Method of programming a flash memory device using self boosting
A method of programming a flash memory device controls a channel boosting level to ensure device properties. The flash memory device is programmed in an Incremental Step Pulse Program (ISPP) manner by applying a program voltage to a selected memory cell and a pass voltage to unselected memory cells. The programming is performed by varying the pass voltage so that a gap of a predetermined range is maintained between a channel voltage and a word line voltage of the unselected memory cell.
1. A method of programming a flash memory device using incremental step pulse programming (ISPP), the method comprising:
applying a program voltage to a selected memory cell; and
applying a pass voltage to unselected memory cells,
wherein the pass voltage is increased to the unselected memory cells in response to the program voltage during a program loop of the ISPP to maintain a gap of a predetermined range between a channel voltage and a word line voltage of the unselected memory cell.
2. The method of claim 1 , wherein the pass voltage is increased based on a level of the program voltage.
3. The method of claim 2 , wherein the pass voltage is increased by a first step voltage when the level of the program voltage is higher than 19 V.
4. The method of claim 1 , wherein the pass voltage is increased based on the number of program loop of the selected memory cell.
5. The method of claim 4 , wherein the pass voltage is increased by a first step voltage after the program loop is performed half of a total number of program loop.
6. The method of claim 3 , wherein the first step voltage is 0.2 to 1.0 V.
7. A method of programming a flash memory device, the method comprising:
programming a selected memory cell by applying a program voltage to the selected memory cell and a pass voltage to unselected memory cells;
verifying the selected memory cell;
determining whether the level of the program voltage is higher than a first voltage, when the programming is not passed; and
repeating the programming and verifying the selected memory cell by applying the program voltage gradually increased by a first step voltage to the selected memory cell and the pass voltage increased by a second step voltage to the unselected memory cells, respectively, until the programming is passed, when the program voltage is higher than the first voltage.
8. The method of claim 7 , wherein the first voltage is approximately 19 V.
9. The method of claim 7 , wherein the second step voltage is equal to or lower than the first step voltage.
10. The method of claim 7 , wherein the second step voltage is 0.2 to 1.0 V.
11. The method of claim 5 , wherein the first step voltage is 0.2 to 1.0 V.
12. The method of claim 4 , wherein the number of program loop is approximately 8.
13. The method of claim 7 , further comprising:
repeating the programming and verifying the selected memory cell by applying the program voltage gradually increased by the first step voltage to the selected memory cell and the pass voltage to the unselected memory cells, when the program voltage is not higher than the first voltage.
14. A method of programming a flash memory device, the method comprising:
programming a selected memory cell by applying a program voltage to the selected memory cell and a pass voltage to unselected memory cells;
verifying the selected memory cell;
determining whether the number of program loop is more than a first number; and
repeating the programming and verifying the selected memory cell by applying the program voltage gradually increased by a first step voltage to the selected memory cell and the pass voltage increased by a second step voltage to the unselected memory cells, respectively, until the programming is passed when the number of the program loop is more than the first number.
15. The method of claim 14 , wherein the first number is half of the total number of the program loop.
16. The method of claim 14 , wherein the first number is approximately 8.
17. The method of claim 14 , wherein the second step voltage is equal to or lower than the first step voltage.
18. The method of claim 14 , wherein the second step voltage is 0.2 to 1.0 V.
19. The method of claim 14 , further comprising:
repeating the programming and verifying the selected memory cell by applying the program voltage gradually increased by the first step voltage to the selected memory cell and the pass voltage to the unselected memory cells, when the program loop is not more than the first number.