Rapid thermal process requirements for the annealing of ultra-shallow junctions

2.0 keV B-11(+), 2.2 keV (BF2+)-B-49 ion implanted and 1.0 kV Plasma Doped (PLAD) wafers of a dose of 1E15/cm(2) were annealed at various times and temperatures in a variety of ambients: 600 to 50,000 ppm O-2 in N-2; 5% NH3 in N-2; N2O; N-2 or Ar, in order to investigate the effects of the annealing ambient on the formation of ultra-shallow junctions. RGA data was collected during some of the anneals to assist in identifying the complex surface chemistry responsible for boron outdiffusion. Subsequent to the anneals, ellipsometric, XPS, four-point probe sheet resistance and SIMS measurements were performed to further elucidate the effects of the different ambients on the retained boron dose, the sheet resistance value, the RTP grown oxide layer and the junction depth. In the cases where oxygen was present, e.g. N2O and O-2 in N-2, an oxidation enhanced diffusion of the boron was observed. This was most dramatic for the N2O anneals, which at 1050 degrees C 10 s diffused the boron an additional 283 to 427 Angstrom, depending on the particular doping condition and species. For the case of BF2 implants and PLAD, anneals in 5% NH3 in N-2 reduced the junction depth by a nitridation reduced diffusion mechanism. RGA data indicated that the out-diffusion mechanisms for B and BF2 implanted wafers are different, with the BF2 exhibiting dopant loss mechanisms during the 950 degrees C anneals, producing F containing compounds. B implants did not show doping loss mechanisms, as observed by the RGA until the 1050 degrees C anneals and these signals did not contain F containing compounds. Equivalent effective energy boron implants of 8.9 keV BF2 vs. 2.0 keV B, however, indicated that the overall effect of the F in the BF2 implants is very beneficial in the creation of ultrashallow junctions ( compared to B implants): reducing the junction depth by 428 Angstrom, and increasing the electrical activation( determined by SRP) by 11.7%, even though the retained dose (resulting from an increased out-diffusion of B), was decreased by 5.4%.