The effects of a protective capping layer on the microstructure of ultrathin separation by implantation of oxygen (SIMOX) materials formed by ion implantation were studied using transmission electron microscopy. A set of SIMOX wafers were implanted at 65 keV in a dose range of 1.5 to 7.0 × 1017 O+/cm2 followed by a high temperature (1350°C) annealing with and without a protective cap. The lowest dose to form a continuous buried oxide (BOX) layer without Si islands at 65 keV is 2.0 × 1017 O+/cm2 without a protective cap and 2.5 × 1017 O+/cm2 with a protective cap. Above 2.5 × 1017 O+/cm2 under both annealing conditions, the BOX layer formed continuously but with Si islands present. The uncapped samples show slightly lower density of Si islands. Oxygen from the annealing ambient can diffuse in the uncapped samples through the thin lop Si layer, which helps the BOX layer grow laterally and lower the Si island density. The density of defects in the lop Si layer is also slightly lower in the uncapped samples because of the ability of Si interstitials to incorporate into the surface and the effective annihilation of extended defects during the final annealing step. The top Si layers of the uncapped samples are thinner than those of the capped samples due to surface thermal oxidation.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry