PHOSPHORUS-ENHANCED DIFFUSION IN SILICON INDUCED BY IMPLANTATION DAMAGE - DEPENDENCE ON DEFECT DEPTH POSITION

Phosphorus junctions having depths in the range between 008 and 5 μm fabricated in silicon wafers by a thermal pre-deposition and drive-in heatings. The wafers are then implanted with silicon ions to create lattice damage both below and above the amorphization threshold. Subsequent thermal treatment leads to recovery of the damage induced by the implant. The resulting excess interstitials favour enhanced dopant diffusion. Anomalous diffusivity is relevent for non-amorphizing implants, whatever the depth position of the junction with respect to that of the damaged region. By contrast, inappreciable or strong anomalous diffusivity is detected for amorphizing implants, according to whether the initial phosphorus junction is shallower or deeper than the amorphous-crystalline interface. The asymmetric behaviour of phosphorus diffusivity across the interface between amorphous and crystalline silicon is confirmed by secondary-ion mass spectrometry used to profile phosphorus in an ion-implanted, uniformly doped silicon wafer. The enhanced diffusion phenomena are closely related to the evolution of the implant damage during furnace heating, as analysed by double-crystal X-ray diffraction. © 1990 Taylor & Francis Group, LLC.