The effect of as-implanted damage on the microstructure of threading dislocations in MeV implanted silicon

The dose dependence of as-implanted damage and the density of threading dis locations formed after MeV implants into Si is measured. The role of the da mage and amorphization in the evolution of dislocation microstructure is as sessed. As-implanted damage is analyzed by Rutherford backscattering spectr oscopy and channeling. Defect etching is used to delineate threading disloc ations in near-surface regions of annealed (900 degrees C, 30 min) samples. For a variety of implants with 1.1 mu m projected range (600 keV B, 1 MeV P, and 2 MeV As) we observe a sharp onset for formation of threading disloc ations with a peak in dislocation density at a dose of about 1 X 10(14) cm( -2), this dose depends on the ion mass. With a further increase in dose, th e dislocation density decreases. This decrease, however, is drastically dif ferent for the different ions: sharp (4-5 orders of magnitude) reduction fo r P and As implants and slow decline for B implant. The sharp decrease in t he density of threading dislocations at higher doses is correlated with the onset of amorphization observed by channeling for P and As implants. Our d ata for low-temperature implants provide conclusive proof that a reduction in the dislocation density for P and As implants is a result of amorphizati on. (C) 1999 American Institute of Physics. [S0021-8979(99)05915-0].