Correlation of local structure and electrical activation in arsenic ultrashallow junctions in silicon

Abstract

The understanding of the behavior of arsenic in highly doped near surface silicon layers is of crucial importance for the formation of N-type ultrashallow junctions in current and future very large scale integrated technology. This is of particular relevance when studying recently developed implantation and annealing methods. Past theoretical as well as experimental investigations have suggested that the increase in As concentration, and therefore the reciprocal proximity of several As atoms, leads to a drastic increase in electrically inactive defects giving only marginal reduction in sheet resistance. Monoclinic SiAs aggregates as well as various arsenic-vacancy clusters contribute to the deactivation of arsenic. This study aims to correlate between the results of electrical activation measurements and x-ray absorption fine structure measurements. Samples were doped with a nominal fluence of 1 ϫ 10 15-3ϫ 10 15 atoms/ cm 2 , implanted at 2 keV, and annealed by rapid thermal treatments, laser submelt treatments, and a combination of both. 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.

Evolution of arsenic in high fluence plasma immersion ion implanted silicon: Behavior of the as-implanted surface

“…The angle of incidence was set to 0.34 • , which is well above the critical angle of external total reflection of X-rays of the selected energy and a Si substrate at ∼0.15 • . This angle was selected on the basis of the X-ray penetration depth into the substrate to ensure that the entire arsenic distribution was probed [14][15][16]. For the sample S1 an additional GI angle (∼0.05 • ) was selected to restrict the probing depth to the top 3 nm and to exclusively examine the near surface layer and the expected arsenolite crystals on the surface of the Si wafer.…”

Use of p- and n-type vapor phase doping and sub-melt laser anneal for extension junctions in sub-32 nm CMOS technology

“…11). On the other hand, deactivation of As during anneal through the formation of electrically inactive complexes such as dopant-vacancy clusters was reported in ion-implanted Si [16,17]. Therefore, our results suggest that the low activation level in junctions made from As-VPD could also be explained by an important electrical deactivation of the in-diffused dopant atoms.…”

Characterization of Local Structures in Plasma Deposited Semiconductors by X-ray Absorption Spectroscopy

“…These χ j (k)'s are then fed into EXAFS fitting routines in order to compute the local structural parameters of the unknown from its experimental EXAFS data. Previous similar work on EXAFS characterization of complicated systems like layered superconductors [8][9][10] and similar EXAFS modeling and analysis work on the dopant-related electrically inactive structures in semiconductors [11][12][13][14][15][16] proved that with careful theoretical modeling and the EXAFS data analysis and interpretation could lead to crucial information about the subtle structural modifications under pressure, ion implantation and post annealing [17][18][19].…”

“…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 [11]. Monoclinic SiAs clusters, as well as various arsenic-vacancy aggregates contribute to the deactivation of the arsenic.…”

“…Monoclinic SiAs clusters, as well as various arsenic-vacancy aggregates contribute to the deactivation of the arsenic. Giubertoni et al [11] correlated the results of electrical activation measurements with EXAFS measurements. Specifically, a quantitative interpretation of the EXAFS spectra has been carried out in order to correlate the local atomic order of arsenic to the electrical characteristics as determined by Hall Effect measurement.…”