The Stability of Dielectric Coatings under Radiation
Final rept. 1 Oct 1974-31 Mar 1976
PRINCETON UNIV NJ SOLID STATE AND MATERIALS LAB
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Research performed was directed at understanding the effects of ion implantation on the radiation hardness of the SiO2 gate oxide of MOS devices. MOS capacitors were used as test structures and capacitance-voltage measurements were combined with photoinjection, photodepopulation, thermal annealing and variable temperature measurements on both implanted and unimplanted samples in order that the modified oxide charge trapping could be probed. Some measurements were made using the scanning electron microscope as a source of electrons of controlled energy. C-V and G-V data was taken with the MOS samples in the microscope environment, the beam energy being slowly increased to probe the oxide to increasing depths. The experimental data indicates that the primary effect of the implantation process is to produce electron traps associated with the implantation induced displacement damage. At room temperature, electrons in these traps can charge compensate holes trapped near the SiSiO2 interface. At low temperatures however, the increased hole trapping at this interface overcomes the effects of the trapped electrons and dominates the flat band voltage shifts. A model of the charge trapping behavior has been developed which satisfactorily explains the observed behavior.
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