A new and flexible scheme for hot-electron programming of nonvolatile memory cells

A new hot electron writing scheme for flash EEPROMs is proposed that combines a positive source to bulk voltage and a ramped voltage on the control gate. The scheme exploits the equilibrium between hot electron injection and displacement current at the floating gate electrode in order to achieve a transient regime where the drain current of the cell is virtually constant. The new method allows one to accurately control the threshold voltage and the programming drain current that is essentially determined by the slope of the control gate ramp and can thus be traded off with programming time over a wide range of values. The main features of the new scheme are experimentally demonstrated on up-to-date 0.6 μm stacked gate flash EEPROM devices