Generation of Interface States by Ionizing Radiation in Very Thin MOS Oxides

The creation of interface states Dit by ionizing radiation is investigated in MOS capacitors as a function of oxide thickness in the range 6-50 nm. A comparison of the thickness dependence in etchback and asgrown oxides supports the idea that the number of defects at the Si-SiO2 interface increases with oxidation time. For relatively thin oxides (tox<12 nm), the rate of increase in Dit is significantly smaller than would be extrapolated from the behavior of thicker oxides for both oxide types. This effect is probably caused by tunneling of trapped holes near the oxide interfaces.