FORMATION OF EXTENDED DEFECTS IN SILICON BY HIGH-ENERGY B-IMPLANTATION AND P-IMPLANTATION

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 di slocation dipoles generated in the region of the ion projected range w hich grew up to the surface. The formation of threading dislocations i s shown to have a strong dependence on the implantation dose and O con centration. After 900 degrees C annealing, a high density of threading dislocations was formed for B and P implants in a dose range of 5x10( 13)-2x10(14) cm(-2) and 5x10(13)-3x10(14) cm(-2), respectively. The th reading dislocation density in B-implanted Czochralski Si substrates w as found to be much higher than that in B-imptanted epitaxial Si subst rates. This difference is attributed to the strong pinning effect of o xygen immobilizing dislocations in Czochralski substrates. Because P i mpurities are also efficient at pinning dislocation motion in Si, a hi gh density of threading dislocations was observed even in epitaxial Si substrates with P implantation. Two-step annealing with a first step at 700 degrees C (to precipitate oxygen) and a second step at 900 degr ees C was found to be very effective at eliminating the formation of t hreading dislocations. (C) 1996 American Institute of Physics.