Damage removal/dopant diffusion tradeoffs in ultra-shallowimplanted p+-n junctions

The tradeoffs between implant damage annealing and shallow junction formation are investigated. For very-low-energy amorphizing implants the time for damage anneal has a fourth-power dependence on depth below the Si surface. The depth effect depends on the type of amorphizing ion. It is shown that as a result, implanted B in Ge-preamorphized Si diffuses with no detectable self-interstitial supersaturation if the damage is <600 Å deep. Conditions for forming defect-free, shallow p⁺-n junctions are described in design curves and comparisons are made between several junction-formation approaches. Implantation of B at energies below 2 keV offers an attractive way of achieving 500-Å junctions