Cathodoluminescence microcharacterization of the radiation-sensitive defect microstructure of in situ buried oxide in silicon

Abstract

Cathodoluminescence (CL) spectroscopy in a scanning electron microscope has been used to investigate the radiation-sensitive defect structure of the buried amorphous oxide layer produced by oxygen ion implantation in silicon (Si⟨1 0 0⟩) in comparison with bulk amorphous silicon dioxide (a-SiO2). CL microanalysis allows the defect structure of the buried oxide (BOX) layer to be investigated without removal of the silicon-on-insulator (SOI) top layer. CL emissions are observed at 1.63, 2.10, 2.31 and 2.66 eV and are associated with silicon clusters and nanoparticles that form in the BOX as a result of the post-implantation, high-temperature anneal. CL emission at ∼3 eV may be associated with excess silicon and/or inclusions of high-pressure crystalline SiO2 polymorph (coesite) in the BOX near the SiO2–Si substrate. A partially resolved CL emission may also be observed at 1.88 eV and is possibly associated with a native non-bridging oxygen defect of SiO2. CL emission from the confined strained BOX is dominated by defects associated with large surface-to-volume ratio nanoscale silicon clusters and their interfaces. CL spectra from the in situ BOX are electron radiation sensitive. Electron irradiation results in localized trapped charge-induced electric fields which are enhanced within the strained confined BOX layer at nanoscale silicon cluster defects and interfaces. These enhanced electric fields and residual strain near the interfaces can contribute to breakdown of the BOX.