Formation of extended defects in silicon by high energy implantation of B and P

Abstract

The extended defects induced in silicon by high energy implantation (1.5 MeV B and 2.6 MeV P) have been investigated by plan-view and cross-sectional transmission electron microscopy studies and defect etching measurements. The threading dislocations were identified to be long dislocation dipoles generated in the region of the ion projected range which grew up to the surface. The formation of threading dislocations is shown to have a strong dependence on the implantation dose and O concentration. After 900 °C annealing, a high density of threading dislocations was formed for B and P implants in a dose range of 5×1013–2×1014 cm−2 and 5×1013–3×1014 cm−2, respectively. The threading dislocation density in B-implanted Czochralski Si substrates was found to be much higher than that in B-implanted epitaxial Si substrates. This difference is attributed to the strong pinning effect of oxygen immobilizing dislocations in Czochralski substrates. Because P impurities are also efficient at pinning dislocation motion in Si, a high density of threading dislocations was observed even in epitaxial Si substrates with P implantation. Two-step annealing with a first step at 700 °C (to precipitate oxygen) and a second step at 900 °C was found to be very effective at eliminating the formation of threading dislocations.