Integrated reliability in EEPROM nonvolatile memory cell design

We propose a new way to design new memory cells assisted with a physical model taking into account reliability. First, we study the coupling ratio impact on the electric field and its consequences on cell hardness. The choice of coupling ratio in a new cell design should result from a compromise between a high K/sub e/ value in order to use low supply voltages and reduce the charge pump area, and low K/sub e/ value to increase the cell's endurance. Secondly, we investigate the Fowler-Nordheim parameters evolution with operating cycling stress. The experimental measurements necessary to extract these parameters turn out to be more stressing than the operating stress. We propose a new extraction process based on a two-point nonstressing measurement method. At last, the best way to design a robust cell should be to include this degradation effect in the model.