Harnessing reverse annealing phenomenon for shallow p-n junction formation

Monocrystalline silicon was implanted with 60 keV fluorine and 20 keV boron ions and annealed. Carrier profile, fluorine and boron redistribution, and the parameters of p+-n junctions were investigated. In ion implanted Si two specific regions were observed in which peculiarities in carrier concentration, resistivity, and F atoms redistribution occurred. It was reasoned that the “under-surface” specific region is enriched with vacancy-type defects while the “amorphous/crystalline (a/c) interface” region is enriched with interstitial type defects. After annealing at a temperature corresponding to the reverse annealing phenomenon, boron atoms were activated in the “under-surface” and deactivated in the “a/c interface” region. The possibility of PMOS transistor fabrication with ultrashallow p+-n junction (60 nm) and low leakage current by F++B+ implantation and low temperature (600–700) °C annealing by using this phenomenon was demonstrated.