Quantitative measurement of reduction of phosphorus diffusion by substitutional carbon incorporation

Complete suppression of transient enhanced boron diffusion (TED) and oxidation enhanced boron diffusion (OED) in silicon have been achieved using substitutional carbon to reduce the excess point defect concentration in the dopant region. Recent efforts have focused on removing the carbon from the active regions of the device to avoid device degradation due to electrically active carbon defects and exploring remote carbon's effect on boron TED and OED, while using the boron diffusion to probe point defect concentrations. In this paper we measure quantitatively the effect of remotely located carbon on phosphorus and boron diffusion above a buried SiGeC layer at 850 °C in oxygen or nitrogen ambients. Remote carbon, located 1250 angstroms below the phosphorus edge, is found to reduce the phosphorus diffusion enhancement factor due to OED from 8 to 2. The effect of the remotely located SiGeC buried layer on the excess interstitial concentration profile, which is responsible for the enhanced dopant diffusion, is probed by measuring boron and phosphorus diffusivites of in-situ doped boron and phosphorus layers above a buried SiGe(C) layer after oxidation or nitrogen anneals at 850 °C. The enhanced boron diffusivity during oxidation is found to have a near linear dependence on depth ranging from 5-1.25. Finally, using x-ray diffraction and photoluminescence measurements of as-grown, buried, strained SiGe(C) structures and annealed SiGe(C) structures in oxygen or nitrogen ambient at 850 °C the number of substitutional carbon atoms effectively consumed by oxidation is unambiguously correlated to the absolute number of injected interstitials using published values for the interstitial injection rate during oxidation.