Methods and apparatus for NAND flash memory
Methods and apparatus for memory operations disclosed. In an embodiment, a method is provided for programming multiple-level-cells. The method includes programming data to single-level-cells (SLC) on SLC word lines using SLC programming operations, applying ramp data to the SLC word lines to determine selected ramp data that matches the data stored in (SLC) cells, and programming multiple-level cells to have a voltage threshold level that is associated with the ramp data. In an embodiment, an apparatus includes a first plane having a plurality of first cell strings coupled to a first page buffer. Each first cell string comprises a plurality of multiple-level cells. The apparatus also includes a second plane having a plurality of second cell strings coupled to a second page buffer. Each second cell string comprises a plurality of single-level cells. The apparatus is also configured so that the first page buffer is connected to communicate with the second page buffer.
1. A method for programming multiple-level-cells, the method comprising:
programming data to single-level-cells (SLC) on SLC word lines using SLC programming operations;
sequentially applying ramp data to the SLC word lines to determine selected ramp data that matches the data stored in (SLC) cells; and
programming multiple-level cells to have a voltage threshold level that is associated with the ramp data.
2. The method of claim 1 , wherein SLC cells storing the data are connected in series, and wherein the method comprises turning on SLC cells having stored data that matches the ramp data applied to the SLC word lines.
3. The method of claim 1 , wherein SLC cells storing the data are connected in parallel, and wherein the method comprises turning off SLC cells having stored data that matches the ramp data applied to the SLC word lines.
4. The method of claim 1 , further comprising performing program-verification in which voltages applied to the multiple level word lines correspond to the ramp data applied to the SLC word lines.
5. The method of claim 1 , wherein the multiple-level cells and SLC cells are located in first and second planes, respectively, and perform operations independently.
6. A method for programming an apparatus comprising multiple memory chips, wherein the memory chips comprise cells that can store multiple-level data, the method comprising:
programming first data into a first memory chip using an SLC programming operation;
reading the first data from the first memory chip using an SLC reading operation;
reprogramming the first data into a selected memory chip using a multiple-level-cell programming operation; and
during the operation of reprogramming, programming second data into a second chip using the SLC programming operation.
7. The method of claim 6 , wherein the selected multiple-level cells are located in the first chip.
8. The method of claim 6 , wherein the selected multiple-level cells are located in a third chip.
9. An apparatus comprising:
a first plane having a plurality of first cell strings coupled to a first page buffer through a plurality of first bit line select gates, wherein each first cell string comprises a plurality of multiple-level cells;
a second plane having a plurality of second cell strings coupled to a second page buffer through a plurality of second bit line select gates, wherein each second cell string comprises a plurality of single-level cells;
wherein the first page buffer is connected to the second page buffer; and
wherein word lines of the plurality of single-level cells receive ramped data to match data stored in the single-level cells during program-verification.
10. The apparatus of claim 9 , wherein the plurality of single-level cells are connected to each other in series in a cell string.
11. The apparatus of claim 9 , wherein the plurality of single-level cells are located in multiple cell strings.
12. The apparatus of claim 9 , wherein the plurality of single-level cells store input data and complementary input data for the multiple-level cells.