ULTRASHALLOW SI P+-N JUNCTION FABRICATION BY LOW-ENERGY GA+ FOCUSED ION-BEAM IMPLANTATION

The fabrication of ultrashallow Si p+-n junctions by low energy Ga+ focused ion beam implantation has been investigated at energies ranging from 5 to 15 keV. Post-implantation rapid thermal annealing was performed at 600-degrees-C for 30 s to activate the implanted Ga and to regrow the implanted layer. Secondary ion mass spectroscopy (SIMS), spreading resistance profile (SRP), and cross-sectional transmission electron microscopy (TEM) have been employed to characterize the resulting Ga atomic concentration depth profile and the structure of the implanted layer. For 5 keV Ga+ implantation, the cross-sectional TEM (xTEM) measurement yielded an amorphous layer thickness of 9 nm and a line of end-of-range defects 16 nm below the surface [after rapid thermal annealing (RTA)]. The SIMS profiles indicate that only minor Ga channeling occurred during implantation. The SRP measurements give a junction depth of only 20 nm for the 5-keV Ga implants. Leakage current density of 20 nA/cm2 has been measured at 5 V reverse bias.