An investigation of as-implanted material formed by high dose 40 keV oxygen implantation into silicon at 550 °C

Abstract

Device grade 〈100〉 single crystal silicon wafers have been implanted with 40 keV oxygen ions (16O+) over the dose range of 1×1017–8×1017/cm2 at a temperature of 550±10 °C. Transmission electron microscopy, ion channeling, and secondary ion mass spectroscopy studies show that during implantation the critical dose required to form a buried oxygen-rich amorphous (SiOx, x<2) layer is lower than 1×1017 O+/cm2. As the dose increases from 1×1017 to 4×1017/cm2 the thickness of the buried SiOx layer increases and there is a corresponding decrease in the thickness of the single crystal silicon top layer, with the oxygen concentration and residual radiation damage playing important roles in determining its position and thickness. A dose of 5×1017/cm2 results in a continuous surface amorphous layer, with a buried SiO2 sublayer being formed in the region corresponding to the implanted oxygen peak. With further increasing dose, the buried SiO2 sublayer grows primarily towards the surface. The results for the sample implanted at a dose of 1×1017/cm2 show that surface defects can be attributed to agglomeration of interstitial silicon atoms created by the internal oxidation process.