Dose and energy dependence of interface trap formation in cobalt-60 and X-ray environments

The radiation-induced buildup of interface traps is examined on radiation-hardened 20-nm-gate-oxide n-channel transistors irradiated with /sup 60/Co and 10 keV X-rays. A variation in the fundamental dependence of interface-trap ( Delta D/sub it/) growth on dose from linear with dose to a square-root dependence was observed. The samples with the largest low-dose interface-trap buildup showed the slowest rate of growth (D/sup 1/2/), while the samples with the smallest low-dose Delta D/sub it/ showed the fastest buildup (linear with dose). A possible qualitative explanation of this behavior based on cluster centers is given. The interface-trap density growth was observed to tend toward saturation at doses above 3 Mrad (SiO/sub 2/). A photon energy dependence of D/sub it/ formation between /sup 60/Co and X-ray irradiation was not observed.<
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