Substitutional Carbon Loss in Si:C Stressor Layers Probed by Deep-Level Transient Spectroscopy

Abstract

This paper reports on a Deep-Level Transient Spectroscopy (DLTS) study of the electrically active defects formed by chemical vapor deposition of ~100 nm Si:C stressors on p-type Czochralski silicon substrates. In addition, the impact of a post-deposition Rapid Thermal Annealing (RTA) at 850 oC is investigated. It is shown that a dominant hole trap is found in the silicon depletion region, with an activation energy of 0.4 eV with respect to the valence band and assigned to CiOi. This indicates the presence of interstitial carbon (Ci), injected from the Si:C epi layer. It is demonstrated that the concentration of CiOi increases significantly after the RTA treatment, indicating that more carbon is driven out of lattice sites in the stressor. In addition, a second broad peak appears in the spectra, when biasing close to the epitaxial layer/substrate interface, demonstrating the presence of a band of hole traps which could be associated with precipitated carbon.