Highly reliable, high-C DRAM storage capacitors with CVD TA/sub 2/O/sub 5/ films on rugged polysilicon

The authors report on a highly reliable stacked storage capacitor with ultrahigh capacitance using rapid-thermal-annealed low-pressure chemical vapor deposited (LPCVD) Ta/sub 2/O/sub 5/ films ( approximately 100 AA) deposited on NH/sub 3/-nitrided rugged poly-Si electrodes. Capacitances as high as 20.4 fF/ mu /sup 2/ (corresponding to the thinnest t/sub ox.eff/ (16.9 AA) ever reported using LPCVD-Ta/sub 2/O/sub 5/ and poly-Si technologies) have been achieved with excellent leakage current and time-dependent dielectric breakdown (TDDB) characteristics. Extensive electrical characterization over a wide temperature range ( approximately 25-300 degrees C) shows that Ta/sub 2/O/sub 5/ films on rugged poly-Si electrodes have a better temperature stability in dielectric leakage and breakdown compared to the films on smooth poly-Si electrodes.<
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