Modelling of Boron Trapping at End-of-Range defects in pre-amorphized ultra-shallow junctions

Abstract

In this work, the evolution of boron trapping at End-of-Range (EOR) defects was investigated by secondary ion mass spectrometry (SIMS) and transmission electron microscope (TEM). Si wafers with a constant boron concentration of 2 × 10 18 cm −3 were implanted with 30 keV germanium and with a dose of 10 15 cm −2 and then annealed at 700, 800, or 900 °C in an N 2 ambient for various times. The experimental results suggest that the evolution of boron-trapping peak is driven by the evolution of {3 1 1} defects and that the dislocation loops contribution to the trapping mechanism is less pronounced. An analytic model for the concurrent boron trapping at {3 1 1} defects and dislocation loops was developed by taking into account the geometry of the EOR defects. The trapped species is represented by neutral BI pairs which can be captured either by {3 1 1} defects or by dislocation loops. The model accurately reproduces the complex evolution of the trapping peak as a function of both the annealing time and temperature. These results confirm that the evolution of the boron-trapping peak is closely related to the evolution of the {3 1 1} defects, therefore suggesting that boron trapping is associated to the capture and release of boron atoms at the {3 1 1} defects formed in the EOR region.