Synchrotron microbeam x-ray radiation damage in semiconductor layers

Radiation induced structural damage is observed in silicon-on-insulator (SOI) and SiGe on SOI samples illuminated with monochromatic ( 11.2 keV ) x-ray microbeams approximately 250 nm in diameter. The x-ray diffraction peaks from the irradiated layers irreversibly degrade with time, indicating permanent structural damage to the crystal lattice. The size of the damaged regions is almost an order of magnitude larger than the beam size. The magnitude of damage decreases as one moves away from the center of the illuminated volume. We discuss the threshold dosage required for damage initiation and possible mechanisms for the observed damage.