Effects of gamma ray irradiation on HCl oxides

Silicon dioxide films grown in the presence of controlled amounts of gaseous HCl and O2 at 11250C were irradiated by gamma rays from a cobalt-60 gamma source, up to total dose levels of 106 rad (Si). The mole percentage ratios of HCl/O2 used during the gate oxide formation were ''0'', 1, 4, and 6 percent, where the ''0'' percent oxides represented those oxides grown in pure oxygen following tube cleaning by a mixture of HCl and O2. The effects of irradiation on these oxides as a function of the mole percentage ratios HCl/O2 introduced during oxide formation were monitored for various gate bias and radiation dose levels. It was found that the addition of HCl gas to the oxidizing ambient alters the structure of the resulting oxide in such a way as to increase the number of hole trapping sites available during irradiation. The magnitude of the hole traps formed in the oxide increased as the mole percentage ratio HCl/O2 increased. It was also observed that, in general, the number of radioinduced surface states increased as the mole percentage ratio HCl/O2 increased. This is attributed primarily to the breaking of Si--H bonds that were formed during oxide formation