Deactivation of Solid Phase Epitaxy-Activated Boron Ultrashallow Junctions
Résumé
The solid phase epitaxial growth technique appears to be a promising method for achieving junction depths and sheet resistance values low enough to meet the performance specifications of the 65 and 45 nm node for boron, BF2 , and BF3 doping profiles in amorphous silicon. Room-temperature implants of these three dopant species into Si(100) preamorphized by Ge+74 (30 keV, 1.0×1015cm−2 ) lead to boron concentration profiles that fulfill the technological requirements. It was found that even for ultrashallow junctions the time for the regrowth process at 650°C has to be optimized with regard to the implanted species in the range between 5 and 60 s, especially when fluorine is present. The thermal stability of the boron profile distribution that meets 65-nm-node requirements was evaluated by subsequent thermal anneals simulating the thermal effects expected for typical silicidation processes. For a more detailed investigation, the postannealing temperatures ranged from 250 to 1050°C with times from a few to several hundred seconds. All the junctions were analyzed by four-point probe and selected samples by secondary ion mass spectroscopy, transmission electron microscopy, and high-resolution electron microscopy.