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Radiation Effects on the Electrical Properties of MOS Device Materials.

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Final rept. 2 Mar 76-28 Feb 77,

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Radiation-hard SiO2 on Si grown by three different processes dry, pyrogenic steam, and hybrid has been examined by vacuum ultraviolet techniques. Flatband shift vs time measurements provide estimates of capture cross sections and trap densities. Current-enhancement measurements provide qualitative information about trapping at both the Si-SiO2 and gate-SiO2 interface. Results show that unannealed dry oxides have the lowest interface-state density after irradiation, making them more desirable for applications where switching speed is important. Annealing in argon at 800 C increases both the hole-trap and interface-state density. All dry oxides have a dominant trap with capture cross section S approx. 5 x 10 to the -14th power sq cm at applied oxide fields E sub o 1 MVcm. Pyrogenic steam oxides have many more interface stfores after irradiation than dry oxides and can be characterized by a dominant trap with S approx. 5 x 10 the the -14th power to 10 to the -13th power sq. cm. for E sub 0 1 MVcm. Hybrid oxides grown in 3 HCl steam followed by dry O2 show S approx. 2 x 10 to the -13th power sq. cm. at E sub 0 1 MVcM. The larger capture cross section for these oxides is believed to be due to the presence of HCl. All oxides show a neutral trap capture cross section which is approximately inversely proportional to applied oxide field. Both pyrogenic steam and dry hard oxides can be characterized by the same trap. The difference between the two oxides appears to be only the density of interface states. Author

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  • Solid State Physics

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