Buried oxide layers formed by low-dose oxygen implantation

The structure of buried oxide layers formed by low-dose ¹⁶O⁺ implantation of 0.4 and 0.7 × 10¹⁸ cm⁻² at 180 keV and by subsequent annealing in the temperature range of 1150 to 1350 °C has been investigated using cross-sectional transmission electron microscopy (XTEM). At a dose of 0.4 × 10¹⁸ cm⁻², an 80-nm continuous uniform buried oxide layer having a breakdown voltage of approximately 40 V is formed after annealing at 1350 °C. At a dose of 0.7 × 10¹⁸ cm⁻², multiple buried oxide layers having Si islands between them are formed at an anneal temperature of 1150 °C. The number of multiple layers is reduced as the annealing temperature increases, but the Si islands do not dissolve even after annealing at 1350 °C. The existence of the Si islands causes the breakdown voltage to fall to 0 V despite the higher dose.