The interaction between Xe and F in Si (100) pre-amorphised with 20keV Xe and implanted with low energy BF2

The pre-amorphisation of Si by Xe+ ions, before source/drain and extension implants, is an attractive alternative to Ge+ or Si+, as it produces sharper amorphous/crystalline interfaces. Si (1 0 0) samples pre-amorphised with 20 keV Xe+ to a nominal dose of 2E14 cm−2 were implanted with 1 and 3 keV BF2+ to doses of 7E14 cm−2. Samples were annealed at temperatures ranging from 600 to 1130 °C and investigated by medium energy ion scattering (MEIS) and secondary ion mass spectrometry (SIMS). Following annealing, it was observed that implanted Xe has interacted with F originating from the BF2+ implant. MEIS studies showed that for all annealing conditions, approximately half of the Xe accumulated at depths of 7 nm for the 1 keV and at 13 nm for the 3 keV BF2+ implant. This equates to the end of range of B and F within the amorphous Si. SIMS showed that in the pre-amorphised samples, approximately 10% of the F migrates into the bulk and is trapped at the same depth in a ∼1:1 ratio to Xe. A small fraction of the implanted B is also trapped. The effect is interpreted in terms of the formation of a defect structure within the amorphised Si, leading to F stabilised Xe bubble or XeF compound formation.