Effects of pulsed ruby-laser annealing on As and Sb implanted silicon

Abstract

The effects of pulsed (Q-switched) ruby-laser annealing of arsenic- and antimony-implanted silicon (1×1015 to ∼2×1016 cm−2) has been studied by Rutherford ion backscattering, TEM, and ion channeling. The laser pulses were of ∼50-nsec time width and of 1.5–1.7 J/cm2 energy density. Analysis of the dopant profiles before and after annealing leads to the conclusion that the dopants diffuse under normal kinetics in a melted silicon layer over an average time interval of about 0.27-μsec after the laser power has been absorbed. Recrystallization of the melt layer is by liquid-phase epitaxial regrowth from the substrate. The recrystallized zone is found to be free of significant structural defects for all specimens except the very highest antimony doses, in which case some near-surface (∼400 Å) precipitation at dislocations is observed. Atom-location measurements reveal that 98–99% of the retained dopant is in substitutional lattice sites even when the dopant concentration greatly exceeds the limit of solid solubility. Only in the high-dose (≳1016 cm−2) antimony case was significant loss of dopant (20–35%) observed as a consequence of laser processing. The high-dose antimony also had a lower substitutional fraction (∼87%) compared to the other specimens.