Nuclear reaction analysis of shallow B and BF2 implants in Si

Abstract

Impurity diffusion induced by rapid thermal annealing has been investigated for low-energy 11B and 49BF2 implants in Si. Samples were annealed with an oxide cap in an AG Associates Heatpulse system. Depth profiles were determined with nuclear reaction analysis. This technique is sensitive to impurities at or near the surface and can reveal impurity diffusion to near-surface regions not usually detectable with secondary ion mass spectrometry. Significant B diffusion to the SiO2/Si interface was observed for a 1050 °C/20-s anneal of 10-keV 11B implanted in crystalline and preamorphized Si. B interfacial concentrations were comparable to peak concentrations in unannealed samples. Diffusion of B and F to the SiO2/Si interface and impurity gettering by ion straggling damage was observed for a 1050 °C/20-s anneal of 45-keV 49BF2 implanted in crystalline Si. Impurity segregation at the SiO2/Si interface was minimal for a 1050 °C/20-s anneal of 45-keV 49BF2 implanted in preamorphized Si, although a loss of F was apparent.