Ultradry annealing after polysilicon electrode formation for improving the TDDB lifetime of ultrathin silicon oxide films in MOS diodes

Effects of ultradry annealing on time-dependent dielectric breakdown (TDDB) lifetime (T/sub TDDB/) were investigated for Si MOS diodes with 5-nm-thick silicon oxide and P-doped polysilicon gate electrode films. This annealing was performed at 800 degrees C in ultradry N/sub 2/ of less than 1-ppm moisture concentration after the electrode formation. Under an accumulation-bias stress condition, T/sub TDDB/ for the ultradry-annealed n-type Si diodes was larger than that for the conventionally annealed ones, while such T/sub TDDB/ enhancement was not confirmed in the p-type ones. Since positive charges induced near anode-side oxide interfaces are closely related to T/sub TDDB/, the T/sub TDDB/ enhancement for the ultradry-annealed n-type Si diodes probably reflects a qualitative improvement of the anode-side, i.e., gate-electrode-oxide, interfaces by ultradry annealing.<
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