Determination of Diffusivities of Si Self-Diffusion and Si Self-Interstitials using Isotopically Enriched Single-or Multi-³⁰Si Epitaxial Layers

<jats:title>Abstract</jats:title><jats:p>Self-diffusivity of Si has been obtained over a wide temperature range (867°C-1300°C) using highly isotopically enriched <jats:sup>30</jats:sup>Si epi-layers (99.88%) as a diffusion source into natural Si substrates. <jats:sup>30</jats:sup>Si epi-layers were grown on both CZ-Si substrates and non-doped epi-layers grown on CZ-Si substrates using low pressure CVD with <jats:sup>30</jats:sup>SiH<jats:sub>4</jats:sub>. Diffusion was performed in resistance-heated furnaces under a pure Ar atmosphere. After annealing, the concentrations of the respective Si isotopes were measured with secondary ion mass spectroscopy (SIMS). Diffusivity of <jats:sup>30</jats:sup>Si (called Si self-diffusivity, DSD) was determined using a numerical fitting process with <jats:sup>30</jats:sup>Si SIMS profiles. We found no major differences in self-diffusivity between bulk Si and epi-Si. Within the 867°C -1300°C range investigated, D<jats:sub>SD</jats:sub> can be described by an Arrhenius equation with one single activation enthalpy: D<jats:sub>SD</jats:sub> =14 exp (—4.37 eV/kT) cm<jats:sup>2</jats:sup>/s. The present result is in good agreement with that of Bracht <jats:italic>et. al</jats:italic>.</jats:p><jats:p>Diffusivity and thermal equilibrium concentration of Si self-interstitials have been determined using multi-<jats:sup>30</jats:sup>Si epi-layers consisting of alternative layers with isotopically pure <jats:sup>30</jats:sup>Si and natural Si. The sample surface was oxidized and the Si self-interstitials were introduced from the surface. Spreading of <jats:sup>30</jats:sup>Si spikes of each layer due to the diffusion of Si self-interstitials generated at the surface was measured with SIMS analysis. The diffusivity of Si self-interstitials, <jats:italic>D</jats:italic><jats:sub>I</jats:sub>, is obtained by fitting with experimental results. In the temperature range between 820 -920°C, <jats:italic>D</jats:italic><jats:sub>I</jats:sub> and thermal equilibrium concentration of Si self-interstitials, C<jats:sub>Ii</jats:sub>, are described by the Arrhenius equations <jats:italic>D</jats:italic><jats:sub>I</jats:sub>3.48×10<jats:sup>4</jats:sup> exp (—3.82eV/KT) cm<jats:sup>2</jats:sup>/s and <jats:italic>C</jats:italic><jats:sub>Ii</jats:sub>= 9.62×10<jats:sup>18</jats:sup> exp (—0.475eV/KT) cm<jats:sup>-3</jats:sup>, respectively.</jats:p>