Cross-section transmission electron microscopy study of carbon-implanted layers in silicon

We have used cross-section transmission electron microscopy (XTEM) to study microstructures of carbon-implanted silicon layers after high-temperature annealing. It was found that the threshold dose for extended defect formation was much higher for carbon implantation than for other ion species such as B, P, and O. In 2.4 MeV carbon-implanted layers, no dislocations were formed for doses as high as 2×10¹⁶ cm^-2 after annealing at 1000°C for 1 h. The threshold was found to be lower for low-energy implantation (100 keV): at a dose of 2×10¹⁶ cm^-2, when an amorphous layer was formed, microtwins were formed near the projected range upon annealing. Microprecipitates around 50 Å in size were observed in low-energy carbon-implanted samples and the precipitates appeared to be under strain.