Damage and dopant profiles produced by ultra-shallow boron and arsenic ion implants into silicon at different temperatures characterised by medium energy ion scattering

摘要

Medium energy ion scattering (MEIS), operated at sub-nm depth resolution in the double alignment configuration, has been used to examine implant and damage depth profiles formed in Si(100) substrates irradiated with 2.5 keV As~+ and 1 keV B~+ ions. Samples were implanted at temperatures varying between -150℃, and 300℃ to doses ranging from 3 x 10~(14) to 2 x 10~(16) cm~(-2) . For the As implants the MEIS studies demonstrate the occurrence of effects such as a dopant accommodation linked to the growth in depth of the damage layer, dopant clustering, as well as damage and dopant movement upon annealing. Following epitaxial regrowth at 600℃, approximately half of the As was observed to be in substitutional sites, consistent with the reported formation of As_nV complexes (n≤4), while the remainder became segregated and became trapped within a narrow, 1.1 nm wide layer at the Si/oxide interface. MEIS measurements of the B implants indicate the formation of two distinct damage regions each with a different dependence on implant dose, the importance of dynamic annealing for implants at room temperature and above, and a competing point defect trapping effect at the Si/oxide interface. B~+ implantation at low temperature resulted in the formation of an amorphous layer due to the drastic reduction of dynamic annealing processes. Notably different dopant distributions were measured by SIMS in the samples implanted with As at different temperatures following rapid thermal annealing (RTA) up to 1100℃ in an oxidising environment. Implant temperature dependent interactions between defects and dopants are reflected in the transient enhanced diffusion (TED) behaviour of As.