The response of open-volume defects in Si_0.92Ge_0.08 to annealing in nitrogen or oxygen ambient

Abstract

While the dynamics of thermal oxidation of Si has been adequately described for over three decades, details of SiGe oxidation are not entirely clear. In particular, the injection into the Si substrate of a super-saturation of interstitial defects during the formation of SiO₂ may not be replicated in the SiGe system. Here we describe the response of relatively stable open-volume defects in a Si₀₉₂Ge_0.08 substrate to annealing at 900°C for 30 min in either an inert (nitrogen) or wet oxidizing ambient. The defects are initialized by He⁺ implantation at an energy and dose of 60 keV and 1 × 10¹⁶ cm⁻² respectively, followed by annealing in an inert ambient at 800°C for 10 min. Confirmation of the creation and thermal evolution of the open-volume defects was provided by beam-based variable-energy positron annihilation spectroscopy. The positron measurements suggest that the defects are considerably reduced in size following the secondary nitrogen annealing step. In comparison, the average size of the open-volume defects is reduced to a significantly smaller degree following secondary oxygen annealing. This result is consistent with a suppression of interstitial formation during oxidation, in contrast with the case for the thermal oxidation of silicon, but further work is currently underway to test this interpretation.