Formation of silicided shallow p(+) n junctions by BF2+ implantation into thin amorphous-Si or Ni/amorphous-Si films on Si substrates and subsequent Ni silicidation

The process scheme that forms NiSi-silicided shallow p(+)n junctions by BF2 + implantation into thin amorphous-Si (a-Si) or Ni/a-Si films on Si substra tes and subsequent Ni silicidation has been studied. As for the scheme usin g a-Si as an implantation barrier, an NiSi-silicided junction with a leakag e of about 0.7 nA/cm(2) at - 5 V is obtained by the sample Ni silicided at 700 degrees C for 30 min. The implantation energy and the crystallinity of the deposited Si films after annealing would greatly affect the junctions f ormed at various temperatures, attributable to different, implantation effe cts and boron depth profile. However, the junctions formed by rapid thermal processing or high implant energy are considerably degraded at 800 degrees C, attributable to anomalous Ni penetration into the Si substrate with the further silicidation of NiSi into NiSi2. On the other hand, the specimens with Ni/a-Si as an implantation barrier sustain few defects, thus significa ntly suppressing the junction degradation at 800 degrees C. However the for med junctions are worse than those by the former scheme, mainly due to lowe r dopant drive-in efficiency. (C) 1999 American Vacuum Society. [S0734-211X (99)03902-5].