Study on Irradiation Effects of Semiconductors by Measurement of Deep Level Defect

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1. Seven kinds of silicon wafers with different oxygen concentration and with different production processes were irradiated by neutrons with different energy spectra, i.e., at pneumatic tube facility and thermal column facility of Kyoto University Research Reactor Institute, and at the fast neutron source of YAYOI (Nuclear Engineering Research Laboratory, University of Tokyo). The resistivities of the irradiated silicon wafers were measured by four probe method. The energy levels and their concentrations were measured at 90K to 350K by the semiconductor impurity measuring system. With these measurements, thermal neutron, which was taken as ineffective for the production of the lattice defects, was found effective. A lattice defect with unfamiliar energy level was observed.2. Oxygen ions and silicon ions were injected into silicon wafers by using tandem accelerator of Department of Engineering, Kyoto University. The concentration of the produced lattice defects were observed by the channeling method : low concentration defect with no irradiation dose dependence at the surface and high concentration defect with strong dependence on dose at the end of ion range. A model was developed which included the recombination, diffusion of point defects, production of defect clusters and amorphous and their accumulation. With model calculations, the defects at the surface were shown as point defects, and at the end of range as amorphous defects.