MNOS charge versus centroid determination by staircase charging

The charge versus centroid relationship is determined by staircase charging, in which a sequence of identical pulses is applied, the memory device is returned to flat-band condition after each pulse, and the subsequent pulse is superimposed on the flat-band voltage corresponding to the accumulated memory charge distribution resulting from the preceding pulses. Staircase patterns of accumulated negative charge and of device voltage are analyzed, and effects arising from back-tunneling and leakage currents are identified. Comparison of the initial injection current during a voltage pulse with the steady-state current indicates that hole injection from the gate does not contribute significantly to the steady-state oxide tunnel current.