The understanding of the behavior of arsenic in highly doped near surface silicon layers is of crucial importance for the formation of N-type Ultra Shallow Junctions in current and future VLSI technology. This is of peculiar relevance when studying novel implantation and annealing methods. Past theoretical as well as experimental investigations have suggested that the increase of As concentrations, and therefore the vicinity of the dopant atoms, leads to a drastic increase of electrically inactive defects giving only marginal effects on reducing sheet resistance. Monoclinic SiAs clusters, as well as various arsenic-vacancy aggregates contribute to the deactivation of the arsenic.This study aims to correlate between the results of electrical activation measurements and X-Ray Absorption Fine Structure measurements. The samples were doped with a nominal fluence of 1E15 to 3E15 at/cm2 implanted at 2 keV and annealed by rapid thermal treatments, laser submelt treatments and a combination of the two. Hall Effect and sheet resistance measurements have been performed to obtain the density of charge carriers. Secondary Ion Mass Spectrometry has been employed to measure the depth profile and the total retained fluences. The percentage of substitutional Arsenic has been obtained by least squares fits of the measured X-Ray Absorption spectra with simulated spectra of relaxed structures of the defects obtained by Density Functional Theory. A good agreement with the Hall effect measured electrically active dose fraction has been obtained and a quantification of the population of the different defects involved has been attempted.
Citation: Journal of Applied Physics
Pub Type: Journals
As shallow junction, EXAFS