System and method for programming split-gate, non-volatile memory cells
View Patent ↗The disclosed embodiments comprise a flash memory device and a method of programming the device in a way that reduces degradation of the device compared to prior art methods.
1. A method of programming a plurality of split-gate memory cells, each cell comprising a floating gate, a control gate terminal, a word line terminal, an erase gate terminal, a bit line terminal, and a source line terminal, the method comprising:
applying a pre-programming voltage to the control gate terminal of each of the plurality of cells, wherein the pre-programming voltage is insufficient to program the plurality of cells; and
applying a programming voltage to the control gate terminal of at least some of the plurality of cells, wherein the programming voltage is sufficient to program the at least some of the plurality of cells;
wherein the programming voltage is larger than 10.5 volts and the total duration of the steps of applying a pre-programming voltage step and applying a programming voltage step is shorter than 10 μs; and
wherein the maximum potential on the floating gate of each of the plurality of cells during the step of applying the programming voltage is between 2-3 volts lower than would result by programming the plurality of cells without first applying the pre-programming voltage.
2. The method of claim 1 , wherein the plurality of cells comprises multiple words.
3. The method of claim 2 , wherein the plurality of cells comprises a page.
4. The method of claim 2 , wherein the at least some of the plurality of cells comprises one and only one word.
5. The method of claim 3 , wherein the at least some of the plurality of cells comprises one and only one word.
6. The method of claim 1 , wherein no verification of the plurality of cells occurs after the pre-programming voltage is applied and before the programming voltage is applied.
7. The method of claim 1 , wherein the pre-programming voltage is between 3 volts and 6 volts lower than the programming voltage.
8. The method of claim 1 , wherein the duration of the applying of the pre-programming voltage is three to ten times shorter than the duration of the applying of the programming voltage.