Method of programming a flash memory device using multilevel charge storage
Disclosed is a method of programming a flash memory device to store an amount of charge corresponding to one of a plurality of charged program states. The method can include pulsing the memory device with program voltages including at least a gate voltage. If the gate voltage is greater than or equal to a predetermined minimum threshold voltage for the one of the plurality of charged program states, an amount of charge stored by the memory device can be verified. Otherwise the memory device can be repulsed. This procedure can be carried out until verifying is conducted and the verifying indicates that the amount of charge stored by the memory device corresponds to the one of the plurality of charged program states.
1. A method of programming a flash memory device to store an amount of charge corresponding to a target charged program state from a plurality of charged program states, comprising:
successively pulsing the memory device with program voltages including a gate voltage until the gate voltage is greater than or equal to a minimum threshold voltage for the target charged program state; and
verifying the program state of the memory device when the gate voltage is greater than or equal to a minimum threshold voltage for the target charged program state;
wherein each successive pulse before the gate voltage is greater than or equal to the minimum threshold voltage for the target charged program state is carried out without being followed by a verify operation.
2. The method according to claim 1 , wherein if the verifying fails, then repulsing and reverifying the memory device.
3. The method according to claim 2 , wherein the repulsing includes incrementing the gate voltage according to a pulse count.
4. The method according to claim 1 , wherein for each successive pulse, the gate voltage is incremented according to a pulse count.
5. The method according to claim 1 , wherein the memory device is a floating gate device.
6. The method according to claim 5 , wherein there are three charged program states and a blank program state.
7. The method according to claim 1 , wherein the memory device is a charge trapping dielectric memory device having plural charge trapping regions.
8. The method according to claim 7 , wherein each charge trapping region stores an amount of charge corresponding to one of three charged program states or a blank program state.
9. The method according to claim 1 , wherein storing charge is accomplished by channel hot electron injection.