New self-adjusted dynamic source multilevel p-channel flash memory

In this work a new multilevel programming approach employing the new self-adjusted dynamic source (SADS) structure for p-channel flash memory is studied. The memory unit is composed of a current source and a p-channel stacked-gate transistor. Using SADS structure, the final source voltage, which is not grounded, is found to be dependent on the applied drain voltage. Programmed threshold voltage is observed to be proportional to the final source voltage. Adjusting drain voltages during programming results in the predictable multilevel threshold voltages due to the self-adjusted dynamic source mechanism. The programming drain current in p-channel flash memory can be limited to a low level to achieve low power programming by adjusting the conducting current of the current source. Furthermore, the drain disturbance, which alters the stored charge of other memory cells, can be suppressed in the SADS structure by shutting off the current source and employing negative word line voltages on the unselected cells.