Electrical and irradiation performance of MNOS arrays

This paper describes the methods used to evaluate and characterize MNOS arrays and includes test data on the most important parameters of such arrays from the standpoint of large systems. MNOS 256-bit and 2240-bit charge storage memory arrays are evaluated, primarily, in terms of switching speed, level separation uniformity across the chip, nonvolatility, adjacent word disturb during writing, and the effects of temperature and γ-radiation. For a 2240-bit array, a minimum level separation of more than 5 volts across the chip was obtained using a 30 volt pulse with a one millisecond pulse width for writing and erasing and a read cycle time of 500 ns. The information can be stored for more than 10 years. The adjacent word disturb was less than 3% after 20000 successive write-clear cycles and it was not cumulative. There was no degradation of the cell after 109 successive cycles. In the temperature range -55 to +125°C, there was little degradation in the writing, erasing and storage characteristics. Useful information can be stored at radiation levels of up to 5×105 Rads (Si). The window is completely closed after a dosage of 106 Rads (Si), in good agreement with the model developed during this study.