The reliability of three types of stacked insulating films (ONO, ON, NO) with thicknesses of 10 nm and below deposited on highly doped polysilicon are compared. It is shown that the doping process of the underlaying polysilicon plays an important role in the dielectric breakdown behavior. Evaluation of I‐E characteristics from voltage ramp measurements demonstrates the influence of top and bottom oxide thickness. Under NO double layers generally a native oxide is found. This leads to similar reliability results as found for triple layers. Real double layers (ON) without any potential barrier at the top electrode show significantly shorter lifetimes at positive gate voltage. Hence the native oxide between bottom electrode and nitride is not negligible. Extrapolations of the data measured by the constant voltage method on planar and trench capacitors indicate that the investigated ultrathin multilayer films on polysilicon show promise as dielectrics in storage capacitors of future DRAMs.
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Vollertsen et al. (1990) studied this question.