy ion implantation and dual-step annealing processes

Preamorphization, low-energy boron-ion implantation, and dual-step annealing processes were employed for the formation of shallow p+-n junctions. Germanium preamorphization was performed for a group of silicon substrates. Boron, the most commonly used p-type dopant, was implanted at an energy of 2 keV and a dose of 2 X 1015 cm-2 into both preamorphized and non-preamorphized wafers. Dual-step annealing was used to activate implanted ions and to annihilate implantation defects. Furnace annealing (FA) was performed at 850 .deg. C for 10 minutes, and rapid thermal annealing (RTA) was performed at two temperatures of 750 .deg. C and 1000 .deg. C for a total of 10 seconds at each temperature. The junction depth, the sheet resistance, and the leakage current were measured to characterize the junction properties. The FA + RTA annealing sequence produced better junction properties than the RTA + FA thermal cycle.