Oxidized Ta/sub 2/O/sub 5//Si/sub 3/N/sub 4/ dielectric films on poly-crystalline Si for dRAMs

A dielectric film technology characterized by a novel multilayer structure formed by oxidation of Ta/sub 2/O/sub 5//Si/sub 3/N/sub 4/ films on polysilicon has been developed to realize high-density dRAMs. The dry oxidation of the Ta/sub 2/O/sub 5//Si/sub 3/N/sub 4/ layers was performed at temperatures higher than 900 degrees C. This film has a capacitance per unit area from 5.5 to 6.0 fF/ mu m/sup 2/, which is equivalent to that of a 6.0- to 6.5-nm-thick SiO/sub 2/. The leakage current at an effective electric field of 5 MV/cm is less than 10/sup -9/ A/cm/sup 2/. Under such an electric field, the extrapolated time to failure for 50% cumulative failure can be as high as 1000 years.<
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