Remaining Oxide and Low-Energy Ion Implantation of BF+2

We investigated the behavior of boron by varying the 49BF+ 2 ion-implantation energy and the rapid thermal annealing (RTA) temperature with the remaining oxide. The 49BF+ 2 ions were implanted into p-type Si (100) without removal of the native oxide. The used 49BF+ 2 ion-implantation energies were 0.5 keV, 1 keV, 2.5 keV, 5 keV, and 10 keV. The dose was fixed at 5 × 1015 atoms/cm2. RTA was performed under a N2 ambient (760 Torr) at 1000 C and 1050 C for 10 s. In order to investigate the boron behavior with 49BF+ 2 ion implantation, we measured the surface roughness Rrms, the junction depth Xj, the dose, the sheet resistance Rs, and the thickness of the silicon oxide layer by using atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), ellipsometry, 4-point probe without removal of the native oxide layer. By these results, Rs in as-implanted samples increased abruptly (from 174 /cm2 to 1706 /cm2 for 49BF+ 2 implantation energy 0.5 keV and 10 keV, respectively) when Xj increased (from 27 nm for 0.5 keV to 57 nm for 10 keV) because of inactive dopants. After RTA, Rs decreased (from 128 /cm2 for 0.5 keV to 70 /cm2 for 10 keV at 1050 C) when Xj increased (from 147 nm for 0.5 keV to 221 nm for 10 keV at 1050 C). The inactive borons in as-implanted samples become the electrical active dopants after RTA treatment.