Seiichi Iwata1, Yuzuru Ohji2 and Akitoshi Ishizaka1
1Central Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo 185
In the study of X-ray-induced surface potential changes of ultrathin SiO2 films on Si caused by X-ray irradiation, we investigated why the time constant for the X-ray-irradiation time dependence decreases with increasing oxide thickness and saturates at about 10 nm thickness. We conclude that the above changes are caused by the hole trapping at traps close to the SiO2/Si interface and that the time constant is greater at small thicknesses because the hole concentration is effectively smaller at thicknesses close to the hole mean free path, which could be estimated to be about 1.8 nm.
(Received May 17, 1996)
ultrathin silicon oxide films, X-ray irradiation, charging, surface potential changes, dry oxide films, X-ray-irradiation time, time constant, hole traps, silicon oxide/silicon interfaces, oxide thickness, hole mean free path
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