  Ion implantation is a non-equilibrium doping technique which introduces
impurity atoms into a solid regardless of thermodynamic considerations. The
formation of metastable alloys above the solubility limit, minimized
contribution of lateral diffusion processes in device fabrication, and
possibility to reach high concentrations of doping impurities can be considered
as distinct advantages of ion implantation. Owing to excellent controllability,
uniformity, and the dose insensitive relative accuracy ion implantation has
grown to be the principal doping technology used in the manufacturing of
integrated circuits. Originally developed from particle accelerator technology
ion implanters operate in the energy range from tens eV to several MeV
(corresponding to a few nm to several microns in depth). The main feature of
ion implantation is the formation of point defects in the energetic ion
collisions. Very minute concentrations of defects and impurities in
semiconductors drastically alter their electrical and optical properties. This
chapter presents methods of defect spectroscopy to study the defect origin and
characterize the defect density of states in thin film and semiconductor
interfaces. The methods considered are positron annihilation spectroscopy,
electron spin resonance, and approaches for electrical characterization of
semiconductor devices.
