On the manifestation of phosphorus-vacancy complexes in epitaxial Si:P films

Sathish Kumar Dhayalan*, Jiri Kujala, Jonatan Slotte, Geoffrey Pourtois, Eddy Simoen, Erik Rosseel, Andriy Hikavyy, Yosuke Shimura, Serena Iacovo, Andre Stesmans, Roger Loo, Wilfried Vandervorst

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

In situ doped epitaxial Si:P films with P concentrations >1 × 1021 at./cm3 are suitable for source-drain stressors of n-FinFETs. These films combine the advantages of high conductivity derived from the high P doping with the creation of tensile strain in the Si channel. It has been suggested that the tensile strain developed in the Si:P films is due to the presence of local Si3P4 clusters, which however do not contribute to the electrical conductivity. During laser annealing, the Si3P4 clusters are expected to disperse resulting in an increased conductivity while the strain reduces slightly. However, the existence of Si3P4 is not proven. Based on first-principles simulations, we demonstrate that the formation of vacancy centered Si3P4 clusters, in the form of four P atoms bonded to a Si vacancy, is thermodynamically favorable at such high P concentrations. We suggest that during post epi-growth annealing, a fraction of the P atoms from these clusters are activated, while the remaining part goes into interstitial sites, thereby reducing strain. We corroborate our conjecture experimentally using positron annihilation spectroscopy, electron spin resonance, and Rutherford backscattering ion channeling studies.

Original languageEnglish
Article number082106
Number of pages4
JournalApplied Physics Letters
Volume108
Issue number8
DOIs
Publication statusPublished - 22 Feb 2016
MoE publication typeA1 Journal article-refereed

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