Quantification of germanium-induced suppression of interstitial injection during oxidation of silicon

The oxidation of silicon is known to inject interstitials, and the presence of silicon–germanium (SiGe) alloys at the Si/SiO₂ interface during oxidation is known to suppress the injection of silicon self-interstitials. This study uses a layer of implantation-induced dislocation loops to measure interstitial injection as a function of SiGe layer thickness. The loops were introduced by a 50 keV 2 × 10¹⁴ cm⁻² P⁺ room-temperature implantation and thermal annealing. Germanium was subsequently introduced via a second implant at 3 keV Ge⁺ over a range of doses between 1.7 × 10¹⁴ cm⁻² and 1.4 × 10¹⁵ cm⁻². Results show that upon oxidizing at 850 °C for 3 h or 900 °C for 70 min to condense the germanium at the Si/SiO₂ interface, where if forms a Si_0.5Ge_0.5 alloy. Upon subsequent oxidations of 850 °C for 6 h or 900 °C for 2 h, partial suppression of interstitial injection can be observed for sub-monolayer doses of germanium, and more than three monolayers of Si_0.5Ge_0.5 (1.4 × 10¹⁵ cm⁻²) are necessary to suppress interstitial injection below the detection limit during oxidation. These results show that low-energy implantation of germanium can be used to eliminate or modulate injection of oxidation-induced interstitials.