Implant temperature dependence of transient-enhanced diffusion in silicon (100) implanted with low-energy arsenic ions

摘要

The diffusion of arsenic implanted into silicon at low ion energies (2.5 keV) has been studied with medium-energy ion scattering, secondary ion mass spectrometry and four-point probe measurements. The dopant redistribution together with the corresponding damage recovery and electrical activation produced by high-temperature (559-975℃) rapid thermal anneals has been investigated for a range of substrate temperatures (+25, +300 and -120℃) during implant. Initial results show an implant temperature dependence of the damage structure and arsenic lattice position prior to anneal. Solid-phase epitaxial regrowth was observed following 550℃, 10s anneals for all implant temperatures and resulted in approximately 60% of the implanted arsenic moving to substitutional positions. Annealing at 875℃ resulted in similar arsenic redistribution for all implant temperatures. Following annealing at 925℃, transient-enhanced diffusion was observed in all samples with more rapid diffusion in the +25℃ samples than either the -120 or +300℃ implants, which had similar dopant profiles. In the 975℃ anneal range, similar rates of implant redistribution were observed for the +300 and +25℃ implants, while diffusion in the -120℃ sample was reduced. These observations are discussed qualitatively in terms of the nature and density of the complex defects existing in the as-implanted samples.