Methods and apparatus for writing nonvolatile 3D NAND flash memory using multiple-page programming

1. A method for multiple-page programming of a 3D NAND flash memory array having a block that includes a plurality of page groups and each page group includes a plurality of cell strings that form a plurality of pages, the method comprising:

deactivating drain select gates (DSGs) and source select gates (SSG) of the block;

applying a programming voltage to a selected word line that is coupled to a selected page in each page group;

applying an inhibit middle high voltage to unselected word lines that are coupled to other pages in each page group;

repeating multiple programming operations while maintaining the word line voltage levels from a first programming operation to a last programming operation, wherein the multiple programming operations program a selected page in each of two or more page groups, respectively, and wherein each programming operation comprises:

loading data onto bit lines coupled to the page groups; and

pulsing a drain select gate associated with a selected page group to begin programming the data on the bit lines into the selected page of the selected page group; and

maintaining the word line voltage levels after a last programming operation for an additional time interval to complete the programming operations.

2. The method of claim 1 , further comprising pre-charging the cell strings of the block by applying VDD to all the bit lines and to all the drain select gates of the block before the operation of applying the programming voltage to the selected word line.

3. The method of claim 1 , further comprising pre-charging the cell strings of the block by applying VDD to all the bit lines and drain select gates of the block, and then applying Vss to all the drain select gates of the block, before the operation of applying the programming voltage to the selected word line.

4. The method of claim 1 , further comprising pre-charging the cell strings of the block by performing operations of:

applying VDD or a higher voltage to all the source lines and source select gates of the block;

applying Vss to all the drain select gates of the block;

performing the above operations before the operation of applying the programming voltage to the selected word line; and

applying Vss to a source select gate of the block either before or after the operation of applying the programming voltage to the selected word line.

5. The method of claim 1 , wherein each cell string comprises a plurality of NAND nonvolatile memory cells.

6. The method of claim 1 , wherein the programming voltage is in a range of 15-20 volts and the inhibit middle high voltage is in a range of 8-10 volts.

7. The method of claim 1 , further comprising obtaining the data from a second block that includes a plurality of second page groups, and wherein one or more of the second page groups is configured as a DRAM page.

8. A nonvolatile memory device, comprising:

a 3D NAND flash memory array having a block that includes a plurality of page groups and each page group includes a plurality of cell strings that form a plurality of pages; and

a decoder coupled to the block and configured to provide multiple-page programming by performing operations of:

deactivating drain select gates (DSGs) and source select gates (SSG) of the block;

applying a programming voltage to a selected word line that is coupled to a selected page in each page group;

applying an inhibit middle high voltage to unselected word lines that are coupled to other pages in each page group;

repeating multiple programming operations while maintaining the word line voltage levels from a first programming operation to a last programming operation, wherein the multiple programming operations program a selected page in each of two or more page groups, respectively, and wherein each programming operation comprises:

loading data onto bit lines coupled to the page groups; and

pulsing a drain select gate associated with a selected page group to begin programming the data on the bit lines into the selected page of the selected page group; and

maintaining the word line voltage levels after a last programming operation for an additional time interval to complete the programming operations.

9. The device of claim 8 , wherein the decoder pre-charges the cell strings of the block by applying VDD to all the bit lines and to all the drain select gates of the block before the operation of applying the programming voltage to the selected word line.

10. The device of claim 8 , wherein the decoder pre-charges the cell strings of the block by applying VDD to all the bit lines and drain select gates of the block, and then applying Vss to all the drain select gates of the block, before the operation of applying the programming voltage to the selected word line.

11. The device of claim 8 , wherein the decoder pre-charges the cell strings of the block by performing operations of:

applying VDD or a higher voltage to all the source lines and source select gates of the block;

applying Vss to all the drain select gates of the block;

performing the above operations before the operation of applying the programming voltage to the selected word line; and

applying Vss to a source select gate of the block either before or after the operation of applying the programming voltage to the selected word line.

12. The device of claim 8 , wherein each cell string comprises a plurality of NAND nonvolatile memory cells.

13. The device of claim 8 , wherein the programming voltage is in a range of 15-20 volts and the inhibit middle high voltage is in a range of 8-10 volts.

14. The device of claim 8 , wherein the data buffer obtains the data from a second block that includes a plurality of second page groups, and wherein one or more of the second page groups is configured as a DRAM page.

15. A method for multiple-page programming of a 3D NAND flash memory array having a block that includes a plurality of page groups and each page group includes a plurality of cell strings that form a plurality of pages, and wherein the page groups in the block are coupled to a common set of word lines, the method comprising:

applying a programming voltage to a selected word line and an inhibit middle high voltage to unselected word lines;

pulsing a first drain select gate associated with a first page group to begin programming bit line data into a page of the first page group that is connected to the selected word line;

pulsing a second drain select gate associated with a second page group to begin programming bit line data into a page of the second page group that is connected to the selected word line; and

maintaining the word line voltage levels associated with the first and second page groups beginning from the pulsing the first drain select gate to the pulsing of the second drain select gate and wherein the word line voltage levels are maintained after the pulsing of the second drain select gate for an additional time interval to complete programming operations.

16. The method of claim 15 , further comprising pre-charging the cell strings of the block by applying VDD to all the bit lines and to all the drain select gates of the block before the operation of applying the programming voltage to the selected word line.

17. The method of claim 15 , further comprising pre-charging the cell strings of the block by applying VDD to all the bit lines and drain select gates of the block, and then applying Vss to all the drain select gates of the block, before the operation of applying the programming voltage to the selected word line.

18. The method of claim 15 , further comprising pre-charging the cell strings of the block by performing operations of:

applying VDD or a higher voltage to all the source lines and source select gates of the block;

applying Vss to all the drain select gates of the block;

performing the above operations before the operation of applying the programming voltage to the selected word line; and

applying Vss to a source select gate of the block either before or after the operation of applying the programming voltage to the selected word line.