High reliability electron-ejection method for high density flash memories

To minimize the electrical stress for electron-ejection of each flash memory cell, the variable word-line voltage (VVP) method and the variable pulse width VVP (VVWP) method are proposed. Both methods make it possible to achieve high reliability while maintaining the total operating time of the conventional method, and both provide a sufficient disturb margin, Simulation results show that both methods reduce the maximum Fowler-Nordheim tunnel current density by 1.4 orders of magnitude compared to that of the conventional method, and the VVWP method increases the number of verifications by much less than the VVP method, This is expected to triple the charge-to-breakdown (Q(bd)) by decreasing the trap generation, A Q(bd) higher than the injection charge is obtained, as needed for high density flash memories.