Non-volatile memory device and inspection method for non-volatile memory device
View Patent ↗A non-volatile memory device comprises a plurality of bit lines extending in a first direction, a plurality of word lines extending in a second direction substantially perpendicular to the first direction, a plurality of memory cells provided respectively so as to correspond to the positions of the intersections between the plurality of bit lines and the plurality of word lines, a plurality of source lines corresponding to a plurality of memory cells which are connected to a same bit line, a current source capable of supplying the constant current to a selected memory cell and the corresponding bit line and a voltage control circuit which keeps a voltage of a selected bit line equal to or higher than a predetermined voltage.
1. A non-volatile memory device comprising: a plurality of bit lines extending in a first direction; a plurality of word lines extending in a second direction substantially perpendicular to the first direction; a plurality of memory cells provided respectively so as to correspond to the positions of the intersections between the plurality of bit lines and the plurality of word lines; a plurality of source lines corresponding to a plurality of memory cells which are connected to a same bit line; a current source capable of supplying the constant current to a selected memory cell and the corresponding bit line; and a voltage control circuit which keeps a voltage of a selected bit line equal to or higher than a predetermined voltage.
2. The non-volatile memory device according to claim 1 , wherein the voltage control circuit keeps the voltage of the selected bit line equal to or higher than a predetermined voltage when a writing operation to a selected cell is performed.
3. The non-volatile memory device according to claim 1 , wherein the predetermined voltage prevents a non-selected cell from an unintended writing when the voltage of the selected bit line is equal to or higher than the predetermined voltage.
4. The non-volatile memory device according to claim 1 , wherein the voltage control circuit keeps the voltage of the selected bit line equal to or higher than a predetermined voltage when the writing operation in the writing test of the memory cell.
5. The non-volatile memory device according to claim 1 , wherein the voltage control circuit includes a clamp circuit.
6. The non-volatile memory device according to claim 2 , wherein the non-volatile memory device determines the selected memory cell as a failure when the write operation is not performed successfully.
7. The non-volatile memory device according to claim 1 ,
wherein the voltage control circuit includes a transistor, and the voltage of the selected bit line is clamped at V dp -V tn if the voltage of the selected bit line is lower than V dp -V tn , wherein V dp is an external voltage applied to a gate of the transistor and V tn is a threshold voltage of the transistor; and
the predetermined voltage is given by VWW-V th , wherein VWW is a gate voltage applied to a selected word line corresponding to the selected memory cell, and V th is a threshold voltage of the selected memory cell.
8. The non-volatile memory device according to claim 1 , wherein the voltage control circuit keeps the voltage of the selected bit line equal to or higher than a predetermined voltage during a writing operation in a writing test of the memory cell.
9. An inspection method for a non-volatile memory device comprising: selecting a selected word line among a plurality of word lines; selecting a selected bit line among a plurality of bit lines; writing data to a selected cell by causing a constant current on the selected cell and the selected bit line while keeping a voltage of the selected bit line equal to or higher than a predetermined voltage; and determining whether data is written to the selected cell or not.
10. The inspection method for a non-volatile memory device according to claim 9 , wherein the non-volatile memory comprises a plurality of source lines corresponding to a plurality of memory cells which are connected to a same bit line.
11. The inspection method for a non-volatile memory device according to claim 9 , wherein the predetermined voltage prevents a non-selected cell from an unintended writing when the voltage of the selected bit line is equal to or higher than the predetermined voltage.
12. The inspection method for a non-volatile memory device according to claim 10 , wherein the predetermined voltage prevents a non-selected cell from an unintended writing when the voltage of the selected bit line is equal to or higher than the predetermined voltage.
13. The inspection method for a non-volatile memory device according to claim 9 , further comprising: determining the selected cell as failure when the data is not written to the selected cell.
14. The inspection method for a non-volatile memory device according to claim 9 , wherein the non-volatile memory comprises a voltage control circuit which keeps the voltage of the selected bit line equal to or higher than the predetermined voltage.
15. The inspection method for a non-volatile memory device according to claim 10 , wherein the non-volatile memory comprises a voltage control circuit which keeps the voltage of the selected bit line equal to or higher than the predetermined voltage.
16. The inspection method for a non-volatile memory device according to claim 14 , wherein the voltage control circuit includes a clamp circuit.
17. A computer program product, in a computer readable medium, for executing an inspection method for a non-volatile memory device, wherein the program causes a computer to execute an inspection method comprising:
selecting a selected word line from a plurality of word lines;
selecting a selected bit line from a plurality of bit lines;
writing data to a selected cell by causing a constant current on the selected cell and the selected bit line while keeping a voltage of the selected bit line equal to or higher than a predetermined voltage;
determining whether data is written to the selected cell or not; and
determining the selected cell as failure when the data is not written to the selected cell.
18. The non-volatile memory device according to claim 1 , wherein the plurality of memory cells which are connected to the same bit line are connected to a same source line of the plurality of source lines.
19. The inspection method according to claim 10 , wherein the plurality of memory cells which are connected to the same bit line are connected to a same source line of the plurality of source lines.
20. A computer program product, in a computer readable medium, for executing an inspection method for a non-volatile memory device, wherein the program causes a computer to execute an inspection method comprising:
selecting a selected word line from a plurality of word lines;
selecting a selected bit line from a plurality of bit lines;
writing data to a selected cell by causing a constant current on the selected cell and the selected bit line while keeping a voltage of the selected bit line equal to or higher than a predetermined voltage; and
determining whether data is written to the selected cell or not,
wherein the non-volatile memory comprises a plurality of source lines corresponding to a plurality of memory cells which are connected to a same bit line.
21. The computer program according to claim 20 , wherein the plurality of memory cells which are connected to the same bit line are connected to a same source line of the plurality of source lines.