The use of nanocavities for the fabrication of ultrathin buried oxide layers

A continuous buried oxide (BOX) layer with a thickness of only 58 nm is formed in silicon by oxygen implantation at 185 keV with a very low ion dose of 1×1017 cm-2 and subsequent He implantation. Due to the implanted He efficient oxygen gettering occurs at the implantation induced damage and results in the accumulation of the implanted oxygen as well as of oxygen in-diffused from the annealing atmosphere. The morphology and the resistivity of the resulting silicon-on-insulator (SOI) structure are analyzed by cross section transmission electron microscopy and by cross section scanning spreading resistance microscopy, which is demonstrated to be a promising tool for the characterisation of a thin BOX layer.